Adding upstream version 1:9.2p1.upstream/1%9.2p1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1148 insertions, 0 deletions

diff --git a/sshsig.c b/sshsig.c
new file mode 100644
index 0000000..eb2a931
--- /dev/null
+++ b/sshsig.c
@@ -0,0 +1,1148 @@
+/* $OpenBSD: sshsig.c,v 1.30 2022/08/19 03:06:30 djm Exp $ */
+/*
+ * Copyright (c) 2019 Google LLC
+ *
+ * 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.
+ */
+
+#include "includes.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "authfd.h"
+#include "authfile.h"
+#include "log.h"
+#include "misc.h"
+#include "sshbuf.h"
+#include "sshsig.h"
+#include "ssherr.h"
+#include "sshkey.h"
+#include "match.h"
+#include "digest.h"
+
+#define SIG_VERSION		0x01
+#define MAGIC_PREAMBLE		"SSHSIG"
+#define MAGIC_PREAMBLE_LEN	(sizeof(MAGIC_PREAMBLE) - 1)
+#define BEGIN_SIGNATURE		"-----BEGIN SSH SIGNATURE-----\n"
+#define END_SIGNATURE		"-----END SSH SIGNATURE-----"
+#define RSA_SIGN_ALG		"rsa-sha2-512" /* XXX maybe make configurable */
+#define RSA_SIGN_ALLOWED	"rsa-sha2-512,rsa-sha2-256"
+#define HASHALG_DEFAULT		"sha512" /* XXX maybe make configurable */
+#define HASHALG_ALLOWED		"sha256,sha512"
+
+int
+sshsig_armor(const struct sshbuf *blob, struct sshbuf **out)
+{
+	struct sshbuf *buf = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	*out = NULL;
+
+	if ((buf = sshbuf_new()) == NULL) {
+		error_f("sshbuf_new failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+
+	if ((r = sshbuf_put(buf, BEGIN_SIGNATURE,
+	    sizeof(BEGIN_SIGNATURE)-1)) != 0) {
+		error_fr(r, "sshbuf_putf");
+		goto out;
+	}
+
+	if ((r = sshbuf_dtob64(blob, buf, 1)) != 0) {
+		error_fr(r, "base64 encode signature");
+		goto out;
+	}
+
+	if ((r = sshbuf_put(buf, END_SIGNATURE,
+	    sizeof(END_SIGNATURE)-1)) != 0 ||
+	    (r = sshbuf_put_u8(buf, '\n')) != 0) {
+		error_fr(r, "sshbuf_put");
+		goto out;
+	}
+	/* success */
+	*out = buf;
+	buf = NULL; /* transferred */
+	r = 0;
+ out:
+	sshbuf_free(buf);
+	return r;
+}
+
+int
+sshsig_dearmor(struct sshbuf *sig, struct sshbuf **out)
+{
+	int r;
+	size_t eoffset = 0;
+	struct sshbuf *buf = NULL;
+	struct sshbuf *sbuf = NULL;
+	char *b64 = NULL;
+
+	if ((sbuf = sshbuf_fromb(sig)) == NULL) {
+		error_f("sshbuf_fromb failed");
+		return SSH_ERR_ALLOC_FAIL;
+	}
+
+	if ((r = sshbuf_cmp(sbuf, 0,
+	    BEGIN_SIGNATURE, sizeof(BEGIN_SIGNATURE)-1)) != 0) {
+		error("Couldn't parse signature: missing header");
+		goto done;
+	}
+
+	if ((r = sshbuf_consume(sbuf, sizeof(BEGIN_SIGNATURE)-1)) != 0) {
+		error_fr(r, "consume");
+		goto done;
+	}
+
+	if ((r = sshbuf_find(sbuf, 0, "\n" END_SIGNATURE,
+	    sizeof("\n" END_SIGNATURE)-1, &eoffset)) != 0) {
+		error("Couldn't parse signature: missing footer");
+		goto done;
+	}
+
+	if ((r = sshbuf_consume_end(sbuf, sshbuf_len(sbuf)-eoffset)) != 0) {
+		error_fr(r, "consume");
+		goto done;
+	}
+
+	if ((b64 = sshbuf_dup_string(sbuf)) == NULL) {
+		error_f("sshbuf_dup_string failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto done;
+	}
+
+	if ((buf = sshbuf_new()) == NULL) {
+		error_f("sshbuf_new() failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto done;
+	}
+
+	if ((r = sshbuf_b64tod(buf, b64)) != 0) {
+		error_fr(r, "decode base64");
+		goto done;
+	}
+
+	/* success */
+	*out = buf;
+	r = 0;
+	buf = NULL; /* transferred */
+done:
+	sshbuf_free(buf);
+	sshbuf_free(sbuf);
+	free(b64);
+	return r;
+}
+
+static int
+sshsig_wrap_sign(struct sshkey *key, const char *hashalg,
+    const char *sk_provider, const char *sk_pin, const struct sshbuf *h_message,
+    const char *sig_namespace, struct sshbuf **out,
+    sshsig_signer *signer, void *signer_ctx)
+{
+	int r;
+	size_t slen = 0;
+	u_char *sig = NULL;
+	struct sshbuf *blob = NULL;
+	struct sshbuf *tosign = NULL;
+	const char *sign_alg = NULL;
+
+	if ((tosign = sshbuf_new()) == NULL ||
