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

/*
 *  PDKIM - a RFC4871 (DKIM) implementation
 *
 *  Copyright (C) 2009 - 2016  Tom Kistner <tom@duncanthrax.net>
 *  Copyright (C) 2016  Jeremy Harris <jgh@exim.org>
 *
 *  http://duncanthrax.net/pdkim/
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "../exim.h"


#ifndef DISABLE_DKIM	/* entire file */

#ifndef SUPPORT_TLS
# error Need SUPPORT_TLS for DKIM
#endif

#include "crypt_ver.h"

#ifdef RSA_OPENSSL
# include <openssl/rsa.h>
# include <openssl/ssl.h>
# include <openssl/err.h>
#elif defined(RSA_GNUTLS)
# include <gnutls/gnutls.h>
# include <gnutls/x509.h>
# include <gnutls/abstract.h>
#endif

#ifdef SHA_GNUTLS
# include <gnutls/crypto.h>
#elif defined(SHA_POLARSSL)
# include "polarssl/sha1.h"
# include "polarssl/sha2.h"
#endif

#include "pdkim.h"

#define PDKIM_SIGNATURE_VERSION     "1"
#define PDKIM_PUB_RECORD_VERSION    "DKIM1"

#define PDKIM_MAX_HEADER_LEN        65536
#define PDKIM_MAX_HEADERS           512
#define PDKIM_MAX_BODY_LINE_LEN     16384
#define PDKIM_DNS_TXT_MAX_NAMELEN   1024
#define PDKIM_DEFAULT_SIGN_HEADERS "From:Sender:Reply-To:Subject:Date:"\
                             "Message-ID:To:Cc:MIME-Version:Content-Type:"\
                             "Content-Transfer-Encoding:Content-ID:"\
                             "Content-Description:Resent-Date:Resent-From:"\
                             "Resent-Sender:Resent-To:Resent-Cc:"\
                             "Resent-Message-ID:In-Reply-To:References:"\
                             "List-Id:List-Help:List-Unsubscribe:"\
                             "List-Subscribe:List-Post:List-Owner:List-Archive"

/* -------------------------------------------------------------------------- */
struct pdkim_stringlist {
  char *value;
  int  tag;
  void *next;
};

#define PDKIM_STR_ALLOC_FRAG 256
struct pdkim_str {
  char         *str;
  unsigned int  len;
  unsigned int  allocated;
};

/* -------------------------------------------------------------------------- */
/* A bunch of list constants */
const char *pdkim_querymethods[] = {
  "dns/txt",
  NULL
};
const char *pdkim_algos[] = {
  "rsa-sha256",
  "rsa-sha1",
  NULL
};
const char *pdkim_canons[] = {
  "simple",
  "relaxed",
  NULL
};
const char *pdkim_hashes[] = {
  "sha256",
  "sha1",
  NULL
};
const char *pdkim_keytypes[] = {
  "rsa",
  NULL
};

typedef struct pdkim_combined_canon_entry {
  const char *str;
  int canon_headers;
  int canon_body;
} pdkim_combined_canon_entry;

pdkim_combined_canon_entry pdkim_combined_canons[] = {
  { "simple/simple",    PDKIM_CANON_SIMPLE,   PDKIM_CANON_SIMPLE },
  { "simple/relaxed",   PDKIM_CANON_SIMPLE,   PDKIM_CANON_RELAXED },
  { "relaxed/simple",   PDKIM_CANON_RELAXED,  PDKIM_CANON_SIMPLE },
  { "relaxed/relaxed",  PDKIM_CANON_RELAXED,  PDKIM_CANON_RELAXED },
  { "simple",           PDKIM_CANON_SIMPLE,   PDKIM_CANON_SIMPLE },
  { "relaxed",          PDKIM_CANON_RELAXED,  PDKIM_CANON_SIMPLE },
  { NULL,               0,                    0 }
};


/* -------------------------------------------------------------------------- */

const char *
pdkim_verify_status_str(int status)
{
  switch(status) {
    case PDKIM_VERIFY_NONE:    return "PDKIM_VERIFY_NONE";
    case PDKIM_VERIFY_INVALID: return "PDKIM_VERIFY_INVALID";
    case PDKIM_VERIFY_FAIL:    return "PDKIM_VERIFY_FAIL";
    case PDKIM_VERIFY_PASS:    return "PDKIM_VERIFY_PASS";
    default:                   return "PDKIM_VERIFY_UNKNOWN";
  }
}

const char *
pdkim_verify_ext_status_str(int ext_status)
{
  switch(ext_status) {
    case PDKIM_VERIFY_FAIL_BODY: return "PDKIM_VERIFY_FAIL_BODY";
    case PDKIM_VERIFY_FAIL_MESSAGE: return "PDKIM_VERIFY_FAIL_MESSAGE";
    case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: return "PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE";
    case PDKIM_VERIFY_INVALID_BUFFER_SIZE: return "PDKIM_VERIFY_INVALID_BUFFER_SIZE";
    case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: return "PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD";
    case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: return "PDKIM_VERIFY_INVALID_PUBKEY_IMPORT";
    default: return "PDKIM_VERIFY_UNKNOWN";
  }
}


/* -------------------------------------------------------------------------- */
/* Print debugging functions */
void
pdkim_quoteprint(const char *data, int len, int lf)
{
int i;
const unsigned char *p = (const unsigned char *)data;

for (i = 0; i < len; i++)
  {
  const int c = p[i];
  switch (c)
    {
    case ' ' : debug_printf("{SP}"); break;
    case '\t': debug_printf("{TB}"); break;
    case '\r': debug_printf("{CR}"); break;
    case '\n': debug_printf("{LF}"); break;
    case '{' : debug_printf("{BO}"); break;
    case '}' : debug_printf("{BC}"); break;
    default:
      if ( (c < 32) || (c > 127) )
	debug_printf("{%02x}", c);
      else
	debug_printf("%c", c);
      break;
    }
  }
if (lf)
  debug_printf("\n");
}

void
pdkim_hexprint(const char *data, int len, int lf)
{
int i;
const unsigned char *p = (const unsigned char *)data;

for (i = 0 ; i < len; i++)
  debug_printf("%02x", p[i]);
if (lf)
  debug_printf("\n");
}



/* String package: should be replaced by Exim standard ones */

static pdkim_stringlist *
pdkim_prepend_stringlist(pdkim_stringlist *base, char *str)
{
pdkim_stringlist *new_entry = malloc(sizeof(pdkim_stringlist));

if (!new_entry) return NULL;
memset(new_entry, 0, sizeof(pdkim_stringlist));
if (!(new_entry->value = strdup(str))) return NULL;
if (base)
  {
  pdkim_stringlist *last = base;
  while (last->next != NULL) { last = last->next; }
  last->next = new_entry;
  return base;
  }
else
  return new_entry;
}


/* -------------------------------------------------------------------------- */
/* A small "growing string" implementation to escape malloc/realloc hell */

static pdkim_str *
pdkim_strnew (const char *cstr)
{
unsigned int len = cstr ? strlen(cstr) : 0;
pdkim_str *p = malloc(sizeof(pdkim_str));

if (!p) return NULL;
memset(p, 0, sizeof(pdkim_str));
if (!(p->str = malloc(len+1)))
  {
  free(p);
  return NULL;
  }
p->allocated = len+1;
p->len = len;
if (cstr)
  strcpy(p->str, cstr);
else
  p->str[p->len] = '\0';
return p;
}

static char *
pdkim_strncat(pdkim_str *str, const char *data, int len)
{
if ((str->allocated - str->len) < (len+1))
  {
  /* Extend the buffer */
  int num_frags = ((len+1)/PDKIM_STR_ALLOC_FRAG)+1;
  char *n = realloc(str->str,
		    (str->allocated+(num_frags*PDKIM_STR_ALLOC_FRAG)));
  if (n == NULL) return NULL;
  str->str = n;
  str->allocated += (num_frags*PDKIM_STR_ALLOC_FRAG);
  }
strncpy(&(str->str[str->len]), data, len);
str->len += len;
str->str[str->len] = '\0';
return str->str;
}

static char *
pdkim_strcat(pdkim_str *str, const char *cstr)
{
return pdkim_strncat(str, cstr, strlen(cstr));
}

static char *
pdkim_strtrim(pdkim_str *str)
{
char *p = str->str;
char *q = str->str;
while ( (*p != '\0') && ((*p == '\t') || (*p == ' ')) ) p++;
while (*p != '\0') {*q = *p; q++; p++;}
*q = '\0';
while ( (q != str->str) && ( (*q == '\0') || (*q == '\t') || (*q == ' ') ) )
  {
  *q = '\0';
  q--;
  }
str->len = strlen(str->str);
return str->str;
}

static char *
pdkim_strclear(pdkim_str *str)
{
str->str[0] = '\0';
str->len = 0;
return str->str;
}

static void
pdkim_strfree(pdkim_str *str)
{
if (!str) return;
if (str->str) free(str->str);
free(str);
}



