[exim.git] / src / src / acl.c

/* $Cambridge: exim/src/src/acl.c,v 1.39 2005/06/10 19:27:05 fanf2 Exp $ */

/*************************************************
*     Exim - an Internet mail transport agent    *
*************************************************/

/* Copyright (c) University of Cambridge 1995 - 2005 */
/* See the file NOTICE for conditions of use and distribution. */

/* Code for handling Access Control Lists (ACLs) */

#include "exim.h"


/* Default callout timeout */

#define CALLOUT_TIMEOUT_DEFAULT 30

/* ACL verb codes - keep in step with the table of verbs that follows */

enum { ACL_ACCEPT, ACL_DEFER, ACL_DENY, ACL_DISCARD, ACL_DROP, ACL_REQUIRE,
       ACL_WARN };

/* ACL verbs */

static uschar *verbs[] =
  { US"accept", US"defer", US"deny", US"discard", US"drop", US"require",
    US"warn" };

/* For each verb, the condition for which "message" is used */

static int msgcond[] = { FAIL, OK, OK, FAIL, OK, FAIL, OK };

/* ACL condition and modifier codes - keep in step with the table that
follows. */

enum { ACLC_ACL, ACLC_AUTHENTICATED,
#ifdef EXPERIMENTAL_BRIGHTMAIL
       ACLC_BMI_OPTIN,
#endif
ACLC_CONDITION, ACLC_CONTROL,
#ifdef WITH_CONTENT_SCAN
       ACLC_DECODE,
#endif
       ACLC_DELAY,
#ifdef WITH_OLD_DEMIME
       ACLC_DEMIME,
#endif
#ifdef EXPERIMENTAL_DOMAINKEYS
       ACLC_DK_DOMAIN_SOURCE,
       ACLC_DK_POLICY,
       ACLC_DK_SENDER_DOMAINS,
       ACLC_DK_SENDER_LOCAL_PARTS,
       ACLC_DK_SENDERS,
       ACLC_DK_STATUS,
#endif
       ACLC_DNSLISTS, ACLC_DOMAINS, ACLC_ENCRYPTED, ACLC_ENDPASS,
       ACLC_HOSTS, ACLC_LOCAL_PARTS, ACLC_LOG_MESSAGE, ACLC_LOGWRITE,
#ifdef WITH_CONTENT_SCAN
       ACLC_MALWARE,
#endif
       ACLC_MESSAGE,
#ifdef WITH_CONTENT_SCAN
       ACLC_MIME_REGEX,
#endif
       ACLC_RATELIMIT,
       ACLC_RECIPIENTS,
#ifdef WITH_CONTENT_SCAN
       ACLC_REGEX,
#endif
       ACLC_SENDER_DOMAINS, ACLC_SENDERS, ACLC_SET,
#ifdef WITH_CONTENT_SCAN
       ACLC_SPAM,
#endif
#ifdef EXPERIMENTAL_SPF
       ACLC_SPF,
#endif
       ACLC_VERIFY };

/* ACL conditions/modifiers: "delay", "control", "endpass", "message",
"log_message", "logwrite", and "set" are modifiers that look like conditions
but always return TRUE. They are used for their side effects. */

static uschar *conditions[] = { US"acl", US"authenticated",
#ifdef EXPERIMENTAL_BRIGHTMAIL
  US"bmi_optin",
#endif
  US"condition",
  US"control",
#ifdef WITH_CONTENT_SCAN
  US"decode",
#endif
  US"delay",
#ifdef WITH_OLD_DEMIME
  US"demime",
#endif
#ifdef EXPERIMENTAL_DOMAINKEYS
  US"dk_domain_source",
  US"dk_policy",
  US"dk_sender_domains",
  US"dk_sender_local_parts",
  US"dk_senders",
  US"dk_status",
#endif
  US"dnslists", US"domains", US"encrypted",
  US"endpass", US"hosts", US"local_parts", US"log_message", US"logwrite",
#ifdef WITH_CONTENT_SCAN
  US"malware",
#endif
  US"message",
#ifdef WITH_CONTENT_SCAN
  US"mime_regex",
#endif
  US"ratelimit",
  US"recipients",
#ifdef WITH_CONTENT_SCAN
  US"regex",
#endif
  US"sender_domains", US"senders", US"set",
#ifdef WITH_CONTENT_SCAN
  US"spam",
#endif
#ifdef EXPERIMENTAL_SPF
  US"spf",
#endif
  US"verify" };

/* ACL control names */

static uschar *controls[] = { US"error", US"caseful_local_part",
  US"caselower_local_part", US"enforce_sync", US"no_enforce_sync", US"freeze",
  US"queue_only", US"submission", US"no_multiline"};

/* Flags to indicate for which conditions /modifiers a string expansion is done
at the outer level. In the other cases, expansion already occurs in the
checking functions. */

static uschar cond_expand_at_top[] = {
  TRUE,    /* acl */
  FALSE,   /* authenticated */
#ifdef EXPERIMENTAL_BRIGHTMAIL
  TRUE,    /* bmi_optin */
#endif
  TRUE,    /* condition */
  TRUE,    /* control */
#ifdef WITH_CONTENT_SCAN
  TRUE,    /* decode */
#endif
  TRUE,    /* delay */
#ifdef WITH_OLD_DEMIME
  TRUE,    /* demime */
#endif
#ifdef EXPERIMENTAL_DOMAINKEYS
  TRUE,    /* dk_domain_source */
  TRUE,    /* dk_policy */
  TRUE,    /* dk_sender_domains */
  TRUE,    /* dk_sender_local_parts */
  TRUE,    /* dk_senders */
  TRUE,    /* dk_status */
#endif
  TRUE,    /* dnslists */
  FALSE,   /* domains */
  FALSE,   /* encrypted */
  TRUE,    /* endpass */
  FALSE,   /* hosts */
  FALSE,   /* local_parts */
  TRUE,    /* log_message */
  TRUE,    /* logwrite */
#ifdef WITH_CONTENT_SCAN
  TRUE,    /* malware */
#endif
  TRUE,    /* message */
#ifdef WITH_CONTENT_SCAN
  TRUE,    /* mime_regex */
#endif
  TRUE,    /* ratelimit */
  FALSE,   /* recipients */
#ifdef WITH_CONTENT_SCAN
  TRUE,    /* regex */
#endif
  FALSE,   /* sender_domains */
  FALSE,   /* senders */
  TRUE,    /* set */
#ifdef WITH_CONTENT_SCAN
  TRUE,    /* spam */
#endif
#ifdef EXPERIMENTAL_SPF
  TRUE,    /* spf */
#endif
  TRUE     /* verify */
};

/* Flags to identify the modifiers */

static uschar cond_modifiers[] = {
  FALSE,   /* acl */
  FALSE,   /* authenticated */
#ifdef EXPERIMENTAL_BRIGHTMAIL
  TRUE,    /* bmi_optin */
#endif
  FALSE,   /* condition */
  TRUE,    /* control */
#ifdef WITH_CONTENT_SCAN
  FALSE,   /* decode */
#endif
  TRUE,    /* delay */
#ifdef WITH_OLD_DEMIME
  FALSE,   /* demime */
#endif
#ifdef EXPERIMENTAL_DOMAINKEYS
  FALSE,   /* dk_domain_source */
  FALSE,   /* dk_policy */
  FALSE,   /* dk_sender_domains */
  FALSE,   /* dk_sender_local_parts */
  FALSE,   /* dk_senders */
  FALSE,   /* dk_status */
#endif
  FALSE,   /* dnslists */
  FALSE,   /* domains */
  FALSE,   /* encrypted */
  TRUE,    /* endpass */
  FALSE,   /* hosts */
  FALSE,   /* local_parts */
  TRUE,    /* log_message */
  TRUE,    /* logwrite */
#ifdef WITH_CONTENT_SCAN
  FALSE,   /* malware */
#endif
  TRUE,    /* message */
#ifdef WITH_CONTENT_SCAN
  FALSE,   /* mime_regex */
#endif
  FALSE,   /* ratelimit */
  FALSE,   /* recipients */
#ifdef WITH_CONTENT_SCAN
  FALSE,   /* regex */
#endif
  FALSE,   /* sender_domains */
  FALSE,   /* senders */
  TRUE,    /* set */
#ifdef WITH_CONTENT_SCAN
  FALSE,   /* spam */
#endif
#ifdef EXPERIMENTAL_SPF
  FALSE,   /* spf */
#endif
  FALSE    /* verify */
};

/* Bit map vector of which conditions are not allowed at certain times. For
each condition, there's a bitmap of dis-allowed times. For some, it is easier
to specify the negation of a small number of allowed times. */

static unsigned int cond_forbids[] = {
  0,                                               /* acl */

  (1<<ACL_WHERE_NOTSMTP)|(1<<ACL_WHERE_CONNECT)|   /* authenticated */
    (1<<ACL_WHERE_HELO),

#ifdef EXPERIMENTAL_BRIGHTMAIL
  (1<<ACL_WHERE_AUTH)|                             /* bmi_optin */
    (1<<ACL_WHERE_CONNECT)|(1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_DATA)|(1<<ACL_WHERE_MIME)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_MAILAUTH)|
    (1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_STARTTLS)|
    (1<<ACL_WHERE_VRFY)|(1<<ACL_WHERE_PREDATA),
#endif

  0,                                               /* condition */

  /* Certain types of control are always allowed, so we let it through
  always and check in the control processing itself. */

  0,                                               /* control */

#ifdef WITH_CONTENT_SCAN
  (unsigned int)
  ~(1<<ACL_WHERE_MIME),                            /* decode */
#endif

  0,                                               /* delay */

#ifdef WITH_OLD_DEMIME
  (unsigned int)
  ~((1<<ACL_WHERE_DATA)|(1<<ACL_WHERE_NOTSMTP)),   /* demime */
#endif

#ifdef EXPERIMENTAL_DOMAINKEYS
  (1<<ACL_WHERE_AUTH)|                             /* dk_domain_source */
    (1<<ACL_WHERE_CONNECT)|(1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_RCPT)|(1<<ACL_WHERE_PREDATA)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_MAILAUTH)|(1<<ACL_WHERE_QUIT)|
    (1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_STARTTLS)|
    (1<<ACL_WHERE_VRFY),

  (1<<ACL_WHERE_AUTH)|                             /* dk_policy */
    (1<<ACL_WHERE_CONNECT)|(1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_RCPT)|(1<<ACL_WHERE_PREDATA)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_MAILAUTH)|(1<<ACL_WHERE_QUIT)|
    (1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_STARTTLS)|
    (1<<ACL_WHERE_VRFY),

  (1<<ACL_WHERE_AUTH)|                             /* dk_sender_domains */
    (1<<ACL_WHERE_CONNECT)|(1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_RCPT)|(1<<ACL_WHERE_PREDATA)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_MAILAUTH)|(1<<ACL_WHERE_QUIT)|
    (1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_STARTTLS)|
    (1<<ACL_WHERE_VRFY),

  (1<<ACL_WHERE_AUTH)|                             /* dk_sender_local_parts */
    (1<<ACL_WHERE_CONNECT)|(1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_RCPT)|(1<<ACL_WHERE_PREDATA)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_MAILAUTH)|(1<<ACL_WHERE_QUIT)|
    (1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_STARTTLS)|
    (1<<ACL_WHERE_VRFY),

  (1<<ACL_WHERE_AUTH)|                             /* dk_senders */
    (1<<ACL_WHERE_CONNECT)|(1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_RCPT)|(1<<ACL_WHERE_PREDATA)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_MAILAUTH)|(1<<ACL_WHERE_QUIT)|
    (1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_STARTTLS)|
    (1<<ACL_WHERE_VRFY),

  (1<<ACL_WHERE_AUTH)|                             /* dk_status */
    (1<<ACL_WHERE_CONNECT)|(1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_RCPT)|(1<<ACL_WHERE_PREDATA)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_MAILAUTH)|(1<<ACL_WHERE_QUIT)|
    (1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_STARTTLS)|
    (1<<ACL_WHERE_VRFY),
#endif

  (1<<ACL_WHERE_NOTSMTP),                          /* dnslists */

  (unsigned int)
  ~(1<<ACL_WHERE_RCPT),                            /* domains */

  (1<<ACL_WHERE_NOTSMTP)|(1<<ACL_WHERE_CONNECT)|   /* encrypted */
    (1<<ACL_WHERE_HELO),

  0,                                               /* endpass */

  (1<<ACL_WHERE_NOTSMTP),                          /* hosts */

  (unsigned int)
  ~(1<<ACL_WHERE_RCPT),                            /* local_parts */

  0,                                               /* log_message */

  0,                                               /* logwrite */

#ifdef WITH_CONTENT_SCAN
  (unsigned int)
  ~((1<<ACL_WHERE_DATA)|(1<<ACL_WHERE_NOTSMTP)),   /* malware */
#endif

  0,                                               /* message */

#ifdef WITH_CONTENT_SCAN
  (unsigned int)
  ~(1<<ACL_WHERE_MIME),                            /* mime_regex */
#endif

  0,                                               /* ratelimit */

  (unsigned int)
  ~(1<<ACL_WHERE_RCPT),                            /* recipients */

#ifdef WITH_CONTENT_SCAN
  (unsigned int)
  ~((1<<ACL_WHERE_DATA)|(1<<ACL_WHERE_NOTSMTP)|    /* regex */
    (1<<ACL_WHERE_MIME)),
#endif

  (1<<ACL_WHERE_AUTH)|(1<<ACL_WHERE_CONNECT)|      /* sender_domains */
    (1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_MAILAUTH)|(1<<ACL_WHERE_QUIT)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_STARTTLS)|(1<<ACL_WHERE_VRFY),

  (1<<ACL_WHERE_AUTH)|(1<<ACL_WHERE_CONNECT)|      /* senders */
    (1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_MAILAUTH)|(1<<ACL_WHERE_QUIT)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_STARTTLS)|(1<<ACL_WHERE_VRFY),

