de-fatal kex-ecdh

ssh/kex.h

@@ -164,10 +164,10 @@ int
 kexgex_hash(const EVP_MD *, char *, char *, char *, size_t, char *,
     size_t, u_char *, size_t, int, int, int, BIGNUM *, BIGNUM *, BIGNUM *,
     BIGNUM *, BIGNUM *, u_char **, size_t *);
-void
-kex_ecdh_hash(const EVP_MD *, const EC_GROUP *, char *, char *, char *, int,
-    char *, int, u_char *, int, const EC_POINT *, const EC_POINT *,
-    const BIGNUM *, u_char **, u_int *);
+int
+kex_ecdh_hash(const EVP_MD *, const EC_GROUP *, char *, char *, char *, size_t,
+    char *, size_t, u_char *, size_t, const EC_POINT *, const EC_POINT *,
+    const BIGNUM *, u_char **, size_t *);
 
 int	kex_ecdh_name_to_nid(const char *);
 const EVP_MD *kex_ecdh_name_to_evpmd(const char *);

ssh/kexecdh.c

@@ -40,12 +40,13 @@
 #include "cipher.h"
 #include "kex.h"
 #include "log.h"
+#include "err.h"
 
 int
 kex_ecdh_name_to_nid(const char *kexname)
 {
 	if (strlen(kexname) < sizeof(KEX_ECDH_SHA2_STEM) - 1)
-		fatal("%s: kexname too short \"%s\"", __func__, kexname);
+		return -1;
 	return sshkey_curve_name_to_nid(kexname +
 	    sizeof(KEX_ECDH_SHA2_STEM) - 1);
 }
@@ -60,54 +61,57 @@ kex_ecdh_name_to_evpmd(const char *kexname)
 	return sshkey_ec_nid_to_evpmd(nid);
 }
 
-void
+int
 kex_ecdh_hash(
     const EVP_MD *evp_md,
     const EC_GROUP *ec_group,
     char *client_version_string,
     char *server_version_string,
-    char *ckexinit, int ckexinitlen,
-    char *skexinit, int skexinitlen,
-    u_char *serverhostkeyblob, int sbloblen,
+    char *ckexinit, size_t ckexinitlen,
+    char *skexinit, size_t skexinitlen,
+    u_char *serverhostkeyblob, size_t sbloblen,
     const EC_POINT *client_dh_pub,
     const EC_POINT *server_dh_pub,
     const BIGNUM *shared_secret,
-    u_char **hash, u_int *hashlen)
+    u_char **hash, size_t *hashlen)
 {
-	Buffer b;
+	struct sshbuf *b;
 	EVP_MD_CTX md;
 	static u_char digest[EVP_MAX_MD_SIZE];
+	int r;
 
