Be user-friendly when opening a pfx/p12 file

Before this change the user had to provide a password callback, even if the
PKCS#12 encoded file has no or an empty password.

This changes the behavior, so we first try to open the file without a
password and only then ask the user to provide one.

This fixes #204.

Signed-off-by: Steffen Jaeckel <jaeckel-floss@eyet-services.de>

Makefile.am

@@ -116,6 +116,8 @@ EXTRA_DIST = \
 	src/tls_schannel.c \
 	tests/cert.pem \
 	tests/cert.pfx \
+	tests/cert.emptypass.pfx \
+	tests/cert.nopass.pfx \
 	tests/key.pem \
 	tests/key_encrypted.pem \
 	tests/res_query_dump.c

src/tls_gnutls.c

@@ -93,10 +93,6 @@ static gnutls_x509_crt_t _tls_load_cert_p12(xmpp_conn_t *conn)
     gnutls_x509_privkey_t key;
     unsigned int cert_num = 0, retries = 0;
     int err = -1;
-    if (!conn->password_callback) {
-        strophe_error(conn->ctx, "tls", "No password callback set");
-        return NULL;
-    }
     if (gnutls_pkcs12_init(&p12) < 0)
         return NULL;
     if (gnutls_load_file(conn->tls_client_key, &data) < 0)
@@ -104,6 +100,22 @@ static gnutls_x509_crt_t _tls_load_cert_p12(xmpp_conn_t *conn)
     if (gnutls_pkcs12_import(p12, &data, GNUTLS_X509_FMT_DER, 0) < 0)
         goto error_out2;
 
+    /* First try to open file with no pass */
+    if ((err = gnutls_pkcs12_simple_parse(p12, NULL, &key, &cert, &cert_num,
+                                          NULL, NULL, NULL, 0)) == 0) {
+        goto done;
+    }
+    /* Now let's try to open file with an empty pass */
+    if ((err = gnutls_pkcs12_simple_parse(p12, "", &key, &cert, &cert_num, NULL,
+                                          NULL, NULL, 0)) == 0) {
+        goto done;
+    }
+
+    if (!conn->password_callback) {
+        strophe_error(conn->ctx, "tls", "No password callback set");
+        goto error_out2;
+    }
+    /* ... and only now ask the user for a password */
     while (retries++ < conn->password_retries) {
         char pass[GNUTLS_PKCS11_MAX_PIN_LEN];
         int passlen =
@@ -125,6 +137,7 @@ static gnutls_x509_crt_t _tls_load_cert_p12(xmpp_conn_t *conn)
         strophe_debug(conn->ctx, "tls", "wrong password?");
     }
 
+done:
     gnutls_pkcs12_deinit(p12);
     gnutls_free(data.data);
     if (err < 0)

src/tls_openssl.c

@@ -948,6 +948,25 @@ static X509 *_tls_cert_read_x509(xmpp_conn_t *conn)
     return c;
 }
 
+static int _tls_parse_p12(PKCS12 *p12,
+                          const char *pass,
+                          EVP_PKEY **pkey,
+                          X509 **cert,
+                          STACK_OF(X509) * *ca)
+{
+    /* For some reason `PKCS12_parse()` fails without a `EVP_PKEY`
+     * so if the user doesn't want it, use a local one and free it
+     * again directly after parsing.
+     */
+    EVP_PKEY *pkey_;
+    if (!pkey)
+        pkey = &pkey_;
+    int parse_ok = PKCS12_parse(p12, pass, pkey, cert, ca);
+    if (pkey == &pkey_ && pkey_)
+        EVP_PKEY_free(pkey_);
+    return parse_ok;
+}
+
 static X509 *
 _tls_cert_read_p12(xmpp_conn_t *conn, EVP_PKEY **pkey, STACK_OF(X509) * *ca)
 {
@@ -967,6 +986,12 @@ _tls_cert_read_p12(xmpp_conn_t *conn, EVP_PKEY **pkey, STACK_OF(X509) * *ca)
         goto error_out;
     }
 
+    /* First try to open file w/o a pass */
+    if (_tls_parse_p12(p12, NULL, pkey, &cert, ca)) {
+        goto success;
+    }
+    cert = NULL;
+
     unsigned int retries = 0;
 
     pem_password_cb *cb = PEM_def_callback;
@@ -981,17 +1006,7 @@ _tls_cert_read_p12(xmpp_conn_t *conn, EVP_PKEY **pkey, STACK_OF(X509) * *ca)
         int passlen = cb(pass, PEM_BUFSIZE, 0, userdata);
         if (passlen < 0 || passlen > PEM_BUFSIZE)
             goto error_out;
-
-        /* For some reason `PKCS12_parse()` fails without a `EVP_PKEY`
-         * so if the user doesn't want it, use a local one and free it
-         * again directly after parsing.
-         */
-        EVP_PKEY *pkey_;
-        if (!pkey)
-            pkey = &pkey_;
-        int parse_ok = PKCS12_parse(p12, pass, pkey, &cert, ca);
-        if (pkey == &pkey_ && pkey_)
-            EVP_PKEY_free(pkey_);
+        int parse_ok = _tls_parse_p12(p12, pass, pkey, &cert, ca);
         if (parse_ok) {
             goto success;
         }

tests/test_xmppaddr.c

@@ -33,10 +33,15 @@ int main()
     xmpp_ctx_t *ctx;
     xmpp_conn_t *conn;
     xmpp_log_t *log;
-    char *client_cert[][2] = {
-        {"tests/cert.pem", "tests/key.pem"},
-        {"tests/cert.pem", "tests/key_encrypted.pem"},
-        {NULL, "tests/cert.pfx"},
+    struct {
+        int needs_callback;
+        char *pem, *key;
+    } client_cert[] = {
+        {0, "tests/cert.pem", "tests/key.pem"},
+        {1, "tests/cert.pem", "tests/key_encrypted.pem"},
+        {0, NULL, "tests/cert.emptypass.pfx"},
+        {0, NULL, "tests/cert.nopass.pfx"},
+        {1, NULL, "tests/cert.pfx"},
     };
 
     char xmppaddr_num[] = "0";
@@ -49,9 +54,10 @@ int main()
     for (m = 0; m < sizeof(client_cert) / sizeof(client_cert[0]); ++m) {
         conn = xmpp_conn_new(ctx);
 
-        xmpp_conn_set_password_callback(conn, password_callback, NULL);
+        if (client_cert[m].needs_callback)
+            xmpp_conn_set_password_callback(conn, password_callback, NULL);
 
-        xmpp_conn_set_client_cert(conn, client_cert[m][0], client_cert[m][1]);
+        xmpp_conn_set_client_cert(conn, client_cert[m].pem, client_cert[m].key);
 
         xmppaddr_num[0] = '0' + xmpp_conn_cert_xmppaddr_num(conn);