/* -------------------------------------------------------------------------- */

static void
pdkim_free_pubkey(pdkim_pubkey *pub)
{
if (pub)
  {
  if (pub->version    ) free(pub->version);
  if (pub->granularity) free(pub->granularity);
  if (pub->hashes     ) free(pub->hashes);
  if (pub->keytype    ) free(pub->keytype);
  if (pub->srvtype    ) free(pub->srvtype);
  if (pub->notes      ) free(pub->notes);
/*  if (pub->key        ) free(pub->key); */
  free(pub);
  }
}


/* -------------------------------------------------------------------------- */

static void
pdkim_free_sig(pdkim_signature *sig)
{
if (sig)
  {
  pdkim_signature *next = (pdkim_signature *)sig->next;

  pdkim_stringlist *e = sig->headers;
  while(e)
    {
    pdkim_stringlist *c = e;
    if (e->value) free(e->value);
    e = e->next;
    free(c);
    }

  if (sig->selector        ) free(sig->selector);
  if (sig->domain          ) free(sig->domain);
  if (sig->identity        ) free(sig->identity);
  if (sig->headernames     ) free(sig->headernames);
  if (sig->copiedheaders   ) free(sig->copiedheaders);
  if (sig->rsa_privkey     ) free(sig->rsa_privkey);
  if (sig->sign_headers    ) free(sig->sign_headers);
  if (sig->signature_header) free(sig->signature_header);

  if (sig->pubkey) pdkim_free_pubkey(sig->pubkey);

  free(sig);
  if (next) pdkim_free_sig(next);
  }
}


/* -------------------------------------------------------------------------- */

DLLEXPORT void
pdkim_free_ctx(pdkim_ctx *ctx)
{
if (ctx)
  {
  pdkim_stringlist *e = ctx->headers;
  while(e)
    {
    pdkim_stringlist *c = e;
    if (e->value) free(e->value);
    e = e->next;
    free(c);
    }
  pdkim_free_sig(ctx->sig);
  pdkim_strfree(ctx->cur_header);
  free(ctx);
  }
}


/* -------------------------------------------------------------------------- */
/* Matches the name of the passed raw "header" against
   the passed colon-separated "list", starting at entry
   "start". Returns the position of the header name in
   the list. */

static int
header_name_match(const char *header,
                      char       *tick,
                      int         do_tick)
{
char *hname;
char *lcopy;
char *p;
char *q;
int rc = PDKIM_FAIL;

/* Get header name */
char *hcolon = strchr(header, ':');

if (!hcolon) return rc; /* This isn't a header */

if (!(hname = malloc((hcolon-header)+1)))
  return PDKIM_ERR_OOM;
memset(hname, 0, (hcolon-header)+1);
strncpy(hname, header, (hcolon-header));

/* Copy tick-off list locally, so we can punch zeroes into it */
if (!(lcopy = strdup(tick)))
  {
  free(hname);
  return PDKIM_ERR_OOM;
  }
p = lcopy;
q = strchr(p, ':');
while (q)
  {
  *q = '\0';

  if (strcasecmp(p, hname) == 0)
    {
    rc = PDKIM_OK;
    /* Invalidate header name instance in tick-off list */
    if (do_tick) tick[p-lcopy] = '_';
    goto BAIL;
    }

  p = q+1;
  q = strchr(p, ':');
  }

if (strcasecmp(p, hname) == 0)
  {
  rc = PDKIM_OK;
  /* Invalidate header name instance in tick-off list */
  if (do_tick) tick[p-lcopy] = '_';
  }

BAIL:
free(hname);
free(lcopy);
return rc;
}


/* -------------------------------------------------------------------------- */
/* Performs "relaxed" canonicalization of a header. The returned pointer needs
   to be free()d. */

static char *
pdkim_relax_header (char *header, int crlf)
{
BOOL past_field_name = FALSE;
BOOL seen_wsp = FALSE;
char *p;
char *q;
char *relaxed = malloc(strlen(header)+3);

if (!relaxed) return NULL;

q = relaxed;
for (p = header; *p != '\0'; p++)
  {
  int c = *p;
  /* Ignore CR & LF */
  if (c == '\r' || c == '\n')
    continue;
  if (c == '\t' || c == ' ')
    {
    if (seen_wsp)
      continue;
    c = ' ';			/* Turns WSP into SP */
    seen_wsp = TRUE;
    }
  else
    if (!past_field_name && c == ':')
      {
      if (seen_wsp) q--;	/* This removes WSP before the colon */
      seen_wsp = TRUE;		/* This removes WSP after the colon */
      past_field_name = TRUE;
      }
    else
      seen_wsp = FALSE;

  /* Lowercase header name */
  if (!past_field_name) c = tolower(c);
  *q++ = c;
  }

if (q > relaxed && q[-1] == ' ') q--; /* Squash eventual trailing SP */
*q = '\0';

if (crlf) strcat(relaxed, "\r\n");
return relaxed;
}


/* -------------------------------------------------------------------------- */
#define PDKIM_QP_ERROR_DECODE -1

static char *
pdkim_decode_qp_char(char *qp_p, int *c)
{
char *initial_pos = qp_p;

/* Advance one char */
qp_p++;

/* Check for two hex digits and decode them */
if (isxdigit(*qp_p) && isxdigit(qp_p[1]))
  {
  /* Do hex conversion */
  *c = (isdigit(*qp_p) ? *qp_p - '0' : toupper(*qp_p) - 'A' + 10) << 4;
  *c |= isdigit(qp_p[1]) ? qp_p[1] - '0' : toupper(qp_p[1]) - 'A' + 10;
  return qp_p + 2;
  }

/* Illegal char here */
*c = PDKIM_QP_ERROR_DECODE;
return initial_pos;
}


/* -------------------------------------------------------------------------- */

static char *
pdkim_decode_qp(char *str)
{
int nchar = 0;
char *q;
char *p = str;
char *n = malloc(strlen(p)+1);

if (!n) return NULL;

*n = '\0';
q = n;
while (*p != '\0')
  {
  if (*p == '=')
    {
    p = pdkim_decode_qp_char(p, &nchar);
    if (nchar >= 0)
      {
      *q++ = nchar;
      continue;
      }
    }
  else
    *q++ = *p;
  p++;
  }
*q = '\0';
return n;
}


/* -------------------------------------------------------------------------- */

static char *
pdkim_decode_base64(char *str, int *num_decoded)
{
int dlen = 0;
char *res;
int old_pool = store_pool;

/* There is a store-reset between header & body reception
so cannot use the main pool */

store_pool = POOL_PERM;
dlen = b64decode(US str, USS &res);
store_pool = old_pool;

if (dlen < 0) return NULL;

if (num_decoded) *num_decoded = dlen;
return res;
}


/* -------------------------------------------------------------------------- */

static char *
pdkim_encode_base64(char *str, int num)
{
char * ret;
int old_pool = store_pool;

store_pool = POOL_PERM;
ret = CS b64encode(US str, num);
store_pool = old_pool;
return ret;
}


/* -------------------------------------------------------------------------- */
#define PDKIM_HDR_LIMBO 0
#define PDKIM_HDR_TAG   1
#define PDKIM_HDR_VALUE 2

static pdkim_signature *
pdkim_parse_sig_header(pdkim_ctx *ctx, char *raw_hdr)
{
pdkim_signature *sig ;
char *p, *q;
pdkim_str *cur_tag = NULL;
pdkim_str *cur_val = NULL;
BOOL past_hname = FALSE;
BOOL in_b_val = FALSE;
int where = PDKIM_HDR_LIMBO;
int i;

if (!(sig = malloc(sizeof(pdkim_signature)))) return NULL;
memset(sig, 0, sizeof(pdkim_signature));
sig->bodylength = -1;

if (!(sig->rawsig_no_b_val = malloc(strlen(raw_hdr)+1)))
  {
  free(sig);
  return NULL;
  }

q = sig->rawsig_no_b_val;

for (p = raw_hdr; ; p++)
  {
  char c = *p;

  /* Ignore FWS */
  if (c == '\r' || c == '\n')
    goto NEXT_CHAR;