  0,                                               /* set */

#ifdef WITH_CONTENT_SCAN
  (unsigned int)
  ~((1<<ACL_WHERE_DATA)|(1<<ACL_WHERE_NOTSMTP)),   /* spam */
#endif

#ifdef EXPERIMENTAL_SPF
  (1<<ACL_WHERE_AUTH)|(1<<ACL_WHERE_CONNECT)|      /* spf */
    (1<<ACL_WHERE_HELO)|
    (1<<ACL_WHERE_MAILAUTH)|
    (1<<ACL_WHERE_ETRN)|(1<<ACL_WHERE_EXPN)|
    (1<<ACL_WHERE_STARTTLS)|(1<<ACL_WHERE_VRFY),
#endif

  /* Certain types of verify are always allowed, so we let it through
  always and check in the verify function itself */

  0                                                /* verify */
};


/* Return values from decode_control() */

enum {
#ifdef EXPERIMENTAL_BRIGHTMAIL
  CONTROL_BMI_RUN,
#endif
#ifdef EXPERIMENTAL_DOMAINKEYS
  CONTROL_DK_VERIFY,
#endif
  CONTROL_ERROR, CONTROL_CASEFUL_LOCAL_PART, CONTROL_CASELOWER_LOCAL_PART,
  CONTROL_ENFORCE_SYNC, CONTROL_NO_ENFORCE_SYNC, CONTROL_FREEZE,
  CONTROL_QUEUE_ONLY, CONTROL_SUBMISSION,
#ifdef WITH_CONTENT_SCAN
  CONTROL_NO_MBOX_UNSPOOL,
#endif
  CONTROL_FAKEDEFER, CONTROL_FAKEREJECT, CONTROL_NO_MULTILINE };

/* Bit map vector of which controls are not allowed at certain times. For
each control, there's a bitmap of dis-allowed times. For some, it is easier to
specify the negation of a small number of allowed times. */

static unsigned int control_forbids[] = {
#ifdef EXPERIMENTAL_BRIGHTMAIL
  0,                                               /* bmi_run */
#endif
#ifdef EXPERIMENTAL_DOMAINKEYS
  (1<<ACL_WHERE_DATA)|(1<<ACL_WHERE_NOTSMTP),      /* dk_verify */
#endif

  0,                                               /* error */

  (unsigned int)
  ~(1<<ACL_WHERE_RCPT),                            /* caseful_local_part */

  (unsigned int)
  ~(1<<ACL_WHERE_RCPT),                            /* caselower_local_part */

  (1<<ACL_WHERE_NOTSMTP),                          /* enforce_sync */

  (1<<ACL_WHERE_NOTSMTP),                          /* no_enforce_sync */

  (unsigned int)
  ~((1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_RCPT)|       /* freeze */
    (1<<ACL_WHERE_PREDATA)|(1<<ACL_WHERE_DATA)|
    (1<<ACL_WHERE_NOTSMTP)|(1<<ACL_WHERE_MIME)),

  (unsigned int)
  ~((1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_RCPT)|       /* queue_only */
    (1<<ACL_WHERE_PREDATA)|(1<<ACL_WHERE_DATA)|
    (1<<ACL_WHERE_NOTSMTP)|(1<<ACL_WHERE_MIME)),

  (unsigned int)
  ~((1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_RCPT)|       /* submission */
    (1<<ACL_WHERE_PREDATA)),

#ifdef WITH_CONTENT_SCAN
  (unsigned int)
  ~((1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_RCPT)|       /* no_mbox_unspool */
    (1<<ACL_WHERE_PREDATA)|(1<<ACL_WHERE_DATA)|
    (1<<ACL_WHERE_MIME)),
#endif

  (unsigned int)
  ~((1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_RCPT)|       /* fakedefer */
    (1<<ACL_WHERE_PREDATA)|(1<<ACL_WHERE_DATA)|
    (1<<ACL_WHERE_MIME)),

  (unsigned int)
  ~((1<<ACL_WHERE_MAIL)|(1<<ACL_WHERE_RCPT)|       /* fakereject */
    (1<<ACL_WHERE_PREDATA)|(1<<ACL_WHERE_DATA)|
    (1<<ACL_WHERE_MIME)),

  (1<<ACL_WHERE_NOTSMTP)                           /* no_multiline */
};

/* Structure listing various control arguments, with their characteristics. */

typedef struct control_def {
  uschar *name;
  int    value;                  /* CONTROL_xxx value */
  BOOL   has_option;             /* Has /option(s) following */
} control_def;

static control_def controls_list[] = {
#ifdef EXPERIMENTAL_BRIGHTMAIL
  { US"bmi_run",                CONTROL_BMI_RUN, FALSE},
#endif
#ifdef EXPERIMENTAL_DOMAINKEYS
  { US"dk_verify",              CONTROL_DK_VERIFY, FALSE},
#endif
  { US"caseful_local_part",     CONTROL_CASEFUL_LOCAL_PART, FALSE},
  { US"caselower_local_part",   CONTROL_CASELOWER_LOCAL_PART, FALSE},
  { US"enforce_sync",           CONTROL_ENFORCE_SYNC, FALSE},
  { US"freeze",                 CONTROL_FREEZE, FALSE},
  { US"no_enforce_sync",        CONTROL_NO_ENFORCE_SYNC, FALSE},
  { US"no_multiline_responses", CONTROL_NO_MULTILINE, FALSE},
  { US"queue_only",             CONTROL_QUEUE_ONLY, FALSE},
#ifdef WITH_CONTENT_SCAN
  { US"no_mbox_unspool",        CONTROL_NO_MBOX_UNSPOOL, FALSE},
#endif
  { US"fakedefer",              CONTROL_FAKEDEFER, TRUE},
  { US"fakereject",             CONTROL_FAKEREJECT, TRUE},
  { US"submission",             CONTROL_SUBMISSION, TRUE}
  };

/* Support data structures for Client SMTP Authorization. acl_verify_csa()
caches its result in a tree to avoid repeated DNS queries. The result is an
integer code which is used as an index into the following tables of
explanatory strings and verification return codes. */

static tree_node *csa_cache = NULL;

enum { CSA_UNKNOWN, CSA_OK, CSA_DEFER_SRV, CSA_DEFER_ADDR,
 CSA_FAIL_EXPLICIT, CSA_FAIL_DOMAIN, CSA_FAIL_NOADDR, CSA_FAIL_MISMATCH };

/* The acl_verify_csa() return code is translated into an acl_verify() return
code using the following table. It is OK unless the client is definitely not
authorized. This is because CSA is supposed to be optional for sending sites,
so recipients should not be too strict about checking it - especially because
DNS problems are quite likely to occur. It's possible to use $csa_status in
further ACL conditions to distinguish ok, unknown, and defer if required, but
the aim is to make the usual configuration simple. */

static int csa_return_code[] = {
  OK, OK, OK, OK,
  FAIL, FAIL, FAIL, FAIL
};

static uschar *csa_status_string[] = {
  US"unknown", US"ok", US"defer", US"defer",
  US"fail", US"fail", US"fail", US"fail"
};

static uschar *csa_reason_string[] = {
  US"unknown",
  US"ok",
  US"deferred (SRV lookup failed)",
  US"deferred (target address lookup failed)",
  US"failed (explicit authorization required)",
  US"failed (host name not authorized)",
  US"failed (no authorized addresses)",
  US"failed (client address mismatch)"
};

/* Enable recursion between acl_check_internal() and acl_check_condition() */

static int acl_check_internal(int, address_item *, uschar *, int, uschar **,
         uschar **);


/*************************************************
*         Pick out name from list                *
*************************************************/

/* Use a binary chop method

Arguments:
  name        name to find
  list        list of names
  end         size of list

Returns:      offset in list, or -1 if not found
*/

static int
acl_checkname(uschar *name, uschar **list, int end)
{
int start = 0;

while (start < end)
  {
  int mid = (start + end)/2;
  int c = Ustrcmp(name, list[mid]);
  if (c == 0) return mid;
  if (c < 0) end = mid; else start = mid + 1;
  }

return -1;
}


/*************************************************
*            Read and parse one ACL              *
*************************************************/

/* This function is called both from readconf in order to parse the ACLs in the
configuration file, and also when an ACL is encountered dynamically (e.g. as
the result of an expansion). It is given a function to call in order to
retrieve the lines of the ACL. This function handles skipping comments and
blank lines (where relevant).

Arguments:
  func        function to get next line of ACL
  error       where to put an error message

Returns:      pointer to ACL, or NULL
              NULL can be legal (empty ACL); in this case error will be NULL
*/

acl_block *
acl_read(uschar *(*func)(void), uschar **error)
{
acl_block *yield = NULL;
acl_block **lastp = &yield;
acl_block *this = NULL;
acl_condition_block *cond;
acl_condition_block **condp = NULL;
uschar *s;

*error = NULL;

while ((s = (*func)()) != NULL)
  {
  int v, c;
  BOOL negated = FALSE;
  uschar *saveline = s;
  uschar name[64];

  /* Conditions (but not verbs) are allowed to be negated by an initial
  exclamation mark. */

  while (isspace(*s)) s++;
  if (*s == '!')
    {
    negated = TRUE;
    s++;
    }

  /* Read the name of a verb or a condition, or the start of a new ACL, which
  can be started by a name, or by a macro definition. */

  s = readconf_readname(name, sizeof(name), s);
  if (*s == ':' || isupper(name[0] && *s == '=')) return yield;

  /* If a verb is unrecognized, it may be another condition or modifier that
  continues the previous verb. */

  v = acl_checkname(name, verbs, sizeof(verbs)/sizeof(char *));
  if (v < 0)
    {
    if (this == NULL)
      {
      *error = string_sprintf("unknown ACL verb in \"%s\"", saveline);
      return NULL;
      }
    }

  /* New verb */

  else
    {
    if (negated)
      {
      *error = string_sprintf("malformed ACL line \"%s\"", saveline);
      return NULL;
      }
    this = store_get(sizeof(acl_block));
    *lastp = this;
    lastp = &(this->next);
    this->next = NULL;
    this->verb = v;
    this->condition = NULL;
    condp = &(this->condition);
    if (*s == 0) continue;               /* No condition on this line */
    if (*s == '!')
      {
      negated = TRUE;
      s++;
      }
    s = readconf_readname(name, sizeof(name), s);  /* Condition name */
    }

  /* Handle a condition or modifier. */

  c = acl_checkname(name, conditions, sizeof(conditions)/sizeof(char *));
  if (c < 0)
    {
    *error = string_sprintf("unknown ACL condition/modifier in \"%s\"",
      saveline);
    return NULL;
    }

  /* The modifiers may not be negated */

  if (negated && cond_modifiers[c])
    {
    *error = string_sprintf("ACL error: negation is not allowed with "
      "\"%s\"", conditions[c]);
    return NULL;
    }

  /* ENDPASS may occur only with ACCEPT or DISCARD. */

  if (c == ACLC_ENDPASS &&
      this->verb != ACL_ACCEPT &&
      this->verb != ACL_DISCARD)
    {
    *error = string_sprintf("ACL error: \"%s\" is not allowed with \"%s\"",
      conditions[c], verbs[this->verb]);
    return NULL;
    }

  cond = store_get(sizeof(acl_condition_block));
  cond->next = NULL;
  cond->type = c;
  cond->u.negated = negated;

  *condp = cond;
  condp = &(cond->next);

  /* The "set" modifier is different in that its argument is "name=value"
  rather than just a value, and we can check the validity of the name, which
  gives us a variable number to insert into the data block. */

  if (c == ACLC_SET)
    {
    if (Ustrncmp(s, "acl_", 4) != 0 || (s[4] != 'c' && s[4] != 'm') ||
        !isdigit(s[5]) || (!isspace(s[6]) && s[6] != '='))
      {
      *error = string_sprintf("unrecognized name after \"set\" in ACL "
        "modifier \"set %s\"", s);
      return NULL;
      }

    cond->u.varnumber = s[5] - '0';
    if (s[4] == 'm') cond->u.varnumber += ACL_C_MAX;
    s += 6;
    while (isspace(*s)) s++;
    }

  /* For "set", we are now positioned for the data. For the others, only
  "endpass" has no data */

  if (c != ACLC_ENDPASS)
    {
    if (*s++ != '=')
      {
      *error = string_sprintf("\"=\" missing after ACL \"%s\" %s", name,
        cond_modifiers[c]? US"modifier" : US"condition");
      return NULL;
      }
    while (isspace(*s)) s++;
    cond->arg = string_copy(s);
    }
  }

return yield;
}


/*************************************************
*               Handle warnings                  *
*************************************************/

/* This function is called when a WARN verb's conditions are true. It adds to
the message's headers, and/or writes information to the log. In each case, this
only happens once (per message for headers, per connection for log).

