Add new structure for signature options

This is populated during signature verification with additional fields
that are present in and covered by the signature. At the moment, it is
only used to record security key-specific options, especially the flags
field.

with and ok markus@

17 files changed, 147 insertions, 50 deletions

diff --git a/usr.bin/ssh/auth2-hostbased.c b/usr.bin/ssh/auth2-hostbased.c
index 68c050631ed..a1fe6fe0f13 100644
--- a/usr.bin/ssh/auth2-hostbased.c
+++ b/usr.bin/ssh/auth2-hostbased.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-hostbased.c,v 1.41 2019/09/06 04:53:27 djm Exp $ */
+/* $OpenBSD: auth2-hostbased.c,v 1.42 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -150,7 +150,7 @@ userauth_hostbased(struct ssh *ssh)
 	if (PRIVSEP(hostbased_key_allowed(ssh, authctxt->pw, cuser,
 	    chost, key)) &&
 	    PRIVSEP(sshkey_verify(key, sig, slen,
-	    sshbuf_ptr(b), sshbuf_len(b), pkalg, ssh->compat)) == 0)
+	    sshbuf_ptr(b), sshbuf_len(b), pkalg, ssh->compat, NULL)) == 0)
 		authenticated = 1;
 
 	auth2_record_key(authctxt, authenticated, key);
diff --git a/usr.bin/ssh/auth2-pubkey.c b/usr.bin/ssh/auth2-pubkey.c
index 455dee1be38..d5438fe220f 100644
--- a/usr.bin/ssh/auth2-pubkey.c
+++ b/usr.bin/ssh/auth2-pubkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth2-pubkey.c,v 1.94 2019/09/06 04:53:27 djm Exp $ */
+/* $OpenBSD: auth2-pubkey.c,v 1.95 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
@@ -95,6 +95,7 @@ userauth_pubkey(struct ssh *ssh)
 	int r, pktype;
 	int authenticated = 0;
 	struct sshauthopt *authopts = NULL;
+	struct sshkey_sig_details *sig_details = NULL;
 
 	if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
 	    (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
@@ -210,9 +211,14 @@ userauth_pubkey(struct ssh *ssh)
 		    PRIVSEP(sshkey_verify(key, sig, slen,
 		    sshbuf_ptr(b), sshbuf_len(b),
 		    (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
-		    ssh->compat)) == 0) {
+		    ssh->compat, &sig_details)) == 0) {
 			authenticated = 1;
 		}
+		if (sig_details != NULL) {
+			debug("%s: sk_counter = %u, sk_flags = 0x%02x",
+			    __func__, sig_details->sk_counter,
+			    sig_details->sk_flags);
+		}
 		auth2_record_key(authctxt, authenticated, key);
 	} else {
 		debug("%s: test pkalg %s pkblob %s%s%s",
@@ -263,6 +269,7 @@ done:
 	free(key_s);
 	free(ca_s);
 	free(sig);
+	sshkey_sig_details_free(sig_details);
 	return authenticated;
 }
 
diff --git a/usr.bin/ssh/clientloop.c b/usr.bin/ssh/clientloop.c
index 4838b72fba5..76a8c50fdbc 100644
--- a/usr.bin/ssh/clientloop.c
+++ b/usr.bin/ssh/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.328 2019/11/13 04:47:52 deraadt Exp $ */
+/* $OpenBSD: clientloop.c,v 1.329 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1989,7 +1989,8 @@ client_global_hostkeys_private_confirm(struct ssh *ssh, int type,
 		    sshkey_type_plain(ctx->keys[i]->type) == KEY_RSA;
 		if ((r = sshkey_verify(ctx->keys[i], sig, siglen,
 		    sshbuf_ptr(signdata), sshbuf_len(signdata),
-		    use_kexsigtype ? ssh->kex->hostkey_alg : NULL, 0)) != 0) {
+		    use_kexsigtype ? ssh->kex->hostkey_alg : NULL, 0,
+		    NULL)) != 0) {
 			error("%s: server gave bad signature for %s key %zu",
 			    __func__, sshkey_type(ctx->keys[i]), i);
 			goto out;
diff --git a/usr.bin/ssh/kexgen.c b/usr.bin/ssh/kexgen.c
index dbf99d436e4..583c21fd78b 100644
--- a/usr.bin/ssh/kexgen.c
+++ b/usr.bin/ssh/kexgen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgen.c,v 1.3 2019/09/06 05:23:55 djm Exp $ */
+/* $OpenBSD: kexgen.c,v 1.4 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright (c) 2019 Markus Friedl.  All rights reserved.
  *
@@ -209,7 +209,7 @@ input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh)
 		goto out;
 
