Annotation of src/usr.bin/ssh/ssh-ecdsa-sk.c, Revision 1.1
1.1 ! djm 1: /* $OpenBSD$ */
! 2: /*
! 3: * Copyright (c) 2000 Markus Friedl. All rights reserved.
! 4: * Copyright (c) 2010 Damien Miller. All rights reserved.
! 5: * Copyright (c) 2019 Google Inc. All rights reserved.
! 6: *
! 7: * Redistribution and use in source and binary forms, with or without
! 8: * modification, are permitted provided that the following conditions
! 9: * are met:
! 10: * 1. Redistributions of source code must retain the above copyright
! 11: * notice, this list of conditions and the following disclaimer.
! 12: * 2. Redistributions in binary form must reproduce the above copyright
! 13: * notice, this list of conditions and the following disclaimer in the
! 14: * documentation and/or other materials provided with the distribution.
! 15: *
! 16: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
! 17: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
! 18: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
! 19: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
! 20: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
! 21: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
! 22: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
! 23: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
! 24: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
! 25: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
! 26: */
! 27:
! 28: /* #define DEBUG_SK 1 */
! 29:
! 30: #include <sys/types.h>
! 31:
! 32: #include <openssl/bn.h>
! 33: #include <openssl/ec.h>
! 34: #include <openssl/ecdsa.h>
! 35: #include <openssl/evp.h>
! 36:
! 37: #include <string.h>
! 38: #include <stdio.h> /* needed for DEBUG_SK only */
! 39:
! 40: #include "sshbuf.h"
! 41: #include "ssherr.h"
! 42: #include "digest.h"
! 43: #define SSHKEY_INTERNAL
! 44: #include "sshkey.h"
! 45:
! 46: /* ARGSUSED */
! 47: int
! 48: ssh_ecdsa_sk_verify(const struct sshkey *key,
! 49: const u_char *signature, size_t signaturelen,
! 50: const u_char *data, size_t datalen, u_int compat)
! 51: {
! 52: ECDSA_SIG *sig = NULL;
! 53: BIGNUM *sig_r = NULL, *sig_s = NULL;
! 54: u_char sig_flags;
! 55: u_char msghash[32], apphash[32], sighash[32];
! 56: u_int sig_counter;
! 57: int ret = SSH_ERR_INTERNAL_ERROR;
! 58: struct sshbuf *b = NULL, *sigbuf = NULL, *original_signed = NULL;
! 59: char *ktype = NULL;
! 60: #ifdef DEBUG_SK
! 61: char *tmp = NULL;
! 62: #endif
! 63:
! 64: if (key == NULL || key->ecdsa == NULL ||
! 65: sshkey_type_plain(key->type) != KEY_ECDSA_SK ||
! 66: signature == NULL || signaturelen == 0)
! 67: return SSH_ERR_INVALID_ARGUMENT;
! 68:
! 69: if (key->ecdsa_nid != NID_X9_62_prime256v1)
! 70: return SSH_ERR_INTERNAL_ERROR;
! 71:
! 72: /* fetch signature */
! 73: if ((b = sshbuf_from(signature, signaturelen)) == NULL)
! 74: return SSH_ERR_ALLOC_FAIL;
! 75: if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
! 76: sshbuf_froms(b, &sigbuf) != 0) {
! 77: ret = SSH_ERR_INVALID_FORMAT;
! 78: goto out;
! 79: }
! 80: if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
! 81: ret = SSH_ERR_KEY_TYPE_MISMATCH;
! 82: goto out;
! 83: }
! 84: if (sshbuf_len(b) != 0) {
! 85: ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
! 86: goto out;
! 87: }
! 88:
! 89: /* parse signature */
