From 25505898530a333011f4fd5cbc841ad6b26c089c Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 16:40:04 +0200 Subject: Adding upstream version 1:9.2p1. Signed-off-by: Daniel Baumann --- ssh-ecdsa-sk.c | 468 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 468 insertions(+) create mode 100644 ssh-ecdsa-sk.c (limited to 'ssh-ecdsa-sk.c') diff --git a/ssh-ecdsa-sk.c b/ssh-ecdsa-sk.c new file mode 100644 index 0000000..729e548 --- /dev/null +++ b/ssh-ecdsa-sk.c @@ -0,0 +1,468 @@ +/* $OpenBSD: ssh-ecdsa-sk.c,v 1.17 2022/10/28 00:44:44 djm Exp $ */ +/* + * Copyright (c) 2000 Markus Friedl. All rights reserved. + * Copyright (c) 2010 Damien Miller. All rights reserved. + * Copyright (c) 2019 Google Inc. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +/* #define DEBUG_SK 1 */ + +#include "includes.h" + +#include + +#ifdef WITH_OPENSSL +#include +#include +#include +#include +#endif + +#include +#include /* needed for DEBUG_SK only */ + +#include "openbsd-compat/openssl-compat.h" + +#include "sshbuf.h" +#include "ssherr.h" +#include "digest.h" +#define SSHKEY_INTERNAL +#include "sshkey.h" + +#ifndef OPENSSL_HAS_ECC +/* ARGSUSED */ +int +ssh_ecdsa_sk_verify(const struct sshkey *key, + const u_char *signature, size_t signaturelen, + const u_char *data, size_t datalen, u_int compat, + struct sshkey_sig_details **detailsp) +{ + return SSH_ERR_FEATURE_UNSUPPORTED; +} +#else /* OPENSSL_HAS_ECC */ + +/* Reuse some ECDSA internals */ +extern struct sshkey_impl_funcs sshkey_ecdsa_funcs; + +static void +ssh_ecdsa_sk_cleanup(struct sshkey *k) +{ + sshkey_sk_cleanup(k); + sshkey_ecdsa_funcs.cleanup(k); +} + +static int +ssh_ecdsa_sk_equal(const struct sshkey *a, const struct sshkey *b) +{ + if (!sshkey_sk_fields_equal(a, b)) + return 0; + if (!sshkey_ecdsa_funcs.equal(a, b)) + return 0; + return 1; +} + +static int +ssh_ecdsa_sk_serialize_public(const struct sshkey *key, struct sshbuf *b, + enum sshkey_serialize_rep opts) +{ + int r; + + if ((r = sshkey_ecdsa_funcs.serialize_public(key, b, opts)) != 0) + return r; + if ((r = sshkey_serialize_sk(key, b)) != 0) + return r; + + return 0; +} + +static int +ssh_ecdsa_sk_serialize_private(const struct sshkey *key, struct sshbuf *b, + enum sshkey_serialize_rep opts) +{ + int r; + + if (!sshkey_is_cert(key)) { + if ((r = sshkey_ecdsa_funcs.serialize_public(key, + b, opts)) != 0) + return r; + } + if ((r = sshkey_serialize_private_sk(key, b)) != 0) + return r; + + return 0; +} + +static int +ssh_ecdsa_sk_copy_public(const struct sshkey *from, struct sshkey *to) +{ + int r; + + if ((r = sshkey_ecdsa_funcs.copy_public(from, to)) != 0) + return r; + if ((r = sshkey_copy_public_sk(from, to)) != 0) + return r; + return 0; +} + +static int +ssh_ecdsa_sk_deserialize_public(const char *ktype, struct sshbuf *b, + struct sshkey *key) +{ + int r; + + if ((r = sshkey_ecdsa_funcs.deserialize_public(ktype, b, key)) != 0) + return r; + if ((r = sshkey_deserialize_sk(b, key)) != 0) + return r; + return 0; +} + +static int +ssh_ecdsa_sk_deserialize_private(const char *ktype, struct sshbuf *b, + struct sshkey *key) +{ + int r; + + if (!sshkey_is_cert(key)) { + if ((r = sshkey_ecdsa_funcs.deserialize_public(ktype, + b, key)) != 0) + return r; + } + if ((r = sshkey_private_deserialize_sk(b, key)) != 0) + return r; + + return 0; +} + +/* + * Check FIDO/W3C