  /* Fast-forward through header name */
  if (!past_hname)
    {
    if (c == ':') past_hname = TRUE;
    goto NEXT_CHAR;
    }

  if (where == PDKIM_HDR_LIMBO)
    {
    /* In limbo, just wait for a tag-char to appear */
    if (!(c >= 'a' && c <= 'z'))
      goto NEXT_CHAR;

    where = PDKIM_HDR_TAG;
    }

  if (where == PDKIM_HDR_TAG)
    {
    if (!cur_tag)
      cur_tag = pdkim_strnew(NULL);

    if (c >= 'a' && c <= 'z')
      pdkim_strncat(cur_tag, p, 1);

    if (c == '=')
      {
      if (strcmp(cur_tag->str, "b") == 0)
        {
	*q = '='; q++;
	in_b_val = TRUE;
	}
      where = PDKIM_HDR_VALUE;
      goto NEXT_CHAR;
      }
    }

  if (where == PDKIM_HDR_VALUE)
    {
    if (!cur_val)
      cur_val = pdkim_strnew(NULL);

    if (c == '\r' || c == '\n' || c == ' ' || c == '\t')
      goto NEXT_CHAR;

    if (c == ';' || c == '\0')
      {
      if (cur_tag->len > 0)
        {
	pdkim_strtrim(cur_val);

	DEBUG(D_acl) debug_printf(" %s=%s\n", cur_tag->str, cur_val->str);

	switch (cur_tag->str[0])
	  {
	  case 'b':
	    if (cur_tag->str[1] == 'h')
	      sig->bodyhash = pdkim_decode_base64(cur_val->str,
		  &sig->bodyhash_len);
	    else
	      sig->sigdata = pdkim_decode_base64(cur_val->str,
		  &sig->sigdata_len);
	    break;
	  case 'v':
	      /* We only support version 1, and that is currently the
		 only version there is. */
	    if (strcmp(cur_val->str, PDKIM_SIGNATURE_VERSION) == 0)
	      sig->version = 1;
	    break;
	  case 'a':
	    for (i = 0; pdkim_algos[i]; i++)
	      if (strcmp(cur_val->str, pdkim_algos[i]) == 0)
	        {
		sig->algo = i;
		break;
		}
	    break;
	  case 'c':
	    for (i = 0; pdkim_combined_canons[i].str; i++)
	      if (strcmp(cur_val->str, pdkim_combined_canons[i].str) == 0)
	        {
		sig->canon_headers = pdkim_combined_canons[i].canon_headers;
		sig->canon_body    = pdkim_combined_canons[i].canon_body;
		break;
		}
	    break;
	  case 'q':
	    for (i = 0; pdkim_querymethods[i]; i++)
	      if (strcmp(cur_val->str, pdkim_querymethods[i]) == 0)
	        {
		sig->querymethod = i;
		break;
		}
	    break;
	  case 's':
	    sig->selector = strdup(cur_val->str); break;
	  case 'd':
	    sig->domain = strdup(cur_val->str); break;
	  case 'i':
	    sig->identity = pdkim_decode_qp(cur_val->str); break;
	  case 't':
	    sig->created = strtoul(cur_val->str, NULL, 10); break;
	  case 'x':
	    sig->expires = strtoul(cur_val->str, NULL, 10); break;
	  case 'l':
	    sig->bodylength = strtol(cur_val->str, NULL, 10); break;
	  case 'h':
	    sig->headernames = strdup(cur_val->str); break;
	  case 'z':
	    sig->copiedheaders = pdkim_decode_qp(cur_val->str); break;
	  default:
	    DEBUG(D_acl) debug_printf(" Unknown tag encountered\n");
	    break;
	  }
	}
      pdkim_strclear(cur_tag);
      pdkim_strclear(cur_val);
      in_b_val = FALSE;
      where = PDKIM_HDR_LIMBO;
      }
    else
      pdkim_strncat(cur_val, p, 1);
    }

NEXT_CHAR:
  if (c == '\0')
    break;

  if (!in_b_val)
    *q++ = c;
  }

/* Make sure the most important bits are there. */
if (!(sig->domain      && (*(sig->domain)      != '\0') &&
      sig->selector    && (*(sig->selector)    != '\0') &&
      sig->headernames && (*(sig->headernames) != '\0') &&
      sig->bodyhash    &&
      sig->sigdata     &&
      sig->version))
  {
  pdkim_free_sig(sig);
  return NULL;
  }

*q = '\0';
/* Chomp raw header. The final newline must not be added to the signature. */
q--;
while (q > sig->rawsig_no_b_val  && (*q == '\r' || *q == '\n'))
  *q = '\0'; q--;	/*XXX questionable code layout; possible bug */

DEBUG(D_acl)
  {
  debug_printf(
	  "PDKIM >> Raw signature w/o b= tag value >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
  pdkim_quoteprint(sig->rawsig_no_b_val, strlen(sig->rawsig_no_b_val), 1);
  debug_printf(
	  "PDKIM >> Sig size: %4d bits\n", sig->sigdata_len*8);
  debug_printf(
	  "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
  }

#ifdef SHA_OPENSSL

SHA1_Init  (&sig->sha1_body);
SHA256_Init(&sig->sha2_body);

#elif defined(SHA_GNUTLS)

gnutls_hash_init(&sig->sha_body,
  sig->algo == PDKIM_ALGO_RSA_SHA1 ? GNUTLS_DIG_SHA1 : GNUTLS_DIG_SHA256);

#elif defined(SHA_POLARSSL)

if (  !(sig->sha1_body = malloc(sizeof(sha1_context)))
   || !(sig->sha2_body = malloc(sizeof(sha2_context)))
   )
  {
  pdkim_free_sig(sig);
  return NULL;
  }

sha1_starts(sig->sha1_body);
sha2_starts(sig->sha2_body, 0);

#endif	/* SHA impl */

return sig;
}


/* -------------------------------------------------------------------------- */

static pdkim_pubkey *
pdkim_parse_pubkey_record(pdkim_ctx *ctx, char *raw_record)
{
pdkim_pubkey *pub;
char *p;
pdkim_str *cur_tag = NULL;
pdkim_str *cur_val = NULL;
int where = PDKIM_HDR_LIMBO;

if (!(pub = malloc(sizeof(pdkim_pubkey)))) return NULL;
memset(pub, 0, sizeof(pdkim_pubkey));

for (p = raw_record; ; p++)
  {
  char c = *p;

  /* Ignore FWS */
  if (c == '\r' || c == '\n')
    goto NEXT_CHAR;

  if (where == PDKIM_HDR_LIMBO)
    {
    /* In limbo, just wait for a tag-char to appear */
    if (!(c >= 'a' && c <= 'z'))
      goto NEXT_CHAR;

    where = PDKIM_HDR_TAG;
    }

  if (where == PDKIM_HDR_TAG)
    {
    if (!cur_tag)
      cur_tag = pdkim_strnew(NULL);

    if (c >= 'a' && c <= 'z')
      pdkim_strncat(cur_tag, p, 1);

    if (c == '=')
      {
      where = PDKIM_HDR_VALUE;
      goto NEXT_CHAR;
      }
    }

  if (where == PDKIM_HDR_VALUE)
    {
    if (!cur_val)
      cur_val = pdkim_strnew(NULL);

    if (c == '\r' || c == '\n')
      goto NEXT_CHAR;

    if (c == ';' || c == '\0')
      {
      if (cur_tag->len > 0)
        {
	pdkim_strtrim(cur_val);
	DEBUG(D_acl) debug_printf(" %s=%s\n", cur_tag->str, cur_val->str);

	switch (cur_tag->str[0])
	  {
	  case 'v':
	    /* This tag isn't evaluated because:
	       - We only support version DKIM1.
	       - Which is the default for this value (set below)
	       - Other versions are currently not specified.      */
	    break;
	  case 'h':
	    pub->hashes = strdup(cur_val->str); break;
	  case 'g':
	    pub->granularity = strdup(cur_val->str); break;
	  case 'n':
	    pub->notes = pdkim_decode_qp(cur_val->str); break;
	  case 'p':
	    pub->key = pdkim_decode_base64(cur_val->str, &(pub->key_len)); break;
	  case 'k':
	    pub->hashes = strdup(cur_val->str); break;
	  case 's':
	    pub->srvtype = strdup(cur_val->str); break;
	  case 't':
	    if (strchr(cur_val->str, 'y') != NULL) pub->testing = 1;
	    if (strchr(cur_val->str, 's') != NULL) pub->no_subdomaining = 1;
	    break;
	  default:
	    DEBUG(D_acl) debug_printf(" Unknown tag encountered\n");
	    break;
	  }
	}
      pdkim_strclear(cur_tag);
      pdkim_strclear(cur_val);
      where = PDKIM_HDR_LIMBO;
      }
    else
      pdkim_strncat(cur_val, p, 1);
    }