Arguments:
  where          ACL_WHERE_xxxx indicating which ACL this is
  user_message   message for adding to headers
  log_message    message for logging, if different

Returns:         nothing
*/

static void
acl_warn(int where, uschar *user_message, uschar *log_message)
{
int hlen;

if (log_message != NULL && log_message != user_message)
  {
  uschar *text;
  string_item *logged;

  text = string_sprintf("%s Warning: %s",  host_and_ident(TRUE),
    string_printing(log_message));

  /* If a sender verification has failed, and the log message is "sender verify
  failed", add the failure message. */

  if (sender_verified_failed != NULL &&
      sender_verified_failed->message != NULL &&
      strcmpic(log_message, US"sender verify failed") == 0)
    text = string_sprintf("%s: %s", text, sender_verified_failed->message);

  /* Search previously logged warnings. They are kept in malloc
  store so they can be freed at the start of a new message. */

  for (logged = acl_warn_logged; logged != NULL; logged = logged->next)
    if (Ustrcmp(logged->text, text) == 0) break;

  if (logged == NULL)
    {
    int length = Ustrlen(text) + 1;
    log_write(0, LOG_MAIN, "%s", text);
    logged = store_malloc(sizeof(string_item) + length);
    logged->text = (uschar *)logged + sizeof(string_item);
    memcpy(logged->text, text, length);
    logged->next = acl_warn_logged;
    acl_warn_logged = logged;
    }
  }

/* If there's no user message, we are done. */

if (user_message == NULL) return;

/* If this isn't a message ACL, we can't do anything with a user message.
Log an error. */

if (where > ACL_WHERE_NOTSMTP)
  {
  log_write(0, LOG_MAIN|LOG_PANIC, "ACL \"warn\" with \"message\" setting "
    "found in a non-message (%s) ACL: cannot specify header lines here: "
    "message ignored", acl_wherenames[where]);
  return;
  }

/* Treat the user message as a sequence of one or more header lines. */

hlen = Ustrlen(user_message);
if (hlen > 0)
  {
  uschar *text, *p, *q;

  /* Add a final newline if not present */

  text = ((user_message)[hlen-1] == '\n')? user_message :
    string_sprintf("%s\n", user_message);

  /* Loop for multiple header lines, taking care about continuations */

  for (p = q = text; *p != 0; )
    {
    uschar *s;
    int newtype = htype_add_bot;
    header_line **hptr = &acl_warn_headers;

    /* Find next header line within the string */

    for (;;)
      {
      q = Ustrchr(q, '\n');
      if (*(++q) != ' ' && *q != '\t') break;
      }

    /* If the line starts with a colon, interpret the instruction for where to
    add it. This temporarily sets up a new type. */

    if (*p == ':')
      {
      if (strncmpic(p, US":after_received:", 16) == 0)
        {
        newtype = htype_add_rec;
        p += 16;
        }
      else if (strncmpic(p, US":at_start_rfc:", 14) == 0)
        {
        newtype = htype_add_rfc;
        p += 14;
        }
      else if (strncmpic(p, US":at_start:", 10) == 0)
        {
        newtype = htype_add_top;
        p += 10;
        }
      else if (strncmpic(p, US":at_end:", 8) == 0)
        {
        newtype = htype_add_bot;
        p += 8;
        }
      while (*p == ' ' || *p == '\t') p++;
      }

    /* See if this line starts with a header name, and if not, add X-ACL-Warn:
    to the front of it. */

    for (s = p; s < q - 1; s++)
      {
      if (*s == ':' || !isgraph(*s)) break;
      }

    s = string_sprintf("%s%.*s", (*s == ':')? "" : "X-ACL-Warn: ", q - p, p);
    hlen = Ustrlen(s);

    /* See if this line has already been added */

    while (*hptr != NULL)
      {
      if (Ustrncmp((*hptr)->text, s, hlen) == 0) break;
      hptr = &((*hptr)->next);
      }

    /* Add if not previously present */

    if (*hptr == NULL)
      {
      header_line *h = store_get(sizeof(header_line));
      h->text = s;
      h->next = NULL;
      h->type = newtype;
      h->slen = hlen;
      *hptr = h;
      hptr = &(h->next);
      }

    /* Advance for next header line within the string */

    p = q;
    }
  }
}


/*************************************************
*         Verify and check reverse DNS           *
*************************************************/

/* Called from acl_verify() below. We look up the host name(s) of the client IP
address if this has not yet been done. The host_name_lookup() function checks
that one of these names resolves to an address list that contains the client IP
address, so we don't actually have to do the check here.

Arguments:
  user_msgptr  pointer for user message
  log_msgptr   pointer for log message

Returns:       OK        verification condition succeeded
               FAIL      verification failed
               DEFER     there was a problem verifying
*/

static int
acl_verify_reverse(uschar **user_msgptr, uschar **log_msgptr)
{
int rc;

user_msgptr = user_msgptr;  /* stop compiler warning */

/* Previous success */

if (sender_host_name != NULL) return OK;

/* Previous failure */

if (host_lookup_failed)
  {
  *log_msgptr = string_sprintf("host lookup failed%s", host_lookup_msg);
  return FAIL;
  }

/* Need to do a lookup */

HDEBUG(D_acl)
  debug_printf("looking up host name to force name/address consistency check\n");

if ((rc = host_name_lookup()) != OK)
  {
  *log_msgptr = (rc == DEFER)?
    US"host lookup deferred for reverse lookup check"
    :
    string_sprintf("host lookup failed for reverse lookup check%s",
      host_lookup_msg);
  return rc;    /* DEFER or FAIL */
  }

host_build_sender_fullhost();
return OK;
}


/*************************************************
*   Check client IP address matches CSA target   *
*************************************************/

/* Called from acl_verify_csa() below. This routine scans a section of a DNS
response for address records belonging to the CSA target hostname. The section
is specified by the reset argument, either RESET_ADDITIONAL or RESET_ANSWERS.
If one of the addresses matches the client's IP address, then the client is
authorized by CSA. If there are target IP addresses but none of them match
then the client is using an unauthorized IP address. If there are no target IP
addresses then the client cannot be using an authorized IP address. (This is
an odd configuration - why didn't the SRV record have a weight of 1 instead?)

Arguments:
  dnsa       the DNS answer block
  dnss       a DNS scan block for us to use
  reset      option specifing what portion to scan, as described above
  target     the target hostname to use for matching RR names

Returns:     CSA_OK             successfully authorized
             CSA_FAIL_MISMATCH  addresses found but none matched
             CSA_FAIL_NOADDR    no target addresses found
*/

static int
acl_verify_csa_address(dns_answer *dnsa, dns_scan *dnss, int reset,
                       uschar *target)
{
dns_record *rr;
dns_address *da;

BOOL target_found = FALSE;

for (rr = dns_next_rr(dnsa, dnss, reset);
     rr != NULL;
     rr = dns_next_rr(dnsa, dnss, RESET_NEXT))
  {
  /* Check this is an address RR for the target hostname. */

  if (rr->type != T_A
    #if HAVE_IPV6
      && rr->type != T_AAAA
      #ifdef SUPPORT_A6
        && rr->type != T_A6
      #endif
    #endif
  ) continue;

  if (strcmpic(target, rr->name) != 0) continue;

  target_found = TRUE;

  /* Turn the target address RR into a list of textual IP addresses and scan
  the list. There may be more than one if it is an A6 RR. */

  for (da = dns_address_from_rr(dnsa, rr); da != NULL; da = da->next)
    {
    /* If the client IP address matches the target IP address, it's good! */

    DEBUG(D_acl) debug_printf("CSA target address is %s\n", da->address);

    if (strcmpic(sender_host_address, da->address) == 0) return CSA_OK;
    }
  }

/* If we found some target addresses but none of them matched, the client is
using an unauthorized IP address, otherwise the target has no authorized IP
addresses. */

if (target_found) return CSA_FAIL_MISMATCH;
else return CSA_FAIL_NOADDR;
}


/*************************************************
*       Verify Client SMTP Authorization         *
*************************************************/

/* Called from acl_verify() below. This routine calls dns_lookup_special()
to find the CSA SRV record corresponding to the domain argument, or
$sender_helo_name if no argument is provided. It then checks that the
client is authorized, and that its IP address corresponds to the SRV
target's address by calling acl_verify_csa_address() above. The address
should have been returned in the DNS response's ADDITIONAL section, but if
not we perform another DNS lookup to get it.

Arguments:
  domain    pointer to optional parameter following verify = csa

Returns:    CSA_UNKNOWN    no valid CSA record found
            CSA_OK         successfully authorized
            CSA_FAIL_*     client is definitely not authorized
            CSA_DEFER_*    there was a DNS problem
*/

static int
acl_verify_csa(uschar *domain)
{
tree_node *t;
uschar *found, *p;
int priority, weight, port;
dns_answer dnsa;
dns_scan dnss;
dns_record *rr;
int rc, type;
uschar target[256];

/* Work out the domain we are using for the CSA lookup. The default is the
client's HELO domain. If the client has not said HELO, use its IP address
instead. If it's a local client (exim -bs), CSA isn't applicable. */

while (isspace(*domain) && *domain != '\0') ++domain;
if (*domain == '\0') domain = sender_helo_name;
if (domain == NULL) domain = sender_host_address;
if (sender_host_address == NULL) return CSA_UNKNOWN;

/* If we have an address literal, strip off the framing ready for turning it
into a domain. The framing consists of matched square brackets possibly
containing a keyword and a colon before the actual IP address. */

if (domain[0] == '[')
  {
  uschar *start = Ustrchr(domain, ':');
  if (start == NULL) start = domain;
  domain = string_copyn(start + 1, Ustrlen(start) - 2);
  }

/* Turn domains that look like bare IP addresses into domains in the reverse
DNS. This code also deals with address literals and $sender_host_address. It's
not quite kosher to treat bare domains such as EHLO 192.0.2.57 the same as
address literals, but it's probably the most friendly thing to do. This is an
extension to CSA, so we allow it to be turned off for proper conformance. */

if (string_is_ip_address(domain, NULL))
  {
  if (!dns_csa_use_reverse) return CSA_UNKNOWN;
  dns_build_reverse(domain, target);
  domain = target;
  }

/* Find out if we've already done the CSA check for this domain. If we have,
return the same result again. Otherwise build a new cached result structure
for this domain. The name is filled in now, and the value is filled in when
we return from this function. */

t = tree_search(csa_cache, domain);
if (t != NULL) return t->data.val;

t = store_get_perm(sizeof(tree_node) + Ustrlen(domain));
Ustrcpy(t->name, domain);
(void)tree_insertnode(&csa_cache, t);

/* Now we are ready to do the actual DNS lookup(s). */

found = domain;
switch (dns_special_lookup(&dnsa, domain, T_CSA, &found))
  {
  /* If something bad happened (most commonly DNS_AGAIN), defer. */

  default:
  return t->data.val = CSA_DEFER_SRV;

  /* If we found nothing, the client's authorization is unknown. */

  case DNS_NOMATCH:
  case DNS_NODATA:
  return t->data.val = CSA_UNKNOWN;

  /* We got something! Go on to look at the reply in more detail. */

  case DNS_SUCCEED:
  break;
  }

/* Scan the reply for well-formed CSA SRV records. */

for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
     rr != NULL;
     rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
  {
  if (rr->type != T_SRV) continue;

  /* Extract the numerical SRV fields (p is incremented) */

  p = rr->data;
  GETSHORT(priority, p);
  GETSHORT(weight, p);
  GETSHORT(port, p);

  DEBUG(D_acl)
    debug_printf("CSA priority=%d weight=%d port=%d\n", priority, weight, port);

  /* Check the CSA version number */

  if (priority != 1) continue;

  /* If the domain does not have a CSA SRV record of its own (i.e. the domain
  found by dns_special_lookup() is a parent of the one we asked for), we check
  the subdomain assertions in the port field. At the moment there's only one
  assertion: legitimate SMTP clients are all explicitly authorized with CSA
  SRV records of their own. */

  if (found != domain)
    {
    if (port & 1)
      return t->data.val = CSA_FAIL_EXPLICIT;
    else
      return t->data.val = CSA_UNKNOWN;
    }

  /* This CSA SRV record refers directly to our domain, so we check the value
  in the weight field to work out the domain's authorization. 0 and 1 are
  unauthorized; 3 means the client is authorized but we can't check the IP
  address in order to authenticate it, so we treat it as unknown; values
  greater than 3 are undefined. */

  if (weight < 2) return t->data.val = CSA_FAIL_DOMAIN;

  if (weight > 2) continue;

  /* Weight == 2, which means the domain is authorized. We must check that the
  client's IP address is listed as one of the SRV target addresses. Save the
  target hostname then break to scan the additional data for its addresses. */

  (void)dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
    (DN_EXPAND_ARG4_TYPE)target, sizeof(target));

  DEBUG(D_acl) debug_printf("CSA target is %s\n", target);

  break;
  }

/* If we didn't break the loop then no appropriate records were found. */

if (rr == NULL) return t->data.val = CSA_UNKNOWN;

/* Do not check addresses if the target is ".", in accordance with RFC 2782.
A target of "." indicates there are no valid addresses, so the client cannot
be authorized. (This is an odd configuration because weight=2 target=. is
equivalent to weight=1, but we check for it in order to keep load off the
root name servers.) Note that dn_expand() turns "." into "". */

if (Ustrcmp(target, "") == 0) return t->data.val = CSA_FAIL_NOADDR;

/* Scan the additional section of the CSA SRV reply for addresses belonging
to the target. If the name server didn't return any additional data (e.g.
because it does not fully support SRV records), we need to do another lookup
to obtain the target addresses; otherwise we have a definitive result. */

rc = acl_verify_csa_address(&dnsa, &dnss, RESET_ADDITIONAL, target);
if (rc != CSA_FAIL_NOADDR) return t->data.val = rc;

/* The DNS lookup type corresponds to the IP version used by the client. */

#if HAVE_IPV6
if (Ustrchr(sender_host_address, ':') != NULL)
  type = T_AAAA;
else
#endif /* HAVE_IPV6 */
  type = T_A;


#if HAVE_IPV6 && defined(SUPPORT_A6)
DNS_LOOKUP_AGAIN:
#endif

switch (dns_lookup(&dnsa, target, type, NULL))
  {
  /* If something bad happened (most commonly DNS_AGAIN), defer. */

  default:
  return t->data.val = CSA_DEFER_ADDR;

  /* If the query succeeded, scan the addresses and return the result. */

  case DNS_SUCCEED:
  rc = acl_verify_csa_address(&dnsa, &dnss, RESET_ANSWERS, target);
  if (rc != CSA_FAIL_NOADDR) return t->data.val = rc;
  /* else fall through */

  /* If the target has no IP addresses, the client cannot have an authorized
  IP address. However, if the target site uses A6 records (not AAAA records)
  we have to do yet another lookup in order to check them. */

  case DNS_NOMATCH:
  case DNS_NODATA:

  #if HAVE_IPV6 && defined(SUPPORT_A6)
  if (type == T_AAAA) { type = T_A6; goto DNS_LOOKUP_AGAIN; }
  #endif

  return t->data.val = CSA_FAIL_NOADDR;
  }
}


/*************************************************
*     Handle verification (address & other)      *
*************************************************/

/* This function implements the "verify" condition. It is called when
encountered in any ACL, because some tests are almost always permitted. Some
just don't make sense, and always fail (for example, an attempt to test a host
lookup for a non-TCP/IP message). Others are restricted to certain ACLs.

