Add interface documentation for the DANE library

[exim.git] / src / src / dane-openssl.c

#include <stdio.h>
#include <string.h>
#include <stdint.h>

#include <openssl/opensslv.h>
#include <openssl/err.h>
#include <openssl/crypto.h>
#include <openssl/safestack.h>
#include <openssl/objects.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <openssl/evp.h>

#if OPENSSL_VERSION_NUMBER < 0x1000000fL
# error "OpenSSL 1.0.0 or higher required"
#else   /* remainder of file */

#include "danessl.h"

#define DANE_F_ADD_SKID                 100
#define DANE_F_CHECK_END_ENTITY         101
#define DANE_F_GROW_CHAIN               102
#define DANE_F_LIST_ALLOC               103
#define DANE_F_MATCH                    104
#define DANE_F_PUSH_EXT                 105
#define DANE_F_SET_TRUST_ANCHOR         106
#define DANE_F_SSL_CTX_DANE_INIT        107
#define DANE_F_SSL_DANE_ADD_TLSA        108
#define DANE_F_SSL_DANE_INIT            109
#define DANE_F_SSL_DANE_LIBRARY_INIT    110
#define DANE_F_VERIFY_CERT              111
#define DANE_F_WRAP_CERT                112

#define DANE_R_BAD_CERT                 100
#define DANE_R_BAD_CERT_PKEY            101
#define DANE_R_BAD_DATA_LENGTH          102
#define DANE_R_BAD_DIGEST               103
#define DANE_R_BAD_NULL_DATA            104
#define DANE_R_BAD_PKEY                 105
#define DANE_R_BAD_SELECTOR             106
#define DANE_R_BAD_USAGE                107
#define DANE_R_DANE_INIT                108
#define DANE_R_DANE_SUPPORT             109
#define DANE_R_LIBRARY_INIT             110
#define DANE_R_NOSIGN_KEY               111
#define DANE_R_SCTX_INIT                112

#ifndef OPENSSL_NO_ERR
# define DANE_F_PLACEHOLDER              0               /* FIRST! Value TBD */
static ERR_STRING_DATA dane_str_functs[] =
{
    {DANE_F_PLACEHOLDER,                "DANE library"},        /* FIRST!!! */
    {DANE_F_ADD_SKID,                   "add_skid"},
    {DANE_F_CHECK_END_ENTITY,           "check_end_entity"},
    {DANE_F_GROW_CHAIN,                 "grow_chain"},
    {DANE_F_LIST_ALLOC,                 "list_alloc"},
    {DANE_F_MATCH,                      "match"},
    {DANE_F_PUSH_EXT,                   "push_ext"},
    {DANE_F_SET_TRUST_ANCHOR,           "set_trust_anchor"},
    {DANE_F_SSL_CTX_DANE_INIT,          "SSL_CTX_dane_init"},
    {DANE_F_SSL_DANE_ADD_TLSA,          "SSL_dane_add_tlsa"},
    {DANE_F_SSL_DANE_INIT,              "SSL_dane_init"},
    {DANE_F_SSL_DANE_LIBRARY_INIT,      "SSL_dane_library_init"},
    {DANE_F_VERIFY_CERT,                "verify_cert"},
    {DANE_F_WRAP_CERT,                  "wrap_cert"},
    {0,                                 NULL}
};
static ERR_STRING_DATA dane_str_reasons[] =
{
    {DANE_R_BAD_CERT,           "Bad TLSA record certificate"},
    {DANE_R_BAD_CERT_PKEY,      "Bad TLSA record certificate public key"},
    {DANE_R_BAD_DATA_LENGTH,    "Bad TLSA record digest length"},
    {DANE_R_BAD_DIGEST,         "Bad TLSA record digest"},
    {DANE_R_BAD_NULL_DATA,      "Bad TLSA record null data"},
    {DANE_R_BAD_PKEY,           "Bad TLSA record public key"},
    {DANE_R_BAD_SELECTOR,       "Bad TLSA record selector"},
    {DANE_R_BAD_USAGE,          "Bad TLSA record usage"},
    {DANE_R_DANE_INIT,          "SSL_dane_init() required"},
    {DANE_R_DANE_SUPPORT,       "DANE library features not supported"},
    {DANE_R_LIBRARY_INIT,       "SSL_dane_library_init() required"},
    {DANE_R_SCTX_INIT,          "SSL_CTX_dane_init() required"},
    {DANE_R_NOSIGN_KEY,         "Certificate usage 2 requires EC support"},
    {0,                         NULL}
};
#endif  /*OPENSSL_NO_ERR*/

#define DANEerr(f, r) ERR_PUT_error(err_lib_dane, (f), (r), __FILE__, __LINE__)

static int err_lib_dane = -1;
static int dane_idx = -1;

#ifdef X509_V_FLAG_PARTIAL_CHAIN       /* OpenSSL >= 1.0.2 */
static int wrap_to_root = 0;
#else
static int wrap_to_root = 1;
#endif

static void (*cert_free)(void *) = (void (*)(void *)) X509_free;
static void (*pkey_free)(void *) = (void (*)(void *)) EVP_PKEY_free;

typedef struct dane_list
{
    struct dane_list *next;
    void *value;
} *dane_list;