 	if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
-	    kex->hostkey_alg, ssh->compat)) != 0)
+	    kex->hostkey_alg, ssh->compat, NULL)) != 0)
 		goto out;
 
 	if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
diff --git a/usr.bin/ssh/kexgexc.c b/usr.bin/ssh/kexgexc.c
index 889db0dfdcc..e8749ef6894 100644
--- a/usr.bin/ssh/kexgexc.c
+++ b/usr.bin/ssh/kexgexc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexc.c,v 1.34 2019/01/23 00:30:41 djm Exp $ */
+/* $OpenBSD: kexgexc.c,v 1.35 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -192,7 +192,7 @@ input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh)
 		goto out;
 
 	if ((r = sshkey_verify(server_host_key, signature, slen, hash,
-	    hashlen, kex->hostkey_alg, ssh->compat)) != 0)
+	    hashlen, kex->hostkey_alg, ssh->compat, NULL)) != 0)
 		goto out;
 
 	if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
diff --git a/usr.bin/ssh/krl.c b/usr.bin/ssh/krl.c
index 212ea198ae6..1d00bfe38fe 100644
--- a/usr.bin/ssh/krl.c
+++ b/usr.bin/ssh/krl.c
@@ -14,7 +14,7 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $OpenBSD: krl.c,v 1.45 2019/10/31 21:23:19 djm Exp $ */
+/* $OpenBSD: krl.c,v 1.46 2019/11/25 00:51:37 djm Exp $ */
 
 #include <sys/types.h>
 #include <sys/tree.h>
@@ -1077,7 +1077,7 @@ ssh_krl_from_blob(struct sshbuf *buf, struct ssh_krl **krlp,
 		}
 		/* Check signature over entire KRL up to this point */
 		if ((r = sshkey_verify(key, blob, blen,
-		    sshbuf_ptr(buf), sig_off, NULL, 0)) != 0)
+		    sshbuf_ptr(buf), sig_off, NULL, 0, NULL)) != 0)
 			goto out;
 		/* Check if this key has already signed this KRL */
 		for (i = 0; i < nca_used; i++) {
diff --git a/usr.bin/ssh/monitor.c b/usr.bin/ssh/monitor.c
index 99c1dbba427..bca521c8597 100644
--- a/usr.bin/ssh/monitor.c
+++ b/usr.bin/ssh/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.201 2019/11/19 22:21:15 djm Exp $ */
+/* $OpenBSD: monitor.c,v 1.202 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -1147,6 +1147,7 @@ mm_answer_keyverify(struct ssh *ssh, int sock, struct sshbuf *m)
 	char *sigalg;
 	size_t signaturelen, datalen, bloblen;
 	int r, ret, valid_data = 0, encoded_ret;
+	struct sshkey_sig_details *sig_details = NULL;
 
 	if ((r = sshbuf_get_string(m, &blob, &bloblen)) != 0 ||
 	    (r = sshbuf_get_string(m, &signature, &signaturelen)) != 0 ||
@@ -1186,7 +1187,7 @@ mm_answer_keyverify(struct ssh *ssh, int sock, struct sshbuf *m)
 		fatal("%s: bad signature data blob", __func__);
 
 	ret = sshkey_verify(key, signature, signaturelen, data, datalen,
-	    sigalg, ssh->compat);
+	    sigalg, ssh->compat, &sig_details);
 	debug3("%s: %s %p signature %s%s%s", __func__, auth_method, key,
 	    (ret == 0) ? "verified" : "unverified",
 	    (ret != 0) ? ": " : "", (ret != 0) ? ssh_err(ret) : "");
@@ -1206,8 +1207,15 @@ mm_answer_keyverify(struct ssh *ssh, int sock, struct sshbuf *m)
 
