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authorChristophe Fergeau <cfergeau@redhat.com>2013-08-23 09:29:44 (GMT)
committerChristophe Fergeau <cfergeau@redhat.com>2013-10-30 09:40:50 (GMT)
commit8af619009660b24e0b41ad26b30289eea288fcc2 (patch)
tree817b95b2976a8500328b203932f91a8d918a3051
parentef9a8bf05328d290f82613037f5419f0d5e87eb5 (diff)
Fix buffer overflow when decrypting client SPICE ticket
reds_handle_ticket uses a fixed size 'password' buffer for the decrypted password whose size is SPICE_MAX_PASSWORD_LENGTH. However, RSA_private_decrypt which we call for the decryption expects the destination buffer to be at least RSA_size(link->tiTicketing.rsa) bytes long. On my spice-server build, SPICE_MAX_PASSWORD_LENGTH is 60 while RSA_size() is 128, so we end up overflowing 'password' when using long passwords (this was reproduced using the string: 'fullscreen=1proxy=#enter proxy here; e.g spice_proxy = http://[proxy]:[port]' as a password). When the overflow occurs, QEMU dies with: *** stack smashing detected ***: qemu-system-x86_64 terminated This commit ensures we use a corectly sized 'password' buffer, and that it's correctly nul-terminated so that we can use strcmp instead of strncmp. To keep using strncmp, we'd need to figure out which one of 'password' and 'taTicket.password' is the smaller buffer, and use that size. This fixes rhbz#999839
-rw-r--r--server/reds.c44
1 files changed, 32 insertions, 12 deletions
diff --git a/server/reds.c b/server/reds.c
index 892d247..2a0002b 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -1926,39 +1926,59 @@ static void reds_handle_link(RedLinkInfo *link)
static void reds_handle_ticket(void *opaque)
{
RedLinkInfo *link = (RedLinkInfo *)opaque;
- char password[SPICE_MAX_PASSWORD_LENGTH];
+ char *password;
time_t ltime;
+ int password_size;
//todo: use monotonic time
time(&ltime);
- RSA_private_decrypt(link->tiTicketing.rsa_size,
- link->tiTicketing.encrypted_ticket.encrypted_data,
- (unsigned char *)password, link->tiTicketing.rsa, RSA_PKCS1_OAEP_PADDING);
+ if (RSA_size(link->tiTicketing.rsa) < SPICE_MAX_PASSWORD_LENGTH) {
+ spice_warning("RSA modulus size is smaller than SPICE_MAX_PASSWORD_LENGTH (%d < %d), "
+ "SPICE ticket sent from client may be truncated",
+ RSA_size(link->tiTicketing.rsa), SPICE_MAX_PASSWORD_LENGTH);
+ }
+
+ password = g_malloc0(RSA_size(link->tiTicketing.rsa) + 1);
+ password_size = RSA_private_decrypt(link->tiTicketing.rsa_size,
+ link->tiTicketing.encrypted_ticket.encrypted_data,
+ (unsigned char *)password,
+ 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));
+ goto error;
+ }
+ password[password_size] = '\0';
if (ticketing_enabled && !link->skip_auth) {
int expired = taTicket.expiration_time < ltime;
if (strlen(taTicket.password) == 0) {
- reds_send_link_result(link, SPICE_LINK_ERR_PERMISSION_DENIED);
spice_warning("Ticketing is enabled, but no password is set. "
- "please set a ticket first");
- reds_link_free(link);
- return;
+ "please set a ticket first");
+ goto error;
}
- if (expired || strncmp(password, taTicket.password, SPICE_MAX_PASSWORD_LENGTH) != 0) {
+ if (expired || strcmp(password, taTicket.password) != 0) {
if (expired) {
spice_warning("Ticket has expired");
} else {
spice_warning("Invalid password");
}
- reds_send_link_result(link, SPICE_LINK_ERR_PERMISSION_DENIED);
- reds_link_free(link);
- return;
+ goto error;
}
}
reds_handle_link(link);
+ goto end;
+
+error:
+ reds_send_link_result(link, SPICE_LINK_ERR_PERMISSION_DENIED);
+ reds_link_free(link);
+
+end:
+ g_free(password);
}
static inline void async_read_clear_handlers(AsyncRead *obj)