+	    (blob = sshbuf_new()) == NULL) {
+		error_f("sshbuf_new failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto done;
+	}
+
+	if ((r = sshbuf_put(tosign, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
+	    (r = sshbuf_put_cstring(tosign, sig_namespace)) != 0 ||
+	    (r = sshbuf_put_string(tosign, NULL, 0)) != 0 || /* reserved */
+	    (r = sshbuf_put_cstring(tosign, hashalg)) != 0 ||
+	    (r = sshbuf_put_stringb(tosign, h_message)) != 0) {
+		error_fr(r, "assemble message to sign");
+		goto done;
+	}
+
+	/* If using RSA keys then default to a good signature algorithm */
+	if (sshkey_type_plain(key->type) == KEY_RSA)
+		sign_alg = RSA_SIGN_ALG;
+
+	if (signer != NULL) {
+		if ((r = signer(key, &sig, &slen,
+		    sshbuf_ptr(tosign), sshbuf_len(tosign),
+		    sign_alg, sk_provider, sk_pin, 0, signer_ctx)) != 0) {
+			error_r(r, "Couldn't sign message (signer)");
+			goto done;
+		}
+	} else {
+		if ((r = sshkey_sign(key, &sig, &slen,
+		    sshbuf_ptr(tosign), sshbuf_len(tosign),
+		    sign_alg, sk_provider, sk_pin, 0)) != 0) {
+			error_r(r, "Couldn't sign message");
+			goto done;
+		}
+	}
+
+	if ((r = sshbuf_put(blob, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
+	    (r = sshbuf_put_u32(blob, SIG_VERSION)) != 0 ||
+	    (r = sshkey_puts(key, blob)) != 0 ||
+	    (r = sshbuf_put_cstring(blob, sig_namespace)) != 0 ||
+	    (r = sshbuf_put_string(blob, NULL, 0)) != 0 || /* reserved */
+	    (r = sshbuf_put_cstring(blob, hashalg)) != 0 ||
+	    (r = sshbuf_put_string(blob, sig, slen)) != 0) {
+		error_fr(r, "assemble signature object");
+		goto done;
+	}
+
+	if (out != NULL) {
+		*out = blob;
+		blob = NULL;
+	}
+	r = 0;
+done:
+	free(sig);
+	sshbuf_free(blob);
+	sshbuf_free(tosign);
+	return r;
+}
+
+/* Check preamble and version. */
+static int
+sshsig_parse_preamble(struct sshbuf *buf)
+{
+	int r = SSH_ERR_INTERNAL_ERROR;
+	uint32_t sversion;
+
+	if ((r = sshbuf_cmp(buf, 0, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
+	    (r = sshbuf_consume(buf, (sizeof(MAGIC_PREAMBLE)-1))) != 0 ||
+	    (r = sshbuf_get_u32(buf, &sversion)) != 0) {
+		error("Couldn't verify signature: invalid format");
+		return r;
+	}
+
+	if (sversion > SIG_VERSION) {
+		error("Signature version %lu is larger than supported "
+		    "version %u", (unsigned long)sversion, SIG_VERSION);
+		return SSH_ERR_INVALID_FORMAT;
+	}
+	return 0;
+}
+
+static int
+sshsig_check_hashalg(const char *hashalg)
+{
+	if (hashalg == NULL ||
+	    match_pattern_list(hashalg, HASHALG_ALLOWED, 0) == 1)
+		return 0;
+	error_f("unsupported hash algorithm \"%.100s\"", hashalg);
+	return SSH_ERR_SIGN_ALG_UNSUPPORTED;
+}
+
+static int
+sshsig_peek_hashalg(struct sshbuf *signature, char **hashalgp)
+{
+	struct sshbuf *buf = NULL;
+	char *hashalg = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	if (hashalgp != NULL)
+		*hashalgp = NULL;
+	if ((buf = sshbuf_fromb(signature)) == NULL)
+		return SSH_ERR_ALLOC_FAIL;
+	if ((r = sshsig_parse_preamble(buf)) != 0)
+		goto done;
+	if ((r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
+	    (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
+	    (r = sshbuf_get_string(buf, NULL, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(buf, &hashalg, NULL)) != 0 ||
+	    (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0) {
+		error_fr(r, "parse signature object");
+		goto done;
+	}
+
+	/* success */
+	r = 0;
+	*hashalgp = hashalg;
+	hashalg = NULL;
+ done:
+	free(hashalg);
+	sshbuf_free(buf);
+	return r;
+}
+
+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_sig_details **sig_details)
+{
+	int r = SSH_ERR_INTERNAL_ERROR;
+	struct sshbuf *buf = NULL, *toverify = NULL;
+	struct sshkey *key = NULL;
+	const u_char *sig;
+	char *got_namespace = NULL, *sigtype = NULL, *sig_hashalg = NULL;
+	size_t siglen;
+