 	/* encode ret != 0 as positive integer, since we're sending u32 */
 	encoded_ret = (ret != 0);
-	if ((r = sshbuf_put_u32(m, encoded_ret)) != 0)
+	if ((r = sshbuf_put_u32(m, encoded_ret)) != 0 ||
+	    (r = sshbuf_put_u8(m, sig_details != NULL != 0)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	if (sig_details != NULL) {
+		if ((r = sshbuf_put_u32(m, sig_details->sk_counter)) != 0 ||
+		    (r = sshbuf_put_u8(m, sig_details->sk_flags)) != 0)
+			fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	}
+	sshkey_sig_details_free(sig_details);
 	mm_request_send(sock, MONITOR_ANS_KEYVERIFY, m);
 
 	return ret == 0;
diff --git a/usr.bin/ssh/monitor_wrap.c b/usr.bin/ssh/monitor_wrap.c
index aeb0766da27..a27270ab2a8 100644
--- a/usr.bin/ssh/monitor_wrap.c
+++ b/usr.bin/ssh/monitor_wrap.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor_wrap.c,v 1.115 2019/11/18 16:10:05 naddy Exp $ */
+/* $OpenBSD: monitor_wrap.c,v 1.116 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -477,15 +477,19 @@ mm_key_allowed(enum mm_keytype type, const char *user, const char *host,
 
 int
 mm_sshkey_verify(const struct sshkey *key, const u_char *sig, size_t siglen,
-    const u_char *data, size_t datalen, const char *sigalg, u_int compat)
+    const u_char *data, size_t datalen, const char *sigalg, u_int compat,
+    struct sshkey_sig_details **sig_detailsp)
 {
 	struct sshbuf *m;
 	u_int encoded_ret = 0;
 	int r;
+	u_char sig_details_present, flags;
+	u_int counter;
 
 	debug3("%s entering", __func__);
 
-
+	if (sig_detailsp != NULL)
+		*sig_detailsp = NULL;
 	if ((m = sshbuf_new()) == NULL)
 		fatal("%s: sshbuf_new failed", __func__);
 	if ((r = sshkey_puts(key, m)) != 0 ||
@@ -500,8 +504,19 @@ mm_sshkey_verify(const struct sshkey *key, const u_char *sig, size_t siglen,
 	mm_request_receive_expect(pmonitor->m_recvfd,
 	    MONITOR_ANS_KEYVERIFY, m);
 
-	if ((r = sshbuf_get_u32(m, &encoded_ret)) != 0)
+	if ((r = sshbuf_get_u32(m, &encoded_ret)) != 0 ||
+	    (r = sshbuf_get_u8(m, &sig_details_present)) != 0)
 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	if (sig_details_present && encoded_ret == 0) {
+		if ((r = sshbuf_get_u32(m, &counter)) != 0 ||
+		    (r = sshbuf_get_u8(m, &flags)) != 0)
+			fatal("%s: buffer error: %s", __func__, ssh_err(r));
+		if (sig_detailsp != NULL) {
+			*sig_detailsp = xcalloc(1, sizeof(**sig_detailsp));
+			(*sig_detailsp)->sk_counter = counter;
+			(*sig_detailsp)->sk_flags = flags;
+		}
+	}
 
 	sshbuf_free(m);
 
diff --git a/usr.bin/ssh/monitor_wrap.h b/usr.bin/ssh/monitor_wrap.h
index c1efc879ede..b2c64adfbf6 100644
--- a/usr.bin/ssh/monitor_wrap.h
+++ b/usr.bin/ssh/monitor_wrap.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor_wrap.h,v 1.43 2019/10/31 21:23:19 djm Exp $ */
+/* $OpenBSD: monitor_wrap.h,v 1.44 2019/11/25 00:51:37 djm Exp $ */
 
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
@@ -38,6 +38,7 @@ struct monitor;
 struct Authctxt;
 struct sshkey;
 struct sshauthopt;
+struct sshkey_sig_details;
 
 void mm_log_handler(LogLevel, const char *, void *);
 int mm_is_monitor(void);
@@ -57,7 +58,7 @@ int mm_user_key_allowed(struct ssh *, struct passwd *, struct sshkey *, int,
 int mm_hostbased_key_allowed(struct ssh *, struct passwd *, const char *,
     const char *, struct sshkey *);
 int mm_sshkey_verify(const struct sshkey *, const u_char *, size_t,
-    const u_char *, size_t, const char *, u_int);
+    const u_char *, size_t, const char *, u_int, struct sshkey_sig_details **);
 
