ssl: Dump OpenSSL error stack on errors

Bugs such as https://bugzilla.redhat.com/show_bug.cgi?id=1651882 can be
quite tricky to figure out without the detailed OpenSSL error. This
commit adds a detailed dump of the OpenSSL error stack when an OpenSSL
failure happens.

In the bug above, this would have displayed:
(process:13154): Spice-WARNING **: 05:43:10.139: reds.c:2816:reds_init_ssl: Could not load certificates from /etc/pki/libvirt-spice/server-cert.pem

(process:13154): Spice-WARNING **: 05:43:10.140: error:140AB18F:SSL routines:SSL_CTX_use_certificate:ee key too small

Signed-off-by: Christophe Fergeau <cfergeau@redhat.com>
Acked-by: Uri Lublin <uril@redhat.com>

server/red-stream.c

@@ -500,7 +500,7 @@ RedStreamSslStatus red_stream_ssl_accept(RedStream *stream)
         }
     }
 
-    ERR_print_errors_fp(stderr);
+    red_dump_openssl_errors();
     spice_warning("SSL_accept failed, error=%d", ssl_error);
     SSL_free(stream->priv->ssl);
     stream->priv->ssl = NULL;

server/reds.c

@@ -1705,11 +1705,13 @@ static bool reds_send_link_ack(RedsState *reds, RedLinkInfo *link)
         || !red_link_info_test_capability(link, SPICE_COMMON_CAP_AUTH_SASL)) {
         if (!(link->tiTicketing.rsa = RSA_new())) {
             spice_warning("RSA new failed");
+            red_dump_openssl_errors();
             return FALSE;
         }
 
         if (!(bio = BIO_new(BIO_s_mem()))) {
             spice_warning("BIO new failed");
+            red_dump_openssl_errors();
             return FALSE;
         }
 
@@ -1717,9 +1719,9 @@ static bool reds_send_link_ack(RedsState *reds, RedLinkInfo *link)
                                 SPICE_TICKET_KEY_PAIR_LENGTH,
                                 link->tiTicketing.bn,
                                 NULL) != 1) {
-            spice_warning("Failed to generate %d bits RSA key: %s",
-                          SPICE_TICKET_KEY_PAIR_LENGTH,
-                          ERR_error_string(ERR_get_error(), NULL));
+            spice_warning("Failed to generate %d bits RSA key",
+                          SPICE_TICKET_KEY_PAIR_LENGTH);
+            red_dump_openssl_errors();
             goto end;
         }
         link->tiTicketing.rsa_size = RSA_size(link->tiTicketing.rsa);
@@ -2019,6 +2021,7 @@ static void openssl_init(RedLinkInfo *link)
     link->tiTicketing.bn = BN_new();
 
     if (!link->tiTicketing.bn) {
+        red_dump_openssl_errors();
         spice_error("OpenSSL BIGNUMS alloc failed");
     }
 
@@ -2217,8 +2220,8 @@ static void reds_handle_ticket(void *opaque)
                                         link->tiTicketing.rsa,
                                         RSA_PKCS1_OAEP_PADDING);
     if (password_size == -1) {
-        spice_warning("failed to decrypt RSA encrypted password: %s",
-                      ERR_error_string(ERR_get_error(), NULL));
+        spice_warning("failed to decrypt RSA encrypted password");
+        red_dump_openssl_errors();
         goto error;
     }
     password[password_size] = '\0';
@@ -2817,6 +2820,7 @@ static int load_dh_params(SSL_CTX *ctx, char *file)
 
     if ((bio = BIO_new_file(file, "r")) == NULL) {
         spice_warning("Could not open DH file");
+        red_dump_openssl_errors();
         return -1;
     }
 
@@ -2824,12 +2828,14 @@ static int load_dh_params(SSL_CTX *ctx, char *file)
     BIO_free(bio);
     if (ret == 0) {
         spice_warning("Could not read DH params");
+        red_dump_openssl_errors();
         return -1;
     }
 
 
     if (SSL_CTX_set_tmp_dh(ctx, ret) < 0) {
         spice_warning("Could not set DH params");
+        red_dump_openssl_errors();
         return -1;
     }
 
@@ -2877,6 +2883,7 @@ static void openssl_thread_setup(void)
      * don't do it twice to avoid possible races.
      */
     if (CRYPTO_get_locking_callback() != NULL) {
+        red_dump_openssl_errors();
         return;
     }
 
@@ -2924,6 +2931,7 @@ static int reds_init_ssl(RedsState *reds)
     reds->ctx = SSL_CTX_new(ssl_method);
     if (!reds->ctx) {
         spice_warning("Could not allocate new SSL context");
+        red_dump_openssl_errors();
         return -1;
     }
 
@@ -2936,6 +2944,7 @@ static int reds_init_ssl(RedsState *reds)
         spice_debug("Loaded certificates from %s", reds->config->ssl_parameters.certs_file);
     } else {
         spice_warning("Could not load certificates from %s", reds->config->ssl_parameters.certs_file);
+        red_dump_openssl_errors();
         return -1;
     }
 
@@ -2957,6 +2966,7 @@ static int reds_init_ssl(RedsState *reds)
         spice_debug("Loaded CA certificates from %s", reds->config->ssl_parameters.ca_certificate_file);
     } else {
         spice_warning("Could not use CA file %s", reds->config->ssl_parameters.ca_certificate_file);
+        red_dump_openssl_errors();
         return -1;
     }
 

server/utils.c

@@ -20,6 +20,7 @@
 
 #include <glib.h>
 #include <spice/enums.h>
+#include <openssl/err.h>
 #include <common/macros.h>
 
 #include "utils.h"
@@ -114,3 +115,16 @@ int red_channel_name_to_type(const char *name)
     }
     return -1;
 }
+
+void red_dump_openssl_errors(void)
+{
+    int ssl_error;
+
+    ssl_error = ERR_get_error();
+    while (ssl_error != 0) {
+        char error_str[256];
+        ERR_error_string_n(ssl_error, error_str, sizeof(error_str));
+        g_warning("%s", error_str);
+        ssl_error = ERR_get_error();
+    }
+}

server/utils.h

@@ -73,4 +73,6 @@ int rgb32_data_has_alpha(int width, int height, size_t stride,
 const char *red_channel_type_to_str(int type);
 int red_channel_name_to_type(const char *name);
 
+void red_dump_openssl_errors(void);
+
 #endif /* UTILS_H_ */