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-rw-r--r--sshsig.c1044
1 files changed, 1044 insertions, 0 deletions
diff --git a/sshsig.c b/sshsig.c
new file mode 100644
index 0000000..0bd7e5c
--- /dev/null
+++ b/sshsig.c
@@ -0,0 +1,1044 @@
+/* $OpenBSD: sshsig.c,v 1.17 2020/08/31 00:17:41 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("%s: sshbuf_new failed", __func__);
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+
+ if ((r = sshbuf_put(buf, BEGIN_SIGNATURE,
+ sizeof(BEGIN_SIGNATURE)-1)) != 0) {
+ error("%s: sshbuf_putf failed: %s", __func__, ssh_err(r));
+ goto out;
+ }
+
+ if ((r = sshbuf_dtob64(blob, buf, 1)) != 0) {
+ error("%s: Couldn't base64 encode signature blob: %s",
+ __func__, ssh_err(r));
+ goto out;
+ }
+
+ if ((r = sshbuf_put(buf, END_SIGNATURE,
+ sizeof(END_SIGNATURE)-1)) != 0 ||
+ (r = sshbuf_put_u8(buf, '\n')) != 0) {
+ error("%s: sshbuf_put failed: %s", __func__, ssh_err(r));
+ 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("%s: sshbuf_fromb failed", __func__);
+ 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("%s: sshbuf_consume failed: %s", __func__, ssh_err(r));
+ 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("%s: sshbuf_consume failed: %s", __func__, ssh_err(r));
+ goto done;
+ }
+
+ if ((b64 = sshbuf_dup_string(sbuf)) == NULL) {
+ error("%s: sshbuf_dup_string failed", __func__);
+ r = SSH_ERR_ALLOC_FAIL;
+ goto done;
+ }
+
+ if ((buf = sshbuf_new()) == NULL) {
+ error("%s: sshbuf_new() failed", __func__);
+ r = SSH_ERR_ALLOC_FAIL;
+ goto done;
+ }
+
+ if ((r = sshbuf_b64tod(buf, b64)) != 0) {
+ error("Couldn't decode signature: %s", ssh_err(r));
+ 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("%s: sshbuf_new failed", __func__);
+ 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("Couldn't construct message to sign: %s", ssh_err(r));
+ 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("Couldn't sign message: %s", ssh_err(r));
+ 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("Couldn't sign message: %s", ssh_err(r));
+ 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("Couldn't populate blob: %s", ssh_err(r));
+ 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("%s: unsupported hash algorithm \"%.100s\"", __func__, 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("Couldn't parse signature blob: %s", ssh_err(r));
+ 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("%s: verify message length %zu", __func__, sshbuf_len(h_message));
+ if (sig_details != NULL)
+ *sig_details = NULL;
+ if (sign_keyp != NULL)
+ *sign_keyp = NULL;
+
+ if ((toverify = sshbuf_new()) == NULL) {
+ error("%s: sshbuf_new failed", __func__);
+ 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("Couldn't construct message to verify: %s", ssh_err(r));
+ 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("Couldn't parse signature blob: %s", ssh_err(r));
+ 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("%s: expected namespace \"%s\" received \"%s\"",
+ __func__, 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("%s: expected algorithm \"%s\" received \"%s\"",
+ __func__, 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("Couldn't verify signature: unable to get "
+ "signature type: %s", ssh_err(r));
+ 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("Signature verification failed: %s", ssh_err(r));
+ 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("%s: can't look up hash algorithm %s",
+ __func__, hashalg);
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ if ((r = ssh_digest_buffer(alg, m, hash, sizeof(hash))) != 0) {
+ error("%s: ssh_digest_buffer failed: %s", __func__, ssh_err(r));
+ return r;
+ }
+ if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
+ debug3("%s: final hash: %s", __func__, 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("%s: sshbuf_put: %s", __func__, ssh_err(r));
