/* check whether cert is preauthorized. If host is not null, verify that
* it matches the certificate.
* Return > 0: authorized, < 0: problems, 0: unknown validity */
static int ssl_check_preauth (X509 *cert, const char* host)
{
char buf[SHORT_STRING];
/* check session cache first */
if (check_certificate_cache (cert)) {
dprint (2, (debugfile, "ssl_check_preauth: using cached certificate\n"));
return 1;
}
buf[0] = 0;
if (host && option (OPTSSLVERIFYHOST) != M_NO) {
if (!check_host (cert, host, buf, sizeof (buf))) {
mutt_error (_("Certificate host check failed: %s"), buf);
mutt_sleep (2);
return -1;
}
dprint (2, (debugfile, "ssl_check_preauth: hostname check passed\n"));
}
if (check_certificate_by_signer (cert)) {
dprint (2, (debugfile, "ssl_check_preauth: signer check passed\n"));
return 1;
}
/* automatic check from user's database */
if (SslCertFile && check_certificate_by_digest (cert)) {
dprint (2, (debugfile, "ssl_check_preauth: digest check passed\n"));
return 1;
}
return 0;
}
/**
* ssl_verify_callback - Certificate verification callback
* @param preverify_ok If true, don't question the user if they skipped verification
* @param ctx X509 store context
* @retval true Certificate is valid
* @retval false Error, or Certificate is invalid
*
* Called for each certificate in the chain sent by the peer, starting from the
* root; returning true means that the given certificate is trusted, returning
* false immediately aborts the SSL connection
*/
static int ssl_verify_callback(int preverify_ok, X509_STORE_CTX *ctx)
{
char buf[256];
const char *host = NULL;
size_t len;
int pos;
X509 *cert = NULL;
SSL *ssl = NULL;
bool skip_mode;
ssl = X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
if (!ssl)
{
mutt_debug(LL_DEBUG1,
"failed to retrieve SSL structure from X509_STORE_CTX\n");
return false;
}
host = SSL_get_ex_data(ssl, HostExDataIndex);
if (!host)
{
mutt_debug(LL_DEBUG1, "failed to retrieve hostname from SSL structure\n");
return false;
}
/* This is true when a previous entry in the certificate chain did
* not verify and the user manually chose to skip it via the
* $ssl_verify_partial_chains option.
* In this case, all following certificates need to be treated as non-verified
* until one is actually verified. */
skip_mode = (SSL_get_ex_data(ssl, SkipModeExDataIndex));
cert = X509_STORE_CTX_get_current_cert(ctx);
pos = X509_STORE_CTX_get_error_depth(ctx);
len = sk_X509_num(X509_STORE_CTX_get0_chain(ctx));
mutt_debug(LL_DEBUG1, "checking cert chain entry %s (preverify: %d skipmode: %d)\n",
X509_NAME_oneline(X509_get_subject_name(cert), buf, sizeof(buf)),
preverify_ok, skip_mode);
#ifdef HAVE_SSL_PARTIAL_CHAIN
/* Sometimes, when a certificate is (s)kipped, OpenSSL will pass it
* a second time with preverify_ok = 1. Don't show it or the user
* will think their "s" key is broken. */
if (C_SslVerifyPartialChains)
{
static int last_pos = 0;
static X509 *last_cert = NULL;
if (skip_mode && preverify_ok && (pos == last_pos) && last_cert)
{
unsigned char last_cert_md[EVP_MAX_MD_SIZE];
unsigned int last_cert_mdlen;
if (X509_digest(last_cert, EVP_sha256(), last_cert_md, &last_cert_mdlen) &&
compare_certificates(cert, last_cert, last_cert_md, last_cert_mdlen))
{
mutt_debug(LL_DEBUG2, "ignoring duplicate skipped certificate.\n");
return true;
}
}
last_pos = pos;
if (last_cert)
X509_free(last_cert);
last_cert = X509_dup(cert);
}
#endif
/* check session cache first */
if (check_certificate_cache(cert))
{
mutt_debug(LL_DEBUG2, "using cached certificate\n");
SSL_set_ex_data(ssl, SkipModeExDataIndex, NULL);
return true;
}
/* check hostname only for the leaf certificate */
buf[0] = '\0';
if ((pos == 0) && (C_SslVerifyHost != MUTT_NO))
{
if (check_host(cert, host, buf, sizeof(buf)) == 0)
{
mutt_error(_("Certificate host check failed: %s"), buf);
/* we disallow (a)ccept always in the prompt, because it will have no effect
* for hostname mismatches. */
return interactive_check_cert(cert, pos, len, ssl, false);
}
mutt_debug(LL_DEBUG2, "hostname check passed\n");
}
if (!preverify_ok || skip_mode)
{
/* automatic check from user's database */
if (C_CertificateFile && check_certificate_by_digest(cert))
{
mutt_debug(LL_DEBUG2, "digest check passed\n");
SSL_set_ex_data(ssl, SkipModeExDataIndex, NULL);
return true;
}
/* log verification error */
int err = X509_STORE_CTX_get_error(ctx);
snprintf(buf, sizeof(buf), "%s (%d)", X509_verify_cert_error_string(err), err);
mutt_debug(LL_DEBUG2, "X509_verify_cert: %s\n", buf);
/* prompt user */
return interactive_check_cert(cert, pos, len, ssl, true);
}
return true;
}