NEXT_CHAR:
  if (c == '\0') break;
  }

/* Set fallback defaults */
if (!pub->version    ) pub->version     = strdup(PDKIM_PUB_RECORD_VERSION);
if (!pub->granularity) pub->granularity = strdup("*");
if (!pub->keytype    ) pub->keytype     = strdup("rsa");
if (!pub->srvtype    ) pub->srvtype     = strdup("*");

/* p= is required */
if (pub->key)
  return pub;

pdkim_free_pubkey(pub);
return NULL;
}


/* -------------------------------------------------------------------------- */

static int
pdkim_update_bodyhash(pdkim_ctx *ctx, const char *data, int len)
{
pdkim_signature *sig = ctx->sig;
/* Cache relaxed version of data */
char *relaxed_data = NULL;
int   relaxed_len  = 0;

/* Traverse all signatures, updating their hashes. */
while (sig)
  {
  /* Defaults to simple canon (no further treatment necessary) */
  const char *canon_data = data;
  int         canon_len = len;

  if (sig->canon_body == PDKIM_CANON_RELAXED)
    {
    /* Relax the line if not done already */
    if (!relaxed_data)
      {
      BOOL seen_wsp = FALSE;
      const char *p;
      int q = 0;

      if (!(relaxed_data = malloc(len+1)))
	return PDKIM_ERR_OOM;

      for (p = data; *p; p++)
        {
	char c = *p;
	if (c == '\r')
	  {
	  if (q > 0 && relaxed_data[q-1] == ' ')
	    q--;
	  }
	else if (c == '\t' || c == ' ')
	  {
	  c = ' '; /* Turns WSP into SP */
	  if (seen_wsp)
	    continue;
	  seen_wsp = TRUE;
	  }
	else
	  seen_wsp = FALSE;
	relaxed_data[q++] = c;
	}
      relaxed_data[q] = '\0';
      relaxed_len = q;
      }
    canon_data = relaxed_data;
    canon_len  = relaxed_len;
    }

  /* Make sure we don't exceed the to-be-signed body length */
  if (  sig->bodylength >= 0
     && sig->signed_body_bytes + (unsigned long)canon_len > sig->bodylength
     )
    canon_len = sig->bodylength - sig->signed_body_bytes;

  if (canon_len > 0)
    {
#ifdef SHA_GNUTLS
    gnutls_hash(sig->sha_body, canon_data, canon_len);
#else
    if (sig->algo == PDKIM_ALGO_RSA_SHA1)
# ifdef SHA_OPENSSL
      SHA1_Update  (&sig->sha1_body, canon_data, canon_len);
    else
      SHA256_Update(&sig->sha2_body, canon_data, canon_len);
# elif defined(SHA_POLARSSL)
      sha1_update(sig->sha1_body, US canon_data, canon_len);
    else
      sha2_update(sig->sha2_body, US canon_data, canon_len);
# endif
#endif

    sig->signed_body_bytes += canon_len;
    DEBUG(D_acl) pdkim_quoteprint(canon_data, canon_len, 1);
    }

  sig = sig->next;
  }

if (relaxed_data) free(relaxed_data);
return PDKIM_OK;
}


/* -------------------------------------------------------------------------- */

static int
pdkim_finish_bodyhash(pdkim_ctx *ctx)
{
pdkim_signature *sig;

/* Traverse all signatures */
for (sig = ctx->sig; sig; sig = sig->next)
  {					/* Finish hashes */
  uschar bh[32]; /* SHA-256 = 32 Bytes,  SHA-1 = 20 Bytes */

#ifdef SHA_GNUTLS
  gnutls_hash_output(sig->sha_body, bh);
#else
  if (sig->algo == PDKIM_ALGO_RSA_SHA1)
# ifdef SHA_OPENSSL
    SHA1_Final  (bh, &sig->sha1_body);
  else
    SHA256_Final(bh, &sig->sha2_body);
# elif defined(SHA_POLARSSL)
    sha1_finish(sig->sha1_body, bh);
  else
    sha2_finish(sig->sha2_body, bh);
# endif
#endif

  DEBUG(D_acl)
    {
    debug_printf("PDKIM [%s] Body bytes hashed: %lu\n"
		 "PDKIM [%s] bh  computed: ",
		sig->domain, sig->signed_body_bytes, sig->domain);
    pdkim_hexprint((char *)bh, sig->algo == PDKIM_ALGO_RSA_SHA1 ? 20 : 32, 1);
    }

  /* SIGNING -------------------------------------------------------------- */
  if (ctx->mode == PDKIM_MODE_SIGN)
    {
    sig->bodyhash_len = sig->algo == PDKIM_ALGO_RSA_SHA1 ? 20:32;
    sig->bodyhash = CS string_copyn(US bh, sig->bodyhash_len);

    /* If bodylength limit is set, and we have received less bytes
       than the requested amount, effectively remove the limit tag. */
    if (sig->signed_body_bytes < sig->bodylength)
      sig->bodylength = -1;
    }

  /* VERIFICATION --------------------------------------------------------- */
  else
    {
    /* Compare bodyhash */
    if (memcmp(bh, sig->bodyhash,
	       (sig->algo == PDKIM_ALGO_RSA_SHA1)?20:32) == 0)
      {
      DEBUG(D_acl) debug_printf("PDKIM [%s] Body hash verified OK\n", sig->domain);
      }
    else
      {
      DEBUG(D_acl)
        {
	debug_printf("PDKIM [%s] bh signature: ", sig->domain);
	pdkim_hexprint(sig->bodyhash,
			 sig->algo == PDKIM_ALGO_RSA_SHA1 ? 20 : 32, 1);
	debug_printf("PDKIM [%s] Body hash did NOT verify\n", sig->domain);
	}
      sig->verify_status     = PDKIM_VERIFY_FAIL;
      sig->verify_ext_status = PDKIM_VERIFY_FAIL_BODY;
      }
    }
  }

return PDKIM_OK;
}



/* -------------------------------------------------------------------------- */
/* Callback from pdkim_feed below for processing complete body lines */

static int
pdkim_bodyline_complete(pdkim_ctx *ctx)
{
char *p = ctx->linebuf;
int   n = ctx->linebuf_offset;
pdkim_signature *sig = ctx->sig;	/*XXX assumes only one sig */

/* Ignore extra data if we've seen the end-of-data marker */
if (ctx->seen_eod) goto BAIL;

/* We've always got one extra byte to stuff a zero ... */
ctx->linebuf[ctx->linebuf_offset] = '\0';

/* Terminate on EOD marker */
if (memcmp(p, ".\r\n", 3) == 0)
  {
  /* In simple body mode, if any empty lines were buffered,
  replace with one. rfc 4871 3.4.3 */
  /*XXX checking the signed-body-bytes is a gross hack; I think
  it indicates that all linebreaks should be buffered, including
  the one terminating a text line */
  if (  sig && sig->canon_body == PDKIM_CANON_SIMPLE
     && sig->signed_body_bytes == 0
     && ctx->num_buffered_crlf > 0
     )
    pdkim_update_bodyhash(ctx, "\r\n", 2);

  ctx->seen_eod = TRUE;
  goto BAIL;
  }
/* Unstuff dots */
if (memcmp(p, "..", 2) == 0)
  {
  p++;
  n--;
  }

/* Empty lines need to be buffered until we find a non-empty line */
if (memcmp(p, "\r\n", 2) == 0)
  {
  ctx->num_buffered_crlf++;
  goto BAIL;
  }

if (sig && sig->canon_body == PDKIM_CANON_RELAXED)
  {
  /* Lines with just spaces need to be buffered too */
  char *check = p;
  while (memcmp(check, "\r\n", 2) != 0)
    {
    char c = *check;

    if (c != '\t' && c != ' ')
      goto PROCESS;
    check++;
    }

  ctx->num_buffered_crlf++;
  goto BAIL;
}

PROCESS:
/* At this point, we have a non-empty line, so release the buffered ones. */
while (ctx->num_buffered_crlf)
  {
  pdkim_update_bodyhash(ctx, "\r\n", 2);
  ctx->num_buffered_crlf--;
  }

pdkim_update_bodyhash(ctx, p, n);

