Full Disclosure mailing list archives
possible backdoor in OpenSSL X509 verification
From: Arnis <arnis () ut ee>
Date: Fri, 06 Sep 2013 17:28:34 +0300
Can someone take a look on this shady X.509 certificate verification code (fails open in case of out-of-memory error): http://rt.openssl.org/Ticket/Display.html?id=2924 "Certificate chain verification in crypto/x509/x509_vfy.c X509_verify_cert() fails badly and may allow verification bypass if check_issued() on line 259 returns false negative on check whether the last certificate in chain is self signed. For example, check_issued() may return false negative in case of memory allocation failure (although could not find how to force that). 253 /* Examine last certificate in chain and see if it 254 * is self signed. 255 */ 256 257 i=sk_X509_num(ctx->chain); 258 x=sk_X509_value(ctx->chain,i-1); 259 if (ctx->check_issued(ctx, x, x)) This is because "for" loop later does not require to find even a single issuer certificate from trust store and will happily break loop if last certificate is actually self signed." Noone from OpenSSL team has commented whether this is exploitable or should it be rewritten in safer manner. P.S. Subject field inspired by latest NSA stories ;) _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
Current thread:
- possible backdoor in OpenSSL X509 verification Arnis (Sep 06)
- Re: possible backdoor in OpenSSL X509 verification Jeffrey Walton (Sep 06)
- Re: possible backdoor in OpenSSL X509 verification Ben Laurie (Sep 06)
- Re: possible backdoor in OpenSSL X509 verification Jeffrey Walton (Sep 06)