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Fix invalid handling of verify errors in libssl

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In the event that X509_verify() returned an internal error result then
libssl would mishandle this and set rwstate to SSL_RETRY_VERIFY. This
subsequently causes SSL_get_error() to return SSL_ERROR_WANT_RETRY_VERIFY.
That return code is supposed to only ever be returned if an application
is using an app verify callback to complete replace the use of
X509_verify(). Applications may not be written to expect that return code
and could therefore crash (or misbehave in some other way) as a result.

CVE-2021-4044

Reviewed-by: Tomas Mraz <tomas@openssl.org>
This commit is contained in:
Matt Caswell 2021-12-03 15:56:58 +00:00
parent 5eef9e1deb
commit c1c1bb7c5e
2 changed files with 14 additions and 3 deletions
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15
ssl/ssl_cert.c
View File

@ -362,6 +362,13 @@ void ssl_cert_set_cert_cb(CERT *c, int (*cb) (SSL *ssl, void *arg), void *arg)
c->cert_cb_arg = arg;
}
/*
* Verify a certificate chain
* Return codes:
* 1: Verify success
* 0: Verify failure or error
* -1: Retry required
*/
int ssl_verify_cert_chain(SSL *s, STACK_OF(X509) *sk)
{
X509 *x;
@ -423,10 +430,14 @@ int ssl_verify_cert_chain(SSL *s, STACK_OF(X509) *sk)
if (s->verify_callback)
X509_STORE_CTX_set_verify_cb(ctx, s->verify_callback);
if (s->ctx->app_verify_callback != NULL)
if (s->ctx->app_verify_callback != NULL) {
i = s->ctx->app_verify_callback(ctx, s->ctx->app_verify_arg);
else
} else {
i = X509_verify_cert(ctx);
/* We treat an error in the same way as a failure to verify */
if (i < 0)
i = 0;
}
s->verify_result = X509_STORE_CTX_get_error(ctx);
sk_X509_pop_free(s->verified_chain, X509_free);

2
ssl/statem/statem_clnt.c
View File

@ -1878,7 +1878,7 @@ WORK_STATE tls_post_process_server_certificate(SSL *s, WORK_STATE wst)
* (less clean) historic behaviour of performing validation if any flag is
* set. The *documented* interface remains the same.
*/
if (s->verify_mode != SSL_VERIFY_NONE && i <= 0) {
if (s->verify_mode != SSL_VERIFY_NONE && i == 0) {
SSLfatal(s, ssl_x509err2alert(s->verify_result),
SSL_R_CERTIFICATE_VERIFY_FAILED);
return WORK_ERROR;