fix memleaks in private key deserialisation; enforce more consistency

between redundant fields in private key certificate and private key
body; ok markus@

diff --git a/usr.bin/ssh/sshkey.c b/usr.bin/ssh/sshkey.c
index 941e9fd..2ae461f 100644 (file)
--- a/usr.bin/ssh/sshkey.c
+++ b/usr.bin/ssh/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.114 2021/01/26 00:49:30 djm Exp $ */
+/* $OpenBSD: sshkey.c,v 1.115 2021/02/02 22:36:46 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -3358,10 +3358,12 @@ int
 sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
 {
        char *tname = NULL, *curve = NULL, *xmss_name = NULL;
+       char *expect_sk_application = NULL;
        struct sshkey *k = NULL;
        size_t pklen = 0, sklen = 0;
        int type, r = SSH_ERR_INTERNAL_ERROR;
        u_char *ed25519_pk = NULL, *ed25519_sk = NULL;
+       u_char *expect_ed25519_pk = NULL;
        u_char *xmss_pk = NULL, *xmss_sk = NULL;
 #ifdef WITH_OPENSSL
        BIGNUM *exponent = NULL;
@@ -3394,6 +3396,14 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                        r = SSH_ERR_KEY_CERT_MISMATCH;
                        goto out;
                }
+               /*
+                * Several fields are redundant between certificate and
+                * private key body, we require these to match.
+                */
+               expect_sk_application = k->sk_application;
+               expect_ed25519_pk = k->ed25519_pk;
+               k->sk_application = NULL;
+               k->ed25519_pk = NULL;
        } else {
                if ((k = sshkey_new(type)) == NULL) {
                        r = SSH_ERR_ALLOC_FAIL;
@@ -3613,6 +3623,13 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                break;
        }
 #endif /* WITH_OPENSSL */
+       if ((expect_sk_application != NULL && (k->sk_application == NULL ||
+           strcmp(expect_sk_application, k->sk_application) != 0)) ||
+           (expect_ed25519_pk != NULL && (k->ed25519_pk == NULL ||
+            memcmp(expect_ed25519_pk, k->ed25519_pk, ED25519_PK_SZ) != 0))) {
+               r = SSH_ERR_KEY_CERT_MISMATCH;
+               goto out;
+       }
        /* success */
        r = 0;
        if (kp != NULL) {
@@ -3642,6 +3659,8 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
        free(xmss_name);
        freezero(xmss_pk, pklen);
        freezero(xmss_sk, sklen);
+       free(expect_sk_application);
+       free(expect_ed25519_pk);
        return r;
 }