-	buffer_init(&b);
-	buffer_put_cstring(&b, client_version_string);
-	buffer_put_cstring(&b, server_version_string);
-
-	/* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
-	buffer_put_int(&b, ckexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, ckexinit, ckexinitlen);
-	buffer_put_int(&b, skexinitlen+1);
-	buffer_put_char(&b, SSH2_MSG_KEXINIT);
-	buffer_append(&b, skexinit, skexinitlen);
-
-	buffer_put_string(&b, serverhostkeyblob, sbloblen);
-	buffer_put_ecpoint(&b, ec_group, client_dh_pub);
-	buffer_put_ecpoint(&b, ec_group, server_dh_pub);
-	buffer_put_bignum2(&b, shared_secret);
-
+	if ((b = sshbuf_new()) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_put_cstring(b, client_version_string)) != 0 ||
+	    (r = sshbuf_put_cstring(b, server_version_string)) != 0 ||
+	    /* kexinit messages: fake header: len+SSH2_MSG_KEXINIT */
+	    (r = sshbuf_put_u32(b, ckexinitlen+1)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshbuf_put(b, ckexinit, ckexinitlen)) != 0 ||
+	    (r = sshbuf_put_u32(b, skexinitlen+1)) != 0 ||
+	    (r = sshbuf_put_u8(b, SSH2_MSG_KEXINIT)) != 0 ||
+	    (r = sshbuf_put(b, skexinit, skexinitlen)) != 0 ||
+	    (r = sshbuf_put_string(b, serverhostkeyblob, sbloblen)) != 0 ||
+	    (r = sshbuf_put_ec(b, client_dh_pub, ec_group)) != 0 ||
+	    (r = sshbuf_put_ec(b, server_dh_pub, ec_group)) != 0 ||
+	    (r = sshbuf_put_bignum2(b, shared_secret)) != 0) {
+		sshbuf_free(b);
+		return r;
+	}
 #ifdef DEBUG_KEX
 	buffer_dump(&b);
 #endif
-	EVP_DigestInit(&md, evp_md);
-	EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
-	EVP_DigestFinal(&md, digest, NULL);
-
-	buffer_free(&b);
-
+	if (EVP_DigestInit(&md, evp_md) != 1 ||
+	    EVP_DigestUpdate(&md, sshbuf_ptr(b), sshbuf_len(b)) != 1 ||
+	    EVP_DigestFinal(&md, digest, NULL) != 1) {
+		sshbuf_free(b);
+		return SSH_ERR_LIBCRYPTO_ERROR;
+	}
+	sshbuf_free(b);
 #ifdef DEBUG_KEX
 	dump_digest("hash", digest, EVP_MD_size(evp_md));
 #endif
 	*hash = digest;
 	*hashlen = EVP_MD_size(evp_md);
+	return 0;
 }
-

ssh/kexecdhc.c

@@ -51,33 +51,46 @@ void
 kexecdh_client(struct ssh *ssh)
 {
 	Kex *kex = ssh->kex;
-	EC_KEY *client_key;
+	EC_KEY *client_key = NULL;
 	const EC_GROUP *group;
-	int curve_nid;
+	const EC_POINT *public_key;
+	int r, curve_nid;
 
-	if ((curve_nid = kex_ecdh_name_to_nid(kex->name)) == -1)
-		fatal("%s: unsupported ECDH curve \"%s\"", __func__, kex->name);
-	if ((client_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL)
-		fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
-	if (EC_KEY_generate_key(client_key) != 1)
-		fatal("%s: EC_KEY_generate_key failed", __func__);
+	if ((curve_nid = kex_ecdh_name_to_nid(kex->name)) == -1) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if ((client_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if (EC_KEY_generate_key(client_key) != 1) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 	group = EC_KEY_get0_group(client_key);
+	public_key = EC_KEY_get0_public_key(client_key);
 
-	ssh_packet_start(ssh, SSH2_MSG_KEX_ECDH_INIT);
-	ssh_packet_put_ecpoint(ssh, group, EC_KEY_get0_public_key(client_key));
-	ssh_packet_send(ssh);
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_INIT)) != 0 ||
+	    (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
 	debug("sending SSH2_MSG_KEX_ECDH_INIT");
 
 #ifdef DEBUG_KEXECDH
 	fputs("client private key:\n", stderr);
 	sshkey_dump_ec_key(client_key);
 #endif
-
 	kex->ec_client_key = client_key;
 	kex->ec_group = group;
 
 	debug("expecting SSH2_MSG_KEX_ECDH_REPLY");
 	ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &input_kex_ecdh_reply);
+	return;
+ out:
+	if (client_key)
+		EC_KEY_free(client_key);
+	fatal("%s: %s", __func__, ssh_err(r));
 }
 
 static int
@@ -85,68 +98,77 @@ input_kex_ecdh_reply(int type, u_int32_t seq, struct ssh *ssh)
 {
 	Kex *kex = ssh->kex;
 	const EC_GROUP *group;
-	EC_POINT *server_public;
+	EC_POINT *server_public = NULL;
 	EC_KEY *client_key;
-	BIGNUM *shared_secret;
-	struct sshkey *server_host_key;
+	BIGNUM *shared_secret = NULL;
+	struct sshkey *server_host_key = NULL;
 	u_char *server_host_key_blob = NULL, *signature = NULL;
-	u_char *kbuf, *hash;
-	u_int klen, slen, sbloblen, hashlen;
+	u_char *kbuf = NULL, *hash;
+	size_t slen, sbloblen;
+	size_t klen = 0, hashlen;
 	int r;
 