+	debug_f("verify message length %zu", sshbuf_len(h_message));
+	if (sig_details != NULL)
+		*sig_details = NULL;
+	if (sign_keyp != NULL)
+		*sign_keyp = NULL;
+
+	if ((toverify = sshbuf_new()) == NULL) {
+		error_f("sshbuf_new failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto done;
+	}
+	if ((r = sshbuf_put(toverify, MAGIC_PREAMBLE,
+	    MAGIC_PREAMBLE_LEN)) != 0 ||
+	    (r = sshbuf_put_cstring(toverify, expect_namespace)) != 0 ||
+	    (r = sshbuf_put_string(toverify, NULL, 0)) != 0 || /* reserved */
+	    (r = sshbuf_put_cstring(toverify, hashalg)) != 0 ||
+	    (r = sshbuf_put_stringb(toverify, h_message)) != 0) {
+		error_fr(r, "assemble message to verify");
+		goto done;
+	}
+
+	if ((r = sshsig_parse_preamble(signature)) != 0)
+		goto done;
+
+	if ((r = sshkey_froms(signature, &key)) != 0 ||
+	    (r = sshbuf_get_cstring(signature, &got_namespace, NULL)) != 0 ||
+	    (r = sshbuf_get_string(signature, NULL, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(signature, &sig_hashalg, NULL)) != 0 ||
+	    (r = sshbuf_get_string_direct(signature, &sig, &siglen)) != 0) {
+		error_fr(r, "parse signature object");
+		goto done;
+	}
+
+	if (sshbuf_len(signature) != 0) {
+		error("Signature contains trailing data");
+		r = SSH_ERR_INVALID_FORMAT;
+		goto done;
+	}
+
+	if (strcmp(expect_namespace, got_namespace) != 0) {
+		error("Couldn't verify signature: namespace does not match");
+		debug_f("expected namespace \"%s\" received \"%s\"",
+		    expect_namespace, got_namespace);
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto done;
+	}
+	if (strcmp(hashalg, sig_hashalg) != 0) {
+		error("Couldn't verify signature: hash algorithm mismatch");
+		debug_f("expected algorithm \"%s\" received \"%s\"",
+		    hashalg, sig_hashalg);
+		r = SSH_ERR_SIGNATURE_INVALID;
+		goto done;
+	}
+	/* Ensure that RSA keys use an acceptable signature algorithm */
+	if (sshkey_type_plain(key->type) == KEY_RSA) {
+		if ((r = sshkey_get_sigtype(sig, siglen, &sigtype)) != 0) {
+			error_r(r, "Couldn't verify signature: unable to get "
+			    "signature type");
+			goto done;
+		}
+		if (match_pattern_list(sigtype, RSA_SIGN_ALLOWED, 0) != 1) {
+			error("Couldn't verify signature: unsupported RSA "
+			    "signature algorithm %s", sigtype);
+			r = SSH_ERR_SIGN_ALG_UNSUPPORTED;
+			goto done;
+		}
+	}
+	if ((r = sshkey_verify(key, sig, siglen, sshbuf_ptr(toverify),
+	    sshbuf_len(toverify), NULL, 0, sig_details)) != 0) {
+		error_r(r, "Signature verification failed");
+		goto done;
+	}
+
+	/* success */
+	r = 0;
+	if (sign_keyp != NULL) {
+		*sign_keyp = key;
+		key = NULL; /* transferred */
+	}
+done:
+	free(got_namespace);
+	free(sigtype);
+	free(sig_hashalg);
+	sshbuf_free(buf);
+	sshbuf_free(toverify);
+	sshkey_free(key);
+	return r;
+}
+
+static int
+hash_buffer(const struct sshbuf *m, const char *hashalg, struct sshbuf **bp)
+{
+	char *hex, hash[SSH_DIGEST_MAX_LENGTH];
+	int alg, r = SSH_ERR_INTERNAL_ERROR;
+	struct sshbuf *b = NULL;
+
+	*bp = NULL;
+	memset(hash, 0, sizeof(hash));
+
+	if ((r = sshsig_check_hashalg(hashalg)) != 0)
+		return r;
+	if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
+		error_f("can't look up hash algorithm %s", hashalg);
+		return SSH_ERR_INTERNAL_ERROR;
+	}
+	if ((r = ssh_digest_buffer(alg, m, hash, sizeof(hash))) != 0) {
+		error_fr(r, "ssh_digest_buffer");
+		return r;
+	}
+	if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
+		debug3_f("final hash: %s", hex);
+		freezero(hex, strlen(hex));
+	}
+	if ((b = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
+		error_fr(r, "sshbuf_put");
+		goto out;
+	}
+	*bp = b;
+	b = NULL; /* transferred */
+	/* success */
+	r = 0;
+ out:
+	sshbuf_free(b);
+	explicit_bzero(hash, sizeof(hash));
+	return r;
+}
+
+int
+sshsig_signb(struct sshkey *key, const char *hashalg,
+    const char *sk_provider, const char *sk_pin,