 #ifdef GSSAPI
 OM_uint32 mm_ssh_gssapi_server_ctx(Gssctxt **, gss_OID);
diff --git a/usr.bin/ssh/ssh-add.c b/usr.bin/ssh/ssh-add.c
index 29f8786a003..7d89a70bd82 100644
--- a/usr.bin/ssh/ssh-add.c
+++ b/usr.bin/ssh/ssh-add.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-add.c,v 1.146 2019/11/18 16:10:05 naddy Exp $ */
+/* $OpenBSD: ssh-add.c,v 1.147 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -444,7 +444,7 @@ test_key(int agent_fd, const char *filename)
 		goto done;
 	}
 	if ((r = sshkey_verify(key, sig, slen, data, sizeof(data),
-	    NULL, 0)) != 0) {
+	    NULL, 0, NULL)) != 0) {
 		error("Signature verification failed for %s: %s",
 		    filename, ssh_err(r));
 		goto done;
diff --git a/usr.bin/ssh/ssh-ecdsa-sk.c b/usr.bin/ssh/ssh-ecdsa-sk.c
index 0b943f45ec8..c75db2acb1c 100644
--- a/usr.bin/ssh/ssh-ecdsa-sk.c
+++ b/usr.bin/ssh/ssh-ecdsa-sk.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-ecdsa-sk.c,v 1.3 2019/11/25 00:38:17 djm Exp $ */
+/* $OpenBSD: ssh-ecdsa-sk.c,v 1.4 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2010 Damien Miller.  All rights reserved.
@@ -47,7 +47,8 @@
 int
 ssh_ecdsa_sk_verify(const struct sshkey *key,
     const u_char *signature, size_t signaturelen,
-    const u_char *data, size_t datalen, u_int compat)
+    const u_char *data, size_t datalen, u_int compat,
+    struct sshkey_sig_details **detailsp)
 {
 	ECDSA_SIG *sig = NULL;
 	BIGNUM *sig_r = NULL, *sig_s = NULL;
@@ -57,10 +58,13 @@ ssh_ecdsa_sk_verify(const struct sshkey *key,
 	int ret = SSH_ERR_INTERNAL_ERROR;
 	struct sshbuf *b = NULL, *sigbuf = NULL, *original_signed = NULL;
 	char *ktype = NULL;
+	struct sshkey_sig_details *details = NULL;
 #ifdef DEBUG_SK
 	char *tmp = NULL;
 #endif
 