Arguments:
  where        where called from
  addr         the recipient address that the ACL is handling, or NULL
  arg          the argument of "verify"
  user_msgptr  pointer for user message
  log_msgptr   pointer for log message
  basic_errno  where to put verify errno

Returns:       OK        verification condition succeeded
               FAIL      verification failed
               DEFER     there was a problem verifying
               ERROR     syntax error
*/

static int
acl_verify(int where, address_item *addr, uschar *arg,
  uschar **user_msgptr, uschar **log_msgptr, int *basic_errno)
{
int sep = '/';
int callout = -1;
int callout_overall = -1;
int callout_connect = -1;
int verify_options = 0;
int rc;
BOOL verify_header_sender = FALSE;
BOOL defer_ok = FALSE;
BOOL callout_defer_ok = FALSE;
BOOL no_details = FALSE;
address_item *sender_vaddr = NULL;
uschar *verify_sender_address = NULL;
uschar *pm_mailfrom = NULL;
uschar *se_mailfrom = NULL;

/* Some of the verify items have slash-separated options; some do not. Diagnose
an error if options are given for items that don't expect them. This code has
now got very message. Refactoring to use a table would be a good idea one day.
*/

uschar *slash = Ustrchr(arg, '/');
uschar *list = arg;
uschar *ss = string_nextinlist(&list, &sep, big_buffer, big_buffer_size);

if (ss == NULL) goto BAD_VERIFY;

/* Handle name/address consistency verification in a separate function. */

if (strcmpic(ss, US"reverse_host_lookup") == 0)
  {
  if (slash != NULL) goto NO_OPTIONS;
  if (sender_host_address == NULL) return OK;
  return acl_verify_reverse(user_msgptr, log_msgptr);
  }

/* TLS certificate verification is done at STARTTLS time; here we just
test whether it was successful or not. (This is for optional verification; for
mandatory verification, the connection doesn't last this long.) */

if (strcmpic(ss, US"certificate") == 0)
  {
  if (slash != NULL) goto NO_OPTIONS;
  if (tls_certificate_verified) return OK;
  *user_msgptr = US"no verified certificate";
  return FAIL;
  }

/* We can test the result of optional HELO verification */

if (strcmpic(ss, US"helo") == 0)
  {
  if (slash != NULL) goto NO_OPTIONS;
  return helo_verified? OK : FAIL;
  }

/* Do Client SMTP Authorization checks in a separate function, and turn the
result code into user-friendly strings. */

if (strcmpic(ss, US"csa") == 0)
  {
  rc = acl_verify_csa(list);
  *log_msgptr = *user_msgptr = string_sprintf("client SMTP authorization %s",
                                              csa_reason_string[rc]);
  csa_status = csa_status_string[rc];
  DEBUG(D_acl) debug_printf("CSA result %s\n", csa_status);
  return csa_return_code[rc];
  }

/* Check that all relevant header lines have the correct syntax. If there is
a syntax error, we return details of the error to the sender if configured to
send out full details. (But a "message" setting on the ACL can override, as
always). */

if (strcmpic(ss, US"header_syntax") == 0)
  {
  if (slash != NULL) goto NO_OPTIONS;
  if (where != ACL_WHERE_DATA && where != ACL_WHERE_NOTSMTP)
    {
    *log_msgptr = string_sprintf("cannot check header contents in ACL for %s "
      "(only possible in ACL for DATA)", acl_wherenames[where]);
    return ERROR;
    }
  rc = verify_check_headers(log_msgptr);
  if (rc != OK && smtp_return_error_details && *log_msgptr != NULL)
    *user_msgptr = string_sprintf("Rejected after DATA: %s", *log_msgptr);
  return rc;
  }


/* The remaining verification tests check recipient and sender addresses,
either from the envelope or from the header. There are a number of
slash-separated options that are common to all of them. */


/* Check that there is at least one verifiable sender address in the relevant
header lines. This can be followed by callout and defer options, just like
sender and recipient. */

if (strcmpic(ss, US"header_sender") == 0)
  {
  if (where != ACL_WHERE_DATA && where != ACL_WHERE_NOTSMTP)
    {
    *log_msgptr = string_sprintf("cannot check header contents in ACL for %s "
      "(only possible in ACL for DATA)", acl_wherenames[where]);
    return ERROR;
    }
  verify_header_sender = TRUE;
  }

/* Otherwise, first item in verify argument must be "sender" or "recipient".
In the case of a sender, this can optionally be followed by an address to use
in place of the actual sender (rare special-case requirement). */

else if (strncmpic(ss, US"sender", 6) == 0)
  {
  uschar *s = ss + 6;
  if (where > ACL_WHERE_NOTSMTP)
    {
    *log_msgptr = string_sprintf("cannot verify sender in ACL for %s "
      "(only possible for MAIL, RCPT, PREDATA, or DATA)",
      acl_wherenames[where]);
    return ERROR;
    }
  if (*s == 0)
    verify_sender_address = sender_address;
  else
    {
    while (isspace(*s)) s++;
    if (*s++ != '=') goto BAD_VERIFY;
    while (isspace(*s)) s++;
    verify_sender_address = string_copy(s);
    }
  }
else
  {
  if (strcmpic(ss, US"recipient") != 0) goto BAD_VERIFY;
  if (addr == NULL)
    {
    *log_msgptr = string_sprintf("cannot verify recipient in ACL for %s "
      "(only possible for RCPT)", acl_wherenames[where]);
    return ERROR;
    }
  }

/* Remaining items are optional; they apply to sender and recipient
verification, including "header sender" verification. */

while ((ss = string_nextinlist(&list, &sep, big_buffer, big_buffer_size))
      != NULL)
  {
  if (strcmpic(ss, US"defer_ok") == 0) defer_ok = TRUE;
  else if (strcmpic(ss, US"no_details") == 0) no_details = TRUE;

  /* These two old options are left for backwards compatibility */

  else if (strcmpic(ss, US"callout_defer_ok") == 0)
    {
    callout_defer_ok = TRUE;
    if (callout == -1) callout = CALLOUT_TIMEOUT_DEFAULT;
    }

  else if (strcmpic(ss, US"check_postmaster") == 0)
     {
     pm_mailfrom = US"";
     if (callout == -1) callout = CALLOUT_TIMEOUT_DEFAULT;
     }

  /* The callout option has a number of sub-options, comma separated */

  else if (strncmpic(ss, US"callout", 7) == 0)
    {
    callout = CALLOUT_TIMEOUT_DEFAULT;
    ss += 7;
    if (*ss != 0)
      {
      while (isspace(*ss)) ss++;
      if (*ss++ == '=')
        {
        int optsep = ',';
        uschar *opt;
        uschar buffer[256];
        while (isspace(*ss)) ss++;

        /* This callout option handling code has become a mess as new options
        have been added in an ad hoc manner. It should be tidied up into some
        kind of table-driven thing. */

        while ((opt = string_nextinlist(&ss, &optsep, buffer, sizeof(buffer)))
              != NULL)
          {
          if (strcmpic(opt, US"defer_ok") == 0) callout_defer_ok = TRUE;
          else if (strcmpic(opt, US"no_cache") == 0)
             verify_options |= vopt_callout_no_cache;
          else if (strcmpic(opt, US"random") == 0)
             verify_options |= vopt_callout_random;
          else if (strcmpic(opt, US"use_sender") == 0)
             verify_options |= vopt_callout_recipsender;
          else if (strcmpic(opt, US"use_postmaster") == 0)
             verify_options |= vopt_callout_recippmaster;
          else if (strcmpic(opt, US"postmaster") == 0) pm_mailfrom = US"";
          else if (strcmpic(opt, US"fullpostmaster") == 0)
            {
            pm_mailfrom = US"";
            verify_options |= vopt_callout_fullpm;
            }

          else if (strncmpic(opt, US"mailfrom", 8) == 0)
            {
            if (!verify_header_sender)
              {
              *log_msgptr = string_sprintf("\"mailfrom\" is allowed as a "
                "callout option only for verify=header_sender (detected in ACL "
                "condition \"%s\")", arg);
              return ERROR;
              }
            opt += 8;
            while (isspace(*opt)) opt++;
            if (*opt++ != '=')
              {
              *log_msgptr = string_sprintf("'=' expected after "
                "\"mailfrom\" in ACL condition \"%s\"", arg);
              return ERROR;
              }
            while (isspace(*opt)) opt++;
            se_mailfrom = string_copy(opt);
            }

          else if (strncmpic(opt, US"postmaster_mailfrom", 19) == 0)
            {
            opt += 19;
            while (isspace(*opt)) opt++;
            if (*opt++ != '=')
              {
              *log_msgptr = string_sprintf("'=' expected after "
                "\"postmaster_mailfrom\" in ACL condition \"%s\"", arg);
              return ERROR;
              }
            while (isspace(*opt)) opt++;
            pm_mailfrom = string_copy(opt);
            }

          else if (strncmpic(opt, US"maxwait", 7) == 0)
            {
            opt += 7;
            while (isspace(*opt)) opt++;
            if (*opt++ != '=')
              {
              *log_msgptr = string_sprintf("'=' expected after \"maxwait\" in "
                "ACL condition \"%s\"", arg);
              return ERROR;
              }
            while (isspace(*opt)) opt++;
            callout_overall = readconf_readtime(opt, 0, FALSE);
            if (callout_overall < 0)
              {
              *log_msgptr = string_sprintf("bad time value in ACL condition "
                "\"verify %s\"", arg);
              return ERROR;
              }
            }
          else if (strncmpic(opt, US"connect", 7) == 0)
            {
            opt += 7;
            while (isspace(*opt)) opt++;
            if (*opt++ != '=')
              {
              *log_msgptr = string_sprintf("'=' expected after "
                "\"callout_overaall\" in ACL condition \"%s\"", arg);
              return ERROR;
              }
            while (isspace(*opt)) opt++;
            callout_connect = readconf_readtime(opt, 0, FALSE);
            if (callout_connect < 0)
              {
              *log_msgptr = string_sprintf("bad time value in ACL condition "
                "\"verify %s\"", arg);
              return ERROR;
              }
            }
          else    /* Plain time is callout connect/command timeout */
            {
            callout = readconf_readtime(opt, 0, FALSE);
            if (callout < 0)
              {
              *log_msgptr = string_sprintf("bad time value in ACL condition "
                "\"verify %s\"", arg);
              return ERROR;
              }
            }
          }
        }
      else
        {
        *log_msgptr = string_sprintf("'=' expected after \"callout\" in "
          "ACL condition \"%s\"", arg);
        return ERROR;
        }
      }
    }

  /* Option not recognized */

  else
    {
    *log_msgptr = string_sprintf("unknown option \"%s\" in ACL "
      "condition \"verify %s\"", ss, arg);
    return ERROR;
    }
  }

if ((verify_options & (vopt_callout_recipsender|vopt_callout_recippmaster)) ==
      (vopt_callout_recipsender|vopt_callout_recippmaster))
  {
  *log_msgptr = US"only one of use_sender and use_postmaster can be set "
    "for a recipient callout";
  return ERROR;
  }

/* Handle sender-in-header verification. Default the user message to the log
message if giving out verification details. */

if (verify_header_sender)
  {
  int verrno;
  rc = verify_check_header_address(user_msgptr, log_msgptr, callout,
    callout_overall, callout_connect, se_mailfrom, pm_mailfrom, verify_options,
    &verrno);
  if (rc != OK)
    {
    *basic_errno = verrno;
    if (smtp_return_error_details)
      {
      if (*user_msgptr == NULL && *log_msgptr != NULL)
        *user_msgptr = string_sprintf("Rejected after DATA: %s", *log_msgptr);
      if (rc == DEFER) acl_temp_details = TRUE;
      }
    }
  }

/* Handle a sender address. The default is to verify *the* sender address, but
optionally a different address can be given, for special requirements. If the
address is empty, we are dealing with a bounce message that has no sender, so
we cannot do any checking. If the real sender address gets rewritten during
verification (e.g. DNS widening), set the flag to stop it being rewritten again
during message reception.

A list of verified "sender" addresses is kept to try to avoid doing to much
work repetitively when there are multiple recipients in a message and they all
require sender verification. However, when callouts are involved, it gets too
complicated because different recipients may require different callout options.
Therefore, we always do a full sender verify when any kind of callout is
specified. Caching elsewhere, for instance in the DNS resolver and in the
callout handling, should ensure that this is not terribly inefficient. */

else if (verify_sender_address != NULL)
  {
  if ((verify_options & (vopt_callout_recipsender|vopt_callout_recippmaster))
       != 0)
    {
    *log_msgptr = US"use_sender or use_postmaster cannot be used for a "
      "sender verify callout";
    return ERROR;
    }

  sender_vaddr = verify_checked_sender(verify_sender_address);
  if (sender_vaddr != NULL &&               /* Previously checked */
      callout <= 0)                         /* No callout needed this time */
    {
    /* If the "routed" flag is set, it means that routing worked before, so
    this check can give OK (the saved return code value, if set, belongs to a
    callout that was done previously). If the "routed" flag is not set, routing
    must have failed, so we use the saved return code. */

    if (testflag(sender_vaddr, af_verify_routed)) rc = OK; else
      {
      rc = sender_vaddr->special_action;
      *basic_errno = sender_vaddr->basic_errno;
      }
    HDEBUG(D_acl) debug_printf("using cached sender verify result\n");
    }

  /* Do a new verification, and cache the result. The cache is used to avoid
  verifying the sender multiple times for multiple RCPTs when callouts are not
  specified (see comments above).