#define LINSERT(h, e) do { (e)->next = (h); (h) = (e); } while (0)

typedef struct dane_host_list
{
    struct dane_host_list *next;
    char *value;
} *dane_host_list;

typedef struct dane_data
{
    size_t datalen;
    unsigned char data[0];
} *dane_data;

typedef struct dane_data_list
{
    struct dane_data_list *next;
    dane_data value;
} *dane_data_list;

typedef struct dane_mtype
{
    int mdlen;
    const EVP_MD *md;
    dane_data_list data;
} *dane_mtype;

typedef struct dane_mtype_list
{
    struct dane_mtype_list *next;
    dane_mtype value;
} *dane_mtype_list;

typedef struct dane_selector
{
    uint8_t selector;
    dane_mtype_list mtype;
} *dane_selector;

typedef struct dane_selector_list
{
    struct dane_selector_list *next;
    dane_selector value;
} *dane_selector_list;

typedef struct dane_pkey_list
{
    struct dane_pkey_list *next;
    EVP_PKEY *value;
} *dane_pkey_list;

typedef struct dane_cert_list
{
    struct dane_cert_list *next;
    X509 *value;
} *dane_cert_list;

typedef struct ssl_dane
{
    int            (*verify)(X509_STORE_CTX *);
    STACK_OF(X509) *roots;
    STACK_OF(X509) *chain;
    const char     *thost;              /* TLSA base domain */
    char           *mhost;              /* Matched, peer name */
    dane_pkey_list pkeys;
    dane_cert_list certs;
    dane_host_list hosts;
    dane_selector_list selectors[SSL_DANE_USAGE_LAST + 1];
    int            depth;
    int            multi;               /* Multi-label wildcards? */
    int            count;               /* Number of TLSA records */
} ssl_dane;

#ifndef X509_V_ERR_HOSTNAME_MISMATCH
# define X509_V_ERR_HOSTNAME_MISMATCH X509_V_ERR_APPLICATION_VERIFICATION
#endif

static int
match(dane_selector_list slist, X509 *cert, int depth)
{
int matched;

/*
 * Note, set_trust_anchor() needs to know whether the match was for a
 * pkey digest or a certificate digest.  We return MATCHED_PKEY or
 * MATCHED_CERT accordingly.
 */
#define MATCHED_CERT (SSL_DANE_SELECTOR_CERT + 1)
#define MATCHED_PKEY (SSL_DANE_SELECTOR_SPKI + 1)

/*
 * Loop over each selector, mtype, and associated data element looking
 * for a match.
 */
for(matched = 0; !matched && slist; slist = slist->next)
  {
  dane_mtype_list m;
  unsigned char mdbuf[EVP_MAX_MD_SIZE];
  unsigned char *buf;
  unsigned char *buf2;
  unsigned int len;

  /*
   * Extract ASN.1 DER form of certificate or public key.
   */
  switch(slist->value->selector)
    {
    case SSL_DANE_SELECTOR_CERT:
      len = i2d_X509(cert, NULL);
      buf2 = buf = (unsigned char *) OPENSSL_malloc(len);
      if(buf) i2d_X509(cert, &buf2);
      break;
    case SSL_DANE_SELECTOR_SPKI:
      len = i2d_X509_PUBKEY(X509_get_X509_PUBKEY(cert), NULL);
      buf2 = buf = (unsigned char *) OPENSSL_malloc(len);
      if(buf) i2d_X509_PUBKEY(X509_get_X509_PUBKEY(cert), &buf2);
      break;
    }

  if(!buf)
    {
    DANEerr(DANE_F_MATCH, ERR_R_MALLOC_FAILURE);
    return 0;
    }
  OPENSSL_assert(buf2 - buf == len);

  /*
   * Loop over each mtype and data element
   */
  for(m = slist->value->mtype; !matched && m; m = m->next)
    {
    dane_data_list d;
    unsigned char *cmpbuf = buf;
    unsigned int cmplen = len;

    /*
     * If it is a digest, compute the corresponding digest of the
     * DER data for comparison, otherwise, use the full object.
     */
    if(m->value->md)
      {
      cmpbuf = mdbuf;
      if(!EVP_Digest(buf, len, cmpbuf, &cmplen, m->value->md, 0))
          matched = -1;
      }
    for(d = m->value->data; !matched && d; d = d->next)
        if(  cmplen == d->value->datalen
          && memcmp(cmpbuf, d->value->data, cmplen) == 0)
            matched = slist->value->selector + 1;
    }

  OPENSSL_free(buf);
  }

return matched;
}

static int
push_ext(X509 *cert, X509_EXTENSION *ext)
{
X509_EXTENSIONS *exts;

if(ext)
  {
  if(!(exts = cert->cert_info->extensions))
    exts = cert->cert_info->extensions = sk_X509_EXTENSION_new_null();
  if (exts && sk_X509_EXTENSION_push(exts, ext))
    return 1;
  X509_EXTENSION_free(ext);
  }
DANEerr(DANE_F_PUSH_EXT, ERR_R_MALLOC_FAILURE);
return 0;
}

static int
add_ext(X509 *issuer, X509 *subject, int ext_nid, char *ext_val)
{
X509V3_CTX v3ctx;

X509V3_set_ctx(&v3ctx, issuer, subject, 0, 0, 0);
return push_ext(subject, X509V3_EXT_conf_nid(0, &v3ctx, ext_nid, ext_val));
}

static int
set_serial(X509 *cert, AUTHORITY_KEYID *akid, X509 *subject)
{
int ret = 0;
BIGNUM *bn;

if(akid && akid->serial)
  return (X509_set_serialNumber(cert, akid->serial));

/*
 * Add one to subject's serial to avoid collisions between TA serial and
 * serial of signing root.
 */
if(  (bn = ASN1_INTEGER_to_BN(X509_get_serialNumber(subject), 0)) != 0
  && BN_add_word(bn, 1)
  && BN_to_ASN1_INTEGER(bn, X509_get_serialNumber(cert)))
  ret = 1;

if(bn)
  BN_free(bn);
return ret;
}

static int
add_akid(X509 *cert, AUTHORITY_KEYID *akid)
{
int nid = NID_authority_key_identifier;
ASN1_STRING *id;
unsigned char c = 0;
int ret = 0;