+	if (detailsp != NULL)
+		*detailsp = NULL;
 	if (key == NULL || key->ecdsa == NULL ||
 	    sshkey_type_plain(key->type) != KEY_ECDSA_SK ||
 	    signature == NULL || signaturelen == 0)
@@ -143,6 +147,12 @@ ssh_ecdsa_sk_verify(const struct sshkey *key,
 	if ((ret = ssh_digest_buffer(SSH_DIGEST_SHA256, original_signed,
 	    sighash, sizeof(sighash))) != 0)
 		goto out;
+	if ((details = calloc(1, sizeof(*details))) == NULL) {
+		ret = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	details->sk_counter = sig_counter;
+	details->sk_flags = sig_flags;
 #ifdef DEBUG_SK
 	fprintf(stderr, "%s: signed buf:\n", __func__);
 	sshbuf_dump(original_signed, stderr);
@@ -162,13 +172,18 @@ ssh_ecdsa_sk_verify(const struct sshkey *key,
 		ret = SSH_ERR_LIBCRYPTO_ERROR;
 		goto out;
 	}
-
+	/* success */
+	if (detailsp != NULL) {
+		*detailsp = details;
+		details = NULL;
+	}
  out:
 	explicit_bzero(&sig_flags, sizeof(sig_flags));
 	explicit_bzero(&sig_counter, sizeof(sig_counter));
 	explicit_bzero(msghash, sizeof(msghash));
 	explicit_bzero(sighash, sizeof(msghash));
 	explicit_bzero(apphash, sizeof(apphash));
+	sshkey_sig_details_free(details);
 	sshbuf_free(original_signed);
 	sshbuf_free(sigbuf);
 	sshbuf_free(b);
diff --git a/usr.bin/ssh/ssh-ed25519-sk.c b/usr.bin/ssh/ssh-ed25519-sk.c
index 622cb45c245..d11fde6fda6 100644
--- a/usr.bin/ssh/ssh-ed25519-sk.c
+++ b/usr.bin/ssh/ssh-ed25519-sk.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-ed25519-sk.c,v 1.2 2019/11/12 19:34:40 markus Exp $ */
+/* $OpenBSD: ssh-ed25519-sk.c,v 1.3 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright (c) 2019 Markus Friedl.  All rights reserved.
  *
@@ -33,7 +33,8 @@
 int
 ssh_ed25519_sk_verify(const struct sshkey *key,
     const u_char *signature, size_t signaturelen,
-    const u_char *data, size_t datalen, u_int compat)
+    const u_char *data, size_t datalen, u_int compat,
+    struct sshkey_sig_details **detailsp)
 {
 	struct sshbuf *b = NULL;
 	struct sshbuf *encoded = NULL;
@@ -49,6 +50,10 @@ ssh_ed25519_sk_verify(const struct sshkey *key,
 	unsigned long long smlen = 0, mlen = 0;
 	int r = SSH_ERR_INTERNAL_ERROR;
 	int ret;
+	struct sshkey_sig_details *details = NULL;
+
+	if (detailsp != NULL)
+		*detailsp = NULL;
 
 	if (key == NULL ||
 	    sshkey_type_plain(key->type) != KEY_ED25519_SK ||
@@ -84,6 +89,12 @@ ssh_ed25519_sk_verify(const struct sshkey *key,
 		r = SSH_ERR_INVALID_ARGUMENT;
 		goto out;
 	}
+	if ((details = calloc(1, sizeof(*details))) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	details->sk_counter = sig_counter;
+	details->sk_flags = sig_flags;
 	if ((encoded = sshbuf_new()) == NULL) {
 		r = SSH_ERR_ALLOC_FAIL;
 		goto out;
@@ -115,11 +126,16 @@ ssh_ed25519_sk_verify(const struct sshkey *key,
 	/* XXX compare 'm' and 'sm + len' ? */
 	/* success */
 	r = 0;
+	if (detailsp != NULL) {
+		*detailsp = details;
+		details = NULL;
+	}
  out:
 	if (m != NULL) {
 		explicit_bzero(m, smlen); /* NB mlen may be invalid if r != 0 */
 		free(m);
 	}
+	sshkey_sig_details_free(details);
 	sshbuf_free(b);
 	sshbuf_free(encoded);
 	free(ktype);
diff --git a/usr.bin/ssh/ssh-keygen.c b/usr.bin/ssh/ssh-keygen.c
index 22e7317b650..fde77f6ab93 100644
--- a/usr.bin/ssh/ssh-keygen.c
+++ b/usr.bin/ssh/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.369 2019/11/18 23:16:49 naddy Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.370 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -570,7 +570,7 @@ do_convert_private_ssh2(struct sshbuf *b)
 	if (sshkey_sign(key, &sig, &slen, data, sizeof(data),
 	    NULL, NULL, 0) != 0 ||
 	    sshkey_verify(key, sig, slen, data, sizeof(data),
-	    NULL, 0) != 0) {
+	    NULL, 0, NULL) != 0) {
 		sshkey_free(key);
 		free(sig);
 		return NULL;
@@ -2639,7 +2639,9 @@ verify(const char *signature, const char *sig_namespace, const char *principal,
 	struct sshbuf *sigbuf = NULL, *abuf = NULL;
 	struct sshkey *sign_key = NULL;
 	char *fp = NULL;
+	struct sshkey_sig_details *sig_details = NULL;
 
+	memset(&sig_details, 0, sizeof(sig_details));
 	if ((abuf = sshbuf_new()) == NULL)
 		fatal("%s: sshbuf_new() failed", __func__);
 