BAIL:
ctx->linebuf_offset = 0;
return PDKIM_OK;
}


/* -------------------------------------------------------------------------- */
/* Callback from pdkim_feed below for processing complete headers */
#define DKIM_SIGNATURE_HEADERNAME "DKIM-Signature:"

static int
pdkim_header_complete(pdkim_ctx *ctx)
{
/* Special case: The last header can have an extra \r appended */
if ( (ctx->cur_header->len > 1) &&
     (ctx->cur_header->str[(ctx->cur_header->len)-1] == '\r') )
  {
  ctx->cur_header->str[(ctx->cur_header->len)-1] = '\0';
  ctx->cur_header->len--;
  }

ctx->num_headers++;
if (ctx->num_headers > PDKIM_MAX_HEADERS) goto BAIL;

/* SIGNING -------------------------------------------------------------- */
if (ctx->mode == PDKIM_MODE_SIGN)
  {
  pdkim_signature *sig;

  for (sig = ctx->sig; sig; sig = sig->next)			/* Traverse all signatures */
    if (header_name_match(ctx->cur_header->str,
			  sig->sign_headers?
			    sig->sign_headers:
			    PDKIM_DEFAULT_SIGN_HEADERS, 0) == PDKIM_OK)
      {
      pdkim_stringlist *list;

      /* Add header to the signed headers list (in reverse order) */
      if (!(list = pdkim_prepend_stringlist(sig->headers,
				    ctx->cur_header->str)))
	return PDKIM_ERR_OOM;
      sig->headers = list;
      }
  }

/* VERIFICATION ----------------------------------------------------------- */
/* DKIM-Signature: headers are added to the verification list */
if (ctx->mode == PDKIM_MODE_VERIFY)
  {
  if (strncasecmp(ctx->cur_header->str,
		  DKIM_SIGNATURE_HEADERNAME,
		  strlen(DKIM_SIGNATURE_HEADERNAME)) == 0)
    {
    pdkim_signature *new_sig;

    /* Create and chain new signature block */
    DEBUG(D_acl) debug_printf(
	"PDKIM >> Found sig, trying to parse >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");

    if ((new_sig = pdkim_parse_sig_header(ctx, ctx->cur_header->str)))
      {
      pdkim_signature *last_sig = ctx->sig;
      if (!last_sig)
	ctx->sig = new_sig;
      else
        {
	while (last_sig->next) last_sig = last_sig->next;
	last_sig->next = new_sig;
	}
      }
    else
      DEBUG(D_acl) debug_printf(
	  "Error while parsing signature header\n"
	  "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
    }

  /* every other header is stored for signature verification */
  else
    {
    pdkim_stringlist *list;

    if (!(list = pdkim_prepend_stringlist(ctx->headers, ctx->cur_header->str)))
      return PDKIM_ERR_OOM;
    ctx->headers = list;
    }
  }

BAIL:
pdkim_strclear(ctx->cur_header); /* Re-use existing pdkim_str */
return PDKIM_OK;
}



/* -------------------------------------------------------------------------- */
#define HEADER_BUFFER_FRAG_SIZE 256

DLLEXPORT int
pdkim_feed (pdkim_ctx *ctx, char *data, int len)
{
int p;

for (p = 0; p<len; p++)
  {
  char c = data[p];

  if (ctx->past_headers)
    {
    /* Processing body byte */
    ctx->linebuf[ctx->linebuf_offset++] = c;
    if (c == '\n')
      {
      int rc = pdkim_bodyline_complete(ctx); /* End of line */
      if (rc != PDKIM_OK) return rc;
      }
    if (ctx->linebuf_offset == (PDKIM_MAX_BODY_LINE_LEN-1))
      return PDKIM_ERR_LONG_LINE;
    }
  else
    {
    /* Processing header byte */
    if (c != '\r')
      {
      if (c == '\n')
        {
	if (ctx->seen_lf)
	  {
	  int rc = pdkim_header_complete(ctx); /* Seen last header line */
	  if (rc != PDKIM_OK) return rc;

	  ctx->past_headers = TRUE;
	  ctx->seen_lf = 0;
	  DEBUG(D_acl) debug_printf(
	      "PDKIM >> Hashed body data, canonicalized >>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
	  continue;
	  }
	else
	  ctx->seen_lf = TRUE;
	}
      else if (ctx->seen_lf)
        {
	if (!(c == '\t' || c == ' '))
	  {
	  int rc = pdkim_header_complete(ctx); /* End of header */
	  if (rc != PDKIM_OK) return rc;
	  }
	ctx->seen_lf = FALSE;
	}
      }

    if (!ctx->cur_header)
      if (!(ctx->cur_header = pdkim_strnew(NULL)))
	return PDKIM_ERR_OOM;

    if (ctx->cur_header->len < PDKIM_MAX_HEADER_LEN)
      if (!pdkim_strncat(ctx->cur_header, &data[p], 1))
	return PDKIM_ERR_OOM;
    }
  }
return PDKIM_OK;
}

/*
 * RFC 5322 specifies that header line length SHOULD be no more than 78
 * lets make it so!
 *  pdkim_headcat
 * returns char*
 *
 * col: this int holds and receives column number (octets since last '\n')
 * str: partial string to append to
 * pad: padding, split line or space after before or after eg: ";"
 * intro: - must join to payload eg "h=", usually the tag name
 * payload: eg base64 data - long data can be split arbitrarily.
 *
 * this code doesn't fold the header in some of the places that RFC4871
 * allows: As per RFC5322(2.2.3) it only folds before or after tag-value
 * pairs and inside long values. it also always spaces or breaks after the
 * "pad"
 *
 * no guarantees are made for output given out-of range input. like tag
 * names longer than 78, or bogus col. Input is assumed to be free of line breaks.
 */

static char *
pdkim_headcat(int *col, pdkim_str *str, const char * pad,
  const char *intro, const char *payload)
{
size_t l;

if (pad)
  {
  l = strlen(pad);
  if (*col + l > 78)
    {
    pdkim_strcat(str, "\r\n\t");
    *col = 1;
    }
  pdkim_strncat(str, pad, l);
  *col += l;
  }

l = (pad?1:0) + (intro?strlen(intro):0);

if (*col + l > 78)
  { /*can't fit intro - start a new line to make room.*/
  pdkim_strcat(str, "\r\n\t");
  *col = 1;
  l = intro?strlen(intro):0;
  }

l += payload ? strlen(payload):0 ;

while (l>77)
  { /* this fragment will not fit on a single line */
  if (pad)
    {
    pdkim_strcat(str, " ");
    *col += 1;
    pad = NULL; /* only want this once */
    l--;
    }

  if (intro)
    {
    size_t sl = strlen(intro);

    pdkim_strncat(str, intro, sl);
    *col += sl;
    l -= sl;
    intro = NULL; /* only want this once */
    }

  if (payload)
    {
    size_t sl = strlen(payload);
    size_t chomp = *col+sl < 77 ? sl : 78-*col;

    pdkim_strncat(str, payload, chomp);
    *col += chomp;
    payload += chomp;
    l -= chomp-1;
    }

  /* the while precondition tells us it didn't fit. */
  pdkim_strcat(str, "\r\n\t");
  *col = 1;
  }

if (*col + l > 78)
  {
  pdkim_strcat(str, "\r\n\t");
  *col = 1;
  pad = NULL;
  }

if (pad)
  {
  pdkim_strcat(str, " ");
  *col += 1;
  pad = NULL;
  }

if (intro)
  {
  size_t sl = strlen(intro);

  pdkim_strncat(str, intro, sl);
  *col += sl;
  l -= sl;
  intro = NULL;
  }

if (payload)
  {
  size_t sl = strlen(payload);

  pdkim_strncat(str, payload, sl);
  *col += sl;
  }

return str->str;
}


/* -------------------------------------------------------------------------- */

static char *
pdkim_create_header(pdkim_signature *sig, int final)
{
char *rc = NULL;
char *base64_bh = NULL;
char *base64_b  = NULL;
int col = 0;
pdkim_str *hdr;
pdkim_str *canon_all;

if (!(hdr = pdkim_strnew("DKIM-Signature: v="PDKIM_SIGNATURE_VERSION)))
  return NULL;

if (!(canon_all = pdkim_strnew(pdkim_canons[sig->canon_headers])))
  goto BAIL;

if (!(base64_bh = pdkim_encode_base64(sig->bodyhash, sig->bodyhash_len)))
  goto BAIL;

col = strlen(hdr->str);

