| /* |
| * 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 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, 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, 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 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, 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, |
| 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, 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; |
| } |