+	if (kex->verify_host_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
 	group = kex->ec_group;
 	client_key = kex->ec_client_key;
 
 	/* hostkey */
-	server_host_key_blob = ssh_packet_get_string(ssh, &sbloblen);
-	if ((r = sshkey_from_blob(server_host_key_blob, sbloblen,
+	if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
+	    &sbloblen)) != 0 ||
+	    (r = sshkey_from_blob(server_host_key_blob, sbloblen,
 	    &server_host_key)) != 0)
-		fatal("%s: could not parse server host key: %s",
-		    __func__, ssh_err(r));
-	if (server_host_key == NULL)
-		fatal("cannot decode server_host_key_blob");
-	if (server_host_key->type != kex->hostkey_type)
-		fatal("type mismatch for decoded server_host_key_blob");
-	if (kex->verify_host_key == NULL)
-		fatal("cannot verify server_host_key");
-	if (kex->verify_host_key(server_host_key, ssh) == -1)
-		fatal("server_host_key verification failed");
+		goto out;
+	if (server_host_key->type != kex->hostkey_type) {
+		r = SSH_ERR_KEY_TYPE_MISMATCH;
+		goto out;
+	}
+	if (kex->verify_host_key(server_host_key, ssh) == -1) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
 
 	/* Q_S, server public key */
-	if ((server_public = EC_POINT_new(group)) == NULL)
-		fatal("%s: EC_POINT_new failed", __func__);
-	ssh_packet_get_ecpoint(ssh, group, server_public);
-
-	if (sshkey_ec_validate_public(group, server_public) != 0)
-		fatal("%s: invalid server public key", __func__);
+	/* signed H */
+	if ((server_public = EC_POINT_new(group)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshpkt_get_ec(ssh, server_public, group)) != 0 ||
+	    (r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
 
 #ifdef DEBUG_KEXECDH
 	fputs("server public key:\n", stderr);
 	sshkey_dump_ec_point(group, server_public);
 #endif
-
-	/* signed H */
-	signature = ssh_packet_get_string(ssh, &slen);
-	ssh_packet_check_eom(ssh);
+	if (sshkey_ec_validate_public(group, server_public) != 0) {
+		sshpkt_disconnect(ssh, "invalid server public key");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
 
 	klen = (EC_GROUP_get_degree(group) + 7) / 8;
-	kbuf = xmalloc(klen);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
 	if (ECDH_compute_key(kbuf, klen, server_public,
-	    client_key, NULL) != (int)klen)
-		fatal("%s: ECDH_compute_key failed", __func__);
+	    client_key, NULL) != (int)klen ||
+	    BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 
 #ifdef DEBUG_KEXECDH
 	dump_digest("shared secret", kbuf, klen);
 #endif
-	if ((shared_secret = BN_new()) == NULL)
-		fatal("%s: BN_new failed", __func__);
-	if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
-		fatal("%s: BN_bin2bn failed", __func__);
-	memset(kbuf, 0, klen);
-	xfree(kbuf);
-
 	/* calc and verify H */
-	kex_ecdh_hash(
+	if ((r = kex_ecdh_hash(
 	    kex->evp_md,
 	    group,
 	    kex->client_version_string,
@@ -157,28 +179,46 @@ input_kex_ecdh_reply(int type, u_int32_t seq, struct ssh *ssh)
 	    EC_KEY_get0_public_key(client_key),
 	    server_public,
 	    shared_secret,
-	    &hash, &hashlen
-	);
-	xfree(server_host_key_blob);
-	EC_POINT_clear_free(server_public);
-	EC_KEY_free(kex->ec_client_key);
-	kex->ec_client_key = NULL;
+	    &hash, &hashlen)) != 0)
+		goto out;
 
 	if ((r = sshkey_verify(server_host_key, signature, slen, hash,
 	    hashlen, datafellows)) != 0)
 		fatal("key_verify failed for server_host_key: %s", ssh_err(r));
-	sshkey_free(server_host_key);
-	xfree(signature);
 