@@ -2657,13 +2659,17 @@ verify(const char *signature, const char *sig_namespace, const char *principal,
 		return r;
 	}
 	if ((r = sshsig_verify_fd(sigbuf, STDIN_FILENO, sig_namespace,
-	    &sign_key)) != 0)
+	    &sign_key, &sig_details)) != 0)
 		goto done; /* sshsig_verify() prints error */
 
 	if ((fp = sshkey_fingerprint(sign_key, fingerprint_hash,
 	    SSH_FP_DEFAULT)) == NULL)
 		fatal("%s: sshkey_fingerprint failed", __func__);
 	debug("Valid (unverified) signature from key %s", fp);
+	if (sig_details != NULL) {
+		debug2("%s: signature details: counter = %u, flags = 0x%02x",
+		    __func__, sig_details->sk_counter, sig_details->sk_flags);
+	}
 	free(fp);
 	fp = NULL;
 
@@ -2708,6 +2714,7 @@ done:
 	sshbuf_free(sigbuf);
 	sshbuf_free(abuf);
 	sshkey_free(sign_key);
+	sshkey_sig_details_free(sig_details);
 	free(fp);
 	return ret;
 }
diff --git a/usr.bin/ssh/sshkey.c b/usr.bin/ssh/sshkey.c
index 64eebf992d2..3e4f1e87c20 100644
--- a/usr.bin/ssh/sshkey.c
+++ b/usr.bin/ssh/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.95 2019/11/18 06:58:00 djm Exp $ */
+/* $OpenBSD: sshkey.c,v 1.96 2019/11/25 00:51:37 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -2262,7 +2262,7 @@ cert_parse(struct sshbuf *b, struct sshkey *key, struct sshbuf *certbuf)
 		goto out;
 	}
 	if ((ret = sshkey_verify(key->cert->signature_key, sig, slen,
-	    sshbuf_ptr(key->cert->certblob), signed_len, NULL, 0)) != 0)
+	    sshbuf_ptr(key->cert->certblob), signed_len, NULL, 0, NULL)) != 0)
 		goto out;
 	if ((ret = sshkey_get_sigtype(sig, slen,
 	    &key->cert->signature_type)) != 0)
@@ -2745,8 +2745,11 @@ sshkey_sign(struct sshkey *key,
 int
 sshkey_verify(const struct sshkey *key,
     const u_char *sig, size_t siglen,
-    const u_char *data, size_t dlen, const char *alg, u_int compat)
+    const u_char *data, size_t dlen, const char *alg, u_int compat,
+    struct sshkey_sig_details **detailsp)
 {
+	if (detailsp != NULL)
+		*detailsp = NULL;
 	if (siglen == 0 || dlen > SSH_KEY_MAX_SIGN_DATA_SIZE)
 		return SSH_ERR_INVALID_ARGUMENT;
 	switch (key->type) {
@@ -2760,7 +2763,7 @@ sshkey_verify(const struct sshkey *key,
 	case KEY_ECDSA_SK_CERT:
 	case KEY_ECDSA_SK:
 		return ssh_ecdsa_sk_verify(key, sig, siglen, data, dlen,
-		    compat);
+		    compat, detailsp);
 	case KEY_RSA_CERT:
 	case KEY_RSA:
 		return ssh_rsa_verify(key, sig, siglen, data, dlen, alg);
@@ -2771,7 +2774,7 @@ sshkey_verify(const struct sshkey *key,
 	case KEY_ED25519_SK:
 	case KEY_ED25519_SK_CERT:
 		return ssh_ed25519_sk_verify(key, sig, siglen, data, dlen,
-		    compat);
+		    compat, detailsp);
 #ifdef WITH_XMSS
 	case KEY_XMSS:
 	case KEY_XMSS_CERT:
@@ -4582,6 +4585,12 @@ sshkey_parse_private_fileblob(struct sshbuf *buffer, const char *passphrase,
 	    passphrase, keyp, commentp);
 }
 
