upstream: fix shield/unshield for xmss keys: - in ssh-agent we need

to delay the call to shield   until we have received key specific options. -
when serializing xmss keys for shield we need to deal with   all optional
components (e.g. state might not be loaded). ok djm@

OpenBSD-Commit-ID: cc2db82524b209468eb176d6b4d6b9486422f41f

ssh-agent.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-agent.c,v 1.241 2019/11/12 22:36:44 djm Exp $ */
+/* $OpenBSD: ssh-agent.c,v 1.242 2019/11/13 07:53:10 markus Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -560,10 +560,6 @@ process_add_identity(SocketEntry *e)
 		error("%s: decode private key: %s", __func__, ssh_err(r));
 		goto err;
 	}
-	if ((r = sshkey_shield_private(k)) != 0) {
-		error("%s: shield private key: %s", __func__, ssh_err(r));
-		goto err;
-	}
 	while (sshbuf_len(e->request)) {
 		if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) {
 			error("%s: buffer error: %s", __func__, ssh_err(r));
@@ -645,6 +641,10 @@ process_add_identity(SocketEntry *e)
 			goto send;
 		}
 	}
+	if ((r = sshkey_shield_private(k)) != 0) {
+		error("%s: shield private key: %s", __func__, ssh_err(r));
+		goto err;
+	}
 
 	success = 1;
 	if (lifetime && !death)

sshkey-xmss.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey-xmss.c,v 1.7 2019/10/14 06:00:02 djm Exp $ */
+/* $OpenBSD: sshkey-xmss.c,v 1.8 2019/11/13 07:53:10 markus Exp $ */
 /*
  * Copyright (c) 2017 Markus Friedl.  All rights reserved.
  *
@@ -69,7 +69,7 @@ struct ssh_xmss_state {
 	u_int32_t	maxidx;		/* restricted # of signatures */
 	int		have_state;	/* .state file exists */
 	int		lockfd;		/* locked in sshkey_xmss_get_state() */
-	int		allow_update;	/* allow sshkey_xmss_update_state() */
+	u_char		allow_update;	/* allow sshkey_xmss_update_state() */
 	char		*enc_ciphername;/* encrypt state with cipher */
 	u_char		*enc_keyiv;	/* encrypt state with key */
 	u_int32_t	enc_keyiv_len;	/* length of enc_keyiv */
@@ -716,6 +716,7 @@ sshkey_xmss_serialize_state_opt(const struct sshkey *k, struct sshbuf *b,
 {
 	struct ssh_xmss_state *state = k->xmss_state;
 	int r = SSH_ERR_INVALID_ARGUMENT;
+	u_char have_stack, have_filename, have_enc;
 
 	if (state == NULL)
 		return SSH_ERR_INVALID_ARGUMENT;
@@ -727,9 +728,35 @@ sshkey_xmss_serialize_state_opt(const struct sshkey *k, struct sshbuf *b,
 		break;
 	case SSHKEY_SERIALIZE_FULL:
 		if ((r = sshkey_xmss_serialize_enc_key(k, b)) != 0)
-			break;
+			return r;
 		r = sshkey_xmss_serialize_state(k, b);
 		break;
+	case SSHKEY_SERIALIZE_SHIELD:
+		/* all of stack/filename/enc are optional */
+		have_stack = state->stack != NULL;
+		if ((r = sshbuf_put_u8(b, have_stack)) != 0)
+			return r;
+		if (have_stack) {
+			state->idx = PEEK_U32(k->xmss_sk);	/* update */
+			if ((r = sshkey_xmss_serialize_state(k, b)) != 0)
+				return r;
+		}
+		have_filename = k->xmss_filename != NULL;
+		if ((r = sshbuf_put_u8(b, have_filename)) != 0)
+			return r;
+		if (have_filename &&
+		    (r = sshbuf_put_cstring(b, k->xmss_filename)) != 0)
+			return r;
+		have_enc = state->enc_keyiv != NULL;
+		if ((r = sshbuf_put_u8(b, have_enc)) != 0)
+			return r;
+		if (have_enc &&
+		    (r = sshkey_xmss_serialize_enc_key(k, b)) != 0)
+			return r;
+		if ((r = sshbuf_put_u32(b, state->maxidx)) != 0 ||
+		    (r = sshbuf_put_u8(b, state->allow_update)) != 0)
+			return r;
+		break;
 	case SSHKEY_SERIALIZE_DEFAULT:
 		r = 0;
 		break;
@@ -808,8 +835,9 @@ sshkey_xmss_deserialize_state(struct sshkey *k, struct sshbuf *b)
 int
 sshkey_xmss_deserialize_state_opt(struct sshkey *k, struct sshbuf *b)
 {
+	struct ssh_xmss_state *state = k->xmss_state;
 	enum sshkey_serialize_rep opts;
-	u_char have_state;
+	u_char have_state, have_stack, have_filename, have_enc;
 	int r;
 
