[Spice-devel] [PATCH v2] Check RSA_generate_key_ex return value

[Christophe Fergeau]

This can fail in fips mode for example. If we ignore the failure, we'll get
a crash:

 #0  0x00007f38d63728a0 in BN_num_bits () from /lib64/libcrypto.so.10
 #1  0x00007f38d639661d in RSA_size () from /lib64/libcrypto.so.10
 #2  0x00007f38d7991762 in reds_handle_read_link_done () from /lib64/libspice-server.so.1
 #3  0x00007f38d7990c06 in spice_server_add_client () from /lib64/libspice-server.so.1
 #4  0x00007f38d7990c6a in reds_accept () from /lib64/libspice-server.so.1
 #5  0x00007f38dc0d2946 in qemu_iohandler_poll (pollfds=0x7f38dedce200, ret=755449965, ret at entry=1) at iohandler.c:143
 #6  0x00007f38dc0d6ea8 in main_loop_wait (nonblocking=<optimized out>) at main-loop.c:465
 #7  0x00007f38dbffd7c0 in main_loop () at vl.c:1988
 #8  main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4357

This commit will cause the client connection to fail but qemu won't
segfault.
---
Changes since v1:
- don't leak BIO when RSA_generate_key_ex fails


 server/reds.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/server/reds.c b/server/reds.c
index c38fa40..6706754 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -1368,8 +1368,15 @@ static int reds_send_link_ack(RedLinkInfo *link)
         return FALSE;
     }
 
-    RSA_generate_key_ex(link->tiTicketing.rsa, SPICE_TICKET_KEY_PAIR_LENGTH, link->tiTicketing.bn,
-                        NULL);
+    if (RSA_generate_key_ex(link->tiTicketing.rsa,
+                            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));
+        goto end;
+    }
     link->tiTicketing.rsa_size = RSA_size(link->tiTicketing.rsa);
 
     i2d_RSA_PUBKEY_bio(bio, link->tiTicketing.rsa);
-- 
1.8.5.3