+void
+sshkey_sig_details_free(struct sshkey_sig_details *details)
+{
+	freezero(details, sizeof(*details));
+}
+
 #ifdef WITH_XMSS
 /*
  * serialize the key with the current state and forward the state
diff --git a/usr.bin/ssh/sshkey.h b/usr.bin/ssh/sshkey.h
index 1e955658740..b6d3b6769c7 100644
--- a/usr.bin/ssh/sshkey.h
+++ b/usr.bin/ssh/sshkey.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.h,v 1.39 2019/11/13 07:53:10 markus Exp $ */
+/* $OpenBSD: sshkey.h,v 1.40 2019/11/25 00:51:37 djm Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -150,6 +150,12 @@ struct sshkey {
 #define	ED25519_SK_SZ	crypto_sign_ed25519_SECRETKEYBYTES
 #define	ED25519_PK_SZ	crypto_sign_ed25519_PUBLICKEYBYTES
 
+/* Additional fields contained in signature */
+struct sshkey_sig_details {
+	uint32_t sk_counter;	/* U2F signature counter */
+	uint8_t sk_flags;	/* U2F signature flags; see ssh-sk.h */
+};
+
 struct sshkey	*sshkey_new(int);
 void		 sshkey_free(struct sshkey *);
 int		 sshkey_equal_public(const struct sshkey *,
@@ -224,7 +230,7 @@ int	 sshkey_putb_plain(const struct sshkey *, struct sshbuf *);
 int	 sshkey_sign(struct sshkey *, u_char **, size_t *,
     const u_char *, size_t, const char *, const char *, u_int);
 int	 sshkey_verify(const struct sshkey *, const u_char *, size_t,
-    const u_char *, size_t, const char *, u_int);
+    const u_char *, size_t, const char *, u_int, struct sshkey_sig_details **);
 int	 sshkey_check_sigtype(const u_char *, size_t, const char *);
 const char *sshkey_sigalg_by_name(const char *);
 int	 sshkey_get_sigtype(const u_char *, size_t, char **);
@@ -260,6 +266,8 @@ int	 sshkey_forward_state(const struct sshkey *, u_int32_t, sshkey_printfn *);
 int	 sshkey_private_serialize_maxsign(struct sshkey *key, struct sshbuf *buf,
     u_int32_t maxsign, sshkey_printfn *pr);
 
+void	 sshkey_sig_details_free(struct sshkey_sig_details *);
+
 #ifdef SSHKEY_INTERNAL
 int ssh_rsa_sign(const struct sshkey *key,
     u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
@@ -279,7 +287,8 @@ int ssh_ecdsa_verify(const struct sshkey *key,
     const u_char *data, size_t datalen, u_int compat);
 int ssh_ecdsa_sk_verify(const struct sshkey *key,
     const u_char *signature, size_t signaturelen,
-    const u_char *data, size_t datalen, u_int compat);
+    const u_char *data, size_t datalen, u_int compat,
+    struct sshkey_sig_details **detailsp);
 int ssh_ed25519_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
     const u_char *data, size_t datalen, u_int compat);
 int ssh_ed25519_verify(const struct sshkey *key,
@@ -287,7 +296,8 @@ int ssh_ed25519_verify(const struct sshkey *key,
     const u_char *data, size_t datalen, u_int compat);
 int ssh_ed25519_sk_verify(const struct sshkey *key,
     const u_char *signature, size_t signaturelen,
-    const u_char *data, size_t datalen, u_int compat);
+    const u_char *data, size_t datalen, u_int compat,
+    struct sshkey_sig_details **detailsp);
 int ssh_xmss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
     const u_char *data, size_t datalen, u_int compat);
 int ssh_xmss_verify(const struct sshkey *key,
diff --git a/usr.bin/ssh/sshsig.c b/usr.bin/ssh/sshsig.c
index 5fe11f248c2..ea1313a5ab2 100644
--- a/usr.bin/ssh/sshsig.c
+++ b/usr.bin/ssh/sshsig.c
@@ -284,7 +284,7 @@ sshsig_peek_hashalg(struct sshbuf *signature, char **hashalgp)
 static int
 sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
     const struct sshbuf *h_message, const char *expect_namespace,
-    struct sshkey **sign_keyp)
+    struct sshkey **sign_keyp, struct sshkey_sig_details **sig_details)
 {
 	int r = SSH_ERR_INTERNAL_ERROR;
 	struct sshbuf *buf = NULL, *toverify = NULL;
@@ -294,6 +294,8 @@ sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
 	size_t siglen;
 
 	debug("%s: verify message length %zu", __func__, sshbuf_len(h_message));
+	if (sig_details != NULL)
+		*sig_details = NULL;
 	if (sign_keyp != NULL)
 		*sign_keyp = NULL;
 
