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@

7 files changed, 106 insertions, 48 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;
 }
diff --git a/src/lib/libssl/ssl_kex.c b/src/lib/libssl/ssl_kex.c
index 78b528b168..cd6713b8b2 100644
--- a/src/lib/libssl/ssl_kex.c
+++ b/src/lib/libssl/ssl_kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_kex.c,v 1.8 2021/12/04 14:03:22 jsing Exp $ */
+/* $OpenBSD: ssl_kex.c,v 1.9 2022/01/11 18:28:41 jsing Exp $ */
 /*
  * Copyright (c) 2020, 2021 Joel Sing <jsing@openbsd.org>
  *
@@ -156,18 +156,24 @@ ssl_kex_public_dhe(DH *dh, CBB *cbb)
 }
 
 int
-ssl_kex_peer_params_dhe(DH *dh, CBS *cbs, int *invalid_params)
+ssl_kex_peer_params_dhe(DH *dh, CBS *cbs, int *decode_error,
+    int *invalid_params)
 {
         BIGNUM *p = NULL, *g = NULL;
         CBS dh_p, dh_g;
         int ret = 0;
 
+        *decode_error = 0;
         *invalid_params = 0;
 
-        if (!CBS_get_u16_length_prefixed(cbs, &dh_p))
+        if (!CBS_get_u16_length_prefixed(cbs, &dh_p)) {
+                *decode_error = 1;
                 goto err;
-        if (!CBS_get_u16_length_prefixed(cbs, &dh_g))
+        }
+        if (!CBS_get_u16_length_prefixed(cbs, &dh_g)) {
+                *decode_error = 1;
                 goto err;
+        }
 
         if ((p = BN_bin2bn(CBS_data(&dh_p), CBS_len(&dh_p), NULL)) == NULL)
                 goto err;
@@ -194,17 +200,21 @@ ssl_kex_peer_params_dhe(DH *dh, CBS *cbs, int *invalid_params)
 }
 
 int
-ssl_kex_peer_public_dhe(DH *dh, CBS *cbs, int *invalid_key)
+ssl_kex_peer_public_dhe(DH *dh, CBS *cbs, int *decode_error,
+    int *invalid_key)
 {
         BIGNUM *pub_key = NULL;
         int check_flags;
         CBS dh_y;
         int ret = 0;
 
+        *decode_error = 0;
         *invalid_key = 0;
 
-        if (!CBS_get_u16_length_prefixed(cbs, &dh_y))
+        if (!CBS_get_u16_length_prefixed(cbs, &dh_y)) {
+                *decode_error = 1;
                 goto err;
+        }
 
         if ((pub_key = BN_bin2bn(CBS_data(&dh_y), CBS_len(&dh_y),
             NULL)) == NULL)
diff --git a/src/lib/libssl/ssl_locl.h b/src/lib/libssl/ssl_locl.h
index fcb369405c..0eca4e673d 100644
--- a/src/lib/libssl/ssl_locl.h
+++ b/src/lib/libssl/ssl_locl.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_locl.h,v 1.380 2022/01/09 15:53:52 jsing Exp $ */
+/* $OpenBSD: ssl_locl.h,v 1.381 2022/01/11 18:28:41 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1424,8 +1424,10 @@ int ssl_kex_generate_dhe(DH *dh, DH *dh_params);
 int ssl_kex_generate_dhe_params_auto(DH *dh, size_t key_len);
 int ssl_kex_params_dhe(DH *dh, CBB *cbb);
 int ssl_kex_public_dhe(DH *dh, CBB *cbb);
-int ssl_kex_peer_params_dhe(DH *dh, CBS *cbs, int *invalid_params);
-int ssl_kex_peer_public_dhe(DH *dh, CBS *cbs, int *invalid_key);
+int ssl_kex_peer_params_dhe(DH *dh, CBS *cbs, int *decode_error,
+    int *invalid_params);
+int ssl_kex_peer_public_dhe(DH *dh, CBS *cbs, int *decode_error,
+    int *invalid_key);
 int ssl_kex_derive_dhe(DH *dh, DH *dh_peer,
     uint8_t **shared_key, size_t *shared_key_len);
 
diff --git a/src/lib/libssl/ssl_srvr.c b/src/lib/libssl/ssl_srvr.c
index 0979750e22..dd622c2831 100644
--- a/src/lib/libssl/ssl_srvr.c
+++ b/src/lib/libssl/ssl_srvr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_srvr.c,v 1.137 2022/01/09 15:40:13 jsing Exp $ */
+/* $OpenBSD: ssl_srvr.c,v 1.138 2022/01/11 18:28:41 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1701,21 +1701,26 @@ ssl3_get_client_kex_dhe(SSL *s, CBS *cbs)
 {
         uint8_t *key = NULL;
         size_t key_len = 0;
-        int invalid_key;
+        int decode_error, invalid_key;
         int ret = 0;
 
