upstream: Refactor private key parsing. Eliminates a fair bit of

duplicated code and fixes oss-fuzz#20074 (NULL deref) caused by a missing key
type check in the ECDSA_CERT parsing path.

feedback and ok markus@

OpenBSD-Commit-ID: 4711981d88afb7196d228f7baad9be1d3b20f9c9

diff --git a/sshkey.c b/sshkey.c
index d6cc6365f0daf21200ae33a26e38f193298b593f..1571e3d93878828eb11b1926a3804979ee829210 100644 (file)
--- a/sshkey.c
+++ b/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.107 2020/04/08 00:08:46 djm Exp $ */
+/* $OpenBSD: sshkey.c,v 1.108 2020/04/11 10:16:11 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -3394,38 +3394,52 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
        if ((r = sshbuf_get_cstring(buf, &tname, NULL)) != 0)
                goto out;
        type = sshkey_type_from_name(tname);
-       switch (type) {
-#ifdef WITH_OPENSSL
-       case KEY_DSA:
+       if (sshkey_type_is_cert(type)) {
+               /*
+                * Certificate key private keys begin with the certificate
+                * itself. Make sure this matches the type of the enclosing
+                * private key.
+                */
+               if ((r = sshkey_froms(buf, &k)) != 0)
+                       goto out;
+               if (k->type != type) {
+                       r = SSH_ERR_KEY_CERT_MISMATCH;
+                       goto out;
+               }
+               /* For ECDSA keys, the group must match too */
+               if (k->type == KEY_ECDSA &&
+                   k->ecdsa_nid != sshkey_ecdsa_nid_from_name(tname)) {
+                       r = SSH_ERR_KEY_CERT_MISMATCH;
+                       goto out;
+               }
+       } else {
                if ((k = sshkey_new(type)) == NULL) {
                        r = SSH_ERR_ALLOC_FAIL;
                        goto out;
                }
+       }
+       switch (type) {
+#ifdef WITH_OPENSSL
+       case KEY_DSA:
                if ((r = sshbuf_get_bignum2(buf, &dsa_p)) != 0 ||
                    (r = sshbuf_get_bignum2(buf, &dsa_q)) != 0 ||
                    (r = sshbuf_get_bignum2(buf, &dsa_g)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &dsa_pub_key)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &dsa_priv_key)) != 0)
+                   (r = sshbuf_get_bignum2(buf, &dsa_pub_key)) != 0)
                        goto out;
                if (!DSA_set0_pqg(k->dsa, dsa_p, dsa_q, dsa_g)) {
                        r = SSH_ERR_LIBCRYPTO_ERROR;
                        goto out;
                }
                dsa_p = dsa_q = dsa_g = NULL; /* transferred */
-               if (!DSA_set0_key(k->dsa, dsa_pub_key, dsa_priv_key)) {
+               if (!DSA_set0_key(k->dsa, dsa_pub_key, NULL)) {
                        r = SSH_ERR_LIBCRYPTO_ERROR;
                        goto out;
                }
-               dsa_pub_key = dsa_priv_key = NULL; /* transferred */
-               break;
+               dsa_pub_key = NULL; /* transferred */
+               /* FALLTHROUGH */
        case KEY_DSA_CERT:
-               if ((r = sshkey_froms(buf, &k)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &dsa_priv_key)) != 0)
+               if ((r = sshbuf_get_bignum2(buf, &dsa_priv_key)) != 0)
                        goto out;
-               if (k->type != type) {
-                       r = SSH_ERR_INVALID_FORMAT;
-                       goto out;
-               }
                if (!DSA_set0_key(k->dsa, NULL, dsa_priv_key)) {
                        r = SSH_ERR_LIBCRYPTO_ERROR;
                        goto out;
@@ -3434,10 +3448,6 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                break;
 # ifdef OPENSSL_HAS_ECC
        case KEY_ECDSA:
-               if ((k = sshkey_new(type)) == NULL) {
-                       r = SSH_ERR_ALLOC_FAIL;
-                       goto out;
-               }
                if ((k->ecdsa_nid = sshkey_ecdsa_nid_from_name(tname)) == -1) {
                        r = SSH_ERR_INVALID_ARGUMENT;
                        goto out;
@@ -3453,27 +3463,12 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                        r = SSH_ERR_LIBCRYPTO_ERROR;
                        goto out;
                }
-               if ((r = sshbuf_get_eckey(buf, k->ecdsa)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &exponent)))
-                       goto out;
-               if (EC_KEY_set_private_key(k->ecdsa, exponent) != 1) {
-                       r = SSH_ERR_LIBCRYPTO_ERROR;
-                       goto out;
-               }
-               if ((r = sshkey_ec_validate_public(EC_KEY_get0_group(k->ecdsa),
-                   EC_KEY_get0_public_key(k->ecdsa))) != 0 ||