  The cache is also used on failure to give details in response to the first
  RCPT that gets bounced for this reason. However, this can be suppressed by
  the no_details option, which sets the flag that says "this detail has already
  been sent". The cache normally contains just one address, but there may be
  more in esoteric circumstances. */

  else
    {
    BOOL routed = TRUE;
    uschar *save_address_data = deliver_address_data;

    sender_vaddr = deliver_make_addr(verify_sender_address, TRUE);
    if (no_details) setflag(sender_vaddr, af_sverify_told);
    if (verify_sender_address[0] != 0)
      {
      /* If this is the real sender address, save the unrewritten version
      for use later in receive. Otherwise, set a flag so that rewriting the
      sender in verify_address() does not update sender_address. */

      if (verify_sender_address == sender_address)
        sender_address_unrewritten = sender_address;
      else
        verify_options |= vopt_fake_sender;

      /* The recipient, qualify, and expn options are never set in
      verify_options. */

      rc = verify_address(sender_vaddr, NULL, verify_options, callout,
        callout_overall, callout_connect, se_mailfrom, pm_mailfrom, &routed);

      HDEBUG(D_acl) debug_printf("----------- end verify ------------\n");

      if (rc == OK)
        {
        if (Ustrcmp(sender_vaddr->address, verify_sender_address) != 0)
          {
          DEBUG(D_acl) debug_printf("sender %s verified ok as %s\n",
            verify_sender_address, sender_vaddr->address);
          }
        else
          {
          DEBUG(D_acl) debug_printf("sender %s verified ok\n",
            verify_sender_address);
          }
        }
      else *basic_errno = sender_vaddr->basic_errno;
      }
    else rc = OK;  /* Null sender */

    /* Cache the result code */

    if (routed) setflag(sender_vaddr, af_verify_routed);
    if (callout > 0) setflag(sender_vaddr, af_verify_callout);
    sender_vaddr->special_action = rc;
    sender_vaddr->next = sender_verified_list;
    sender_verified_list = sender_vaddr;

    /* Restore the recipient address data, which might have been clobbered by
    the sender verification. */

    deliver_address_data = save_address_data;
    }

  /* Put the sender address_data value into $sender_address_data */

  sender_address_data = sender_vaddr->p.address_data;
  }

/* A recipient address just gets a straightforward verify; again we must handle
the DEFER overrides. */

else
  {
  address_item addr2;

  /* We must use a copy of the address for verification, because it might
  get rewritten. */

  addr2 = *addr;
  rc = verify_address(&addr2, NULL, verify_options|vopt_is_recipient, callout,
    callout_overall, callout_connect, se_mailfrom, pm_mailfrom, NULL);
  HDEBUG(D_acl) debug_printf("----------- end verify ------------\n");

  *log_msgptr = addr2.message;
  *user_msgptr = (addr2.user_message != NULL)?
    addr2.user_message : addr2.message;
  *basic_errno = addr2.basic_errno;

  /* Make $address_data visible */
  deliver_address_data = addr2.p.address_data;
  }

/* We have a result from the relevant test. Handle defer overrides first. */

if (rc == DEFER && (defer_ok ||
   (callout_defer_ok && *basic_errno == ERRNO_CALLOUTDEFER)))
  {
  HDEBUG(D_acl) debug_printf("verify defer overridden by %s\n",
    defer_ok? "defer_ok" : "callout_defer_ok");
  rc = OK;
  }

/* If we've failed a sender, set up a recipient message, and point
sender_verified_failed to the address item that actually failed. */

if (rc != OK && verify_sender_address != NULL)
  {
  if (rc != DEFER)
    {
    *log_msgptr = *user_msgptr = US"Sender verify failed";
    }
  else if (*basic_errno != ERRNO_CALLOUTDEFER)
    {
    *log_msgptr = *user_msgptr = US"Could not complete sender verify";
    }
  else
    {
    *log_msgptr = US"Could not complete sender verify callout";
    *user_msgptr = smtp_return_error_details? sender_vaddr->user_message :
      *log_msgptr;
    }

  sender_verified_failed = sender_vaddr;
  }

/* Verifying an address messes up the values of $domain and $local_part,
so reset them before returning if this is a RCPT ACL. */

if (addr != NULL)
  {
  deliver_domain = addr->domain;
  deliver_localpart = addr->local_part;
  }
return rc;

/* Syntax errors in the verify argument come here. */

BAD_VERIFY:
*log_msgptr = string_sprintf("expected \"sender[=address]\", \"recipient\", "
  "\"helo\", \"header_syntax\", \"header_sender\" or "
  "\"reverse_host_lookup\" at start of ACL condition "
  "\"verify %s\"", arg);
return ERROR;

/* Options supplied when not allowed come here */

NO_OPTIONS:
*log_msgptr = string_sprintf("unexpected '/' found in \"%s\" "
  "(this verify item has no options)", arg);
return ERROR;
}


/*************************************************
*        Check argument for control= modifier    *
*************************************************/

/* Called from acl_check_condition() below

Arguments:
  arg         the argument string for control=
  pptr        set to point to the terminating character
  where       which ACL we are in
  log_msgptr  for error messages

Returns:      CONTROL_xxx value
*/

static int
decode_control(uschar *arg, uschar **pptr, int where, uschar **log_msgptr)
{
int len;
control_def *d;

for (d = controls_list;
     d < controls_list + sizeof(controls_list)/sizeof(control_def);
     d++)
  {
  len = Ustrlen(d->name);
  if (Ustrncmp(d->name, arg, len) == 0) break;
  }

if (d >= controls_list + sizeof(controls_list)/sizeof(control_def) ||
   (arg[len] != 0 && (!d->has_option || arg[len] != '/')))
  {
  *log_msgptr = string_sprintf("syntax error in \"control=%s\"", arg);
  return CONTROL_ERROR;
  }

*pptr = arg + len;
return d->value;
}


/*************************************************
*            Handle rate limiting                *
*************************************************/

/* Called by acl_check_condition() below to calculate the result
of the ACL ratelimit condition.

Note that the return value might be slightly unexpected: if the
sender's rate is above the limit then the result is OK. This is
similar to the dnslists condition, and is so that you can write
ACL clauses like: defer ratelimit = 15 / 1h

Arguments:
  arg         the option string for ratelimit=
  log_msgptr  for error messages

Returns:       OK        - Sender's rate is above limit
               FAIL      - Sender's rate is below limit
               DEFER     - Problem opening ratelimit database
               ERROR     - Syntax error in options.
*/

static int
acl_ratelimit(uschar *arg, uschar **log_msgptr)
{
double limit, period;
uschar *ss, *key;
int sep = '/';
BOOL have_key = FALSE, leaky = FALSE, strict = FALSE;
BOOL per_byte = FALSE, per_cmd = FALSE, per_conn = FALSE, per_mail = FALSE;
int old_pool, rc;
tree_node **anchor, *t;
open_db dbblock, *dbm;
dbdata_ratelimit *dbd;
struct timeval tv;

/* Parse the first two options and record their values in expansion
variables. These variables allow the configuration to have informative
error messages based on rate limits obtained from a table lookup. */

/* First is the maximum number of messages per period and maximum burst
size, which must be greater than or equal to zero. Zero is useful for
rate measurement as opposed to rate limiting. */

sender_rate_limit = string_nextinlist(&arg, &sep, NULL, 0);
if (sender_rate_limit == NULL)
  limit = -1.0;
else
  {
  limit = Ustrtod(sender_rate_limit, &ss);
  if (tolower(*ss) == 'k') { limit *= 1024.0; ss++; }
  else if (tolower(*ss) == 'm') { limit *= 1024.0*1024.0; ss++; }
  else if (tolower(*ss) == 'g') { limit *= 1024.0*1024.0*1024.0; ss++; }
  }
if (limit < 0.0 || *ss != 0)
  {
  *log_msgptr = string_sprintf("syntax error in argument for "
    "\"ratelimit\" condition: \"%s\" is not a positive number",
    sender_rate_limit);
  return ERROR;
  }

/* We use the rest of the argument list following the limit as the
lookup key, because it doesn't make sense to use the same stored data
if the period or options are different. */

key = arg;

/* Second is the rate measurement period and exponential smoothing time
constant. This must be strictly greater than zero, because zero leads to
run-time division errors. */

sender_rate_period = string_nextinlist(&arg, &sep, NULL, 0);
if (sender_rate_period == NULL) period = -1.0;
else period = readconf_readtime(sender_rate_period, 0, FALSE);
if (period <= 0.0)
  {
  *log_msgptr = string_sprintf("syntax error in argument for "
    "\"ratelimit\" condition: \"%s\" is not a time value",
    sender_rate_period);
  return ERROR;
  }

/* Parse the other options. Should we check if the per_* options are being
used in ACLs where they don't make sense, e.g. per_mail in the connect ACL? */

while ((ss = string_nextinlist(&arg, &sep, big_buffer, big_buffer_size))
       != NULL)
  {
  if (strcmpic(ss, US"leaky") == 0) leaky = TRUE;
  else if (strcmpic(ss, US"strict") == 0) strict = TRUE;
  else if (strcmpic(ss, US"per_byte") == 0) per_byte = TRUE;
  else if (strcmpic(ss, US"per_cmd") == 0) per_cmd = TRUE;
  else if (strcmpic(ss, US"per_conn") == 0) per_conn = TRUE;
  else if (strcmpic(ss, US"per_mail") == 0) per_mail = TRUE;
  else if (strcmpic(ss, US"per_rcpt") == 0) per_cmd = TRUE; /* alias */
  else have_key = TRUE;
  }
if (leaky + strict > 1 || per_byte + per_cmd + per_conn + per_mail > 1)
  {
  *log_msgptr = US"conflicting options for \"ratelimit\" condition";
  return ERROR;
  }

/* Default option values */
if (!strict) leaky = TRUE;
if (!per_byte && !per_cmd && !per_conn) per_mail = TRUE;

/* If there is no explicit key, use the sender_host_address. If there is no
sender_host_address (e.g. -bs or acl_not_smtp) then we simply omit it. */

if (!have_key && sender_host_address != NULL)
  key = string_sprintf("%s / %s", key, sender_host_address);

HDEBUG(D_acl) debug_printf("ratelimit condition limit=%.0f period=%.0f key=%s\n",
  limit, period, key);

/* See if we have already computed the rate by looking in the relevant tree. For
per-connection rate limiting, store tree nodes and dbdata in the permanent pool
so that they survive across resets. */

anchor = NULL;
old_pool = store_pool;

if (per_conn)
  {
  anchor = &ratelimiters_conn;
  store_pool = POOL_PERM;
  }
else if (per_mail || per_byte)
  anchor = &ratelimiters_mail;
else if (per_cmd)
  anchor = &ratelimiters_cmd;

if (anchor != NULL && (t = tree_search(*anchor, key)) != NULL)
  {
  dbd = t->data.ptr;
  /* The following few lines duplicate some of the code below. */
  if (dbd->rate < limit) rc = FAIL;
    else rc = OK;
  store_pool = old_pool;
  sender_rate = string_sprintf("%.1f", dbd->rate);
  HDEBUG(D_acl)
    debug_printf("ratelimit found pre-computed rate %s\n", sender_rate);
  return rc;
  }

/* We aren't using a pre-computed rate, so get a previously recorded
rate from the database, update it, and write it back. If there's no
previous rate for this key, create one. */

dbm = dbfn_open(US"ratelimit", O_RDWR, &dbblock, TRUE);
if (dbm == NULL)
  {
  store_pool = old_pool;
  sender_rate = NULL;
  HDEBUG(D_acl) debug_printf("ratelimit database not available\n");
  *log_msgptr = US"ratelimit database not available";
  return DEFER;
  }
dbd = dbfn_read(dbm, key);

gettimeofday(&tv, NULL);

if (dbd == NULL)
  {
  HDEBUG(D_acl) debug_printf("ratelimit initializing new key's data\n");
  dbd = store_get(sizeof(dbdata_ratelimit));
  dbd->time_stamp = tv.tv_sec;
  dbd->time_usec = tv.tv_usec;
  dbd->rate = 0.0;
  }
else
  {
  /* The smoothed rate is computed using an exponentially weighted moving
  average adjusted for variable sampling intervals. The standard EWMA for
  a fixed sampling interval is:  f'(t) = (1 - a) * f(t) + a * f'(t - 1)
  where f() is the measured value and f'() is the smoothed value.

  Old data decays out of the smoothed value exponentially, such that data n
  samples old is multiplied by a^n. The exponential decay time constant p
  is defined such that data p samples old is multiplied by 1/e, which means
  that a = exp(-1/p). We can maintain the same time constant for a variable
  sampling interval i by using a = exp(-i/p).

  The rate we are measuring is messages per period, suitable for directly
  comparing with the limit. The average rate between now and the previous
  message is period / interval, which we feed into the EWMA as the sample.

