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sshsig.c
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sshsig.c
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/* $OpenBSD: sshsig.c,v 1.35 2024/03/08 22:16:32 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-----"
#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_putf(buf, "%s\n", BEGIN_SIGNATURE)) != 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;
}
/* Expect and consume preamble + lf/crlf */
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_cmp(sbuf, 0, "\r\n", 2)) == 0)
eoffset = 2;
else if ((r = sshbuf_cmp(sbuf, 0, "\n", 1)) == 0)
eoffset = 1;
else {
r = SSH_ERR_INVALID_FORMAT;
error_f("no header eol");
goto done;
}
if ((r = sshbuf_consume(sbuf, eoffset)) != 0) {
error_fr(r, "consume eol");
goto done;
}
/* Find and consume lf + suffix (any prior cr would be ignored) */
if ((r = sshbuf_find(sbuf, 0, "\n" END_SIGNATURE,
sizeof(END_SIGNATURE), &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\n\r"); /* 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_KEY_NOT_FOUND, 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;
}