-                   (r = sshkey_ec_validate_private(k->ecdsa)) != 0)
+               if ((r = sshbuf_get_eckey(buf, k->ecdsa)) != 0)
                        goto out;
-               break;
+               /* FALLTHROUGH */
        case KEY_ECDSA_CERT:
-               if ((r = sshkey_froms(buf, &k)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &exponent)) != 0)
-                       goto out;
-               if (k->type != type ||
-                   k->ecdsa_nid != sshkey_ecdsa_nid_from_name(tname)) {
-                       r = SSH_ERR_INVALID_FORMAT;
+               if ((r = sshbuf_get_bignum2(buf, &exponent)) != 0)
                        goto out;
-               }
                if (EC_KEY_set_private_key(k->ecdsa, exponent) != 1) {
                        r = SSH_ERR_LIBCRYPTO_ERROR;
                        goto out;
@@ -3484,10 +3479,6 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                        goto out;
                break;
        case KEY_ECDSA_SK:
-               if ((k = sshkey_new(type)) == NULL) {
-                       r = SSH_ERR_ALLOC_FAIL;
-                       goto out;
-               }
                if ((k->ecdsa_nid = sshkey_ecdsa_nid_from_name(tname)) == -1) {
                        r = SSH_ERR_INVALID_ARGUMENT;
                        goto out;
@@ -3520,8 +3511,6 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                        goto out;
                break;
        case KEY_ECDSA_SK_CERT:
-               if ((r = sshkey_froms(buf, &k)) != 0)
-                       goto out;
                if ((k->sk_key_handle = sshbuf_new()) == NULL ||
                    (k->sk_reserved = sshbuf_new()) == NULL) {
                        r = SSH_ERR_ALLOC_FAIL;
@@ -3539,43 +3528,21 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                break;
 # endif /* OPENSSL_HAS_ECC */
        case KEY_RSA:
-               if ((k = sshkey_new(type)) == NULL) {
-                       r = SSH_ERR_ALLOC_FAIL;
-                       goto out;
-               }
                if ((r = sshbuf_get_bignum2(buf, &rsa_n)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &rsa_e)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &rsa_d)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &rsa_iqmp)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &rsa_p)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &rsa_q)) != 0)
-                       goto out;
-               if (!RSA_set0_key(k->rsa, rsa_n, rsa_e, rsa_d)) {
-                       r = SSH_ERR_LIBCRYPTO_ERROR;
+                   (r = sshbuf_get_bignum2(buf, &rsa_e)) != 0)
                        goto out;
-               }
-               rsa_n = rsa_e = rsa_d = NULL; /* transferred */
-               if (!RSA_set0_factors(k->rsa, rsa_p, rsa_q)) {
+               if (!RSA_set0_key(k->rsa, rsa_n, rsa_e, NULL)) {
                        r = SSH_ERR_LIBCRYPTO_ERROR;
                        goto out;
                }
-               rsa_p = rsa_q = NULL; /* transferred */
-               if ((r = check_rsa_length(k->rsa)) != 0)
-                       goto out;
-               if ((r = ssh_rsa_complete_crt_parameters(k, rsa_iqmp)) != 0)
-                       goto out;
-               break;
+               rsa_n = rsa_e = NULL; /* transferred */
+               /* FALLTHROUGH */
        case KEY_RSA_CERT:
-               if ((r = sshkey_froms(buf, &k)) != 0 ||
-                   (r = sshbuf_get_bignum2(buf, &rsa_d)) != 0 ||
+               if ((r = sshbuf_get_bignum2(buf, &rsa_d)) != 0 ||
                    (r = sshbuf_get_bignum2(buf, &rsa_iqmp)) != 0 ||
                    (r = sshbuf_get_bignum2(buf, &rsa_p)) != 0 ||
                    (r = sshbuf_get_bignum2(buf, &rsa_q)) != 0)
                        goto out;
-               if (k->type != type) {
-                       r = SSH_ERR_INVALID_FORMAT;
-                       goto out;
-               }
                if (!RSA_set0_key(k->rsa, NULL, NULL, rsa_d)) {
                        r = SSH_ERR_LIBCRYPTO_ERROR;
                        goto out;
@@ -3593,30 +3560,10 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                break;
 #endif /* WITH_OPENSSL */
        case KEY_ED25519:
-               if ((k = sshkey_new(type)) == NULL) {
-                       r = SSH_ERR_ALLOC_FAIL;
-                       goto out;
-               }
-               if ((r = sshbuf_get_string(buf, &ed25519_pk, &pklen)) != 0 ||
-                   (r = sshbuf_get_string(buf, &ed25519_sk, &sklen)) != 0)
-                       goto out;
-               if (pklen != ED25519_PK_SZ || sklen != ED25519_SK_SZ) {