  It turns out that the number of messages required for the smoothed rate
  to reach the limit when they are sent in a burst is equal to the limit.
  This can be seen by analysing the value of the smoothed rate after N
  messages sent at even intervals. Let k = (1 - a) * p/i

    rate_1 = (1 - a) * p/i + a * rate_0
           = k + a * rate_0
    rate_2 = k + a * rate_1
           = k + a * k + a^2 * rate_0
    rate_3 = k + a * k + a^2 * k + a^3 * rate_0
    rate_N = rate_0 * a^N + k * SUM(x=0..N-1)(a^x)
           = rate_0 * a^N + k * (1 - a^N) / (1 - a)
           = rate_0 * a^N + p/i * (1 - a^N)

  When N is large, a^N -> 0 so rate_N -> p/i as desired.

    rate_N = p/i + (rate_0 - p/i) * a^N
    a^N = (rate_N - p/i) / (rate_0 - p/i)
    N * -i/p = log((rate_N - p/i) / (rate_0 - p/i))
    N = p/i * log((rate_0 - p/i) / (rate_N - p/i))

  Numerical analysis of the above equation, setting the computed rate to
  increase from rate_0 = 0 to rate_N = limit, shows that for large sending
  rates, p/i, the number of messages N = limit. So limit serves as both the
  maximum rate measured in messages per period, and the maximum number of
  messages that can be sent in a fast burst. */

  double this_time = (double)tv.tv_sec
                   + (double)tv.tv_usec / 1000000.0;
  double prev_time = (double)dbd->time_stamp
                   + (double)dbd->time_usec / 1000000.0;
  double interval = this_time - prev_time;

  double i_over_p = interval / period;
  double a = exp(-i_over_p);

  /* We must avoid division by zero, and deal gracefully with the clock going
  backwards. If we blunder ahead when time is in reverse then the computed
  rate will become bogusly huge. Clamp i/p to a very small number instead. */

  if (i_over_p <= 0.0) i_over_p = 1e-9;

  dbd->time_stamp = tv.tv_sec;
  dbd->time_usec = tv.tv_usec;

  /* If we are measuring the rate in bytes per period, multiply the
  measured rate by the message size. If we don't know the message size
  then it's safe to just use a value of zero and let the recorded rate
  decay as if nothing happened. */

  if (per_byte)
    dbd->rate = (message_size < 0 ? 0.0 : (double)message_size)
              * (1 - a) / i_over_p + a * dbd->rate;
  else
    dbd->rate = (1 - a) / i_over_p + a * dbd->rate;
  }

/* Clients sending at the limit are considered to be over the limit. This
matters for edge cases such the first message sent by a client (which gets
the initial rate of 0.0) when the rate limit is zero (i.e. the client should
be completely blocked). */

if (dbd->rate < limit) rc = FAIL;
  else rc = OK;

/* Update the state if the rate is low or if we are being strict. If we
are in leaky mode and the sender's rate is too high, we do not update
the recorded rate in order to avoid an over-aggressive sender's retry
rate preventing them from getting any email through. */

if (rc == FAIL || !leaky)
  dbfn_write(dbm, key, dbd, sizeof(dbdata_ratelimit));
dbfn_close(dbm);

/* Store the result in the tree for future reference, if necessary. */

if (anchor != NULL)
  {
  t = store_get(sizeof(tree_node) + Ustrlen(key));
  t->data.ptr = dbd;
  Ustrcpy(t->name, key);
  (void)tree_insertnode(anchor, t);
  }

/* We create the formatted version of the sender's rate very late in
order to ensure that it is done using the correct storage pool. */

store_pool = old_pool;
sender_rate = string_sprintf("%.1f", dbd->rate);

HDEBUG(D_acl)
  debug_printf("ratelimit computed rate %s\n", sender_rate);

return rc;
}


/*************************************************
*   Handle conditions/modifiers on an ACL item   *
*************************************************/

/* Called from acl_check() below.

Arguments:
  verb         ACL verb
  cb           ACL condition block - if NULL, result is OK
  where        where called from
  addr         the address being checked for RCPT, or NULL
  level        the nesting level
  epp          pointer to pass back TRUE if "endpass" encountered
                 (applies only to "accept" and "discard")
  user_msgptr  user message pointer
  log_msgptr   log message pointer
  basic_errno  pointer to where to put verify error

Returns:       OK        - all conditions are met
               DISCARD   - an "acl" condition returned DISCARD - only allowed
                             for "accept" or "discard" verbs
               FAIL      - at least one condition fails
               FAIL_DROP - an "acl" condition returned FAIL_DROP
               DEFER     - can't tell at the moment (typically, lookup defer,
                             but can be temporary callout problem)
               ERROR     - ERROR from nested ACL or expansion failure or other
                             error
*/

static int
acl_check_condition(int verb, acl_condition_block *cb, int where,
  address_item *addr, int level, BOOL *epp, uschar **user_msgptr,
  uschar **log_msgptr, int *basic_errno)
{
uschar *user_message = NULL;
uschar *log_message = NULL;
uschar *p;
int rc = OK;
#ifdef WITH_CONTENT_SCAN
int sep = '/';
#endif

for (; cb != NULL; cb = cb->next)
  {
  uschar *arg;
  int control_type;

  /* The message and log_message items set up messages to be used in
  case of rejection. They are expanded later. */

  if (cb->type == ACLC_MESSAGE)
    {
    user_message = cb->arg;
    continue;
    }

  if (cb->type == ACLC_LOG_MESSAGE)
    {
    log_message = cb->arg;
    continue;
    }

  /* The endpass "condition" just sets a flag to show it occurred. This is
  checked at compile time to be on an "accept" or "discard" item. */

  if (cb->type == ACLC_ENDPASS)
    {
    *epp = TRUE;
    continue;
    }

  /* For other conditions and modifiers, the argument is expanded now for some
  of them, but not for all, because expansion happens down in some lower level
  checking functions in some cases. */

  if (cond_expand_at_top[cb->type])
    {
    arg = expand_string(cb->arg);
    if (arg == NULL)
      {
      if (expand_string_forcedfail) continue;
      *log_msgptr = string_sprintf("failed to expand ACL string \"%s\": %s",
        cb->arg, expand_string_message);
      return search_find_defer? DEFER : ERROR;
      }
    }
  else arg = cb->arg;

  /* Show condition, and expanded condition if it's different */

  HDEBUG(D_acl)
    {
    int lhswidth = 0;
    debug_printf("check %s%s %n",
      (!cond_modifiers[cb->type] && cb->u.negated)? "!":"",
      conditions[cb->type], &lhswidth);

    if (cb->type == ACLC_SET)
      {
      int n = cb->u.varnumber;
      int t = (n < ACL_C_MAX)? 'c' : 'm';
      if (n >= ACL_C_MAX) n -= ACL_C_MAX;
      debug_printf("acl_%c%d ", t, n);
      lhswidth += 7;
      }

    debug_printf("= %s\n", cb->arg);

    if (arg != cb->arg)
      debug_printf("%.*s= %s\n", lhswidth,
      US"                             ", CS arg);
    }

  /* Check that this condition makes sense at this time */

  if ((cond_forbids[cb->type] & (1 << where)) != 0)
    {
    *log_msgptr = string_sprintf("cannot %s %s condition in %s ACL",
      cond_modifiers[cb->type]? "use" : "test",
      conditions[cb->type], acl_wherenames[where]);
    return ERROR;
    }

  /* Run the appropriate test for each condition, or take the appropriate
  action for the remaining modifiers. */

  switch(cb->type)
    {
    /* A nested ACL that returns "discard" makes sense only for an "accept" or
    "discard" verb. */

    case ACLC_ACL:
    rc = acl_check_internal(where, addr, arg, level+1, user_msgptr, log_msgptr);
    if (rc == DISCARD && verb != ACL_ACCEPT && verb != ACL_DISCARD)
      {
      *log_msgptr = string_sprintf("nested ACL returned \"discard\" for "
        "\"%s\" command (only allowed with \"accept\" or \"discard\")",
        verbs[verb]);
      return ERROR;
      }
    break;

    case ACLC_AUTHENTICATED:
    rc = (sender_host_authenticated == NULL)? FAIL :
      match_isinlist(sender_host_authenticated, &arg, 0, NULL, NULL, MCL_STRING,
        TRUE, NULL);
    break;

#ifdef EXPERIMENTAL_BRIGHTMAIL
    case ACLC_BMI_OPTIN:
      {
      int old_pool = store_pool;
      store_pool = POOL_PERM;
      bmi_current_optin = string_copy(arg);
      store_pool = old_pool;
      }
    break;
#endif

    case ACLC_CONDITION:
    if (Ustrspn(arg, "0123456789") == Ustrlen(arg))     /* Digits, or empty */
      rc = (Uatoi(arg) == 0)? FAIL : OK;
    else
      rc = (strcmpic(arg, US"no") == 0 ||
            strcmpic(arg, US"false") == 0)? FAIL :
           (strcmpic(arg, US"yes") == 0 ||
            strcmpic(arg, US"true") == 0)? OK : DEFER;
    if (rc == DEFER)
      *log_msgptr = string_sprintf("invalid \"condition\" value \"%s\"", arg);
    break;

    case ACLC_CONTROL:
    control_type = decode_control(arg, &p, where, log_msgptr);

    /* Check if this control makes sense at this time */

    if ((control_forbids[control_type] & (1 << where)) != 0)
      {
      *log_msgptr = string_sprintf("cannot use \"control=%s\" in %s ACL",
        controls[control_type], acl_wherenames[where]);
      return ERROR;
      }

    switch(control_type)
      {
#ifdef EXPERIMENTAL_BRIGHTMAIL
      case CONTROL_BMI_RUN:
      bmi_run = 1;
      break;
#endif
#ifdef EXPERIMENTAL_DOMAINKEYS
      case CONTROL_DK_VERIFY:
      dk_do_verify = 1;
      break;
#endif
      case CONTROL_ERROR:
      return ERROR;

      case CONTROL_CASEFUL_LOCAL_PART:
      deliver_localpart = addr->cc_local_part;
      break;

      case CONTROL_CASELOWER_LOCAL_PART:
      deliver_localpart = addr->lc_local_part;
      break;

      case CONTROL_ENFORCE_SYNC:
      smtp_enforce_sync = TRUE;
      break;

      case CONTROL_NO_ENFORCE_SYNC:
      smtp_enforce_sync = FALSE;
      break;

#ifdef WITH_CONTENT_SCAN
      case CONTROL_NO_MBOX_UNSPOOL:
      no_mbox_unspool = TRUE;
      break;
#endif

      case CONTROL_NO_MULTILINE:
      no_multiline_responses = TRUE;
      break;

      case CONTROL_FAKEDEFER:
      case CONTROL_FAKEREJECT:
      fake_response = (control_type == CONTROL_FAKEDEFER) ? DEFER : FAIL;
      if (*p == '/')
        {
        uschar *pp = p + 1;
        while (*pp != 0) pp++;
        fake_response_text = expand_string(string_copyn(p+1, pp-p-1));
        p = pp;
        }
       else
        {
        /* Explicitly reset to default string */
        fake_response_text = US"Your message has been rejected but is being kept for evaluation.\nIf it was a legitimate message, it may still be delivered to the target recipient(s).";
        }
      break;

      case CONTROL_FREEZE:
      deliver_freeze = TRUE;
      deliver_frozen_at = time(NULL);
      break;

      case CONTROL_QUEUE_ONLY:
      queue_only_policy = TRUE;
      break;

      case CONTROL_SUBMISSION:
      originator_name = US"";
      submission_mode = TRUE;
      while (*p == '/')
        {
        if (Ustrncmp(p, "/sender_retain", 14) == 0)
          {
          p += 14;
          active_local_sender_retain = TRUE;
          active_local_from_check = FALSE;
          }
        else if (Ustrncmp(p, "/domain=", 8) == 0)
          {
          uschar *pp = p + 8;
          while (*pp != 0 && *pp != '/') pp++;
          submission_domain = string_copyn(p+8, pp-p-8);
          p = pp;
          }
        else if (Ustrncmp(p, "/name=", 6) == 0)
          {
          uschar *pp = p + 6;
          while (*pp != 0 && *pp != '/') pp++;
          originator_name = string_copy(parse_fix_phrase(p+6, pp-p-6,
            big_buffer, big_buffer_size));
          p = pp;
          }
        else break;
        }
      if (*p != 0)
        {
        *log_msgptr = string_sprintf("syntax error in \"control=%s\"", arg);
        return ERROR;
        }
      break;
      }
    break;

#ifdef WITH_CONTENT_SCAN
    case ACLC_DECODE:
    rc = mime_decode(&arg);
    break;
#endif

    case ACLC_DELAY:
      {
      int delay = readconf_readtime(arg, 0, FALSE);
      if (delay < 0)
        {
        *log_msgptr = string_sprintf("syntax error in argument for \"delay\" "
          "modifier: \"%s\" is not a time value", arg);
        return ERROR;
        }
      else
        {
        HDEBUG(D_acl) debug_printf("delay modifier requests %d-second delay\n",
          delay);
        if (host_checking)
          {
          HDEBUG(D_acl)
            debug_printf("delay skipped in -bh checking mode\n");
          }

        /* It appears to be impossible to detect that a TCP/IP connection has
        gone away without reading from it. This means that we cannot shorten
        the delay below if the client goes away, because we cannot discover
        that the client has closed its end of the connection. (The connection
        is actually in a half-closed state, waiting for the server to close its
        end.) It would be nice to be able to detect this state, so that the
        Exim process is not held up unnecessarily. However, it seems that we
        can't. The poll() function does not do the right thing, and in any case
        it is not always available.