+    const struct sshbuf *message, const char *sig_namespace,
+    struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
+{
+	struct sshbuf *b = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	if (hashalg == NULL)
+		hashalg = HASHALG_DEFAULT;
+	if (out != NULL)
+		*out = NULL;
+	if ((r = hash_buffer(message, hashalg, &b)) != 0) {
+		error_fr(r, "hash buffer");
+		goto out;
+	}
+	if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, sk_pin, b,
+	    sig_namespace, out, signer, signer_ctx)) != 0)
+		goto out;
+	/* success */
+	r = 0;
+ out:
+	sshbuf_free(b);
+	return r;
+}
+
+int
+sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message,
+    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_f("signature made with hash \"%s\"", hashalg);
+	if ((r = hash_buffer(message, hashalg, &b)) != 0) {
+		error_fr(r, "hash buffer");
+		goto out;
+	}
+	if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
+	    sign_keyp, sig_details)) != 0)
+		goto out;
+	/* success */
+	r = 0;
+ out:
+	sshbuf_free(b);
+	free(hashalg);
+	return r;
+}
+
+static int
+hash_file(int fd, const char *hashalg, struct sshbuf **bp)
+{
+	char *hex, rbuf[8192], hash[SSH_DIGEST_MAX_LENGTH];
+	ssize_t n, total = 0;
+	struct ssh_digest_ctx *ctx = NULL;
+	int alg, oerrno, r = SSH_ERR_INTERNAL_ERROR;
+	struct sshbuf *b = NULL;
+
+	*bp = NULL;
+	memset(hash, 0, sizeof(hash));
+
+	if ((r = sshsig_check_hashalg(hashalg)) != 0)
+		return r;
+	if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
+		error_f("can't look up hash algorithm %s", hashalg);
+		return SSH_ERR_INTERNAL_ERROR;
+	}
+	if ((ctx = ssh_digest_start(alg)) == NULL) {
+		error_f("ssh_digest_start failed");
+		return SSH_ERR_INTERNAL_ERROR;
+	}
+	for (;;) {
+		if ((n = read(fd, rbuf, sizeof(rbuf))) == -1) {
+			if (errno == EINTR || errno == EAGAIN)
+				continue;
+			oerrno = errno;
+			error_f("read: %s", strerror(errno));
+			errno = oerrno;
+			r = SSH_ERR_SYSTEM_ERROR;
+			goto out;
+		} else if (n == 0) {
+			debug2_f("hashed %zu bytes", total);
+			break; /* EOF */
+		}
+		total += (size_t)n;
+		if ((r = ssh_digest_update(ctx, rbuf, (size_t)n)) != 0) {
+			error_fr(r, "ssh_digest_update");
+			goto out;
+		}
+	}
+	if ((r = ssh_digest_final(ctx, hash, sizeof(hash))) != 0) {
+		error_fr(r, "ssh_digest_final");
+		goto out;
+	}
+	if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
+		debug3_f("final hash: %s", hex);
+		freezero(hex, strlen(hex));
+	}
+	if ((b = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
+		error_fr(r, "sshbuf_put");
+		goto out;
+	}
+	*bp = b;
+	b = NULL; /* transferred */
+	/* success */
+	r = 0;
+ out:
+	oerrno = errno;
+	sshbuf_free(b);
+	ssh_digest_free(ctx);
+	explicit_bzero(hash, sizeof(hash));
+	errno = oerrno;
+	return r;
+}
+
+int
+sshsig_sign_fd(struct sshkey *key, const char *hashalg,
+    const char *sk_provider, const char *sk_pin,
+    int fd, const char *sig_namespace, struct sshbuf **out,
+    sshsig_signer *signer, void *signer_ctx)
+{
+	struct sshbuf *b = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	if (hashalg == NULL)
+		hashalg = HASHALG_DEFAULT;
+	if (out != NULL)
+		*out = NULL;
+	if ((r = hash_file(fd, hashalg, &b)) != 0) {
+		error_fr(r, "hash_file");
+		return r;
+	}
+	if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, sk_pin, b,
+	    sig_namespace, out, signer, signer_ctx)) != 0)
+		goto out;
+	/* success */
+	r = 0;
+ out:
+	sshbuf_free(b);
+	return r;
+}
+
+int
+sshsig_verify_fd(struct sshbuf *signature, int fd,
+    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_f("signature made with hash \"%s\"", hashalg);
+	if ((r = hash_file(fd, hashalg, &b)) != 0) {
+		error_fr(r, "hash_file");
+		goto out;
+	}
+	if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
+	    sign_keyp, sig_details)) != 0)
+		goto out;
+	/* success */