-                       r = SSH_ERR_INVALID_FORMAT;
-                       goto out;
-               }
-               k->ed25519_pk = ed25519_pk;
-               k->ed25519_sk = ed25519_sk;
-               ed25519_pk = ed25519_sk = NULL;
-               break;
        case KEY_ED25519_CERT:
-               if ((r = sshkey_froms(buf, &k)) != 0 ||
-                   (r = sshbuf_get_string(buf, &ed25519_pk, &pklen)) != 0 ||
+               if ((r = sshbuf_get_string(buf, &ed25519_pk, &pklen)) != 0 ||
                    (r = sshbuf_get_string(buf, &ed25519_sk, &sklen)) != 0)
                        goto out;
-               if (k->type != type) {
-                       r = SSH_ERR_INVALID_FORMAT;
-                       goto out;
-               }
                if (pklen != ED25519_PK_SZ || sklen != ED25519_SK_SZ) {
                        r = SSH_ERR_INVALID_FORMAT;
                        goto out;
@@ -3626,38 +3573,9 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                ed25519_pk = ed25519_sk = NULL; /* transferred */
                break;
        case KEY_ED25519_SK:
-               if ((k = sshkey_new(type)) == NULL) {
-                       r = SSH_ERR_ALLOC_FAIL;
-                       goto out;
-               }
-               if ((r = sshbuf_get_string(buf, &ed25519_pk, &pklen)) != 0)
-                       goto out;
-               if (pklen != ED25519_PK_SZ) {
-                       r = SSH_ERR_INVALID_FORMAT;
-                       goto out;
-               }
-               if ((k->sk_key_handle = sshbuf_new()) == NULL ||
-                   (k->sk_reserved = sshbuf_new()) == NULL) {
-                       r = SSH_ERR_ALLOC_FAIL;
-                       goto out;
-               }
-               if ((r = sshbuf_get_cstring(buf, &k->sk_application,
-                   NULL)) != 0 ||
-                   (r = sshbuf_get_u8(buf, &k->sk_flags)) != 0 ||
-                   (r = sshbuf_get_stringb(buf, k->sk_key_handle)) != 0 ||
-                   (r = sshbuf_get_stringb(buf, k->sk_reserved)) != 0)
-                       goto out;
-               k->ed25519_pk = ed25519_pk;
-               ed25519_pk = NULL;
-               break;
        case KEY_ED25519_SK_CERT:
-               if ((r = sshkey_froms(buf, &k)) != 0 ||
-                   (r = sshbuf_get_string(buf, &ed25519_pk, &pklen)) != 0)
-                       goto out;
-               if (k->type != type) {
-                       r = SSH_ERR_INVALID_FORMAT;
+               if ((r = sshbuf_get_string(buf, &ed25519_pk, &pklen)) != 0)
                        goto out;
-               }
                if (pklen != ED25519_PK_SZ) {
                        r = SSH_ERR_INVALID_FORMAT;
                        goto out;
@@ -3678,10 +3596,7 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                break;
 #ifdef WITH_XMSS
        case KEY_XMSS:
-               if ((k = sshkey_new(type)) == NULL) {
-                       r = SSH_ERR_ALLOC_FAIL;
-                       goto out;
-               }
+       case KEY_XMSS_CERT:
                if ((r = sshbuf_get_cstring(buf, &xmss_name, NULL)) != 0 ||
                    (r = sshkey_xmss_init(k, xmss_name)) != 0 ||
                    (r = sshbuf_get_string(buf, &xmss_pk, &pklen)) != 0 ||
@@ -3699,28 +3614,6 @@ sshkey_private_deserialize(struct sshbuf *buf, struct sshkey **kp)
                if ((r = sshkey_xmss_deserialize_state_opt(k, buf)) != 0)
                        goto out;
                break;
-       case KEY_XMSS_CERT:
-               if ((r = sshkey_froms(buf, &k)) != 0 ||
-                   (r = sshbuf_get_cstring(buf, &xmss_name, NULL)) != 0 ||
-                   (r = sshbuf_get_string(buf, &xmss_pk, &pklen)) != 0 ||
-                   (r = sshbuf_get_string(buf, &xmss_sk, &sklen)) != 0)
-                       goto out;
-               if (k->type != type || strcmp(xmss_name, k->xmss_name) != 0) {
-                       r = SSH_ERR_INVALID_FORMAT;
-                       goto out;
-               }
-               if (pklen != sshkey_xmss_pklen(k) ||
-                   sklen != sshkey_xmss_sklen(k)) {
-                       r = SSH_ERR_INVALID_FORMAT;
-                       goto out;
-               }
-               k->xmss_pk = xmss_pk;
-               k->xmss_sk = xmss_sk;
-               xmss_pk = xmss_sk = NULL;
-               /* optional internal state */
-               if ((r = sshkey_xmss_deserialize_state_opt(k, buf)) != 0)
-                       goto out;
-               break;
 #endif /* WITH_XMSS */
        default:
                r = SSH_ERR_KEY_TYPE_UNKNOWN;