/* Required and static bits */
if (  pdkim_headcat(&col, hdr, ";", "a=", pdkim_algos[sig->algo])
   && pdkim_headcat(&col, hdr, ";", "q=", pdkim_querymethods[sig->querymethod])
   && pdkim_strcat(canon_all, "/")
   && pdkim_strcat(canon_all, pdkim_canons[sig->canon_body])
   && pdkim_headcat(&col, hdr, ";", "c=", canon_all->str)
   && pdkim_headcat(&col, hdr, ";", "d=", sig->domain)
   && pdkim_headcat(&col, hdr, ";", "s=", sig->selector)
   )
  {
  /* list of eader names can be split between items. */
    {
    char *n = strdup(sig->headernames);
    char *f = n;
    char *i = "h=";
    char *s = ";";

    if (!n) goto BAIL;
    while (*n)
      {
      char *c = strchr(n, ':');

      if (c) *c ='\0';

      if (!i)
	if (!pdkim_headcat(&col, hdr, NULL, NULL, ":"))
	  {
	  free(f);
	  goto BAIL;
	  }

      if (!pdkim_headcat(&col, hdr, s, i, n))
	{
	free(f);
	goto BAIL;
	}

      if (!c)
        break;

      n = c+1;
      s = NULL;
      i = NULL;
      }
    free(f);
    }

  if(!pdkim_headcat(&col, hdr, ";", "bh=", base64_bh))
    goto BAIL;

  /* Optional bits */
  if (sig->identity)
    if(!pdkim_headcat(&col, hdr, ";", "i=", sig->identity))
      goto BAIL;

  if (sig->created > 0)
    {
    char minibuf[20];

    snprintf(minibuf, 20, "%lu", sig->created);
    if(!pdkim_headcat(&col, hdr, ";", "t=", minibuf))
      goto BAIL;
  }

  if (sig->expires > 0)
    {
    char minibuf[20];

    snprintf(minibuf, 20, "%lu", sig->expires);
    if(!pdkim_headcat(&col, hdr, ";", "x=", minibuf))
      goto BAIL;
    }

  if (sig->bodylength >= 0)
    {
    char minibuf[20];

    snprintf(minibuf, 20, "%lu", sig->bodylength);
    if(!pdkim_headcat(&col, hdr, ";", "l=", minibuf))
      goto BAIL;
    }

  /* Preliminary or final version? */
  if (final)
    {
    if (!(base64_b = pdkim_encode_base64(sig->sigdata, sig->sigdata_len)))
      goto BAIL;
    if (!pdkim_headcat(&col, hdr, ";", "b=", base64_b))
      goto BAIL;
  }
  else 
    if(!pdkim_headcat(&col, hdr, ";", "b=", ""))
      goto BAIL;

  /* add trailing semicolon: I'm not sure if this is actually needed */
  if (!pdkim_headcat(&col, hdr, NULL, ";", ""))
    goto BAIL;
  }

rc = strdup(hdr->str);

BAIL:
pdkim_strfree(hdr);
if (canon_all) pdkim_strfree(canon_all);
return rc;
}


/* -------------------------------------------------------------------------- */

DLLEXPORT int
pdkim_feed_finish(pdkim_ctx *ctx, pdkim_signature **return_signatures)
{
pdkim_signature *sig = ctx->sig;
pdkim_str *headernames = NULL;             /* Collected signed header names */

/* Check if we must still flush a (partial) header. If that is the
   case, the message has no body, and we must compute a body hash
   out of '<CR><LF>' */
if (ctx->cur_header && ctx->cur_header->len)
  {
  int rc = pdkim_header_complete(ctx);
  if (rc != PDKIM_OK) return rc;
  pdkim_update_bodyhash(ctx, "\r\n", 2);
  }
else
  DEBUG(D_acl) debug_printf(
      "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");

/* Build (and/or evaluate) body hash */
if (pdkim_finish_bodyhash(ctx) != PDKIM_OK)
  return PDKIM_ERR_OOM;

/* SIGNING -------------------------------------------------------------- */
if (ctx->mode == PDKIM_MODE_SIGN)
  if (!(headernames = pdkim_strnew(NULL)))
    return PDKIM_ERR_OOM;
/* ---------------------------------------------------------------------- */

while (sig)
  {
#ifdef SHA_OPENSSL
  SHA_CTX    sha1_headers;
  SHA256_CTX sha2_headers;
#elif defined(SHA_GNUTLS)
  gnutls_hash_hd_t sha_headers;
#elif defined(SHA_POLARSSL)
  sha1_context sha1_headers;
  sha2_context sha2_headers;
#endif

  char *sig_hdr;
  char headerhash[32];

#ifdef RSA_GNUTLS
  uschar * hdata = NULL;
  int hdata_alloc = 0;
  int hdata_size = 0;
#endif

#ifdef SHA_GNUTLS
  gnutls_hash_init(&sha_headers,
    sig->algo == PDKIM_ALGO_RSA_SHA1 ? GNUTLS_DIG_SHA1 : GNUTLS_DIG_SHA256);
#else
  if (sig->algo == PDKIM_ALGO_RSA_SHA1)
# ifdef SHA_OPENSSL
    SHA1_Init(&sha1_headers);
  else
    SHA256_Init(&sha2_headers);
# elif defined(SHA_POLARSSL)
    sha1_starts(&sha1_headers);
  else
    sha2_starts(&sha2_headers, 0);
# endif
#endif

  DEBUG(D_acl) debug_printf(
      "PDKIM >> Hashed header data, canonicalized, in sequence >>>>>>>>>>>>>>\n");

  /* SIGNING ---------------------------------------------------------------- */
  /* When signing, walk through our header list and add them to the hash. As we
     go, construct a list of the header's names to use for the h= parameter. */

  if (ctx->mode == PDKIM_MODE_SIGN)
    {
    pdkim_stringlist *p;

    for (p = sig->headers; p; p = p->next)
      {
      char *rh = NULL;
      /* Collect header names (Note: colon presence is guaranteed here) */
      char *q = strchr(p->value, ':');

      if (!(pdkim_strncat(headernames, p->value,
			(q-(p->value)) + (p->next ? 1 : 0))))
	return PDKIM_ERR_OOM;

      rh = sig->canon_headers == PDKIM_CANON_RELAXED
	? pdkim_relax_header(p->value, 1) /* cook header for relaxed canon */
	: strdup(p->value);              /* just copy it for simple canon */
      if (!rh)
	return PDKIM_ERR_OOM;

      /* Feed header to the hash algorithm */
#ifdef SHA_GNUTLS
      gnutls_hash(sha_headers, rh, strlen(rh));
#else
      if (sig->algo == PDKIM_ALGO_RSA_SHA1)
# ifdef SHA_OPENSSL
	SHA1_Update  (&sha1_headers, rh, strlen(rh));
      else
	SHA256_Update(&sha2_headers, rh, strlen(rh));
# elif defined(SHA_POLARSSL)
	sha1_update(&sha1_headers, US rh, strlen(rh));
      else
	sha2_update(&sha2_headers, US rh, strlen(rh));
# endif
#endif

#ifdef RSA_GNUTLS
      /* Remember headers block for signing */
      hdata = string_append(hdata, &hdata_alloc, &hdata_size, 1, rh);
#endif

      DEBUG(D_acl) pdkim_quoteprint(rh, strlen(rh), 1);
      free(rh);
      }
    }

  /* VERIFICATION ----------------------------------------------------------- */
  /* When verifying, walk through the header name list in the h= parameter and
     add the headers to the hash in that order. */
  else
    {
    char *b = strdup(sig->headernames);
    char *p = b;
    char *q = NULL;
    pdkim_stringlist *hdrs;

    if (!b) return PDKIM_ERR_OOM;

    /* clear tags */
    for (hdrs = ctx->headers; hdrs; hdrs = hdrs->next)
      hdrs->tag = 0;

    while(1)
      {
      if ((q = strchr(p, ':')))
	*q = '\0';

      for (hdrs = ctx->headers; hdrs; hdrs = hdrs->next)
	if (  hdrs->tag == 0
	   && strncasecmp(hdrs->value, p, strlen(p)) == 0
	   && (hdrs->value)[strlen(p)] == ':'
	   )
	  {
	  char *rh;

	  rh = sig->canon_headers == PDKIM_CANON_RELAXED
	    ? pdkim_relax_header(hdrs->value, 1) /* cook header for relaxed canon */
	    : strdup(hdrs->value);               /* just copy it for simple canon */
	  if (!rh)
	    return PDKIM_ERR_OOM;

	  /* Feed header to the hash algorithm */
#ifdef SHA_GNUTLS
	  gnutls_hash(sha_headers, rh, strlen(rh));
#else
	  if (sig->algo == PDKIM_ALGO_RSA_SHA1)
# ifdef SHA_OPENSSL
	    SHA1_Update  (&sha1_headers, rh, strlen(rh));
	  else
	    SHA256_Update(&sha2_headers, rh, strlen(rh));
# elif defined(SHA_POLARSSL)
	    sha1_update(&sha1_headers, US rh, strlen(rh));
	  else
	    sha2_update(&sha2_headers, US rh, strlen(rh));
# endif
#endif