+	r = 0;
+ out:
+	sshbuf_free(b);
+	free(hashalg);
+	return r;
+}
+
+struct sshsigopt {
+	int ca;
+	char *namespaces;
+	uint64_t valid_after, valid_before;
+};
+
+struct sshsigopt *
+sshsigopt_parse(const char *opts, const char *path, u_long linenum,
+    const char **errstrp)
+{
+	struct sshsigopt *ret;
+	int r;
+	char *opt;
+	const char *errstr = NULL;
+
+	if ((ret = calloc(1, sizeof(*ret))) == NULL)
+		return NULL;
+	if (opts == NULL || *opts == '\0')
+		return ret; /* Empty options yields empty options :) */
+
+	while (*opts && *opts != ' ' && *opts != '\t') {
+		/* flag options */
+		if ((r = opt_flag("cert-authority", 0, &opts)) != -1) {
+			ret->ca = 1;
+		} else if (opt_match(&opts, "namespaces")) {
+			if (ret->namespaces != NULL) {
+				errstr = "multiple \"namespaces\" clauses";
+				goto fail;
+			}
+			ret->namespaces = opt_dequote(&opts, &errstr);
+			if (ret->namespaces == NULL)
+				goto fail;
+		} else if (opt_match(&opts, "valid-after")) {
+			if (ret->valid_after != 0) {
+				errstr = "multiple \"valid-after\" clauses";
+				goto fail;
+			}
+			if ((opt = opt_dequote(&opts, &errstr)) == NULL)
+				goto fail;
+			if (parse_absolute_time(opt, &ret->valid_after) != 0 ||
+			    ret->valid_after == 0) {
+				free(opt);
+				errstr = "invalid \"valid-after\" time";
+				goto fail;
+			}
+			free(opt);
+		} else if (opt_match(&opts, "valid-before")) {
+			if (ret->valid_before != 0) {
+				errstr = "multiple \"valid-before\" clauses";
+				goto fail;
+			}
+			if ((opt = opt_dequote(&opts, &errstr)) == NULL)
+				goto fail;
+			if (parse_absolute_time(opt, &ret->valid_before) != 0 ||
+			    ret->valid_before == 0) {
+				free(opt);
+				errstr = "invalid \"valid-before\" time";
+				goto fail;
+			}
+			free(opt);
+		}
+		/*
+		 * Skip the comma, and move to the next option
+		 * (or break out if there are no more).
+		 */
+		if (*opts == '\0' || *opts == ' ' || *opts == '\t')
+			break;		/* End of options. */
+		/* Anything other than a comma is an unknown option */
+		if (*opts != ',') {
+			errstr = "unknown key option";
+			goto fail;
+		}
+		opts++;
+		if (*opts == '\0') {
+			errstr = "unexpected end-of-options";
+			goto fail;
+		}
+	}
+	/* final consistency check */
+	if (ret->valid_after != 0 && ret->valid_before != 0 &&
+	    ret->valid_before <= ret->valid_after) {
+		errstr = "\"valid-before\" time is before \"valid-after\"";
+		goto fail;
+	}
+	/* success */
+	return ret;
+ fail:
+	if (errstrp != NULL)
+		*errstrp = errstr;
+	sshsigopt_free(ret);
+	return NULL;
+}
+
+void
+sshsigopt_free(struct sshsigopt *opts)
+{
+	if (opts == NULL)
+		return;
+	free(opts->namespaces);
+	free(opts);
+}
+
+static int
+parse_principals_key_and_options(const char *path, u_long linenum, char *line,
+    const char *required_principal, char **principalsp, struct sshkey **keyp,
+    struct sshsigopt **sigoptsp)
+{
+	char *opts = NULL, *tmp, *cp, *principals = NULL;
+	const char *reason = NULL;
+	struct sshsigopt *sigopts = NULL;
+	struct sshkey *key = NULL;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	if (principalsp != NULL)
+		*principalsp = NULL;
+	if (sigoptsp != NULL)
+		*sigoptsp = NULL;
+	if (keyp != NULL)
+		*keyp = NULL;
+
+	cp = line;
+	cp = cp + strspn(cp, " \t"); /* skip leading whitespace */
+	if (*cp == '#' || *cp == '\0')
+		return SSH_ERR_KEY_NOT_FOUND; /* blank or all-comment line */
+
+	/* format: identity[,identity...] [option[,option...]] key */
+	if ((tmp = strdelimw(&cp)) == NULL || cp == NULL) {
+		error("%s:%lu: invalid line", path, linenum);
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	if ((principals = strdup(tmp)) == NULL) {
+		error_f("strdup failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	/*
+	 * Bail out early if we're looking for a particular principal and this
+	 * line does not list it.