        NOTE: If ever this state of affairs changes, remember that we may be
        dealing with stdin/stdout here, in addition to TCP/IP connections.
        Whatever is done must work in both cases. To detected the stdin/stdout
        case, check for smtp_in or smtp_out being NULL. */

        else
          {
          while (delay > 0) delay = sleep(delay);
          }
        }
      }
    break;

#ifdef WITH_OLD_DEMIME
    case ACLC_DEMIME:
      rc = demime(&arg);
    break;
#endif

#ifdef EXPERIMENTAL_DOMAINKEYS
  case ACLC_DK_DOMAIN_SOURCE:
    if (dk_verify_block == NULL) { rc = FAIL; break; };
    /* check header source of domain against given string */
    switch (dk_verify_block->address_source) {
      case DK_EXIM_ADDRESS_FROM_FROM:
        rc = match_isinlist(US"from", &arg, 0, NULL,
                            NULL, MCL_STRING, TRUE, NULL);
      break;
      case DK_EXIM_ADDRESS_FROM_SENDER:
        rc = match_isinlist(US"sender", &arg, 0, NULL,
                            NULL, MCL_STRING, TRUE, NULL);
      break;
      case DK_EXIM_ADDRESS_NONE:
        rc = match_isinlist(US"none", &arg, 0, NULL,
                            NULL, MCL_STRING, TRUE, NULL);
      break;
    }
  break;
  case ACLC_DK_POLICY:
    if (dk_verify_block == NULL) { rc = FAIL; break; };
    /* check policy against given string, default FAIL */
    rc = FAIL;
    if (dk_verify_block->signsall)
      rc = match_isinlist(US"signsall", &arg, 0, NULL,
                          NULL, MCL_STRING, TRUE, NULL);
    if (dk_verify_block->testing)
      rc = match_isinlist(US"testing", &arg, 0, NULL,
                          NULL, MCL_STRING, TRUE, NULL);
  break;
  case ACLC_DK_SENDER_DOMAINS:
    if (dk_verify_block == NULL) { rc = FAIL; break; };
    if (dk_verify_block->domain != NULL)
      rc = match_isinlist(dk_verify_block->domain, &arg, 0, &domainlist_anchor,
                          NULL, MCL_DOMAIN, TRUE, NULL);
    else rc = FAIL;
  break;
  case ACLC_DK_SENDER_LOCAL_PARTS:
    if (dk_verify_block == NULL) { rc = FAIL; break; };
    if (dk_verify_block->local_part != NULL)
      rc = match_isinlist(dk_verify_block->local_part, &arg, 0, &localpartlist_anchor,
                          NULL, MCL_LOCALPART, TRUE, NULL);
    else rc = FAIL;
  break;
  case ACLC_DK_SENDERS:
    if (dk_verify_block == NULL) { rc = FAIL; break; };
    if (dk_verify_block->address != NULL)
      rc = match_address_list(dk_verify_block->address, TRUE, TRUE, &arg, NULL, -1, 0, NULL);
    else rc = FAIL;
  break;
  case ACLC_DK_STATUS:
    if (dk_verify_block == NULL) { rc = FAIL; break; };
    if (dk_verify_block->result > 0) {
      switch(dk_verify_block->result) {
        case DK_EXIM_RESULT_BAD_FORMAT:
          rc = match_isinlist(US"bad format", &arg, 0, NULL,
                              NULL, MCL_STRING, TRUE, NULL);
        break;
        case DK_EXIM_RESULT_NO_KEY:
          rc = match_isinlist(US"no key", &arg, 0, NULL,
                              NULL, MCL_STRING, TRUE, NULL);
        break;
        case DK_EXIM_RESULT_NO_SIGNATURE:
          rc = match_isinlist(US"no signature", &arg, 0, NULL,
                              NULL, MCL_STRING, TRUE, NULL);
        break;
        case DK_EXIM_RESULT_REVOKED:
          rc = match_isinlist(US"revoked", &arg, 0, NULL,
                              NULL, MCL_STRING, TRUE, NULL);
        break;
        case DK_EXIM_RESULT_NON_PARTICIPANT:
          rc = match_isinlist(US"non-participant", &arg, 0, NULL,
                              NULL, MCL_STRING, TRUE, NULL);
        break;
        case DK_EXIM_RESULT_GOOD:
          rc = match_isinlist(US"good", &arg, 0, NULL,
                              NULL, MCL_STRING, TRUE, NULL);
        break;
        case DK_EXIM_RESULT_BAD:
          rc = match_isinlist(US"bad", &arg, 0, NULL,
                              NULL, MCL_STRING, TRUE, NULL);
        break;
      }
    }
  break;
#endif

    case ACLC_DNSLISTS:
    rc = verify_check_dnsbl(&arg);
    break;

    case ACLC_DOMAINS:
    rc = match_isinlist(addr->domain, &arg, 0, &domainlist_anchor,
      addr->domain_cache, MCL_DOMAIN, TRUE, &deliver_domain_data);
    break;

    /* The value in tls_cipher is the full cipher name, for example,
    TLSv1:DES-CBC3-SHA:168, whereas the values to test for are just the
    cipher names such as DES-CBC3-SHA. But program defensively. We don't know
    what may in practice come out of the SSL library - which at the time of
    writing is poorly documented. */

    case ACLC_ENCRYPTED:
    if (tls_cipher == NULL) rc = FAIL; else
      {
      uschar *endcipher = NULL;
      uschar *cipher = Ustrchr(tls_cipher, ':');
      if (cipher == NULL) cipher = tls_cipher; else
        {
        endcipher = Ustrchr(++cipher, ':');
        if (endcipher != NULL) *endcipher = 0;
        }
      rc = match_isinlist(cipher, &arg, 0, NULL, NULL, MCL_STRING, TRUE, NULL);
      if (endcipher != NULL) *endcipher = ':';
      }
    break;

    /* Use verify_check_this_host() instead of verify_check_host() so that
    we can pass over &host_data to catch any looked up data. Once it has been
    set, it retains its value so that it's still there if another ACL verb
    comes through here and uses the cache. However, we must put it into
    permanent store in case it is also expected to be used in a subsequent
    message in the same SMTP connection. */

    case ACLC_HOSTS:
    rc = verify_check_this_host(&arg, sender_host_cache, NULL,
      (sender_host_address == NULL)? US"" : sender_host_address, &host_data);
    if (host_data != NULL) host_data = string_copy_malloc(host_data);
    break;

    case ACLC_LOCAL_PARTS:
    rc = match_isinlist(addr->cc_local_part, &arg, 0,
      &localpartlist_anchor, addr->localpart_cache, MCL_LOCALPART, TRUE,
      &deliver_localpart_data);
    break;

    case ACLC_LOGWRITE:
      {
      int logbits = 0;
      uschar *s = arg;
      if (*s == ':')
        {
        s++;
        while (*s != ':')
          {
          if (Ustrncmp(s, "main", 4) == 0)
            { logbits |= LOG_MAIN; s += 4; }
          else if (Ustrncmp(s, "panic", 5) == 0)
            { logbits |= LOG_PANIC; s += 5; }
          else if (Ustrncmp(s, "reject", 6) == 0)
            { logbits |= LOG_REJECT; s += 6; }
          else
            {
            logbits = LOG_MAIN|LOG_PANIC;
            s = string_sprintf(":unknown log name in \"%s\" in "
              "\"logwrite\" in %s ACL", arg, acl_wherenames[where]);
            }
          if (*s == ',') s++;
          }
        s++;
        }
      while (isspace(*s)) s++;
      if (logbits == 0) logbits = LOG_MAIN;
      log_write(0, logbits, "%s", string_printing(s));
      }
    break;

#ifdef WITH_CONTENT_SCAN
    case ACLC_MALWARE:
      {
      /* Seperate the regular expression and any optional parameters. */
      uschar *ss = string_nextinlist(&arg, &sep, big_buffer, big_buffer_size);
      /* Run the malware backend. */
      rc = malware(&ss);
      /* Modify return code based upon the existance of options. */
      while ((ss = string_nextinlist(&arg, &sep, big_buffer, big_buffer_size))
            != NULL) {
        if (strcmpic(ss, US"defer_ok") == 0 && rc == DEFER)
          {
          /* FAIL so that the message is passed to the next ACL */
          rc = FAIL;
          }
        }
      }
    break;

    case ACLC_MIME_REGEX:
      rc = mime_regex(&arg);
    break;
#endif

    case ACLC_RATELIMIT:
      rc = acl_ratelimit(arg, log_msgptr);
    break;

    case ACLC_RECIPIENTS:
    rc = match_address_list(addr->address, TRUE, TRUE, &arg, NULL, -1, 0,
      &recipient_data);
    break;

#ifdef WITH_CONTENT_SCAN
   case ACLC_REGEX:
      rc = regex(&arg);
    break;
#endif

    case ACLC_SENDER_DOMAINS:
      {
      uschar *sdomain;
      sdomain = Ustrrchr(sender_address, '@');
      sdomain = (sdomain == NULL)? US"" : sdomain + 1;
      rc = match_isinlist(sdomain, &arg, 0, &domainlist_anchor,
        sender_domain_cache, MCL_DOMAIN, TRUE, NULL);
      }
    break;

    case ACLC_SENDERS:
    rc = match_address_list(sender_address, TRUE, TRUE, &arg,
      sender_address_cache, -1, 0, &sender_data);
    break;

    /* Connection variables must persist forever */

    case ACLC_SET:
      {
      int old_pool = store_pool;
      if (cb->u.varnumber < ACL_C_MAX) store_pool = POOL_PERM;
      acl_var[cb->u.varnumber] = string_copy(arg);
      store_pool = old_pool;
      }
    break;

#ifdef WITH_CONTENT_SCAN
    case ACLC_SPAM:
      {
      /* Seperate the regular expression and any optional parameters. */
      uschar *ss = string_nextinlist(&arg, &sep, big_buffer, big_buffer_size);
      /* Run the spam backend. */
      rc = spam(&ss);
      /* Modify return code based upon the existance of options. */
      while ((ss = string_nextinlist(&arg, &sep, big_buffer, big_buffer_size))
            != NULL) {
        if (strcmpic(ss, US"defer_ok") == 0 && rc == DEFER)
          {
          /* FAIL so that the message is passed to the next ACL */
          rc = FAIL;
          }
        }
      }
    break;
#endif

#ifdef EXPERIMENTAL_SPF
    case ACLC_SPF:
      rc = spf_process(&arg, sender_address);
    break;
#endif

    /* If the verb is WARN, discard any user message from verification, because
    such messages are SMTP responses, not header additions. The latter come
    only from explicit "message" modifiers. However, put the user message into
    $acl_verify_message so it can be used in subsequent conditions or modifiers
    (until something changes it). */

    case ACLC_VERIFY:
    rc = acl_verify(where, addr, arg, user_msgptr, log_msgptr, basic_errno);
    acl_verify_message = *user_msgptr;
    if (verb == ACL_WARN) *user_msgptr = NULL;
    break;

    default:
    log_write(0, LOG_MAIN|LOG_PANIC_DIE, "internal ACL error: unknown "
      "condition %d", cb->type);
    break;
    }

  /* If a condition was negated, invert OK/FAIL. */

  if (!cond_modifiers[cb->type] && cb->u.negated)
    {
    if (rc == OK) rc = FAIL;
      else if (rc == FAIL || rc == FAIL_DROP) rc = OK;
    }

  if (rc != OK) break;   /* Conditions loop */
  }


/* If the result is the one for which "message" and/or "log_message" are used,
handle the values of these options. Most verbs have but a single return for
which the messages are relevant, but for "discard", it's useful to have the log
message both when it succeeds and when it fails. Also, for an "accept" that
appears in a QUIT ACL, we want to handle the user message. Since only "accept"
and "warn" are permitted in that ACL, we don't need to test the verb.

These modifiers act in different ways:

"message" is a user message that will be included in an SMTP response. Unless
it is empty, it overrides any previously set user message.

"log_message" is a non-user message, and it adds to any existing non-user
message that is already set.

If there isn't a log message set, we make it the same as the user message. */

if (((rc == FAIL_DROP)? FAIL : rc) == msgcond[verb] ||
    (verb == ACL_DISCARD && rc == OK) ||
    (where == ACL_WHERE_QUIT))
  {
  uschar *expmessage;

  /* If the verb is "warn", messages generated by conditions (verification or
  nested ACLs) are discarded. Only messages specified at this level are used.
  However, the value of an existing message is available in $acl_verify_message
  during expansions. */

  uschar *old_user_msgptr = *user_msgptr;
  uschar *old_log_msgptr = (*log_msgptr != NULL)? *log_msgptr : old_user_msgptr;

  if (verb == ACL_WARN) *log_msgptr = *user_msgptr = NULL;

  if (user_message != NULL)
    {
    acl_verify_message = old_user_msgptr;
    expmessage = expand_string(user_message);
    if (expmessage == NULL)
      {
      if (!expand_string_forcedfail)
        log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand ACL message \"%s\": %s",
          user_message, expand_string_message);
      }
    else if (expmessage[0] != 0) *user_msgptr = expmessage;
    }

  if (log_message != NULL)
    {
    acl_verify_message = old_log_msgptr;
    expmessage = expand_string(log_message);
    if (expmessage == NULL)
      {
      if (!expand_string_forcedfail)
        log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand ACL message \"%s\": %s",
          log_message, expand_string_message);
      }
    else if (expmessage[0] != 0)
      {
      *log_msgptr = (*log_msgptr == NULL)? expmessage :
        string_sprintf("%s: %s", expmessage, *log_msgptr);
      }
    }

  /* If no log message, default it to the user message */

  if (*log_msgptr == NULL) *log_msgptr = *user_msgptr;
  }

acl_verify_message = NULL;
return rc;
}


/*************************************************
*        Get line from a literal ACL             *
*************************************************/

/* This function is passed to acl_read() in order to extract individual lines
of a literal ACL, which we access via static pointers. We can destroy the
contents because this is called only once (the compiled ACL is remembered).

This code is intended to treat the data in the same way as lines in the main
Exim configuration file. That is:

  . Leading spaces are ignored.

  . A \ at the end of a line is a continuation - trailing spaces after the \
    are permitted (this is because I don't believe in making invisible things
    significant). Leading spaces on the continued part of a line are ignored.

  . Physical lines starting (significantly) with # are totally ignored, and
    may appear within a sequence of backslash-continued lines.

  . Blank lines are ignored, but will end a sequence of continuations.