/*
 * 0 will never be our subject keyid from a SHA-1 hash, but it could be
 * our subject keyid if forced from child's akid.  If so, set our
 * authority keyid to 1.  This way we are never self-signed, and thus
 * exempt from any potential (off by default for now in OpenSSL)
 * self-signature checks!
 */
id = (ASN1_STRING *) ((akid && akid->keyid) ? akid->keyid : 0);
if(id && M_ASN1_STRING_length(id) == 1 && *M_ASN1_STRING_data(id) == c)
  c = 1;

if(  (akid = AUTHORITY_KEYID_new()) != 0
  && (akid->keyid = ASN1_OCTET_STRING_new()) != 0
  && M_ASN1_OCTET_STRING_set(akid->keyid, (void *) &c, 1)
  && X509_add1_ext_i2d(cert, nid, akid, 0, X509V3_ADD_APPEND))
  ret = 1;
if(akid)
  AUTHORITY_KEYID_free(akid);
return ret;
}

static int
add_skid(X509 *cert, AUTHORITY_KEYID *akid)
{
int nid = NID_subject_key_identifier;

if(!akid || !akid->keyid)
  return add_ext(0, cert, nid, "hash");
return X509_add1_ext_i2d(cert, nid, akid->keyid, 0, X509V3_ADD_APPEND) > 0;
}

static X509_NAME *
akid_issuer_name(AUTHORITY_KEYID *akid)
{
if(akid && akid->issuer)
  {
  int     i;
  GENERAL_NAMES *gens = akid->issuer;

  for(i = 0; i < sk_GENERAL_NAME_num(gens); ++i)
    {
    GENERAL_NAME *gn = sk_GENERAL_NAME_value(gens, i);

    if(gn->type == GEN_DIRNAME)
      return (gn->d.dirn);
    }
  }
return 0;
}

static int
set_issuer_name(X509 *cert, AUTHORITY_KEYID *akid)
{
X509_NAME *name = akid_issuer_name(akid);

/*
 * If subject's akid specifies an authority key identifer issuer name, we
 * must use that.
 */
return X509_set_issuer_name(cert,
                            name ? name : X509_get_subject_name(cert));
}

static int
grow_chain(ssl_dane *dane, int trusted, X509 *cert)
{
STACK_OF(X509) **xs = trusted ? &dane->roots : &dane->chain;
static ASN1_OBJECT *serverAuth = 0;

#define UNTRUSTED 0
#define TRUSTED 1

if(  trusted && !serverAuth
  && !(serverAuth = OBJ_nid2obj(NID_server_auth)))
  {
  DANEerr(DANE_F_GROW_CHAIN, ERR_R_MALLOC_FAILURE);
  return 0;
  }
if(!*xs && !(*xs = sk_X509_new_null()))
  {
  DANEerr(DANE_F_GROW_CHAIN, ERR_R_MALLOC_FAILURE);
  return 0;
  }

if(cert)
  {
  if(trusted && !X509_add1_trust_object(cert, serverAuth))
    return 0;
  CRYPTO_add(&cert->references, 1, CRYPTO_LOCK_X509);
  if (!sk_X509_push(*xs, cert))
    {
    X509_free(cert);
    DANEerr(DANE_F_GROW_CHAIN, ERR_R_MALLOC_FAILURE);
    return 0;
    }
  }
return 1;
}

static int
wrap_issuer(ssl_dane *dane, EVP_PKEY *key, X509 *subject, int depth, int top)
{
int ret = 1;
X509 *cert = 0;
AUTHORITY_KEYID *akid;
X509_NAME *name = X509_get_issuer_name(subject);
EVP_PKEY *newkey = key ? key : X509_get_pubkey(subject);

#define WRAP_MID 0              /* Ensure intermediate. */
#define WRAP_TOP 1              /* Ensure self-signed. */

if(!name || !newkey || !(cert = X509_new()))
  return 0;

/*
 * Record the depth of the trust-anchor certificate.
 */
if(dane->depth < 0)
  dane->depth = depth + 1;

/*
 * XXX: Uncaught error condition:
 *
 * The return value is NULL both when the extension is missing, and when
 * OpenSSL rans out of memory while parsing the extension.
 */
ERR_clear_error();
akid = X509_get_ext_d2i(subject, NID_authority_key_identifier, 0, 0);
/* XXX: Should we peek at the error stack here??? */

/*
 * If top is true generate a self-issued root CA, otherwise an
 * intermediate CA and possibly its self-signed issuer.
 *
 * CA cert valid for +/- 30 days
 */
if(  !X509_set_version(cert, 2)
  || !set_serial(cert, akid, subject)
  || !X509_set_subject_name(cert, name)
  || !set_issuer_name(cert, akid)
  || !X509_gmtime_adj(X509_get_notBefore(cert), -30 * 86400L)
  || !X509_gmtime_adj(X509_get_notAfter(cert), 30 * 86400L)
  || !X509_set_pubkey(cert, newkey)
  || !add_ext(0, cert, NID_basic_constraints, "CA:TRUE")
  || (!top && !add_akid(cert, akid))
  || !add_skid(cert, akid)
  || (  !top && wrap_to_root
     && !wrap_issuer(dane, newkey, cert, depth, WRAP_TOP)))
  ret = 0;

if(akid)
  AUTHORITY_KEYID_free(akid);
if(!key)
  EVP_PKEY_free(newkey);
if(ret)
  ret = grow_chain(dane, !top && wrap_to_root ? UNTRUSTED : TRUSTED, cert);
if(cert)
  X509_free(cert);
return ret;
}

static int
wrap_cert(ssl_dane *dane, X509 *tacert, int depth)
{
if(dane->depth < 0)
  dane->depth = depth + 1;

/*
 * If the TA certificate is self-issued, or need not be, use it directly.
 * Otherwise, synthesize requisuite ancestors.
 */
if(  !wrap_to_root
  || X509_check_issued(tacert, tacert) == X509_V_OK)
  return grow_chain(dane, TRUSTED, tacert);

if(wrap_issuer(dane, 0, tacert, depth, WRAP_MID))
  return grow_chain(dane, UNTRUSTED, tacert);
return 0;
}

static int
ta_signed(ssl_dane *dane, X509 *cert, int depth)
{
dane_cert_list x;
dane_pkey_list k;
EVP_PKEY *pk;
int done = 0;