	  DEBUG(D_acl) pdkim_quoteprint(rh, strlen(rh), 1);
	  free(rh);
	  hdrs->tag = 1;
	  break;
	  }

      if (!q) break;
      p = q+1;
      }
    free(b);
    }

  DEBUG(D_acl) debug_printf(
	    "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");

  /* SIGNING ---------------------------------------------------------------- */
  if (ctx->mode == PDKIM_MODE_SIGN)
    {
    /* Copy headernames to signature struct */
    sig->headernames = strdup(headernames->str);
    pdkim_strfree(headernames);

    /* Create signature header with b= omitted */
    sig_hdr = pdkim_create_header(ctx->sig, 0);
    }

  /* VERIFICATION ----------------------------------------------------------- */
  else
    sig_hdr = strdup(sig->rawsig_no_b_val);
  /* ------------------------------------------------------------------------ */

  if (!sig_hdr)
    return PDKIM_ERR_OOM;

  /* Relax header if necessary */
  if (sig->canon_headers == PDKIM_CANON_RELAXED)
    {
    char *relaxed_hdr = pdkim_relax_header(sig_hdr, 0);

    free(sig_hdr);
    if (!relaxed_hdr)
      return PDKIM_ERR_OOM;
    sig_hdr = relaxed_hdr;
    }

  DEBUG(D_acl)
    {
    debug_printf(
	    "PDKIM >> Signed DKIM-Signature header, canonicalized >>>>>>>>>>>>>>>>>\n");
    pdkim_quoteprint(sig_hdr, strlen(sig_hdr), 1);
    debug_printf(
	    "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
    }

  /* Finalize header hash */
#ifdef SHA_GNUTLS
  gnutls_hash(sha_headers, sig_hdr, strlen(sig_hdr));
  gnutls_hash_output(sha_headers, headerhash);
#else
  if (sig->algo == PDKIM_ALGO_RSA_SHA1)
# ifdef SHA_OPENSSL
    {
    SHA1_Update(&sha1_headers, sig_hdr, strlen(sig_hdr));
    SHA1_Final(US headerhash, &sha1_headers);
    }
  else
    {
    SHA256_Update(&sha2_headers, sig_hdr, strlen(sig_hdr));
    SHA256_Final(US headerhash, &sha2_headers);
    }
# elif defined(SHA_POLARSSL)
    {
    sha1_update(&sha1_headers, US sig_hdr, strlen(sig_hdr));
    sha1_finish(&sha1_headers, US headerhash);
    }
  else
    {
    sha2_update(&sha2_headers, US sig_hdr, strlen(sig_hdr));
    sha2_finish(&sha2_headers, US headerhash);
    }
# endif
#endif

  DEBUG(D_acl)
    {
    debug_printf("PDKIM [%s] hh computed: ", sig->domain);
    pdkim_hexprint(headerhash, sig->algo == PDKIM_ALGO_RSA_SHA1 ? 20:32, 1);
    }

#ifdef RSA_GNUTLS
  if (ctx->mode == PDKIM_MODE_SIGN)
    hdata = string_append(hdata, &hdata_alloc, &hdata_size, 1, sig_hdr);
#endif

  free(sig_hdr);

  /* SIGNING ---------------------------------------------------------------- */
  if (ctx->mode == PDKIM_MODE_SIGN)
    {
#ifdef RSA_OPENSSL
    RSA * rsa;
    uschar * p, * q;
    int len;
#elif defined(RSA_GNUTLS)
    gnutls_x509_privkey_t rsa;
    gnutls_datum_t k;
    int rc;
    size_t sigsize;
#endif

    /* Import private key */
#ifdef RSA_OPENSSL

    if (  !(p = Ustrstr(sig->rsa_privkey, "-----BEGIN RSA PRIVATE KEY-----"))
       || !(q = Ustrstr(p+=31, "-----END RSA PRIVATE KEY-----"))
       )
      return PDKIM_SIGN_PRIVKEY_WRAP;
    *q = '\0';
    if ((len = b64decode(p, &p)) < 0)
      {
      DEBUG(D_acl) debug_printf("b64decode failed\n");
      return PDKIM_SIGN_PRIVKEY_B64D;
      }
    if (!(rsa = d2i_RSAPrivateKey(NULL, CUSS &p, len)))
      {
      DEBUG(D_acl)
	{
	char ssl_errstring[256];
	ERR_error_string(ERR_get_error(), ssl_errstring);
	debug_printf("d2i_RSAPrivateKey: %s\n", ssl_errstring);
	}
      return PDKIM_ERR_RSA_PRIVKEY;
      }

#elif defined(RSA_GNUTLS)

    k.data = sig->rsa_privkey;
    k.size = strlen(sig->rsa_privkey);
    if (  (rc = gnutls_x509_privkey_init(&rsa)) != GNUTLS_E_SUCCESS
       || (rc = gnutls_x509_privkey_import2(rsa, &k,
	      GNUTLS_X509_FMT_PEM, NULL, GNUTLS_PKCS_PLAIN)) != GNUTLS_E_SUCCESS
       )
      {
      DEBUG(D_acl) debug_printf("gnutls_x509_privkey_import2: %s\n",
	gnutls_strerror(rc));
      return PDKIM_ERR_RSA_PRIVKEY;
      }

#endif


    /* Allocate mem for signature */
#ifdef RSA_OPENSSL
    sig->sigdata = store_get(RSA_size(rsa));
#elif defined(RSA_GNUTLS)
    k.data = hdata;
    k.size = hdata_size;
    (void) gnutls_x509_privkey_sign_data(rsa,
      sig->algo == PDKIM_ALGO_RSA_SHA1 ? GNUTLS_DIG_SHA1 : GNUTLS_DIG_SHA256,
      0, &k, NULL, &sigsize);
    sig->sigdata = store_get(sig->sigdata_len = sigsize);
#endif

    /* Do signing */
#ifdef RSA_OPENSSL

    if (RSA_sign(sig->algo == PDKIM_ALGO_RSA_SHA1 ? NID_sha1 : NID_sha256,
	  CUS headerhash, sig->algo == PDKIM_ALGO_RSA_SHA1 ? 20 : 32,
	  US sig->sigdata, (unsigned int *)&sig->sigdata_len,
	  rsa) != 1)
      return PDKIM_ERR_RSA_SIGNING;
    RSA_free(rsa);

#elif defined(RSA_GNUTLS)

    if ((rc = gnutls_x509_privkey_sign_data(rsa,
	  sig->algo == PDKIM_ALGO_RSA_SHA1 ? GNUTLS_DIG_SHA1 : GNUTLS_DIG_SHA256,
	  0, &k, sig->sigdata, &sigsize)) != GNUTLS_E_SUCCESS
       )
      {
      DEBUG(D_acl) debug_printf("gnutls_x509_privkey_sign_data: %s\n",
	gnutls_strerror(rc));
      return PDKIM_ERR_RSA_SIGNING;
      }
    gnutls_x509_privkey_deinit(rsa);

#endif


    DEBUG(D_acl)
      {
      debug_printf( "PDKIM [%s] b computed: ", sig->domain);
      pdkim_hexprint(sig->sigdata, sig->sigdata_len, 1);
      }

    if (!(sig->signature_header = pdkim_create_header(ctx->sig, 1)))
      return PDKIM_ERR_OOM;
    }

  /* VERIFICATION ----------------------------------------------------------- */
  else
    {
#ifdef RSA_OPENSSL
    RSA * rsa;
    const unsigned char * p;
#elif defined(RSA_GNUTLS)
    gnutls_pubkey_t rsa;
    gnutls_datum_t k, s;
    int rc;
#endif
    char *dns_txt_name, *dns_txt_reply;