+	 */
+	if (required_principal != NULL) {
+		if (match_pattern_list(required_principal,
+		    principals, 0) != 1) {
+			/* principal didn't match */
+			r = SSH_ERR_KEY_NOT_FOUND;
+			goto out;
+		}
+		debug_f("%s:%lu: matched principal \"%s\"",
+		    path, linenum, required_principal);
+	}
+
+	if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
+		error_f("sshkey_new failed");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if (sshkey_read(key, &cp) != 0) {
+		/* no key? Check for options */
+		opts = cp;
+		if (sshkey_advance_past_options(&cp) != 0) {
+			error("%s:%lu: invalid options", path, linenum);
+			r = SSH_ERR_INVALID_FORMAT;
+			goto out;
+		}
+		if (cp == NULL || *cp == '\0') {
+			error("%s:%lu: missing key", path, linenum);
+			r = SSH_ERR_INVALID_FORMAT;
+			goto out;
+		}
+		*cp++ = '\0';
+		skip_space(&cp);
+		if (sshkey_read(key, &cp) != 0) {
+			error("%s:%lu: invalid key", path, linenum);
+			r = SSH_ERR_INVALID_FORMAT;
+			goto out;
+		}
+	}
+	debug3("%s:%lu: options %s", path, linenum, opts == NULL ? "" : opts);
+	if ((sigopts = sshsigopt_parse(opts, path, linenum, &reason)) == NULL) {
+		error("%s:%lu: bad options: %s", path, linenum, reason);
+		r = SSH_ERR_INVALID_FORMAT;
+		goto out;
+	}
+	/* success */
+	if (principalsp != NULL) {
+		*principalsp = principals;
+		principals = NULL; /* transferred */
+	}
+	if (sigoptsp != NULL) {
+		*sigoptsp = sigopts;
+		sigopts = NULL; /* transferred */
+	}
+	if (keyp != NULL) {
+		*keyp = key;
+		key = NULL; /* transferred */
+	}
+	r = 0;
+ out:
+	free(principals);
+	sshsigopt_free(sigopts);
+	sshkey_free(key);
+	return r;
+}
+
+static int
+cert_filter_principals(const char *path, u_long linenum,
+    char **principalsp, const struct sshkey *cert, uint64_t verify_time)
+{
+	char *cp, *oprincipals, *principals;
+	const char *reason;
+	struct sshbuf *nprincipals;
+	int r = SSH_ERR_INTERNAL_ERROR, success = 0;
+	u_int i;
+
+	oprincipals = principals = *principalsp;
+	*principalsp = NULL;
+
+	if ((nprincipals = sshbuf_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+
+	while ((cp = strsep(&principals, ",")) != NULL && *cp != '\0') {
+		/* Check certificate validity */
+		if ((r = sshkey_cert_check_authority(cert, 0, 1, 0,
+		    verify_time, NULL, &reason)) != 0) {
+			debug("%s:%lu: principal \"%s\" not authorized: %s",
+			    path, linenum, cp, reason);
+			continue;
+		}
+		/* Return all matching principal names from the cert */
+		for (i = 0; i < cert->cert->nprincipals; i++) {
+			if (match_pattern(cert->cert->principals[i], cp)) {
+				if ((r = sshbuf_putf(nprincipals, "%s%s",
+					sshbuf_len(nprincipals) != 0 ? "," : "",
+						cert->cert->principals[i])) != 0) {
+					error_f("buffer error");
+					goto out;
+				}
+			}
+		}
+	}
+	if (sshbuf_len(nprincipals) == 0) {
+		error("%s:%lu: no valid principals found", path, linenum);
+		r = SSH_ERR_KEY_CERT_INVALID;
+		goto out;
+	}
+	if ((principals = sshbuf_dup_string(nprincipals)) == NULL) {
+		error_f("buffer error");
+		goto out;
+	}
+	/* success */
+	success = 1;
+	*principalsp = principals;
+ out:
+	sshbuf_free(nprincipals);
+	free(oprincipals);
+	return success ? 0 : r;
+}
+
+static int
+check_allowed_keys_line(const char *path, u_long linenum, char *line,
+    const struct sshkey *sign_key, const char *principal,
+    const char *sig_namespace, uint64_t verify_time, char **principalsp)
+{
+	struct sshkey *found_key = NULL;
+	char *principals = NULL;
+	int r, success = 0;
+	const char *reason = NULL;
