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upstream: refactor ECDSA-SK verification a little ahead of adding 

support for FIDO webauthn signature verification support; ok markus@

OpenBSD-Commit-ID: c9f478fd8e0c1bd17e511ce8694f010d8e32043e
This commit is contained in:
djm@openbsd.org 2020-06-22 05:56:23 +00:00 committed by Damien Miller
parent 12848191f8
commit 64bc121097
1 changed files with 23 additions and 21 deletions
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44
ssh-ecdsa-sk.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh-ecdsa-sk.c,v 1.5 2019/11/26 03:04:27 djm Exp $ */
/* $OpenBSD: ssh-ecdsa-sk.c,v 1.6 2020/06/22 05:56:23 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2010 Damien Miller. All rights reserved.
@ -83,15 +83,22 @@ ssh_ecdsa_sk_verify(const struct sshkey *key,
/* fetch signature */
if ((b = sshbuf_from(signature, signaturelen)) == NULL)
return SSH_ERR_ALLOC_FAIL;
if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
sshbuf_froms(b, &sigbuf) != 0 ||
sshbuf_get_u8(b, &sig_flags) != 0 ||
sshbuf_get_u32(b, &sig_counter) != 0) {
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(sshkey_ssh_name_plain(key), ktype) != 0) {
ret = SSH_ERR_KEY_TYPE_MISMATCH;
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 (sshbuf_len(b) != 0) {
@ -105,12 +112,8 @@ ssh_ecdsa_sk_verify(const struct sshkey *key,
ret = SSH_ERR_INVALID_FORMAT;
goto out;
}
if ((sig = ECDSA_SIG_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
if (!ECDSA_SIG_set0(sig, sig_r, sig_s)) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
if (sshbuf_len(sigbuf) != 0) {
ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
goto out;
}
#ifdef DEBUG_SK
@ -123,12 +126,15 @@ ssh_ecdsa_sk_verify(const struct sshkey *key,
fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
__func__, sig_flags, sig_counter);
#endif
sig_r = sig_s = NULL; /* transferred */
if (sshbuf_len(sigbuf) != 0) {
ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
if ((sig = ECDSA_SIG_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
if (!ECDSA_SIG_set0(sig, 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) {
@ -158,10 +164,6 @@ ssh_ecdsa_sk_verify(const struct sshkey *key,
if ((ret = ssh_digest_buffer(SSH_DIGEST_SHA256, original_signed,
sighash, sizeof(sighash))) != 0)
goto out;
if ((details = calloc(1, sizeof(*details))) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
details->sk_counter = sig_counter;
details->sk_flags = sig_flags;
#ifdef DEBUG_SK