webauthn signatures clientData field against the expected + * format and prepare a hash of it for use in signature verification. + * + * webauthn signatures do not sign the hash of the message directly, but + * instead sign a JSON-like "clientData" wrapper structure that contains the + * message hash along with a other information. + * + * Fortunately this structure has a fixed format so it is possible to verify + * that the hash of the signed message is present within the clientData + * structure without needing to implement any JSON parsing. + */ +static int +webauthn_check_prepare_hash(const u_char *data, size_t datalen, + const char *origin, const struct sshbuf *wrapper, + uint8_t flags, const struct sshbuf *extensions, + u_char *msghash, size_t msghashlen) +{ + int r = SSH_ERR_INTERNAL_ERROR; + struct sshbuf *chall = NULL, *m = NULL; + + if ((m = sshbuf_new()) == NULL || + (chall = sshbuf_from(data, datalen)) == NULL) { + r = SSH_ERR_ALLOC_FAIL; + goto out; + } + /* + * Ensure origin contains no quote character and that the flags are + * consistent with what we received + */ + if (strchr(origin, '\"') != NULL || + (flags & 0x40) != 0 /* AD */ || + ((flags & 0x80) == 0 /* ED */) != (sshbuf_len(extensions) == 0)) { + r = SSH_ERR_INVALID_FORMAT; + goto out; + } + + /* + * Prepare the preamble to clientData that we expect, poking the + * challenge and origin into their canonical positions in the + * structure. The crossOrigin flag and any additional extension + * fields present are ignored. + */ +#define WEBAUTHN_0 "{\"type\":\"webauthn.get\",\"challenge\":\"" +#define WEBAUTHN_1 "\",\"origin\":\"" +#define WEBAUTHN_2 "\"" + if ((r = sshbuf_put(m, WEBAUTHN_0, sizeof(WEBAUTHN_0) - 1)) != 0 || + (r = sshbuf_dtourlb64(chall, m, 0)) != 0 || + (r = sshbuf_put(m, WEBAUTHN_1, sizeof(WEBAUTHN_1) - 1)) != 0 || + (r = sshbuf_put(m, origin, strlen(origin))) != 0 || + (r = sshbuf_put(m, WEBAUTHN_2, sizeof(WEBAUTHN_2) - 1)) != 0) + goto out; +#ifdef DEBUG_SK + fprintf(stderr, "%s: received origin: %s\n", __func__, origin); + fprintf(stderr, "%s: received clientData:\n", __func__); + sshbuf_dump(wrapper, stderr); + fprintf(stderr, "%s: expected clientData premable:\n", __func__); + sshbuf_dump(m, stderr); +#endif + /* Check that the supplied clientData has the preamble we expect */ + if ((r = sshbuf_cmp(wrapper, 0, sshbuf_ptr(m), sshbuf_len(m))) != 0) + goto out; + + /* Prepare hash of clientData */ + if ((r = ssh_digest_buffer(SSH_DIGEST_SHA256, wrapper, + msghash, msghashlen)) != 0) + goto out; + + /* success */ + r = 0; + out: + sshbuf_free(chall); + sshbuf_free(m); + return r; +} + +/* ARGSUSED */ +static int +ssh_ecdsa_sk_verify(const struct sshkey *key, + const u_char *sig, size_t siglen, + const u_char *data, size_t dlen, const char *alg, u_int compat, + struct sshkey_sig_details **detailsp) +{ + ECDSA_SIG *esig = NULL; + BIGNUM *sig_r = NULL, *sig_s = NULL; + u_char sig_flags; + u_char msghash[32], apphash[32], sighash[32]; + u_int sig_counter; + int is_webauthn = 0, ret = SSH_ERR_INTERNAL_ERROR; + struct sshbuf *b = NULL, *sigbuf = NULL, *original_signed = NULL; + struct sshbuf *webauthn_wrapper = NULL, *webauthn_exts = NULL; + char *ktype = NULL, *webauthn_origin = NULL; + struct sshkey_sig_details *details = NULL; +#ifdef DEBUG_SK + char *tmp = NULL; +#endif + + if (detailsp != NULL) + *detailsp = NULL; + if (key == NULL || key->ecdsa == NULL || + sshkey_type_plain(key->type) != KEY_ECDSA_SK || + sig == NULL || siglen == 0) + return SSH_ERR_INVALID_ARGUMENT; + + if (key->ecdsa_nid != NID_X9_62_prime256v1) + return SSH_ERR_INTERNAL_ERROR; + + /* fetch signature */ + if ((b = sshbuf_from(sig, siglen)) == NULL) + return SSH_ERR_ALLOC_FAIL; + if ((details = calloc(1, sizeof(*details))) == NULL) { + ret = SSH_ERR_ALLOC_FAIL; + goto out; + } + if (sshbuf_get_cstring(b, &ktype, NULL) != 0) { + ret = SSH_ERR_INVALID_FORMAT; + goto out; + } + if (strcmp(ktype, "webauthn-sk-ecdsa-sha2-nistp256@openssh.com") == 0) + is_webauthn = 1; + else if (strcmp(ktype, "sk-ecdsa-sha2-nistp256@openssh.com") != 0) { + ret = SSH_ERR_INVALID_FORMAT; + goto out; + } + if (sshbuf_froms(b, &sigbuf) != 0 || + sshbuf_get_u8(b, &sig_flags) != 0 || + sshbuf_get_u32(b, &sig_counter) != 0) { + ret = SSH_ERR_INVALID_FORMAT; + goto out; + } + if (is_webauthn) { + if (sshbuf_get_cstring(b, &webauthn_origin, NULL) != 0 || + sshbuf_froms(b, &webauthn_wrapper) != 0 || + sshbuf_froms(b, &webauthn_exts) != 0) { + ret = SSH_ERR_INVALID_FORMAT; + goto out; + } + } + if (sshbuf_len(b) != 0) { + ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; + goto out; + } + + /* parse signature */ + if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 || + sshbuf_get_bignum2(sigbuf, &sig_s) != 0) { + ret = SSH_ERR_INVALID_FORMAT; + goto out; + } + if (sshbuf_len(sigbuf) != 0) { + ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; + goto out; + } + +#ifdef DEBUG_SK + fprintf(stderr, "%s: data: (len %zu)\n", __func__, datalen); + /* sshbuf_dump_data(data, datalen, stderr); */ + fprintf(stderr, "%s: sig_r: %s\n", __func__, (tmp = BN_bn2hex(sig_r))); + free(tmp); + fprintf(stderr, "%s: sig_s: %s\n", __func__, (tmp = BN_bn2hex(sig_s))); + free(tmp); + fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n", + __func__, sig_flags, sig_counter); + if (is_webauthn) { + fprintf(stderr, "%s: webauthn origin: %s\n", __func__, + webauthn_origin); + fprintf(stderr, "%s: webauthn_wrapper:\n", __func__); + sshbuf_dump(webauthn_wrapper, stderr); + } +#endif + if ((esig = ECDSA_SIG_new()) == NULL) { + ret = SSH_ERR_ALLOC_FAIL; + goto out; + } + if (!ECDSA_SIG_set0(esig, sig_r, sig_s)) { + ret = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } + sig_r = sig_s = NULL; /* transferred */ + + /* Reconstruct data that was supposedly signed */ + if ((original_signed = sshbuf_new()) == NULL) { + ret = SSH_ERR_ALLOC_FAIL; + goto out; + } + if (is_webauthn) { + if ((ret = webauthn_check_prepare_hash(data, dlen, + webauthn_origin, webauthn_wrapper, sig_flags, webauthn_exts, + msghash, sizeof(msghash))) != 0) + goto out; + } else if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, data, dlen, + msghash, sizeof(msghash))) != 0) + goto out; + /* Application value is hashed before signature */ + if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application, + strlen(key->sk_application), apphash, sizeof(apphash))) != 0) + goto out; +#ifdef DEBUG_SK + fprintf(stderr, "%s: hashed application:\n", __func__); + sshbuf_dump_data(apphash, sizeof(apphash), stderr); + fprintf(stderr, "%s: hashed message:\n", __func__); + sshbuf_dump_data(msghash, sizeof(msghash), stderr); +#endif + if ((ret = sshbuf_put(original_signed, + apphash, sizeof(apphash))) != 0 || + (ret = sshbuf_put_u8(original_signed, sig_flags)) != 0 || + (ret = sshbuf_put_u32(original_signed, sig_counter)) != 0 || + (ret = sshbuf_putb(original_signed, webauthn_exts)) != 0 || + (ret = sshbuf_put(original_signed, msghash, sizeof(msghash))) != 0) + goto out; + /* Signature is over H(original_signed) */ + if ((ret = ssh_digest_buffer(SSH_DIGEST_SHA256, original_signed, + sighash, sizeof(sighash))) != 0) + goto out; + details->sk_counter = sig_counter; + details->sk_flags = sig_flags; +#ifdef DEBUG_SK + fprintf(stderr, "%s: signed buf:\n", __func__); + sshbuf_dump(original_signed, stderr); + fprintf(stderr, "%s: signed hash:\n", __func__); + sshbuf_dump_data(sighash, sizeof(sighash), stderr); +#endif + + /* Verify it */ + switch (ECDSA_do_verify(sighash, sizeof(sighash), esig, key->ecdsa)) { + case 1: + ret = 0; + break; + case 0: + ret = SSH_ERR_SIGNATURE_INVALID; + goto out; + default: + ret = SSH_ERR_LIBCRYPTO_ERROR; + goto out; + } + /* success */ + if (detailsp != NULL) { + *detailsp = details; + details = NULL; + } + out: + explicit_bzero(&sig_flags, sizeof(sig_flags)); + explicit_bzero(&sig_counter, sizeof(sig_counter)); + explicit_bzero(msghash, sizeof(msghash)); + explicit_bzero(sighash, sizeof(msghash)); + explicit_bzero(apphash, sizeof(apphash)); + sshkey_sig_details_free(details); + sshbuf_free(webauthn_wrapper); + sshbuf_free(webauthn_exts); + free(webauthn_origin); + sshbuf_free(original_signed); + sshbuf_free(sigbuf); + sshbuf_free(b); + ECDSA_SIG_free(esig); + BN_clear_free(sig_r); + BN_clear_free(sig_s); + free(ktype); + return ret; +} + +static const struct sshkey_impl_funcs sshkey_ecdsa_sk_funcs = { + /* .size = */ NULL, + /* .alloc = */ NULL, + /* .cleanup = */ ssh_ecdsa_sk_cleanup, + /* .equal = */ ssh_ecdsa_sk_equal, + /* .ssh_serialize_public = */ ssh_ecdsa_sk_serialize_public, + /* .ssh_deserialize_public = */ ssh_ecdsa_sk_deserialize_public, + /* .ssh_serialize_private = */ ssh_ecdsa_sk_serialize_private, + /* .ssh_deserialize_private = */ ssh_ecdsa_sk_deserialize_private, + /* .generate = */ NULL, + /* .copy_public = */ ssh_ecdsa_sk_copy_public, + /* .sign = */ NULL, + /* .verify = */ ssh_ecdsa_sk_verify, +}; + +const struct sshkey_impl sshkey_ecdsa_sk_impl = { + /* .name = */ "sk-ecdsa-sha2-nistp256@openssh.com", + /* .shortname = */ "ECDSA-SK", + /* .sigalg = */ NULL, + /* .type = */ KEY_ECDSA_SK, + /* .nid = */ NID_X9_62_prime256v1, + /* .cert = */ 0, + /* .sigonly = */ 0, + /* .keybits = */ 256, + /* .funcs = */ &sshkey_ecdsa_sk_funcs, +}; + +const struct sshkey_impl sshkey_ecdsa_sk_cert_impl = { + /* .name = */ "sk-ecdsa-sha2-nistp256-cert-v01@openssh.com", + /* .shortname = */ "ECDSA-SK-CERT", + /* .sigalg = */ NULL, + /* .type = */ KEY_ECDSA_SK_CERT, + /* .nid = */ NID_X9_62_prime256v1, + /* .cert = */ 1, + /* .sigonly = */ 0, + /* .keybits = */ 256, + /* .funcs = */ &sshkey_ecdsa_sk_funcs, +}; + +const struct sshkey_impl sshkey_ecdsa_sk_webauthn_impl = { + /* .name = */ "webauthn-sk-ecdsa-sha2-nistp256@openssh.com", + /* .shortname = */ "ECDSA-SK", + /* .sigalg = */ NULL, + /* .type = */ KEY_ECDSA_SK, + /* .nid = */ NID_X9_62_prime256v1, + /* .cert = */ 0, + /* .sigonly = */ 1, + /* .keybits = */ 256, + /* .funcs = */ &sshkey_ecdsa_sk_funcs, +}; + +#endif /* OPENSSL_HAS_ECC */ -- cgit v1.2.3