Plumb decode errors through key share parsing code.

Distinguish between decode errors and other errors, so that we can send
a SSL_AD_DECODE_ERROR alert when appropriate.

Fixes a tlsfuzzer failure, due to it expecting a decode error alert and
not receiving one.

Prompted by anton@

ok tb@

1 files changed, 25 insertions, 14 deletions

diff --git a/src/lib/libssl/ssl_clnt.c b/src/lib/libssl/ssl_clnt.c
index 19d83653c9..981161290f 100644
--- a/src/lib/libssl/ssl_clnt.c
+++ b/src/lib/libssl/ssl_clnt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_clnt.c,v 1.134 2022/01/09 15:55:37 jsing Exp $ */
+/* $OpenBSD: ssl_clnt.c,v 1.135 2022/01/11 18:28:41 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1214,7 +1214,7 @@ ssl3_get_server_certificate(SSL *s)
 static int
 ssl3_get_server_kex_dhe(SSL *s, CBS *cbs)
 {
-        int invalid_params, invalid_key;
+        int decode_error, invalid_params, invalid_key;
         int nid = NID_dhKeyAgreement;
 
         tls_key_share_free(S3I(s)->hs.key_share);
@@ -1222,29 +1222,35 @@ ssl3_get_server_kex_dhe(SSL *s, CBS *cbs)
                 goto err;
 
         if (!tls_key_share_peer_params(S3I(s)->hs.key_share, cbs,
-            &invalid_params))
-                goto decode_err;
+            &decode_error, &invalid_params)) {
+                if (decode_error) {
+                        SSLerror(s, SSL_R_BAD_PACKET_LENGTH);
+                        ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
+                }
+                goto err;
+        }
         if (!tls_key_share_peer_public(S3I(s)->hs.key_share, cbs,
-            &invalid_key))
-                goto decode_err;
+            &decode_error, &invalid_key)) {
+                if (decode_error) {
+                        SSLerror(s, SSL_R_BAD_PACKET_LENGTH);
+                        ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
+                }
+                goto err;
+        }
 
         if (invalid_params) {
-                ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
                 SSLerror(s, SSL_R_BAD_DH_P_LENGTH);
+                ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
                 goto err;
         }
         if (invalid_key) {
-                ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
                 SSLerror(s, SSL_R_BAD_DH_PUB_KEY_LENGTH);
+                ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_ILLEGAL_PARAMETER);
                 goto err;
         }
 
         return 1;
 
- decode_err:
-        SSLerror(s, SSL_R_BAD_PACKET_LENGTH);
-        ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
-
  err:
         return 0;
 }
@@ -1254,6 +1260,7 @@ ssl3_get_server_kex_ecdhe(SSL *s, CBS *cbs)
 {
         uint8_t curve_type;
         uint16_t curve_id;
+        int decode_error;
         CBS public;
 
         if (!CBS_get_u8(cbs, &curve_type))
@@ -1285,14 +1292,18 @@ ssl3_get_server_kex_ecdhe(SSL *s, CBS *cbs)
         if ((S3I(s)->hs.key_share = tls_key_share_new(curve_id)) == NULL)
                 goto err;
 
-        if (!tls_key_share_peer_public(S3I(s)->hs.key_share, &public, NULL))
+        if (!tls_key_share_peer_public(S3I(s)->hs.key_share, &public,
+            &decode_error, NULL)) {
+                if (decode_error)
+                        goto decode_err;
                 goto err;
+        }
 
         return 1;
 
  decode_err:
-        ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
         SSLerror(s, SSL_R_BAD_PACKET_LENGTH);
+        ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_DECODE_ERROR);
  err:
         return 0;
 }