/*
 * First check whether issued and signed by a TA cert, this is cheaper
 * than the bare-public key checks below, since we can determine whether
 * the candidate TA certificate issued the certificate to be checked
 * first (name comparisons), before we bother with signature checks
 * (public key operations).
 */
for (x = dane->certs; !done && x; x = x->next)
  {
  if(X509_check_issued(x->value, cert) == X509_V_OK)
    {
    if(!(pk = X509_get_pubkey(x->value)))
      {
      /*
       * The cert originally contained a valid pkey, which does
       * not just vanish, so this is most likely a memory error.
       */
      done = -1;
      break;
      }
    /* Check signature, since some other TA may work if not this. */
    if(X509_verify(cert, pk) > 0)
      done = wrap_cert(dane, x->value, depth) ? 1 : -1;
    EVP_PKEY_free(pk);
    }
  }

/*
 * With bare TA public keys, we can't check whether the trust chain is
 * issued by the key, but we can determine whether it is signed by the
 * key, so we go with that.
 *
 * Ideally, the corresponding certificate was presented in the chain, and we
 * matched it by its public key digest one level up.  This code is here
 * to handle adverse conditions imposed by sloppy administrators of
 * receiving systems with poorly constructed chains.
 *
 * We'd like to optimize out keys that should not match when the cert's
 * authority key id does not match the key id of this key computed via
 * the RFC keyid algorithm (SHA-1 digest of public key bit-string sans
 * ASN1 tag and length thus also excluding the unused bits field that is
 * logically part of the length).  However, some CAs have a non-standard
 * authority keyid, so we lose.  Too bad.
 *
 * This may push errors onto the stack when the certificate signature is
 * not of the right type or length, throw these away,
 */
for(k = dane->pkeys; !done && k; k = k->next)
  if(X509_verify(cert, k->value) > 0)
    done = wrap_issuer(dane, k->value, cert, depth, WRAP_MID) ? 1 : -1;
  else
    ERR_clear_error();

return done;
}

static int
set_trust_anchor(X509_STORE_CTX *ctx, ssl_dane *dane, X509 *cert)
{
int matched = 0;
int n;
int i;
int depth = 0;
EVP_PKEY *takey;
X509 *ca;
STACK_OF(X509) *in = ctx->untrusted;        /* XXX: Accessor? */

if(!grow_chain(dane, UNTRUSTED, 0))
  return -1;

/*
 * Accept a degenerate case: depth 0 self-signed trust-anchor.
 */
if(X509_check_issued(cert, cert) == X509_V_OK)
  {
  dane->depth = 0;
  matched = match(dane->selectors[SSL_DANE_USAGE_TRUSTED_CA], cert, 0);
  if(matched > 0 && !grow_chain(dane, TRUSTED, cert))
    matched = -1;
  return matched;
  }

/* Make a shallow copy of the input untrusted chain. */
if(!(in = sk_X509_dup(in)))
  {
  DANEerr(DANE_F_SET_TRUST_ANCHOR, ERR_R_MALLOC_FAILURE);
  return -1;
  }

/*
 * At each iteration we consume the issuer of the current cert.  This
 * reduces the length of the "in" chain by one.  If no issuer is found,
 * we are done.  We also stop when a certificate matches a TA in the
 * peer's TLSA RRset.
 *
 * Caller ensures that the initial certificate is not self-signed.
 */
for(n = sk_X509_num(in); n > 0; --n, ++depth)
  {
  for(i = 0; i < n; ++i)
    if(X509_check_issued(sk_X509_value(in, i), cert) == X509_V_OK)
      break;

  /*
   * Final untrusted element with no issuer in the peer's chain, it may
   * however be signed by a pkey or cert obtained via a TLSA RR.
   */
  if(i == n)
    break;

  /* Peer's chain contains an issuer ca. */
  ca = sk_X509_delete(in, i);

  /* If not a trust anchor, record untrusted ca and continue. */
  if((matched = match(dane->selectors[SSL_DANE_USAGE_TRUSTED_CA], ca, depth+1))
     == 0)
    {
    if(grow_chain(dane, UNTRUSTED, ca))
      {
      if(!X509_check_issued(ca, ca) == X509_V_OK)
        {
        /* Restart with issuer as subject */
        cert = ca;
        continue;
        }
      /* Final self-signed element, skip ta_signed() check. */
      cert = 0;
      }
    else
      matched = -1;
    }
  else if(matched == MATCHED_CERT)
    {
    if(!wrap_cert(dane, ca, depth))
      matched = -1;
    }
  else if(matched == MATCHED_PKEY)
    {
    if(  !(takey = X509_get_pubkey(ca))
      || !wrap_issuer(dane, takey, cert, depth, WRAP_MID))
      {
      if(takey)
        EVP_PKEY_free(takey);
      else
        DANEerr(DANE_F_SET_TRUST_ANCHOR, ERR_R_MALLOC_FAILURE);
      matched = -1;
      }
    }
  break;
  }

/* Shallow free the duplicated input untrusted chain. */
sk_X509_free(in);

/*
 * When the loop exits, if "cert" is set, it is not self-signed and has
 * no issuer in the chain, we check for a possible signature via a DNS
 * obtained TA cert or public key.
 */
if(matched == 0 && cert)
  matched = ta_signed(dane, cert, depth);

return matched;
}

static int
check_end_entity(X509_STORE_CTX *ctx, ssl_dane *dane, X509 *cert)
{
int matched;

matched = match(dane->selectors[SSL_DANE_USAGE_FIXED_LEAF], cert, 0);
if(matched > 0)
  if(!ctx->chain)
    if(  (ctx->chain = sk_X509_new_null())
      && sk_X509_push(ctx->chain, cert))
      CRYPTO_add(&cert->references, 1, CRYPTO_LOCK_X509);
    else
      {
      DANEerr(DANE_F_CHECK_END_ENTITY, ERR_R_MALLOC_FAILURE);
      return -1;
      }
return matched;
}

static int
match_name(const char *certid, ssl_dane *dane)
{
int multi = dane->multi;
dane_host_list hosts;

for(hosts = dane->hosts; hosts; hosts = hosts->next)
  {
  int match_subdomain = 0;
  const char *domain = hosts->value;
  const char *parent;
  int idlen;
  int domlen;

  if(*domain == '.' && domain[1] != '\0')
    {
    ++domain;
    match_subdomain = 1;
    }