! 90: if (sshbuf_get_bignum2(sigbuf, &sig_r) != 0 ||
! 91: sshbuf_get_bignum2(sigbuf, &sig_s) != 0 ||
! 92: sshbuf_get_u8(sigbuf, &sig_flags) != 0 ||
! 93: sshbuf_get_u32(sigbuf, &sig_counter) != 0) {
! 94: ret = SSH_ERR_INVALID_FORMAT;
! 95: goto out;
! 96: }
! 97: if ((sig = ECDSA_SIG_new()) == NULL) {
! 98: ret = SSH_ERR_ALLOC_FAIL;
! 99: goto out;
! 100: }
! 101: if (!ECDSA_SIG_set0(sig, sig_r, sig_s)) {
! 102: ret = SSH_ERR_LIBCRYPTO_ERROR;
! 103: goto out;
! 104: }
! 105: #ifdef DEBUG_SK
! 106: fprintf(stderr, "%s: sig_r: %s\n", __func__, (tmp = BN_bn2hex(sig_r)));
! 107: free(tmp);
! 108: fprintf(stderr, "%s: sig_s: %s\n", __func__, (tmp = BN_bn2hex(sig_s)));
! 109: free(tmp);
! 110: fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
! 111: __func__, sig_flags, sig_counter);
! 112: #endif
! 113: sig_r = sig_s = NULL; /* transferred */
! 114:
! 115: if (sshbuf_len(sigbuf) != 0) {
! 116: ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
! 117: goto out;
! 118: }
! 119:
! 120: /* Reconstruct data that was supposedly signed */
! 121: if ((original_signed = sshbuf_new()) == NULL)
! 122: return SSH_ERR_ALLOC_FAIL;
! 123: if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, data, datalen,
! 124: msghash, sizeof(msghash))) != 0)
! 125: goto out;
! 126: /* Application value is hashed before signature */
! 127: if ((ret = ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application,
! 128: strlen(key->sk_application), apphash, sizeof(apphash))) != 0)
! 129: goto out;
! 130: #ifdef DEBUG_SK
! 131: fprintf(stderr, "%s: hashed message:\n", __func__);
! 132: sshbuf_dump_data(msghash, sizeof(msghash), stderr);
! 133: #endif
! 134: if ((ret = sshbuf_put(original_signed,
! 135: apphash, sizeof(apphash))) != 0 ||
! 136: (ret = sshbuf_put_u8(original_signed, sig_flags)) != 0 ||
! 137: (ret = sshbuf_put_u32(original_signed, sig_counter)) != 0 ||
! 138: (ret = sshbuf_put(original_signed, msghash, sizeof(msghash))) != 0)
! 139: goto out;
! 140: /* Signature is over H(original_signed) */
! 141: if ((ret = ssh_digest_buffer(SSH_DIGEST_SHA256, original_signed,
! 142: sighash, sizeof(sighash))) != 0)
! 143: goto out;
! 144: #ifdef DEBUG_SK
! 145: fprintf(stderr, "%s: signed buf:\n", __func__);
! 146: sshbuf_dump(original_signed, stderr);
! 147: fprintf(stderr, "%s: signed hash:\n", __func__);
! 148: sshbuf_dump_data(sighash, sizeof(sighash), stderr);
! 149: #endif
! 150:
! 151: /* Verify it */
! 152: switch (ECDSA_do_verify(sighash, sizeof(sighash), sig, key->ecdsa)) {
! 153: case 1:
! 154: ret = 0;
! 155: break;
! 156: case 0:
! 157: ret = SSH_ERR_SIGNATURE_INVALID;
! 158: goto out;
! 159: default:
! 160: ret = SSH_ERR_LIBCRYPTO_ERROR;
! 161: goto out;
! 162: }
! 163:
! 164: out:
! 165: explicit_bzero(&sig_flags, sizeof(sig_flags));
! 166: explicit_bzero(&sig_counter, sizeof(sig_counter));
! 167: explicit_bzero(msghash, sizeof(msghash));
! 168: explicit_bzero(sighash, sizeof(msghash));
! 169: explicit_bzero(apphash, sizeof(apphash));
! 170: sshbuf_free(original_signed);
! 171: sshbuf_free(sigbuf);
! 172: sshbuf_free(b);
! 173: ECDSA_SIG_free(sig);
! 174: BN_clear_free(sig_r);
! 175: BN_clear_free(sig_s);
! 176: free(ktype);
! 177: return ret;
! 178: }
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