@@ -359,7 +361,7 @@ sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
 		}
 	}
 	if ((r = sshkey_verify(key, sig, siglen, sshbuf_ptr(toverify),
-	    sshbuf_len(toverify), NULL, 0)) != 0) {
+	    sshbuf_len(toverify), NULL, 0, sig_details)) != 0) {
 		error("Signature verification failed: %s", ssh_err(r));
 		goto done;
 	}
@@ -451,15 +453,17 @@ sshsig_signb(struct sshkey *key, const char *hashalg, const char *sk_provider,
 
 int
 sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message,
-    const char *expect_namespace, struct sshkey **sign_keyp)
+    const char *expect_namespace, struct sshkey **sign_keyp,
+    struct sshkey_sig_details **sig_details)
 {
 	struct sshbuf *b = NULL;
 	int r = SSH_ERR_INTERNAL_ERROR;
 	char *hashalg = NULL;
 
+	if (sig_details != NULL)
+		*sig_details = NULL;
 	if (sign_keyp != NULL)
 		*sign_keyp = NULL;
-
 	if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
 		return r;
 	debug("%s: signature made with hash \"%s\"", __func__, hashalg);
@@ -468,7 +472,7 @@ sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message,
 		goto out;
 	}
 	if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
-	    sign_keyp)) != 0)
+	    sign_keyp, sig_details)) != 0)
 		goto out;
 	/* success */
 	r = 0;
@@ -577,15 +581,17 @@ sshsig_sign_fd(struct sshkey *key, const char *hashalg, const char *sk_provider,
 
 int
 sshsig_verify_fd(struct sshbuf *signature, int fd,
-    const char *expect_namespace, struct sshkey **sign_keyp)
+    const char *expect_namespace, struct sshkey **sign_keyp,
+    struct sshkey_sig_details **sig_details)
 {
 	struct sshbuf *b = NULL;
 	int r = SSH_ERR_INTERNAL_ERROR;
 	char *hashalg = NULL;
 
+	if (sig_details != NULL)
+		*sig_details = NULL;
 	if (sign_keyp != NULL)
 		*sign_keyp = NULL;
-
 	if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
 		return r;
 	debug("%s: signature made with hash \"%s\"", __func__, hashalg);
@@ -594,7 +600,7 @@ sshsig_verify_fd(struct sshbuf *signature, int fd,
 		goto out;
 	}
 	if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
-	    sign_keyp)) != 0)
+	    sign_keyp, sig_details)) != 0)
 		goto out;
 	/* success */
 	r = 0;
diff --git a/usr.bin/ssh/sshsig.h b/usr.bin/ssh/sshsig.h
index 487db116c17..386c8b5d799 100644
--- a/usr.bin/ssh/sshsig.h
+++ b/usr.bin/ssh/sshsig.h
@@ -20,6 +20,7 @@
 struct sshbuf;
 struct sshkey;
 struct sshsigopt;
+struct sshkey_sig_details;
 
 typedef int sshsig_signer(struct sshkey *, u_char **, size_t *,
     const u_char *, size_t, const char *, const char *, u_int, void *);
@@ -43,7 +44,7 @@ int sshsig_signb(struct sshkey *key, const char *hashalg,
  */
 int sshsig_verifyb(struct sshbuf *signature,
     const struct sshbuf *message, const char *sig_namespace,
-    struct sshkey **sign_keyp);
+    struct sshkey **sign_keyp, struct sshkey_sig_details **sig_details);
 
 /* File/FD-oriented API */
 
@@ -62,7 +63,8 @@ int sshsig_sign_fd(struct sshkey *key, const char *hashalg,
  * Returns 0 on success or a negative SSH_ERR_* error code on failure.
  */
 int sshsig_verify_fd(struct sshbuf *signature, int fd,
-    const char *sig_namespace, struct sshkey **sign_keyp);
+    const char *sig_namespace, struct sshkey **sign_keyp,
+    struct sshkey_sig_details **sig_details);
 
 /* Utility functions */