  /*
   * Sub-domain match: certid is any sub-domain of hostname.
   */
  if(match_subdomain)
    if(  (idlen = strlen(certid)) > (domlen = strlen(domain)) + 1
      && certid[idlen - domlen - 1] == '.'
      && !strcasecmp(certid + (idlen - domlen), domain))
      return 1;
    else
      continue;

  /*
   * Exact match and initial "*" match. The initial "*" in a certid
   * matches one (if multi is false) or more hostname components under
   * the condition that the certid contains multiple hostname components.
   */
  if(  !strcasecmp(certid, domain)
    || (  certid[0] == '*' && certid[1] == '.' && certid[2] != 0
       && (parent = strchr(domain, '.')) != 0
       && (idlen = strlen(certid + 1)) <= (domlen = strlen(parent))
       && strcasecmp(multi ? parent + domlen - idlen : parent, certid+1) == 0))
    return 1;
  }
return 0;
}

static char *
check_name(char *name, int len)
{
char *cp = name + len;

while(len > 0 && !*--cp)
  --len;                          /* Ignore trailing NULs */
if(len <= 0)
  return 0;
for(cp = name; *cp; cp++)
  {
  char c = *cp;
  if (!((c >= 'a' && c <= 'z') ||
        (c >= '0' && c <= '9') ||
        (c >= 'A' && c <= 'Z') ||
        (c == '.' || c == '-') ||
        (c == '*')))
    return 0;                   /* Only LDH, '.' and '*' */
  }
if(cp - name != len)               /* Guard against internal NULs */
  return 0;
return name;
}

static char *
parse_dns_name(const GENERAL_NAME *gn)
{
if(gn->type != GEN_DNS)
  return 0;
if(ASN1_STRING_type(gn->d.ia5) != V_ASN1_IA5STRING)
  return 0;
return check_name((char *) ASN1_STRING_data(gn->d.ia5),
                  ASN1_STRING_length(gn->d.ia5));
}

static char *
parse_subject_name(X509 *cert)
{
X509_NAME *name = X509_get_subject_name(cert);
X509_NAME_ENTRY *entry;
ASN1_STRING *entry_str;
unsigned char *namebuf;
int nid = NID_commonName;
int len;
int i;

if(!name || (i = X509_NAME_get_index_by_NID(name, nid, -1)) < 0)
  return 0;
if(!(entry = X509_NAME_get_entry(name, i)))
  return 0;
if(!(entry_str = X509_NAME_ENTRY_get_data(entry)))
  return 0;

if((len = ASN1_STRING_to_UTF8(&namebuf, entry_str)) < 0)
  return 0;
if(len <= 0 || check_name((char *) namebuf, len) == 0)
  {
  OPENSSL_free(namebuf);
  return 0;
  }
return (char *) namebuf;
}

static int
name_check(ssl_dane *dane, X509 *cert)
{
int matched = 0;
BOOL got_altname = FALSE;
GENERAL_NAMES *gens;

gens = X509_get_ext_d2i(cert, NID_subject_alt_name, 0, 0);
if(gens)
  {
  int n = sk_GENERAL_NAME_num(gens);
  int i;

  for(i = 0; i < n; ++i)
    {
    const GENERAL_NAME *gn = sk_GENERAL_NAME_value(gens, i);
    const char *certid;

    if(gn->type != GEN_DNS)
        continue;
    got_altname = TRUE;
    certid = parse_dns_name(gn);
    if(certid && *certid)
      {
      if((matched = match_name(certid, dane)) == 0)
        continue;
      if(!(dane->mhost = OPENSSL_strdup(certid)))
        matched = -1;
      break;
      }
    }
  GENERAL_NAMES_free(gens);
  }

/*
 * XXX: Should the subjectName be skipped when *any* altnames are present,
 * or only when DNS altnames are present?
 */
if(got_altname)
  {
  char *certid = parse_subject_name(cert);
  if(certid != 0 && *certid && (matched = match_name(certid, dane)) != 0)
    dane->mhost = certid;       /* Already a copy */
  }
return matched;
}

static int
verify_chain(X509_STORE_CTX *ctx)
{
dane_selector_list issuer_rrs;
dane_selector_list leaf_rrs;
int (*cb)(int, X509_STORE_CTX *) = ctx->verify_cb;
int ssl_idx = SSL_get_ex_data_X509_STORE_CTX_idx();
SSL *ssl = X509_STORE_CTX_get_ex_data(ctx, ssl_idx);
ssl_dane *dane = SSL_get_ex_data(ssl, dane_idx);
X509 *cert = ctx->cert;             /* XXX: accessor? */
int matched = 0;
int chain_length = sk_X509_num(ctx->chain);

issuer_rrs = dane->selectors[SSL_DANE_USAGE_LIMIT_ISSUER];
leaf_rrs = dane->selectors[SSL_DANE_USAGE_LIMIT_LEAF];
ctx->verify = dane->verify;

if((matched = name_check(dane, cert)) < 0)
  {
  X509_STORE_CTX_set_error(ctx, X509_V_ERR_OUT_OF_MEM);
  return 0;
  }

if(!matched)
  {
  ctx->error_depth = 0;
  ctx->current_cert = cert;
  X509_STORE_CTX_set_error(ctx, X509_V_ERR_HOSTNAME_MISMATCH);
  if(!cb(0, ctx))
    return 0;
  }
matched = 0;