 	/* save session id */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
 
+	/* XXX check error */
 	kex_derive_keys(ssh, hash, hashlen, shared_secret);
-	BN_clear_free(shared_secret);
 	kex_finish(ssh);
-	return 0;
+	r = 0;
+ out:
+	if (kex->ec_client_key) {
+		EC_KEY_free(kex->ec_client_key);
+		kex->ec_client_key = NULL;
+	}
+	if (server_host_key_blob)
+		free(server_host_key_blob);
+	if (server_host_key)
+		sshkey_free(server_host_key);
+	if (server_public)
+		EC_POINT_clear_free(server_public);
+	if (kbuf) {
+		bzero(kbuf, klen);
+		free(kbuf);
+	}
+	if (shared_secret)
+		BN_clear_free(shared_secret);
+	if (signature)
+		free(signature);
+	return r;
 }

ssh/kexecdhs.c

@@ -61,21 +61,29 @@ input_kex_ecdh_init(int type, u_int32_t seq, struct ssh *ssh)
 {
 	Kex *kex = ssh->kex;
 	EC_POINT *client_public;
-	EC_KEY *server_key;
+	EC_KEY *server_key = NULL;
 	const EC_GROUP *group;
-	BIGNUM *shared_secret;
+	const EC_POINT *public_key;
+	BIGNUM *shared_secret = NULL;
 	struct sshkey *server_host_private, *server_host_public;
 	u_char *server_host_key_blob = NULL, *signature = NULL;
-	u_char *kbuf, *hash;
-	u_int klen, slen, sbloblen, hashlen;
+	u_char *kbuf = NULL, *hash;
+	u_int slen, sbloblen;
+	size_t klen = 0, hashlen;
 	int curve_nid, r;
 
-	if ((curve_nid = kex_ecdh_name_to_nid(kex->name)) == -1)
-		fatal("%s: unsupported ECDH curve \"%s\"", __func__, kex->name);
-	if ((server_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL)
-		fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
-	if (EC_KEY_generate_key(server_key) != 1)
-		fatal("%s: EC_KEY_generate_key failed", __func__);
+	if ((curve_nid = kex_ecdh_name_to_nid(kex->name)) == -1) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if ((server_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if (EC_KEY_generate_key(server_key) != 1) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 	group = EC_KEY_get0_group(server_key);
 
 #ifdef DEBUG_KEXECDH
@@ -84,51 +92,57 @@ input_kex_ecdh_init(int type, u_int32_t seq, struct ssh *ssh)
 #endif
 
 	if (kex->load_host_public_key == NULL ||
-	    kex->load_host_private_key == NULL)
-		fatal("Cannot load hostkey");
-	server_host_public = kex->load_host_public_key(kex->hostkey_type, ssh);
-	if (server_host_public == NULL)
-		fatal("Unsupported hostkey type %d", kex->hostkey_type);
-	server_host_private = kex->load_host_private_key(kex->hostkey_type, ssh);
-	if (server_host_private == NULL)
-		fatal("Missing private key for hostkey type %d",
-		    kex->hostkey_type);
-
-	if ((client_public = EC_POINT_new(group)) == NULL)
-		fatal("%s: EC_POINT_new failed", __func__);
-	ssh_packet_get_ecpoint(ssh, group, client_public);
-	ssh_packet_check_eom(ssh);
-
-	if (sshkey_ec_validate_public(group, client_public) != 0)
-		fatal("%s: invalid client public key", __func__);
+	    kex->load_host_private_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	if ((server_host_public = kex->load_host_public_key(kex->hostkey_type,
+	    ssh)) == NULL ||
+	    (server_host_private = kex->load_host_private_key(kex->hostkey_type,
+	    ssh)) == NULL) {
+		r = SSH_ERR_KEY_TYPE_MISMATCH;  /* XXX */
+		goto out;
+	}
+	if ((client_public = EC_POINT_new(group)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshpkt_get_ec(ssh, client_public, group)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
 