 	if ((r = sshbuf_get_u8(b, &have_state)) != 0)
@@ -820,6 +848,26 @@ sshkey_xmss_deserialize_state_opt(struct sshkey *k, struct sshbuf *b)
 	case SSHKEY_SERIALIZE_DEFAULT:
 		r = 0;
 		break;
+	case SSHKEY_SERIALIZE_SHIELD:
+		if ((r = sshbuf_get_u8(b, &have_stack)) != 0)
+			return r;
+		if (have_stack &&
+		    (r = sshkey_xmss_deserialize_state(k, b)) != 0)
+			return r;
+		if ((r = sshbuf_get_u8(b, &have_filename)) != 0)
+			return r;
+		if (have_filename &&
+		    (r = sshbuf_get_cstring(b, &k->xmss_filename, NULL)) != 0)
+			return r;
+		if ((r = sshbuf_get_u8(b, &have_enc)) != 0)
+			return r;
+		if (have_enc &&
+		    (r = sshkey_xmss_deserialize_enc_key(k, b)) != 0)
+			return r;
+		if ((r = sshbuf_get_u32(b, &state->maxidx)) != 0 ||
+		    (r = sshbuf_get_u8(b, &state->allow_update)) != 0)
+			return r;
+		break;
 	case SSHKEY_SERIALIZE_STATE:
 		if ((r = sshkey_xmss_deserialize_state(k, b)) != 0)
 			return r;

sshkey.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.90 2019/11/12 19:33:08 markus Exp $ */
+/* $OpenBSD: sshkey.c,v 1.91 2019/11/13 07:53:10 markus Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -2045,7 +2045,7 @@ sshkey_shield_private(struct sshkey *k)
 	if (sshkey_is_shielded(k) && (r = sshkey_unshield_private(k)) != 0)
 		goto out;
 	if ((r = sshkey_private_serialize_opt(k, prvbuf,
-	     SSHKEY_SERIALIZE_FULL)) != 0)
+	     SSHKEY_SERIALIZE_SHIELD)) != 0)
 		goto out;
 	/* pad to cipher blocksize */
 	i = 0;

sshkey.h

@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.h,v 1.38 2019/11/12 19:33:08 markus Exp $ */
+/* $OpenBSD: sshkey.h,v 1.39 2019/11/13 07:53:10 markus Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -87,9 +87,10 @@ enum sshkey_fp_rep {
 /* Private key serialisation formats, used on the wire */
 enum sshkey_serialize_rep {
 	SSHKEY_SERIALIZE_DEFAULT = 0,
-	SSHKEY_SERIALIZE_STATE = 1,
+	SSHKEY_SERIALIZE_STATE = 1,	/* only state is serialized */
-	SSHKEY_SERIALIZE_FULL = 2,
+	SSHKEY_SERIALIZE_FULL = 2,	/* include keys for saving to disk */
-	SSHKEY_SERIALIZE_INFO = 254,
+	SSHKEY_SERIALIZE_SHIELD = 3,	/* everything, for encrypting in ram */
+	SSHKEY_SERIALIZE_INFO = 254,	/* minimal information */
 };
 
 /* Private key disk formats */