/*
 * Satisfy at least one usage 0 or 1 constraint, unless we've already
 * matched a usage 2 trust anchor.
 *
 * XXX: internal_verify() doesn't callback with top certs that are not
 * self-issued.  This should be fixed in a future OpenSSL.
 */
if(dane->roots && sk_X509_num(dane->roots))
  {
#ifndef NO_CALLBACK_WORKAROUND
  X509 *top = sk_X509_value(ctx->chain, dane->depth);

  if(X509_check_issued(top, top) != X509_V_OK)
    {
    ctx->error_depth = dane->depth;
    ctx->current_cert = top;
    if(!cb(1, ctx))
      return 0;
    }
#endif
  /* Pop synthetic trust-anchor ancestors off the chain! */
  while (--chain_length > dane->depth)
      X509_free(sk_X509_pop(ctx->chain));
  }
else if(issuer_rrs || leaf_rrs)
  {
  int n = chain_length;

  /*
   * Check for an EE match, then a CA match at depths > 0, and
   * finally, if the EE cert is self-issued, for a depth 0 CA match.
   */
  if(leaf_rrs)
    matched = match(leaf_rrs, cert, 0);
  while(!matched && issuer_rrs && --n >= 0)
    {
    X509 *xn = sk_X509_value(ctx->chain, n);

    if(n > 0 || X509_check_issued(xn, xn) == X509_V_OK)
      matched = match(issuer_rrs, xn, n);
    }

  if(matched < 0)
    {
    X509_STORE_CTX_set_error(ctx, X509_V_ERR_OUT_OF_MEM);
    return 0;
    }

  if(!matched)
    {
    ctx->current_cert = cert;
    ctx->error_depth = 0;
    X509_STORE_CTX_set_error(ctx, X509_V_ERR_CERT_UNTRUSTED);
    if(!cb(0, ctx))
      return 0;
    }
  }

return ctx->verify(ctx);
}

static int
verify_cert(X509_STORE_CTX *ctx, void *unused_ctx)
{
static int ssl_idx = -1;
SSL *ssl;
ssl_dane *dane;
int (*cb)(int, X509_STORE_CTX *) = ctx->verify_cb;
int matched;
X509 *cert = ctx->cert;             /* XXX: accessor? */

if(ssl_idx < 0)
  ssl_idx = SSL_get_ex_data_X509_STORE_CTX_idx();
if(dane_idx < 0)
  {
  DANEerr(DANE_F_VERIFY_CERT, ERR_R_MALLOC_FAILURE);
  return -1;
  }

ssl = X509_STORE_CTX_get_ex_data(ctx, ssl_idx);
if(!(dane = SSL_get_ex_data(ssl, dane_idx)) || !cert)
  return X509_verify_cert(ctx);

if(dane->selectors[SSL_DANE_USAGE_FIXED_LEAF])
  {
  if((matched = check_end_entity(ctx, dane, cert)) > 0)
    {
    ctx->error_depth = 0;
    ctx->current_cert = cert;
    return cb(1, ctx);
    }
  if(matched < 0)
    {
    X509_STORE_CTX_set_error(ctx, X509_V_ERR_OUT_OF_MEM);
    return -1;
    }
  }

if(dane->selectors[SSL_DANE_USAGE_TRUSTED_CA])
  {
  if((matched = set_trust_anchor(ctx, dane, cert)) < 0)
    {
    X509_STORE_CTX_set_error(ctx, X509_V_ERR_OUT_OF_MEM);
    return -1;
    }
  if(matched)
    {
    /*
     * Check that setting the untrusted chain updates the expected
     * structure member at the expected offset.
     */
    X509_STORE_CTX_trusted_stack(ctx, dane->roots);
    X509_STORE_CTX_set_chain(ctx, dane->chain);
    OPENSSL_assert(ctx->untrusted == dane->chain);
    }
  }

/*
 * Name checks and usage 0/1 constraint enforcement are delayed until
 * X509_verify_cert() builds the full chain and calls our verify_chain()
 * wrapper.
 */
dane->verify = ctx->verify;
ctx->verify = verify_chain;

return X509_verify_cert(ctx);
}

static dane_list
list_alloc(size_t vsize)
{
void *value = (void *) OPENSSL_malloc(vsize);
dane_list l;

if(!value)
  {
  DANEerr(DANE_F_LIST_ALLOC, ERR_R_MALLOC_FAILURE);
  return 0;
  }
if(!(l = (dane_list) OPENSSL_malloc(sizeof(*l))))
  {
  OPENSSL_free(value);
  DANEerr(DANE_F_LIST_ALLOC, ERR_R_MALLOC_FAILURE);
  return 0;
  }
l->next = 0;
l->value = value;
return l;
}

static void
list_free(void *list, void (*f)(void *))
{
dane_list head;
dane_list next;

for(head = (dane_list) list; head; head = next)
  {
  next = head->next;
  if (f && head->value)
      f(head->value);
  OPENSSL_free(head);
  }
}

static void
dane_mtype_free(void *p)
{
list_free(((dane_mtype) p)->data, OPENSSL_freeFunc);
OPENSSL_free(p);
}

static void
dane_selector_free(void *p)
{
list_free(((dane_selector) p)->mtype, dane_mtype_free);
OPENSSL_free(p);
}



/*

Tidy up once the connection is finished with.

Arguments
  ssl           The ssl connection handle

=> Before calling SSL_free()
tls_close() and tls_getc() [the error path] are the obvious places.
Could we do it earlier - right after verification?  In tls_client_start()
right after SSL_connect() returns, in that case.