Arguments: none
Returns:   a pointer to the next line
*/


static uschar *acl_text;          /* Current pointer in the text */
static uschar *acl_text_end;      /* Points one past the terminating '0' */


static uschar *
acl_getline(void)
{
uschar *yield;

/* This loop handles leading blank lines and comments. */

for(;;)
  {
  while (isspace(*acl_text)) acl_text++;   /* Leading spaces/empty lines */
  if (*acl_text == 0) return NULL;         /* No more data */
  yield = acl_text;                        /* Potential data line */

  while (*acl_text != 0 && *acl_text != '\n') acl_text++;

  /* If we hit the end before a newline, we have the whole logical line. If
  it's a comment, there's no more data to be given. Otherwise, yield it. */

  if (*acl_text == 0) return (*yield == '#')? NULL : yield;

  /* After reaching a newline, end this loop if the physical line does not
  start with '#'. If it does, it's a comment, and the loop continues. */

  if (*yield != '#') break;
  }

/* This loop handles continuations. We know we have some real data, ending in
newline. See if there is a continuation marker at the end (ignoring trailing
white space). We know that *yield is not white space, so no need to test for
cont > yield in the backwards scanning loop. */

for(;;)
  {
  uschar *cont;
  for (cont = acl_text - 1; isspace(*cont); cont--);

  /* If no continuation follows, we are done. Mark the end of the line and
  return it. */

  if (*cont != '\\')
    {
    *acl_text++ = 0;
    return yield;
    }

  /* We have encountered a continuation. Skip over whitespace at the start of
  the next line, and indeed the whole of the next line or lines if they are
  comment lines. */

  for (;;)
    {
    while (*(++acl_text) == ' ' || *acl_text == '\t');
    if (*acl_text != '#') break;
    while (*(++acl_text) != 0 && *acl_text != '\n');
    }

  /* We have the start of a continuation line. Move all the rest of the data
  to join onto the previous line, and then find its end. If the end is not a
  newline, we are done. Otherwise loop to look for another continuation. */

  memmove(cont, acl_text, acl_text_end - acl_text);
  acl_text_end -= acl_text - cont;
  acl_text = cont;
  while (*acl_text != 0 && *acl_text != '\n') acl_text++;
  if (*acl_text == 0) return yield;
  }

/* Control does not reach here */
}


/*************************************************
*        Check access using an ACL               *
*************************************************/

/* This function is called from address_check. It may recurse via
acl_check_condition() - hence the use of a level to stop looping. The ACL is
passed as a string which is expanded. A forced failure implies no access check
is required. If the result is a single word, it is taken as the name of an ACL
which is sought in the global ACL tree. Otherwise, it is taken as literal ACL
text, complete with newlines, and parsed as such. In both cases, the ACL check
is then run. This function uses an auxiliary function for acl_read() to call
for reading individual lines of a literal ACL. This is acl_getline(), which
appears immediately above.

Arguments:
  where        where called from
  addr         address item when called from RCPT; otherwise NULL
  s            the input string; NULL is the same as an empty ACL => DENY
  level        the nesting level
  user_msgptr  where to put a user error (for SMTP response)
  log_msgptr   where to put a logging message (not for SMTP response)

Returns:       OK         access is granted
               DISCARD    access is apparently granted...
               FAIL       access is denied
               FAIL_DROP  access is denied; drop the connection
               DEFER      can't tell at the moment
               ERROR      disaster
*/

static int
acl_check_internal(int where, address_item *addr, uschar *s, int level,
  uschar **user_msgptr, uschar **log_msgptr)
{
int fd = -1;
acl_block *acl = NULL;
uschar *acl_name = US"inline ACL";
uschar *ss;

/* Catch configuration loops */

if (level > 20)
  {
  *log_msgptr = US"ACL nested too deep: possible loop";
  return ERROR;
  }

if (s == NULL)
  {
  HDEBUG(D_acl) debug_printf("ACL is NULL: implicit DENY\n");
  return FAIL;
  }

/* At top level, we expand the incoming string. At lower levels, it has already
been expanded as part of condition processing. */

if (level == 0)
  {
  ss = expand_string(s);
  if (ss == NULL)
    {
    if (expand_string_forcedfail) return OK;
    *log_msgptr = string_sprintf("failed to expand ACL string \"%s\": %s", s,
      expand_string_message);
    return ERROR;
    }
  }
else ss = s;

while (isspace(*ss))ss++;

/* If we can't find a named ACL, the default is to parse it as an inline one.
(Unless it begins with a slash; non-existent files give rise to an error.) */

acl_text = ss;

/* Handle the case of a string that does not contain any spaces. Look for a
named ACL among those read from the configuration, or a previously read file.
It is possible that the pointer to the ACL is NULL if the configuration
contains a name with no data. If not found, and the text begins with '/',
read an ACL from a file, and save it so it can be re-used. */

if (Ustrchr(ss, ' ') == NULL)
  {
  tree_node *t = tree_search(acl_anchor, ss);
  if (t != NULL)
    {
    acl = (acl_block *)(t->data.ptr);
    if (acl == NULL)
      {
      HDEBUG(D_acl) debug_printf("ACL \"%s\" is empty: implicit DENY\n", ss);
      return FAIL;
      }
    acl_name = string_sprintf("ACL \"%s\"", ss);
    HDEBUG(D_acl) debug_printf("using ACL \"%s\"\n", ss);
    }

  else if (*ss == '/')
    {
    struct stat statbuf;
    fd = Uopen(ss, O_RDONLY, 0);
    if (fd < 0)
      {
      *log_msgptr = string_sprintf("failed to open ACL file \"%s\": %s", ss,
        strerror(errno));
      return ERROR;
      }

    if (fstat(fd, &statbuf) != 0)
      {
      *log_msgptr = string_sprintf("failed to fstat ACL file \"%s\": %s", ss,
        strerror(errno));
      return ERROR;
      }

    acl_text = store_get(statbuf.st_size + 1);
    acl_text_end = acl_text + statbuf.st_size + 1;

    if (read(fd, acl_text, statbuf.st_size) != statbuf.st_size)
      {
      *log_msgptr = string_sprintf("failed to read ACL file \"%s\": %s",
        ss, strerror(errno));
      return ERROR;
      }
    acl_text[statbuf.st_size] = 0;
    close(fd);

    acl_name = string_sprintf("ACL \"%s\"", ss);
    HDEBUG(D_acl) debug_printf("read ACL from file %s\n", ss);
    }
  }

/* Parse an ACL that is still in text form. If it came from a file, remember it
in the ACL tree, having read it into the POOL_PERM store pool so that it
persists between multiple messages. */

if (acl == NULL)
  {
  int old_pool = store_pool;
  if (fd >= 0) store_pool = POOL_PERM;
  acl = acl_read(acl_getline, log_msgptr);
  store_pool = old_pool;
  if (acl == NULL && *log_msgptr != NULL) return ERROR;
  if (fd >= 0)
    {
    tree_node *t = store_get_perm(sizeof(tree_node) + Ustrlen(ss));
    Ustrcpy(t->name, ss);
    t->data.ptr = acl;
    (void)tree_insertnode(&acl_anchor, t);
    }
  }

/* Now we have an ACL to use. It's possible it may be NULL. */

while (acl != NULL)
  {
  int cond;
  int basic_errno = 0;
  BOOL endpass_seen = FALSE;

  *log_msgptr = *user_msgptr = NULL;
  acl_temp_details = FALSE;

  if (where == ACL_WHERE_QUIT &&
      acl->verb != ACL_ACCEPT &&
      acl->verb != ACL_WARN)
    {
    *log_msgptr = string_sprintf("\"%s\" is not allowed in a QUIT ACL",
      verbs[acl->verb]);
    return ERROR;
    }

  HDEBUG(D_acl) debug_printf("processing \"%s\"\n", verbs[acl->verb]);

  /* Clear out any search error message from a previous check before testing
  this condition. */

  search_error_message = NULL;
  cond = acl_check_condition(acl->verb, acl->condition, where, addr, level,
    &endpass_seen, user_msgptr, log_msgptr, &basic_errno);

  /* Handle special returns: DEFER causes a return except on a WARN verb;
  ERROR always causes a return. */

  switch (cond)
    {
    case DEFER:
    HDEBUG(D_acl) debug_printf("%s: condition test deferred\n", verbs[acl->verb]);
    if (basic_errno != ERRNO_CALLOUTDEFER)
      {
      if (search_error_message != NULL && *search_error_message != 0)
        *log_msgptr = search_error_message;
      if (smtp_return_error_details) acl_temp_details = TRUE;
      }
    else
      {
      acl_temp_details = TRUE;
      }
    if (acl->verb != ACL_WARN) return DEFER;
    break;

    default:      /* Paranoia */
    case ERROR:
    HDEBUG(D_acl) debug_printf("%s: condition test error\n", verbs[acl->verb]);
    return ERROR;

    case OK:
    HDEBUG(D_acl) debug_printf("%s: condition test succeeded\n",
      verbs[acl->verb]);
    break;

    case FAIL:
    HDEBUG(D_acl) debug_printf("%s: condition test failed\n", verbs[acl->verb]);
    break;

    /* DISCARD and DROP can happen only from a nested ACL condition, and
    DISCARD can happen only for an "accept" or "discard" verb. */

    case DISCARD:
    HDEBUG(D_acl) debug_printf("%s: condition test yielded \"discard\"\n",
      verbs[acl->verb]);
    break;

    case FAIL_DROP:
    HDEBUG(D_acl) debug_printf("%s: condition test yielded \"drop\"\n",
      verbs[acl->verb]);
    break;
    }

  /* At this point, cond for most verbs is either OK or FAIL or (as a result of
  a nested ACL condition) FAIL_DROP. However, for WARN, cond may be DEFER, and
  for ACCEPT and DISCARD, it may be DISCARD after a nested ACL call. */

  switch(acl->verb)
    {
    case ACL_ACCEPT:
    if (cond == OK || cond == DISCARD) return cond;
    if (endpass_seen)
      {
      HDEBUG(D_acl) debug_printf("accept: endpass encountered - denying access\n");
      return cond;
      }
    break;

    case ACL_DEFER:
    if (cond == OK)
      {
      acl_temp_details = TRUE;
      return DEFER;
      }
    break;

    case ACL_DENY:
    if (cond == OK) return FAIL;
    break;

    case ACL_DISCARD:
    if (cond == OK || cond == DISCARD) return DISCARD;
    if (endpass_seen)
      {
      HDEBUG(D_acl) debug_printf("discard: endpass encountered - denying access\n");
      return cond;
      }
    break;

    case ACL_DROP:
    if (cond == OK) return FAIL_DROP;
    break;

    case ACL_REQUIRE:
    if (cond != OK) return cond;
    break;

    case ACL_WARN:
    if (cond == OK)
      acl_warn(where, *user_msgptr, *log_msgptr);
    else if (cond == DEFER)
      log_write(0, LOG_MAIN, "%s Warning: ACL \"warn\" statement skipped: "
        "condition test deferred%s%s", host_and_ident(TRUE),
        (*log_msgptr == NULL)? US"" : US": ",
        (*log_msgptr == NULL)? US"" : *log_msgptr);
    *log_msgptr = *user_msgptr = NULL;  /* In case implicit DENY follows */
    break;

    default:
    log_write(0, LOG_MAIN|LOG_PANIC_DIE, "internal ACL error: unknown verb %d",
      acl->verb);
    break;
    }

  /* Pass to the next ACL item */

  acl = acl->next;
  }

/* We have reached the end of the ACL. This is an implicit DENY. */

HDEBUG(D_acl) debug_printf("end of %s: implicit DENY\n", acl_name);
return FAIL;
}


/*************************************************
*        Check access using an ACL               *
*************************************************/

/* This is the external interface for ACL checks. It sets up an address and the
expansions for $domain and $local_part when called after RCPT, then calls
acl_check_internal() to do the actual work.

Arguments:
  where        ACL_WHERE_xxxx indicating where called from
  data_string  RCPT address, or SMTP command argument, or NULL
  s            the input string; NULL is the same as an empty ACL => DENY
  user_msgptr  where to put a user error (for SMTP response)
  log_msgptr   where to put a logging message (not for SMTP response)

Returns:       OK         access is granted by an ACCEPT verb
               DISCARD    access is granted by a DISCARD verb
               FAIL       access is denied
               FAIL_DROP  access is denied; drop the connection
               DEFER      can't tell at the moment
               ERROR      disaster
*/

int
acl_check(int where, uschar *data_string, uschar *s, uschar **user_msgptr,
  uschar **log_msgptr)
{
int rc;
address_item adb;
address_item *addr;

*user_msgptr = *log_msgptr = NULL;
sender_verified_failed = NULL;
ratelimiters_cmd = NULL;

if (where == ACL_WHERE_RCPT)
  {
  adb = address_defaults;
  addr = &adb;
  addr->address = data_string;
  if (deliver_split_address(addr) == DEFER)
    {
    *log_msgptr = US"defer in percent_hack_domains check";
    return DEFER;
    }
  deliver_domain = addr->domain;
  deliver_localpart = addr->local_part;
  }
else
  {
  addr = NULL;
  smtp_command_argument = data_string;
  }

rc = acl_check_internal(where, addr, s, 0, user_msgptr, log_msgptr);

smtp_command_argument = deliver_domain =
  deliver_localpart = deliver_address_data = sender_address_data = NULL;

/* A DISCARD response is permitted only for message ACLs, excluding the PREDATA
ACL, which is really in the middle of an SMTP command. */

if (rc == DISCARD)
  {
  if (where > ACL_WHERE_NOTSMTP || where == ACL_WHERE_PREDATA)
    {
    log_write(0, LOG_MAIN|LOG_PANIC, "\"discard\" verb not allowed in %s "
      "ACL", acl_wherenames[where]);
    return ERROR;
    }
  return DISCARD;
  }

/* A DROP response is not permitted from MAILAUTH */

if (rc == FAIL_DROP && where == ACL_WHERE_MAILAUTH)
  {
  log_write(0, LOG_MAIN|LOG_PANIC, "\"drop\" verb not allowed in %s "
    "ACL", acl_wherenames[where]);
  return ERROR;
  }

/* Before giving an error response, take a look at the length of any user
message, and split it up into multiple lines if possible. */

if (rc != OK && *user_msgptr != NULL && Ustrlen(*user_msgptr) > 75)
  {
  uschar *s = *user_msgptr = string_copy(*user_msgptr);
  uschar *ss = s;

  for (;;)
    {
    int i = 0;
    while (i < 75 && *ss != 0 && *ss != '\n') ss++, i++;
    if (*ss == 0) break;
    if (*ss == '\n')
      s = ++ss;
    else
      {
      uschar *t = ss + 1;
      uschar *tt = NULL;
      while (--t > s + 35)
        {
        if (*t == ' ')
          {
          if (t[-1] == ':') { tt = t; break; }
          if (tt == NULL) tt = t;
          }
        }

      if (tt == NULL)          /* Can't split behind - try ahead */
        {
        t = ss + 1;
        while (*t != 0)
          {
          if (*t == ' ' || *t == '\n')
            { tt = t; break; }
          t++;
          }
        }

      if (tt == NULL) break;   /* Can't find anywhere to split */
      *tt = '\n';
      s = ss = tt+1;
      }
    }
  }

return rc;
}

/* End of acl.c */