#ifdef RSA_GNUTLS
    gnutls_pubkey_init(&rsa);
#endif

    /* Fetch public key for signing domain, from DNS */

    if (!(dns_txt_name  = malloc(PDKIM_DNS_TXT_MAX_NAMELEN)))
      return PDKIM_ERR_OOM;

    if (!(dns_txt_reply = malloc(PDKIM_DNS_TXT_MAX_RECLEN)))
      {
      free(dns_txt_name);
      return PDKIM_ERR_OOM;
      }

    memset(dns_txt_reply, 0, PDKIM_DNS_TXT_MAX_RECLEN);
    memset(dns_txt_name , 0, PDKIM_DNS_TXT_MAX_NAMELEN);

    if (snprintf(dns_txt_name, PDKIM_DNS_TXT_MAX_NAMELEN,
		 "%s._domainkey.%s.",
		 sig->selector, sig->domain) >= PDKIM_DNS_TXT_MAX_NAMELEN)
      {
      sig->verify_status =      PDKIM_VERIFY_INVALID;
      sig->verify_ext_status =  PDKIM_VERIFY_INVALID_BUFFER_SIZE;
      goto NEXT_VERIFY;
      }

    if (  ctx->dns_txt_callback(dns_txt_name, dns_txt_reply) != PDKIM_OK 
       || dns_txt_reply[0] == '\0')
      {
      sig->verify_status =      PDKIM_VERIFY_INVALID;
      sig->verify_ext_status =  PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE;
      goto NEXT_VERIFY;
      }

    DEBUG(D_acl)
      {
      debug_printf(
	      "PDKIM >> Parsing public key record >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"
	      " Raw record: ");
      pdkim_quoteprint(dns_txt_reply, strlen(dns_txt_reply), 1);
      }

    if (!(sig->pubkey = pdkim_parse_pubkey_record(ctx, dns_txt_reply)))
      {
      sig->verify_status =      PDKIM_VERIFY_INVALID;
      sig->verify_ext_status =  PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD;

      DEBUG(D_acl) debug_printf(
	  " Error while parsing public key record\n"
	  "PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");
      goto NEXT_VERIFY;
      }

    DEBUG(D_acl) debug_printf(
	"PDKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n");

    /* Import public key */
#ifdef RSA_OPENSSL

    p = CUS sig->pubkey->key;
    if (!(rsa = d2i_RSA_PUBKEY(NULL, &p, (long) sig->pubkey->key_len)))

#elif defined(RSA_GNUTLS)

    k.data = sig->pubkey->key;
    k.size = sig->pubkey->key_len;
    if ((rc = gnutls_pubkey_import(rsa, &k, GNUTLS_X509_FMT_DER))
       != GNUTLS_E_SUCCESS)

#endif
      {
      DEBUG(D_acl)
	{
#ifdef RSA_OPENSSL
	long e;
	ERR_load_crypto_strings();	/*XXX move to a startup routine */
	while ((e = ERR_get_error()))
	  debug_printf("Az: %.120s\n", ERR_error_string(e, NULL));
#elif defined(RSA_GNUTLS)
	debug_printf("gnutls_pubkey_import: %s\n", gnutls_strerror(rc));
#endif
	}

      sig->verify_status =      PDKIM_VERIFY_INVALID;
      sig->verify_ext_status =  PDKIM_VERIFY_INVALID_PUBKEY_IMPORT;
      goto NEXT_VERIFY;
      }

    /* Check the signature */
#ifdef RSA_OPENSSL

    if (RSA_verify(sig->algo == PDKIM_ALGO_RSA_SHA1 ? NID_sha1 : NID_sha256,
	  CUS headerhash, sig->algo == PDKIM_ALGO_RSA_SHA1 ? 20 : 32,
	  US sig->sigdata, (unsigned int)sig->sigdata_len,
	  rsa) != 1)

#elif defined(RSA_GNUTLS)

    k.data = headerhash;
    k.size = sig->algo == PDKIM_ALGO_RSA_SHA1 ? 20 : 32;
    s.data = sig->sigdata;
    s.size = sig->sigdata_len;
    if ((rc = gnutls_pubkey_verify_hash2(rsa,
		sig->algo == PDKIM_ALGO_RSA_SHA1
		  ? GNUTLS_SIGN_RSA_SHA1 : GNUTLS_SIGN_RSA_SHA256,
		0, &k, &s)) < 0)

#endif
      {
#if defined(RSA_GNUTLS)
      debug_printf("gnutls_pubkey_verify_hash2: %s\n", gnutls_strerror(rc));
#endif
      sig->verify_status =      PDKIM_VERIFY_FAIL;
      sig->verify_ext_status =  PDKIM_VERIFY_FAIL_MESSAGE;
      goto NEXT_VERIFY;
      }

    /* We have a winner! (if bodydhash was correct earlier) */
    if (sig->verify_status == PDKIM_VERIFY_NONE)
      sig->verify_status = PDKIM_VERIFY_PASS;

NEXT_VERIFY:

    DEBUG(D_acl)
      {
      debug_printf("PDKIM [%s] signature status: %s",
	      sig->domain, pdkim_verify_status_str(sig->verify_status));
      if (sig->verify_ext_status > 0)
	debug_printf(" (%s)\n",
		pdkim_verify_ext_status_str(sig->verify_ext_status));
      else
	debug_printf("\n");
      }

#ifdef RSA_GNUTLS
    gnutls_pubkey_deinit(rsa);
#endif
    free(dns_txt_name);
    free(dns_txt_reply);
    }

  sig = sig->next;
  }

/* If requested, set return pointer to signature(s) */
if (return_signatures)
  *return_signatures = ctx->sig;

return PDKIM_OK;
}


/* -------------------------------------------------------------------------- */

DLLEXPORT pdkim_ctx *
pdkim_init_verify(int(*dns_txt_callback)(char *, char *))
{
pdkim_ctx *ctx = malloc(sizeof(pdkim_ctx));

if (!ctx)
  return NULL;
memset(ctx, 0, sizeof(pdkim_ctx));

if (!(ctx->linebuf = malloc(PDKIM_MAX_BODY_LINE_LEN)))
  {
  free(ctx);
  return NULL;
  }

ctx->mode = PDKIM_MODE_VERIFY;
ctx->dns_txt_callback = dns_txt_callback;

return ctx;
}


/* -------------------------------------------------------------------------- */

DLLEXPORT pdkim_ctx *
pdkim_init_sign(char *domain, char *selector, char *rsa_privkey, int algo)
{
pdkim_ctx *ctx;
pdkim_signature *sig;

if (!domain || !selector || !rsa_privkey)
  return NULL;

if (!(ctx = malloc(sizeof(pdkim_ctx))))
  return NULL;
memset(ctx, 0, sizeof(pdkim_ctx));

if (!(ctx->linebuf = malloc(PDKIM_MAX_BODY_LINE_LEN)))
  {
  free(ctx);
  return NULL;
  }

if (!(sig = malloc(sizeof(pdkim_signature))))
  {
  free(ctx->linebuf);
  free(ctx);
  return NULL;
  }
memset(sig, 0, sizeof(pdkim_signature));

sig->bodylength = -1;

ctx->mode = PDKIM_MODE_SIGN;
ctx->sig = sig;

ctx->sig->domain = strdup(domain);
ctx->sig->selector = strdup(selector);
ctx->sig->rsa_privkey = strdup(rsa_privkey);
ctx->sig->algo = algo;

if (!ctx->sig->domain || !ctx->sig->selector || !ctx->sig->rsa_privkey)
  goto BAIL;

#ifdef SHA_OPENSSL
SHA1_Init  (&ctx->sig->sha1_body);
SHA256_Init(&ctx->sig->sha2_body);

#elif defined(SHA_GNUTLS)
gnutls_hash_init(&ctx->sig->sha_body,
    algo == PDKIM_ALGO_RSA_SHA1 ? GNUTLS_DIG_SHA1 : GNUTLS_DIG_SHA256);

#elif defined(SHA_POLARSSL)
if (!(ctx->sig->sha1_body = malloc(sizeof(sha1_context))))
  goto BAIL;
sha1_starts(ctx->sig->sha1_body);

if (!(ctx->sig->sha2_body = malloc(sizeof(sha2_context))))
  goto BAIL;
sha2_starts(ctx->sig->sha2_body, 0);

#endif

return ctx;

BAIL:
  pdkim_free_ctx(ctx);
  return NULL;
}


/* -------------------------------------------------------------------------- */

DLLEXPORT int
pdkim_set_optional(pdkim_ctx *ctx,
                       char *sign_headers,
                       char *identity,
                       int canon_headers,
                       int canon_body,
                       long bodylength,
                       unsigned long created,
                       unsigned long expires)
{
if (identity)
  if (!(ctx->sig->identity = strdup(identity)))
    return PDKIM_ERR_OOM;

if (sign_headers)
  if (!(ctx->sig->sign_headers = strdup(sign_headers)))
    return PDKIM_ERR_OOM;

ctx->sig->canon_headers = canon_headers;
ctx->sig->canon_body = canon_body;
ctx->sig->bodylength = bodylength;
ctx->sig->created = created;
ctx->sig->expires = expires;

return PDKIM_OK;
}


#endif	/*DISABLE_DKIM*/