*/

void
DANESSL_cleanup(SSL *ssl)
{
ssl_dane *dane;
int u;

if(dane_idx < 0 || !(dane = SSL_get_ex_data(ssl, dane_idx)))
  return;
(void) SSL_set_ex_data(ssl, dane_idx, 0);

if(dane->hosts)
  list_free(dane->hosts, OPENSSL_freeFunc);
if(dane->mhost)
  OPENSSL_free(dane->mhost);
for(u = 0; u <= SSL_DANE_USAGE_LAST; ++u)
  if(dane->selectors[u])
    list_free(dane->selectors[u], dane_selector_free);
if(dane->pkeys)
  list_free(dane->pkeys, pkey_free);
if(dane->certs)
  list_free(dane->certs, cert_free);
if(dane->roots)
  sk_X509_pop_free(dane->roots, X509_free);
if(dane->chain)
  sk_X509_pop_free(dane->chain, X509_free);
OPENSSL_free(dane);
}

static dane_host_list
host_list_init(const char **src)
{
dane_host_list head = NULL;

while(*src)
  {
  dane_host_list elem = (dane_host_list) OPENSSL_malloc(sizeof(*elem));
  if(!elem)
    {
    list_free(head, OPENSSL_freeFunc);
    return 0;
    }
  elem->value = OPENSSL_strdup(*src++);
  LINSERT(head, elem);
  }
return head;
}




/*

Call this for each TLSA record found for the target, after the
DANE setup has been done on the ssl connection handle.

Arguments:
  ssl           Connection handle
  usage         TLSA record field
  selector      TLSA record field
  mdname        ??? message digest name?
  data          ??? TLSA record megalump?
  dlen          length of data

Return
  -1 on error
  0  action not taken
  1  record accepted
*/

int
DANESSL_add_tlsa(SSL *ssl, uint8_t usage, uint8_t selector, const char *mdname,
        unsigned const char *data, size_t dlen)
{
ssl_dane *dane;
dane_selector_list s = 0;
dane_mtype_list m = 0;
dane_data_list d = 0;
dane_cert_list xlist = 0;
dane_pkey_list klist = 0;
const EVP_MD *md = 0;

if(dane_idx < 0 || !(dane = SSL_get_ex_data(ssl, dane_idx)))
  {
  DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_DANE_INIT);
  return -1;
  }

if(usage > SSL_DANE_USAGE_LAST)
  {
  DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_BAD_USAGE);
  return 0;
  }
if(selector > SSL_DANE_SELECTOR_LAST)
  {
  DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_BAD_SELECTOR);
  return 0;
  }
if(mdname && !(md = EVP_get_digestbyname(mdname)))
  {
  DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_BAD_DIGEST);
  return 0;
  }
if(!data)
  {
  DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_BAD_NULL_DATA);
  return 0;
  }
if(mdname && dlen != EVP_MD_size(md))
  {
  DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_BAD_DATA_LENGTH);
  return 0;
  }

if(!mdname)
  {
  X509 *x = 0;
  EVP_PKEY *k = 0;
  const unsigned char *p = data;

#define xklistinit(lvar, ltype, var, freeFunc) do { \
      (lvar) = (ltype) OPENSSL_malloc(sizeof(*(lvar))); \
      if (!(lvar)) { \
          DANEerr(DANE_F_SSL_DANE_ADD_TLSA, ERR_R_MALLOC_FAILURE); \
          freeFunc((var)); \
          return 0; \
      } \
      (lvar)->next = 0; \
      lvar->value = var; \
  } while (0)
#define xkfreeret(ret) do { \
      if (xlist) list_free(xlist, cert_free); \
      if (klist) list_free(klist, pkey_free); \
      return (ret); \
  } while (0)

  switch(selector)
    {
    case SSL_DANE_SELECTOR_CERT:
      if(!d2i_X509(&x, &p, dlen) || dlen != p - data)
        {
        if (x)
            X509_free(x);
        DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_BAD_CERT);
        return 0;
        }
      k = X509_get_pubkey(x);
      EVP_PKEY_free(k);
      if(!k)
        {
        X509_free(x);
        DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_BAD_CERT_PKEY);
        return 0;
        }
      if(usage == SSL_DANE_USAGE_TRUSTED_CA)
        xklistinit(xlist, dane_cert_list, x, X509_free);
      break;

    case SSL_DANE_SELECTOR_SPKI:
      if(!d2i_PUBKEY(&k, &p, dlen) || dlen != p - data)
        {
        if(k)
          EVP_PKEY_free(k);
        DANEerr(DANE_F_SSL_DANE_ADD_TLSA, DANE_R_BAD_PKEY);
        return 0;
        }
      if(usage == SSL_DANE_USAGE_TRUSTED_CA)
        xklistinit(klist, dane_pkey_list, k, EVP_PKEY_free);
      break;
    }
  }

/* Find insertion point and don't add duplicate elements. */
for(s = dane->selectors[usage]; s; s = s->next)
  if(s->value->selector == selector)
    for(m = s->value->mtype; m; m = m->next)
      if(m->value->md == md)
        for(d = m->value->data; d; d = d->next)
          if(  d->value->datalen == dlen
            && memcmp(d->value->data, data, dlen) == 0)
            xkfreeret(1);

if(!(d = (dane_data_list) list_alloc(sizeof(*d->value) + dlen)))
  xkfreeret(0);
d->value->datalen = dlen;
memcpy(d->value->data, data, dlen);
if(!m)
  {
  if(!(m = (dane_mtype_list) list_alloc(sizeof(*m->value))))
    {
    list_free(d, OPENSSL_freeFunc);
    xkfreeret(0);
    }
  m->value->data = 0;
  if((m->value->md = md) != 0)
    m->value->mdlen = dlen;
  if(!s)
    {
    if(!(s = (dane_selector_list) list_alloc(sizeof(*s->value))))
      {
      list_free(m, dane_mtype_free);
      xkfreeret(0);
      }
    s->value->mtype = 0;
    s->value->selector = selector;
    LINSERT(dane->selectors[usage], s);
    }
  LINSERT(s->value->mtype, m);
  }
LINSERT(m->value->data, d);

if(xlist)
  LINSERT(dane->certs, xlist);
else if(klist)
  LINSERT(dane->pkeys, klist);
++dane->count;
return 1;
}




/*
Call this once we have an ssl connection handle but before
making the TLS connection.