+ 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("%s: hash_buffer failed: %s", __func__, ssh_err(r));
+ 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("%s: signature made with hash \"%s\"", __func__, hashalg);
+ if ((r = hash_buffer(message, hashalg, &b)) != 0) {
+ error("%s: hash_buffer failed: %s", __func__, ssh_err(r));
+ 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;
+ 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("%s: can't look up hash algorithm %s",
+ __func__, hashalg);
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ if ((ctx = ssh_digest_start(alg)) == NULL) {
+ error("%s: ssh_digest_start failed", __func__);
+ return SSH_ERR_INTERNAL_ERROR;
+ }
+ for (;;) {
+ if ((n = read(fd, rbuf, sizeof(rbuf))) == -1) {
+ if (errno == EINTR || errno == EAGAIN)
+ continue;
+ oerrno = errno;
+ error("%s: read: %s", __func__, strerror(errno));
+ ssh_digest_free(ctx);
+ errno = oerrno;
+ r = SSH_ERR_SYSTEM_ERROR;
+ goto out;
+ } else if (n == 0) {
+ debug2("%s: hashed %zu bytes", __func__, total);
+ break; /* EOF */
+ }
+ total += (size_t)n;
+ if ((r = ssh_digest_update(ctx, rbuf, (size_t)n)) != 0) {
+ error("%s: ssh_digest_update: %s",
+ __func__, ssh_err(r));
+ goto out;
+ }
+ }
+ if ((r = ssh_digest_final(ctx, hash, sizeof(hash))) != 0) {
+ error("%s: ssh_digest_final: %s", __func__, ssh_err(r));
+ goto out;
+ }
+ if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
+ debug3("%s: final hash: %s", __func__, 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("%s: sshbuf_put: %s", __func__, ssh_err(r));
+ goto out;
+ }
+ *bp = b;
+ b = NULL; /* transferred */
+ /* success */
+ r = 0;
+ out:
+ sshbuf_free(b);
+ ssh_digest_free(ctx);
+ explicit_bzero(hash, sizeof(hash));
+ 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("%s: hash_file failed: %s", __func__, ssh_err(r));
+ 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("%s: signature made with hash \"%s\"", __func__, hashalg);
+ if ((r = hash_file(fd, hashalg, &b)) != 0) {
+ error("%s: hash_file failed: %s", __func__, ssh_err(r));
+ 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;
+};
+
+struct sshsigopt *
+sshsigopt_parse(const char *opts, const char *path, u_long linenum,
+ const char **errstrp)
+{
+ struct sshsigopt *ret;
+ int r;
+ 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;
+ }
+ /*
+ * 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;
+ }
+ }
+ /* 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) {
+ error("%s:%lu: invalid line", path, linenum);
+ r = SSH_ERR_INVALID_FORMAT;
+ goto out;
+ }
+ if ((principals = strdup(tmp)) == NULL) {
+ error("%s: strdup failed", __func__);
+ 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("%s: %s:%lu: matched principal \"%s\"",
+ __func__, path, linenum, required_principal);
+ }
+
+ if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
+ error("%s: sshkey_new failed", __func__);
+ 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;
+ }
+ *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
+check_allowed_keys_line(const char *path, u_long linenum, char *line,
+ const struct sshkey *sign_key, const char *principal,
+ const char *sig_namespace)
+{
+ struct sshkey *found_key = NULL;
+ int r, found = 0;
+ const char *reason = NULL;
+ struct sshsigopt *sigopts = NULL;
+
+ /* Parse the line */
+ if ((r = parse_principals_key_and_options(path, linenum, line,
+ principal, NULL, &found_key, &sigopts)) != 0) {
+ /* error already logged */
+ goto done;
+ }
+
+ /* Check whether options preclude the use of this key */
+ if (sigopts->namespaces != 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;
+ }
+
+ if (!sigopts->ca && sshkey_equal(found_key, sign_key)) {
+ /* Exact match of key */
+ debug("%s:%lu: matched key and principal", path, linenum);
+ /* success */
+ found = 1;
