conn: add flag XMPP_CONN_FLAG_TRUST_TLS

TLS modules accept invalid server's certificates when the flag is set.

src/common.h

@@ -168,6 +168,7 @@ struct _xmpp_conn_t {
     int tls_disabled;
     int tls_mandatory;
     int tls_legacy_ssl;
+    int tls_trust;
     int tls_failed; /* set when tls fails, so we don't try again */
     int sasl_support; /* if true, field is a bitfield of supported 
                          mechanisms */

src/conn.c

@@ -128,6 +128,7 @@ xmpp_conn_t *xmpp_conn_new(xmpp_ctx_t * const ctx)
         conn->tls_disabled = 0;
         conn->tls_mandatory = 0;
         conn->tls_legacy_ssl = 0;
+        conn->tls_trust = 0;
         conn->tls_failed = 0;
         conn->sasl_support = 0;
         conn->secured = 0;
@@ -911,7 +912,8 @@ long xmpp_conn_get_flags(const xmpp_conn_t * const conn)
 
     flags = XMPP_CONN_FLAG_DISABLE_TLS * conn->tls_disabled |
             XMPP_CONN_FLAG_MANDATORY_TLS * conn->tls_mandatory |
-            XMPP_CONN_FLAG_LEGACY_SSL * conn->tls_legacy_ssl;
+            XMPP_CONN_FLAG_LEGACY_SSL * conn->tls_legacy_ssl |
+            XMPP_CONN_FLAG_TRUST_TLS * conn->tls_trust;
 
     return flags;
 }
@@ -928,6 +930,7 @@ long xmpp_conn_get_flags(const xmpp_conn_t * const conn)
  *    - XMPP_CONN_FLAG_DISABLE_TLS
  *    - XMPP_CONN_FLAG_MANDATORY_TLS
  *    - XMPP_CONN_FLAG_LEGACY_SSL
+ *    - XMPP_CONN_FLAG_TRUST_TLS
  *
  *  @param conn a Strophe connection object
  *  @param flags ORed connection flags
@@ -944,7 +947,8 @@ int xmpp_conn_set_flags(xmpp_conn_t * const conn, long flags)
         return XMPP_EINVOP;
     }
     if (flags & XMPP_CONN_FLAG_DISABLE_TLS &&
-        flags & (XMPP_CONN_FLAG_MANDATORY_TLS | XMPP_CONN_FLAG_LEGACY_SSL)) {
+        flags & (XMPP_CONN_FLAG_MANDATORY_TLS | XMPP_CONN_FLAG_LEGACY_SSL |
+                 XMPP_CONN_FLAG_TRUST_TLS)) {
         xmpp_error(conn->ctx, "conn", "Flags 0x%04lx conflict", flags);
         return XMPP_EINVOP;
     }
@@ -952,6 +956,7 @@ int xmpp_conn_set_flags(xmpp_conn_t * const conn, long flags)
     conn->tls_disabled = (flags & XMPP_CONN_FLAG_DISABLE_TLS) ? 1 : 0;
     conn->tls_mandatory = (flags & XMPP_CONN_FLAG_MANDATORY_TLS) ? 1 : 0;
     conn->tls_legacy_ssl = (flags & XMPP_CONN_FLAG_LEGACY_SSL) ? 1 : 0;
+    conn->tls_trust = (flags & XMPP_CONN_FLAG_TRUST_TLS) ? 1 : 0;
 
     return 0;
 }

src/tls_openssl.c

@@ -75,6 +75,7 @@ int tls_error(tls_t *tls)
 tls_t *tls_new(xmpp_conn_t *conn)
 {
     tls_t *tls = xmpp_alloc(conn->ctx, sizeof(*tls));
+    int mode;
 
     if (tls) {
         int ret;
@@ -86,7 +87,8 @@ tls_t *tls_new(xmpp_conn_t *conn)
         if (tls->ssl_ctx == NULL)
             goto err;
 
-        SSL_CTX_set_options(tls->ssl_ctx, SSL_OP_ALL); /* Enable bug workarounds. */
+        /* Enable bug workarounds. */
+        SSL_CTX_set_options(tls->ssl_ctx, SSL_OP_ALL);
 
         /* Disable insecure SSL/TLS versions. */
         SSL_CTX_set_options(tls->ssl_ctx, SSL_OP_NO_SSLv2); /* DROWN */
@@ -101,7 +103,9 @@ tls_t *tls_new(xmpp_conn_t *conn)
         if (tls->ssl == NULL)
             goto err_free_ctx;
 
-        SSL_set_verify(tls->ssl, SSL_VERIFY_PEER, 0);
+        /* Trust server's certificate when user sets the flag explicitly. */
+        mode = conn->tls_trust ? SSL_VERIFY_NONE : SSL_VERIFY_PEER;
+        SSL_set_verify(tls->ssl, mode, 0);
 #if OPENSSL_VERSION_NUMBER >= 0x10002000L
         /* Hostname verification is supported in OpenSSL 1.0.2 and newer. */
         X509_VERIFY_PARAM *param = SSL_get0_param(tls->ssl);

strophe.h

@@ -166,6 +166,10 @@ typedef struct _xmpp_stanza_t xmpp_stanza_t;
 #define XMPP_CONN_FLAG_DISABLE_TLS   (1UL << 0)
 #define XMPP_CONN_FLAG_MANDATORY_TLS (1UL << 1)
 #define XMPP_CONN_FLAG_LEGACY_SSL    (1UL << 2)
+/** @def XMPP_CONN_FLAG_TRUST_TLS
+ *  Trust server's certificate even if it is invalid.
+ */
+#define XMPP_CONN_FLAG_TRUST_TLS     (1UL << 3)
 
 /* connect callback */
 typedef enum {