 #ifdef DEBUG_KEXECDH
 	fputs("client public key:\n", stderr);
 	sshkey_dump_ec_point(group, client_public);
 #endif
+	if (sshkey_ec_validate_public(group, client_public) != 0) {
+		sshpkt_disconnect(ssh, "invalid client public key");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
 
 	/* Calculate shared_secret */
 	klen = (EC_GROUP_get_degree(group) + 7) / 8;
-	kbuf = xmalloc(klen);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
 	if (ECDH_compute_key(kbuf, klen, client_public,
-	    server_key, NULL) != (int)klen)
-		fatal("%s: ECDH_compute_key failed", __func__);
+	    server_key, NULL) != (int)klen ||
+	    BN_bin2bn(kbuf, klen, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
 
-#ifdef DEBUG_KEXDH
+#ifdef DEBUG_KEXECDH
 	dump_digest("shared secret", kbuf, klen);
 #endif
-	if ((shared_secret = BN_new()) == NULL)
-		fatal("%s: BN_new failed", __func__);
-	if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
-		fatal("%s: BN_bin2bn failed", __func__);
-	memset(kbuf, 0, klen);
-	xfree(kbuf);
-
 	/* calc H */
 	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
 	    &sbloblen)) != 0)
-		fatal("%s: sshkey_to_blob: %s", __func__, ssh_err(r));
-	kex_ecdh_hash(
+		goto out;
+	if ((r = kex_ecdh_hash(
 	    kex->evp_md,
 	    group,
 	    kex->client_version_string,
@@ -139,14 +153,17 @@ input_kex_ecdh_init(int type, u_int32_t seq, struct ssh *ssh)
 	    client_public,
 	    EC_KEY_get0_public_key(server_key),
 	    shared_secret,
-	    &hash, &hashlen
-	);
-	EC_POINT_clear_free(client_public);
+	    &hash, &hashlen)) != 0)
+		goto out;
 
 	/* save session id := H */
 	if (kex->session_id == NULL) {
 		kex->session_id_len = hashlen;
-		kex->session_id = xmalloc(kex->session_id_len);
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
 		memcpy(kex->session_id, hash, kex->session_id_len);
 	}
 
@@ -157,20 +174,35 @@ input_kex_ecdh_init(int type, u_int32_t seq, struct ssh *ssh)
 
 	/* destroy_sensitive_data(); */
 
+	public_key = EC_KEY_get0_public_key(server_key);
 	/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
-	ssh_packet_start(ssh, SSH2_MSG_KEX_ECDH_REPLY);
-	ssh_packet_put_string(ssh, server_host_key_blob, sbloblen);
-	ssh_packet_put_ecpoint(ssh, group, EC_KEY_get0_public_key(server_key));
-	ssh_packet_put_string(ssh, signature, slen);
-	ssh_packet_send(ssh);
-
-	xfree(signature);
-	xfree(server_host_key_blob);
-	/* have keys, free server key */
-	EC_KEY_free(server_key);
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
+	    (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
+	    (r = sshpkt_put_ec(ssh, public_key, group)) != 0 ||
+	    (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
 
+	/* have keys */
 	kex_derive_keys(ssh, hash, hashlen, shared_secret);
-	BN_clear_free(shared_secret);
 	kex_finish(ssh);
-	return 0;
+	r = 0;
+ out:
+	if (kex->ec_client_key) {
+		EC_KEY_free(kex->ec_client_key);
+		kex->ec_client_key = NULL;
+	}
+	if (server_host_key_blob)
+		free(server_host_key_blob);
+	if (server_key)
+		EC_KEY_free(server_key);
+	if (kbuf) {
+		bzero(kbuf, klen);
+		free(kbuf);
+	}
+	if (shared_secret)
+		BN_clear_free(shared_secret);
+	if (signature)
+		free(signature);
+	return r;
 }