From 905943af3b43116b64ae815db1a6b9c2f15e0356 Mon Sep 17 00:00:00 2001
From: Matt Caswell <matt@openssl.org>
Date: Thu, 5 Nov 2015 14:52:27 +0000
Subject: [PATCH] Fix error when server does not send CertificateStatus message

If a server sends the status_request extension then it may choose
to send the CertificateStatus message. However this is optional.
We were treating it as mandatory and the connection was failing.

Thanks to BoringSSL for reporting this issue.

RT#4120

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
---
 ssl/s3_clnt.c | 61 ++++++++++++++++++++++++++++-----------------------
 ssl/t1_lib.c  | 12 +++++-----
 2 files changed, 39 insertions(+), 34 deletions(-)

diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index bc5254c811..8cbf46ad2f 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -2350,37 +2350,44 @@ int ssl3_get_cert_status(SSL *s)
     n = s->method->ssl_get_message(s,
                                    SSL3_ST_CR_CERT_STATUS_A,
                                    SSL3_ST_CR_CERT_STATUS_B,
-                                   SSL3_MT_CERTIFICATE_STATUS, 16384, &ok);
+                                   -1, 16384, &ok);
 
     if (!ok)
         return ((int)n);
-    if (n < 4) {
-        /* need at least status type + length */
-        al = SSL_AD_DECODE_ERROR;
-        SSLerr(SSL_F_SSL3_GET_CERT_STATUS, SSL_R_LENGTH_MISMATCH);
-        goto f_err;
-    }
-    p = (unsigned char *)s->init_msg;
-    if (*p++ != TLSEXT_STATUSTYPE_ocsp) {
-        al = SSL_AD_DECODE_ERROR;
-        SSLerr(SSL_F_SSL3_GET_CERT_STATUS, SSL_R_UNSUPPORTED_STATUS_TYPE);
-        goto f_err;
-    }
-    n2l3(p, resplen);
-    if (resplen + 4 != n) {
-        al = SSL_AD_DECODE_ERROR;
-        SSLerr(SSL_F_SSL3_GET_CERT_STATUS, SSL_R_LENGTH_MISMATCH);
-        goto f_err;
-    }
-    if (s->tlsext_ocsp_resp)
-        OPENSSL_free(s->tlsext_ocsp_resp);
-    s->tlsext_ocsp_resp = BUF_memdup(p, resplen);
-    if (!s->tlsext_ocsp_resp) {
-        al = SSL_AD_INTERNAL_ERROR;
-        SSLerr(SSL_F_SSL3_GET_CERT_STATUS, ERR_R_MALLOC_FAILURE);
-        goto f_err;
+
+    if (s->s3->tmp.message_type != SSL3_MT_CERTIFICATE_STATUS) {
+        /*
+         * The CertificateStatus message is optional even if
+         * tlsext_status_expected is set
+         */
+        s->s3->tmp.reuse_message = 1;
+    } else {
+        if (n < 4) {
+            /* need at least status type + length */
+            al = SSL_AD_DECODE_ERROR;
+            SSLerr(SSL_F_SSL3_GET_CERT_STATUS, SSL_R_LENGTH_MISMATCH);
+            goto f_err;
+        }
+        p = (unsigned char *)s->init_msg;
+        if (*p++ != TLSEXT_STATUSTYPE_ocsp) {
+            al = SSL_AD_DECODE_ERROR;
+            SSLerr(SSL_F_SSL3_GET_CERT_STATUS, SSL_R_UNSUPPORTED_STATUS_TYPE);
+            goto f_err;
+        }
+        n2l3(p, resplen);
+        if (resplen + 4 != n) {
+            al = SSL_AD_DECODE_ERROR;
+            SSLerr(SSL_F_SSL3_GET_CERT_STATUS, SSL_R_LENGTH_MISMATCH);
+            goto f_err;
+        }
+        s->tlsext_ocsp_resp = BUF_memdup(p, resplen);
+        if (s->tlsext_ocsp_resp == NULL) {
+            al = SSL_AD_INTERNAL_ERROR;
+            SSLerr(SSL_F_SSL3_GET_CERT_STATUS, ERR_R_MALLOC_FAILURE);
+            goto f_err;
+        }
+        s->tlsext_ocsp_resplen = resplen;
     }
-    s->tlsext_ocsp_resplen = resplen;
     if (s->ctx->tlsext_status_cb) {
         int ret;
         ret = s->ctx->tlsext_status_cb(s, s->ctx->tlsext_status_arg);
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index 37f0ae5be2..24713194e8 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -3157,6 +3157,9 @@ int ssl_check_serverhello_tlsext(SSL *s)
     }
 # endif
 
+    OPENSSL_free(s->tlsext_ocsp_resp);
+    s->tlsext_ocsp_resp = NULL;
+    s->tlsext_ocsp_resplen = -1;
     /*
      * If we've requested certificate status and we wont get one tell the
      * callback
@@ -3165,14 +3168,9 @@ int ssl_check_serverhello_tlsext(SSL *s)
         && s->ctx && s->ctx->tlsext_status_cb) {
         int r;
         /*
-         * Set resp to NULL, resplen to -1 so callback knows there is no
-         * response.
+         * Call callback with resp == NULL and resplen == -1 so callback
+         * knows there is no response
          */
-        if (s->tlsext_ocsp_resp) {
-            OPENSSL_free(s->tlsext_ocsp_resp);
-            s->tlsext_ocsp_resp = NULL;
-        }
-        s->tlsext_ocsp_resplen = -1;
         r = s->ctx->tlsext_status_cb(s, s->ctx->tlsext_status_arg);
         if (r == 0) {
             al = SSL_AD_BAD_CERTIFICATE_STATUS_RESPONSE;
-- 
2.34.1