+	struct sshsigopt *sigopts = NULL;
+	char tvalid[64], tverify[64];
+
+	if (principalsp != NULL)
+		*principalsp = NULL;
+
+	/* Parse the line */
+	if ((r = parse_principals_key_and_options(path, linenum, line,
+	    principal, &principals, &found_key, &sigopts)) != 0) {
+		/* error already logged */
+		goto done;
+	}
+
+	if (!sigopts->ca && sshkey_equal(found_key, sign_key)) {
+		/* Exact match of key */
+		debug("%s:%lu: matched key", path, linenum);
+	} else if (sigopts->ca && sshkey_is_cert(sign_key) &&
+	    sshkey_equal_public(sign_key->cert->signature_key, found_key)) {
+		if (principal) {
+			/* Match certificate CA key with specified principal */
+			if ((r = sshkey_cert_check_authority(sign_key, 0, 1, 0,
+			    verify_time, principal, &reason)) != 0) {
+				error("%s:%lu: certificate not authorized: %s",
+				    path, linenum, reason);
+				goto done;
+			}
+			debug("%s:%lu: matched certificate CA key",
+			    path, linenum);
+		} else {
+			/* No principal specified - find all matching ones */
+			if ((r = cert_filter_principals(path, linenum,
+			    &principals, sign_key, verify_time)) != 0) {
+				/* error already displayed */
+				debug_r(r, "%s:%lu: cert_filter_principals",
+				    path, linenum);
+				goto done;
+			}
+			debug("%s:%lu: matched certificate CA key",
+			    path, linenum);
+		}
+	} else {
+		/* Didn't match key */
+		goto done;
+	}
+
+	/* Check whether options preclude the use of this key */
+	if (sigopts->namespaces != NULL && sig_namespace != NULL &&
+	    match_pattern_list(sig_namespace, sigopts->namespaces, 0) != 1) {
+		error("%s:%lu: key is not permitted for use in signature "
+		    "namespace \"%s\"", path, linenum, sig_namespace);
+		goto done;
+	}
+
+	/* check key time validity */
+	format_absolute_time((uint64_t)verify_time, tverify, sizeof(tverify));
+	if (sigopts->valid_after != 0 &&
+	    (uint64_t)verify_time < sigopts->valid_after) {
+		format_absolute_time(sigopts->valid_after,
+		    tvalid, sizeof(tvalid));
+		error("%s:%lu: key is not yet valid: "
+		    "verify time %s < valid-after %s", path, linenum,
+		    tverify, tvalid);
+		goto done;
+	}
+	if (sigopts->valid_before != 0 &&
+	    (uint64_t)verify_time > sigopts->valid_before) {
+		format_absolute_time(sigopts->valid_before,
+		    tvalid, sizeof(tvalid));
+		error("%s:%lu: key has expired: "
+		    "verify time %s > valid-before %s", path, linenum,
+		    tverify, tvalid);
+		goto done;
+	}
+	success = 1;
+
+ done:
+	if (success && principalsp != NULL) {
+		*principalsp = principals;
+		principals = NULL; /* transferred */
+	}
+	free(principals);
+	sshkey_free(found_key);
+	sshsigopt_free(sigopts);
+	return success ? 0 : SSH_ERR_KEY_NOT_FOUND;
+}
+
+int
+sshsig_check_allowed_keys(const char *path, const struct sshkey *sign_key,
+    const char *principal, const char *sig_namespace, uint64_t verify_time)
+{
+	FILE *f = NULL;
+	char *line = NULL;
+	size_t linesize = 0;
+	u_long linenum = 0;
+	int r = SSH_ERR_INTERNAL_ERROR, oerrno;
+
+	/* Check key and principal against file */
+	if ((f = fopen(path, "r")) == NULL) {
+		oerrno = errno;
+		error("Unable to open allowed keys file \"%s\": %s",
+		    path, strerror(errno));
+		errno = oerrno;
+		return SSH_ERR_SYSTEM_ERROR;
+	}
+
+	while (getline(&line, &linesize, f) != -1) {
+		linenum++;
+		r = check_allowed_keys_line(path, linenum, line, sign_key,
+		    principal, sig_namespace, verify_time, NULL);
+		free(line);
+		line = NULL;
+		linesize = 0;
+		if (r == SSH_ERR_KEY_NOT_FOUND)