+ } else if (sigopts->ca && sshkey_is_cert(sign_key) &&
+ sshkey_equal_public(sign_key->cert->signature_key, found_key)) {
+ /* Match of certificate's CA key */
+ if ((r = sshkey_cert_check_authority(sign_key, 0, 1,
+ principal, &reason)) != 0) {
+ error("%s:%lu: certificate not authorized: %s",
+ path, linenum, reason);
+ goto done;
+ }
+ debug("%s:%lu: matched certificate CA key", path, linenum);
+ /* success */
+ found = 1;
+ } else {
+ /* Principal matched but key didn't */
+ goto done;
+ }
+ done:
+ sshkey_free(found_key);
+ sshsigopt_free(sigopts);
+ return found ? 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)
+{
+ 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);
+ free(line);
+ line = NULL;
+ 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;
+}
+
+static int
+cert_filter_principals(const char *path, u_long linenum,
+ char **principalsp, const struct sshkey *cert)
+{
+ char *cp, *oprincipals, *principals;
+ const char *reason;
+ struct sshbuf *nprincipals;
+ int r = SSH_ERR_INTERNAL_ERROR, success = 0;
+
+ oprincipals = principals = *principalsp;
+ *principalsp = NULL;
+
+ if ((nprincipals = sshbuf_new()) == NULL) {
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+
+ while ((cp = strsep(&principals, ",")) != NULL && *cp != '\0') {
+ if (strcspn(cp, "!?*") != strlen(cp)) {
+ debug("%s:%lu: principal \"%s\" not authorized: "
+ "contains wildcards", path, linenum, cp);
+ continue;
+ }
+ /* Check against principals list in certificate */
+ if ((r = sshkey_cert_check_authority(cert, 0, 1,
+ cp, &reason)) != 0) {
+ debug("%s:%lu: principal \"%s\" not authorized: %s",
+ path, linenum, cp, reason);
+ continue;
+ }
+ if ((r = sshbuf_putf(nprincipals, "%s%s",
+ sshbuf_len(nprincipals) != 0 ? "," : "", cp)) != 0) {
+ error("%s: buffer error", __func__);
+ 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("%s: buffer error", __func__);
+ goto out;
+ }
+ /* success */
+ success = 1;
+ *principalsp = principals;
+ out:
+ sshbuf_free(nprincipals);
+ free(oprincipals);
+ return success ? 0 : r;
+}
+
+static int
+get_matching_principals_from_line(const char *path, u_long linenum, char *line,
+ const struct sshkey *sign_key, char **principalsp)
+{
+ struct sshkey *found_key = NULL;
+ char *principals = NULL;
+ int r, found = 0;
+ struct sshsigopt *sigopts = NULL;
+
+ if (principalsp != NULL)
+ *principalsp = NULL;
+
+ /* Parse the line */
+ if ((r = parse_principals_key_and_options(path, linenum, line,
+ NULL, &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);
+ /* success */
+ found = 1;
+ } else if (sigopts->ca && sshkey_is_cert(sign_key) &&
+ sshkey_equal_public(sign_key->cert->signature_key, found_key)) {
+ /* Remove principals listed in file but not allowed by cert */
+ if ((r = cert_filter_principals(path, linenum,
+ &principals, sign_key)) != 0) {
+ /* error already displayed */
+ debug("%s:%lu: cert_filter_principals: %s",
+ path, linenum, ssh_err(r));
+ goto done;
+ }
+ debug("%s:%lu: matched certificate CA key", path, linenum);
+ /* success */
+ found = 1;
+ } else {
+ /* Key didn't match */
+ goto done;
+ }
+ done:
+ if (found && principalsp != NULL) {
+ *principalsp = principals;
+ principals = NULL; /* transferred */
+ }
+ free(principals);
+ sshkey_free(found_key);
+ sshsigopt_free(sigopts);
+ return found ? 0 : SSH_ERR_KEY_NOT_FOUND;
+}
+
+int
+sshsig_find_principals(const char *path, const struct sshkey *sign_key,
+ 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;
+ }
+
+ while (getline(&line, &linesize, f) != -1) {
+ linenum++;
+ r = get_matching_principals_from_line(path, linenum, line,
+ sign_key, principals);
+ free(line);
+ line = NULL;
+ 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_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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-11 01:06:28 +0000