Add experimental support for PQC XMSS keys (Extended Hash-Based Signatures)

The code is not compiled in by default (see WITH_XMSS in Makefile.inc)
Joint work with stefan-lukas_gazdag at genua.eu
See https://tools.ietf.org/html/draft-irtf-cfrg-xmss-hash-based-signatures-12
ok djm@

1 files changed, 188 insertions, 0 deletions

diff --git a/usr.bin/ssh/ssh-xmss.c b/usr.bin/ssh/ssh-xmss.c
new file mode 100644
index 00000000000..d9dafd762a6
--- /dev/null
+++ b/usr.bin/ssh/ssh-xmss.c
@@ -0,0 +1,188 @@
+/* $OpenBSD: ssh-xmss.c,v 1.1 2018/02/23 15:58:38 markus Exp $*/
+/*
+ * Copyright (c) 2017 Stefan-Lukas Gazdag.
+ * Copyright (c) 2017 Markus Friedl.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#define SSHKEY_INTERNAL
+#include <sys/types.h>
+#include <limits.h>
+
+#include <string.h>
+#include <stdarg.h>
+#include <unistd.h>
+
+#include "log.h"
+#include "sshbuf.h"
+#include "sshkey.h"
+#include "sshkey-xmss.h"
+#include "ssherr.h"
+#include "ssh.h"
+
+#include "xmss_fast.h"
+
+int
+ssh_xmss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
+    const u_char *data, size_t datalen, u_int compat)
+{
+	u_char *sig = NULL;
+	size_t slen = 0, len = 0, required_siglen;
+	unsigned long long smlen;
+	int r, ret;
+	struct sshbuf *b = NULL;
+
+	if (lenp != NULL)
+		*lenp = 0;
+	if (sigp != NULL)
+		*sigp = NULL;
+
+	if (key == NULL ||
+	    sshkey_type_plain(key->type) != KEY_XMSS ||
+	    key->xmss_sk == NULL ||
+	    sshkey_xmss_params(key) == NULL)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
+		return r;
+	if (datalen >= INT_MAX - required_siglen)
+		return SSH_ERR_INVALID_ARGUMENT;
+	smlen = slen = datalen + required_siglen;
+	if ((sig = malloc(slen)) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshkey_xmss_get_state(key, error)) != 0)
+		goto out;
+	if ((ret = xmss_sign(key->xmss_sk, sshkey_xmss_bds_state(key), sig, &smlen,
+	    data, datalen, sshkey_xmss_params(key))) != 0 || smlen <= datalen) {
+		r = SSH_ERR_INVALID_ARGUMENT; /* XXX better error? */
+		goto out;
+	}
+	/* encode signature */
+	if ((b = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshbuf_put_cstring(b, "ssh-xmss@openssh.com")) != 0 ||
+	    (r = sshbuf_put_string(b, sig, smlen - datalen)) != 0)
+		goto out;
+	len = sshbuf_len(b);
+	if (sigp != NULL) {
+		if ((*sigp = malloc(len)) == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
+		memcpy(*sigp, sshbuf_ptr(b), len);
+	}
+	if (lenp != NULL)
+		*lenp = len;
+	/* success */
+	r = 0;
+ out:
+	if ((ret = sshkey_xmss_update_state(key, error)) != 0) {
+		/* discard signature since we cannot update the state */
+		if (r == 0 && sigp != NULL && *sigp != NULL) {
+			explicit_bzero(*sigp, len);
+			free(*sigp);
+		}
+		if (sigp != NULL)
+			*sigp = NULL;
+		if (lenp != NULL)
+			*lenp = 0;
+		r = ret;
+	}
+	sshbuf_free(b);
+	if (sig != NULL) {
+		explicit_bzero(sig, slen);
+		free(sig);
+	}
+
+	return r;
+}
+
+int
+ssh_xmss_verify(const struct sshkey *key,
+    const u_char *signature, size_t signaturelen,
+    const u_char *data, size_t datalen, u_int compat)
+{
+	struct sshbuf *b = NULL;
+	char *ktype = NULL;
+	const u_char *sigblob;
+	u_char *sm = NULL, *m = NULL;
+	size_t len, required_siglen;
+	unsigned long long smlen = 0, mlen = 0;
+	int r, ret;
+
+	if (key == NULL ||
+	    sshkey_type_plain(key->type) != KEY_XMSS ||
+	    key->xmss_pk == NULL ||
+	    sshkey_xmss_params(key) == NULL ||
+	    signature == NULL || signaturelen == 0)
+		return SSH_ERR_INVALID_ARGUMENT;
+	if ((r = sshkey_xmss_siglen(key, &required_siglen)) != 0)
+		return r;
+	if (datalen >= INT_MAX - required_siglen)
+		return SSH_ERR_INVALID_ARGUMENT;
+
+	if ((b = sshbuf_from(signature, signaturelen)) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshbuf_get_cstring(b, &ktype, NULL)) != 0 ||
+	    (r = sshbuf_get_string_direct(b, &sigblob, &len)) != 0)
+		goto out;
+	if (strcmp("ssh-xmss@openssh.com", ktype) != 0) {
+		r = SSH_ERR_KEY_TYPE_MISMATCH;
+		goto out;
+	}
+	if (sshbuf_len(b) != 0) {
+		r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
+		goto out;
+	}
+	if (len != required_siglen) {
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	if (datalen >= SIZE_MAX - len) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	smlen = len + datalen;
+	mlen = smlen;
+	if ((sm = malloc(smlen)) == NULL || (m = malloc(mlen)) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	memcpy(sm, sigblob, len);
+	memcpy(sm+len, data, datalen);
+	if ((ret = xmss_sign_open(m, &mlen, sm, smlen,
+	    key->xmss_pk, sshkey_xmss_params(key))) != 0) {
+		debug2("%s: crypto_sign_xmss_open failed: %d",
+		    __func__, ret);
+	}
+	if (ret != 0 || mlen != datalen) {
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto out;
+	}
+	/* XXX compare 'm' and 'data' ? */
+	/* success */
+	r = 0;
+ out:
+	if (sm != NULL) {
+		explicit_bzero(sm, smlen);
+		free(sm);
+	}
+	if (m != NULL) {
+		explicit_bzero(m, smlen); /* NB mlen may be invalid if r != 0 */
+		free(m);
+	}
+	sshbuf_free(b);
+	free(ktype);
+	return r;
+}