+			continue;
+		else if (r == 0) {
+			/* success */
+			fclose(f);
+			return 0;
+		} else
+			break;
+	}
+	/* Either we hit an error parsing or we simply didn't find the key */
+	fclose(f);
+	free(line);
+	return r == 0 ? SSH_ERR_KEY_NOT_FOUND : r;
+}
+
+int
+sshsig_find_principals(const char *path, const struct sshkey *sign_key,
+    uint64_t verify_time, char **principals)
+{
+	FILE *f = NULL;
+	char *line = NULL;
+	size_t linesize = 0;
+	u_long linenum = 0;
+	int r = SSH_ERR_INTERNAL_ERROR, oerrno;
+
+	if ((f = fopen(path, "r")) == NULL) {
+		oerrno = errno;
+		error("Unable to open allowed keys file \"%s\": %s",
+		    path, strerror(errno));
+		errno = oerrno;
+		return SSH_ERR_SYSTEM_ERROR;
+	}
+
+	r = SSH_ERR_KEY_NOT_FOUND;
+	while (getline(&line, &linesize, f) != -1) {
+		linenum++;
+		r = check_allowed_keys_line(path, linenum, line,
+		    sign_key, NULL, NULL, verify_time, principals);
+		free(line);
+		line = NULL;
+		linesize = 0;
+		if (r == SSH_ERR_KEY_NOT_FOUND)
+			continue;
+		else if (r == 0) {
+			/* success */
+			fclose(f);
+			return 0;
+		} else
+			break;
+	}
+	free(line);
+	/* Either we hit an error parsing or we simply didn't find the key */
+	if (ferror(f) != 0) {
+		oerrno = errno;
+		fclose(f);
+		error("Unable to read allowed keys file \"%s\": %s",
+		    path, strerror(errno));
+		errno = oerrno;
+		return SSH_ERR_SYSTEM_ERROR;
+	}
+	fclose(f);
+	return r == 0 ? SSH_ERR_KEY_NOT_FOUND : r;
+}
+
+int
+sshsig_match_principals(const char *path, const char *principal,
+    char ***principalsp, size_t *nprincipalsp)
+{
+	FILE *f = NULL;
+	char *found, *line = NULL, **principals = NULL, **tmp;
+	size_t i, nprincipals = 0, linesize = 0;
+	u_long linenum = 0;
+	int oerrno = 0, r, ret = 0;
+
+	if (principalsp != NULL)
+		*principalsp = NULL;
+	if (nprincipalsp != NULL)
+		*nprincipalsp = 0;
+
+	/* Check key and principal against file */
+	if ((f = fopen(path, "r")) == NULL) {
+		oerrno = errno;
+		error("Unable to open allowed keys file \"%s\": %s",
+		    path, strerror(errno));
+		errno = oerrno;
+		return SSH_ERR_SYSTEM_ERROR;
+	}
+
+	while (getline(&line, &linesize, f) != -1) {
+		linenum++;
+		/* Parse the line */
+		if ((r = parse_principals_key_and_options(path, linenum, line,
+		    principal, &found, NULL, NULL)) != 0) {
+			if (r == SSH_ERR_KEY_NOT_FOUND)
+				continue;
+			ret = r;
+			oerrno = errno;
+			break; /* unexpected error */
+		}
+		if ((tmp = recallocarray(principals, nprincipals,
+		    nprincipals + 1, sizeof(*principals))) == NULL) {
+			ret = SSH_ERR_ALLOC_FAIL;
+			free(found);
+			break;
+		}
+		principals = tmp;
+		principals[nprincipals++] = found; /* transferred */
+		free(line);
+		line = NULL;
+		linesize = 0;
+	}
+	fclose(f);
+
+	if (ret == 0) {
+		if (nprincipals == 0)
+			ret = SSH_ERR_KEY_NOT_FOUND;
+		if (principalsp != NULL) {
+			*principalsp = principals;
+			principals = NULL; /* transferred */
+		}
+		if (nprincipalsp != 0) {
+			*nprincipalsp = nprincipals;
+			nprincipals = 0;
+		}
+	}
+
+	for (i = 0; i < nprincipals; i++)
+		free(principals[i]);
+	free(principals);
+
+	errno = oerrno;
+	return ret;
+}
+
+int
+sshsig_get_pubkey(struct sshbuf *signature, struct sshkey **pubkey)
+{
+	struct sshkey *pk = NULL;
+	int r = SSH_ERR_SIGNATURE_INVALID;
+
+	if (pubkey == NULL)
+		return SSH_ERR_INTERNAL_ERROR;
+	if ((r = sshsig_parse_preamble(signature)) != 0)
+		return r;
+	if ((r = sshkey_froms(signature, &pk)) != 0)
+		return r;
+
+	*pubkey = pk;
+	pk = NULL;
+	return 0;
+}