=> In tls_client_start() after the call to SSL_new()
and before the call to SSL_connect().  Exactly where
probably does not matter.
We probably want to keep our existing SNI handling;
call this with NULL.

Arguments:
  ssl           Connection handle
  sni_domain    Optional peer server name
  hostnames     ?? list of names - but what names?

Return
  -1 on fatal error
  0  nonfatal error
  1  success
*/

int
DANESSL_init(SSL *ssl, const char *sni_domain, const char **hostnames)
{
ssl_dane *dane;
int i;
#ifdef OPENSSL_INTERNAL
SSL_CTX *sctx = SSL_get_SSL_CTX(ssl);

if(sctx->app_verify_callback != verify_cert)
  {
  DANEerr(DANE_F_SSL_DANE_INIT, DANE_R_SCTX_INIT);
  return -1;
  }
#else
if(dane_idx < 0)
  {
  DANEerr(DANE_F_SSL_DANE_INIT, DANE_R_LIBRARY_INIT);
  return -1;
  }
#endif

if(sni_domain && !SSL_set_tlsext_host_name(ssl, sni_domain))
    return 0;

if(!(dane = (ssl_dane *) OPENSSL_malloc(sizeof(ssl_dane))))
  {
  DANEerr(DANE_F_SSL_DANE_INIT, ERR_R_MALLOC_FAILURE);
  return 0;
  }
if(!SSL_set_ex_data(ssl, dane_idx, dane))
  {
  DANEerr(DANE_F_SSL_DANE_INIT, ERR_R_MALLOC_FAILURE);
  OPENSSL_free(dane);
  return 0;
  }

dane->pkeys = 0;
dane->certs = 0;
dane->chain = 0;
dane->roots = 0;
dane->depth = -1;
dane->mhost = 0;                    /* Future SSL control interface */
dane->multi = 0;                    /* Future SSL control interface */
dane->count = 0;

for(i = 0; i <= SSL_DANE_USAGE_LAST; ++i)
    dane->selectors[i] = 0;

if(hostnames && !(dane->hosts = host_list_init(hostnames)))
  {
  DANEerr(DANE_F_SSL_DANE_INIT, ERR_R_MALLOC_FAILURE);
  DANESSL_cleanup(ssl);
  return 0;
  }

return 1;
}


/*

Call this once we have a context to work with, but
before DANESSL_init()

=> in tls_client_start(), after tls_init() call gives us the ctx,
if we decide we want to (policy) and can (TLSA records available)
replacing (? what about fallback) everything from testing tls_verify_hosts
down to just before calling SSL_new() for the conn handle.

Arguments
  ctx           SSL context

Return
  -1    Error
  1     Success
*/

int
DANESSL_CTX_init(SSL_CTX *ctx)
{
if(dane_idx >= 0)
  {
  SSL_CTX_set_cert_verify_callback(ctx, verify_cert, 0);
  return 1;
  }
DANEerr(DANE_F_SSL_CTX_DANE_INIT, DANE_R_LIBRARY_INIT);
return -1;
}

static int
init_once(volatile int *value, int (*init)(void), void (*postinit)(void))
{
int wlock = 0;

CRYPTO_r_lock(CRYPTO_LOCK_SSL_CTX);
if(*value < 0)
  {
  CRYPTO_r_unlock(CRYPTO_LOCK_SSL_CTX);
  CRYPTO_w_lock(CRYPTO_LOCK_SSL_CTX);
  wlock = 1;
  if(*value < 0)
    {
    *value = init();
    if(postinit)
      postinit();
    }
  }
if (wlock)
    CRYPTO_w_unlock(CRYPTO_LOCK_SSL_CTX);
else
    CRYPTO_r_unlock(CRYPTO_LOCK_SSL_CTX);
return *value;
}

static void
dane_init(void)
{
/*
 * Store library id in zeroth function slot, used to locate the library
 * name.  This must be done before we load the error strings.
 */
#ifndef OPENSSL_NO_ERR
dane_str_functs[0].error |= ERR_PACK(err_lib_dane, 0, 0);
ERR_load_strings(err_lib_dane, dane_str_functs);
ERR_load_strings(err_lib_dane, dane_str_reasons);
#endif

/*
 * Register SHA-2 digests, if implemented and not already registered.
 */
#if defined(LN_sha256) && defined(NID_sha256) && !defined(OPENSSL_NO_SHA256)
if(!EVP_get_digestbyname(LN_sha224)) EVP_add_digest(EVP_sha224());
if(!EVP_get_digestbyname(LN_sha256)) EVP_add_digest(EVP_sha256());
#endif
#if defined(LN_sha512) && defined(NID_sha512) && !defined(OPENSSL_NO_SHA512)
if(!EVP_get_digestbyname(LN_sha384)) EVP_add_digest(EVP_sha384());
if(!EVP_get_digestbyname(LN_sha512)) EVP_add_digest(EVP_sha512());
#endif

/*
 * Register an SSL index for the connection-specific ssl_dane structure.
 * Using a separate index makes it possible to add DANE support to
 * existing OpenSSL releases that don't have a suitable pointer in the
 * SSL structure.
 */
dane_idx = SSL_get_ex_new_index(0, 0, 0, 0, 0);
}



/*

Call this once.  Probably early in startup will do; may need
to be after SSL library init.

*/

int
DANESSL_library_init(void)
{
if(err_lib_dane < 0)
  init_once(&err_lib_dane, ERR_get_next_error_library, dane_init);

#if defined(LN_sha256)
/* No DANE without SHA256 support */
if(dane_idx >= 0 && EVP_get_digestbyname(LN_sha256) != 0)
  return 1;
#endif

DANEerr(DANE_F_SSL_DANE_LIBRARY_INIT, DANE_R_DANE_SUPPORT);
return 0;
}


#endif /* OPENSSL_VERSION_NUMBER */
/* vi: aw ai sw=2
*/