         if (S3I(s)->hs.key_share == NULL) {
-                ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_HANDSHAKE_FAILURE);
                 SSLerror(s, SSL_R_MISSING_TMP_DH_KEY);
+                ssl3_send_alert(s, SSL3_AL_FATAL, SSL_AD_HANDSHAKE_FAILURE);
                 goto err;
         }
 
         if (!tls_key_share_peer_public(S3I(s)->hs.key_share, cbs,
-            &invalid_key))
+            &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_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;
         }
 
@@ -1738,6 +1743,7 @@ ssl3_get_client_kex_ecdhe(SSL *s, CBS *cbs)
 {
         uint8_t *key = NULL;
         size_t key_len = 0;
+        int decode_error;
         CBS public;
         int ret = 0;
 
@@ -1747,10 +1753,19 @@ ssl3_get_client_kex_ecdhe(SSL *s, CBS *cbs)
                 goto err;
         }
 
-        if (!CBS_get_u8_length_prefixed(cbs, &public))
+        if (!CBS_get_u8_length_prefixed(cbs, &public)) {
+                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, &public, NULL))
+        }
+        if (!tls_key_share_peer_public(S3I(s)->hs.key_share, &public,
+            &decode_error, NULL)) {
+                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_derive(S3I(s)->hs.key_share, &key, &key_len))
                 goto err;
diff --git a/src/lib/libssl/ssl_tlsext.c b/src/lib/libssl/ssl_tlsext.c
index 7538efdc8c..69f8ddbc40 100644
--- a/src/lib/libssl/ssl_tlsext.c
+++ b/src/lib/libssl/ssl_tlsext.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_tlsext.c,v 1.107 2022/01/11 18:24:03 jsing Exp $ */
+/* $OpenBSD: ssl_tlsext.c,v 1.108 2022/01/11 18:28:41 jsing Exp $ */
 /*
  * Copyright (c) 2016, 2017, 2019 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -1478,6 +1478,7 @@ int
 tlsext_keyshare_server_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert)
 {
         CBS client_shares, key_exchange;
+        int decode_error;
         uint16_t group;
 
         if (!CBS_get_u16_length_prefixed(cbs, &client_shares))
@@ -1515,8 +1516,11 @@ tlsext_keyshare_server_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert)
                         return 0;
                 }
                 if (!tls_key_share_peer_public(S3I(s)->hs.key_share,
-                    &key_exchange, NULL))
+                    &key_exchange, &decode_error, NULL)) {
+                        if (!decode_error)
+                                *alert = SSL_AD_INTERNAL_ERROR;
                         return 0;
+                }
         }
 
         return 1;
@@ -1561,6 +1565,7 @@ int
 tlsext_keyshare_client_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert)
 {
         CBS key_exchange;
+        int decode_error;
         uint16_t group;
 
         /* Unpack server share. */
@@ -1588,8 +1593,11 @@ tlsext_keyshare_client_parse(SSL *s, uint16_t msg_type, CBS *cbs, int *alert)
                 return 0;
         }
         if (!tls_key_share_peer_public(S3I(s)->hs.key_share,
-            &key_exchange, NULL))
+            &key_exchange, &decode_error, NULL)) {
+                if (!decode_error)
+                        *alert = SSL_AD_INTERNAL_ERROR;
                 return 0;
+        }
 
         return 1;
 }
diff --git a/src/lib/libssl/tls_internal.h b/src/lib/libssl/tls_internal.h
index f7f939215a..a009635a05 100644
--- a/src/lib/libssl/tls_internal.h
+++ b/src/lib/libssl/tls_internal.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls_internal.h,v 1.4 2022/01/07 15:46:30 jsing Exp $ */
+/* $OpenBSD: tls_internal.h,v 1.5 2022/01/11 18:28:41 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019, 2021 Joel Sing <jsing@openbsd.org>
  *
@@ -72,9 +72,9 @@ int tls_key_share_generate(struct tls_key_share *ks);
 int tls_key_share_params(struct tls_key_share *ks, CBB *cbb);
 int tls_key_share_public(struct tls_key_share *ks, CBB *cbb);
 int tls_key_share_peer_params(struct tls_key_share *ks, CBS *cbs,
-    int *invalid_params);
+    int *decode_error, int *invalid_params);
 int tls_key_share_peer_public(struct tls_key_share *ks, CBS *cbs,
-    int *invalid_key);
+    int *decode_error, int *invalid_key);
 int tls_key_share_derive(struct tls_key_share *ks, uint8_t **shared_key,
     size_t *shared_key_len);
 
diff --git a/src/lib/libssl/tls_key_share.c b/src/lib/libssl/tls_key_share.c
index eb30a0ea69..e5e6c304b6 100644
--- a/src/lib/libssl/tls_key_share.c
+++ b/src/lib/libssl/tls_key_share.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls_key_share.c,v 1.3 2022/01/07 15:46:30 jsing Exp $ */
+/* $OpenBSD: tls_key_share.c,v 1.4 2022/01/11 18:28:41 jsing Exp $ */
 /*
  * Copyright (c) 2020, 2021 Joel Sing <jsing@openbsd.org>
  *
@@ -301,14 +301,15 @@ tls_key_share_public(struct tls_key_share *ks, CBB *cbb)
 
 static int
 tls_key_share_peer_params_dhe(struct tls_key_share *ks, CBS *cbs,
-    int *invalid_params)
+    int *decode_error, int *invalid_params)
 {
         if (ks->dhe != NULL || ks->dhe_peer != NULL)
                 return 0;
 
         if ((ks->dhe_peer = DH_new()) == NULL)
                 return 0;
-        if (!ssl_kex_peer_params_dhe(ks->dhe_peer, cbs, invalid_params))
+        if (!ssl_kex_peer_params_dhe(ks->dhe_peer, cbs, decode_error,
+            invalid_params))
                 return 0;
         if ((ks->dhe = DHparams_dup(ks->dhe_peer)) == NULL)
                 return 0;
@@ -318,22 +319,24 @@ tls_key_share_peer_params_dhe(struct tls_key_share *ks, CBS *cbs,
 
 int
 tls_key_share_peer_params(struct tls_key_share *ks, CBS *cbs,
-    int *invalid_params)
+    int *decode_error, int *invalid_params)
 {
         if (ks->nid != NID_dhKeyAgreement)
                 return 0;
 
-        return tls_key_share_peer_params_dhe(ks, cbs, invalid_params);
+        return tls_key_share_peer_params_dhe(ks, cbs, decode_error,
+             invalid_params);
 }
 
 static int
 tls_key_share_peer_public_dhe(struct tls_key_share *ks, CBS *cbs,
-    int *invalid_key)
+    int *decode_error, int *invalid_key)
 {
         if (ks->dhe_peer == NULL)
                 return 0;
 
-        return ssl_kex_peer_public_dhe(ks->dhe_peer, cbs, invalid_key);
+        return ssl_kex_peer_public_dhe(ks->dhe_peer, cbs, decode_error,
+            invalid_key);
 }
 
 static int
@@ -362,30 +365,39 @@ tls_key_share_peer_public_ecdhe_ecp(struct tls_key_share *ks, CBS *cbs)
 }
 
 static int
-tls_key_share_peer_public_x25519(struct tls_key_share *ks, CBS *cbs)
+tls_key_share_peer_public_x25519(struct tls_key_share *ks, CBS *cbs,
+    int *decode_error)
 {
         size_t out_len;
 
+        *decode_error = 0;
+
         if (ks->x25519_peer_public != NULL)
                 return 0;
 
-        if (CBS_len(cbs) != X25519_KEY_LENGTH)
+        if (CBS_len(cbs) != X25519_KEY_LENGTH) {
+                *decode_error = 1;
                 return 0;
+        }
 
         return CBS_stow(cbs, &ks->x25519_peer_public, &out_len);
 }
 
 int
-tls_key_share_peer_public(struct tls_key_share *ks, CBS *cbs, int *invalid_key)
+tls_key_share_peer_public(struct tls_key_share *ks, CBS *cbs, int *decode_error,
+    int *invalid_key)
 {
+        *decode_error = 0;
+
         if (invalid_key != NULL)
                 *invalid_key = 0;
 
         if (ks->nid == NID_dhKeyAgreement)
-                return tls_key_share_peer_public_dhe(ks, cbs, invalid_key);
+                return tls_key_share_peer_public_dhe(ks, cbs, decode_error,
+                    invalid_key);
 
         if (ks->nid == NID_X25519)
-                return tls_key_share_peer_public_x25519(ks, cbs);
+                return tls_key_share_peer_public_x25519(ks, cbs, decode_error);
 
         return tls_key_share_peer_public_ecdhe_ecp(ks, cbs);
 }