[openssh-commits] [openssh] 05/06: upstream: refactor ECDSA-SK verification a little ahead of adding

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djm pushed a commit to branch master
in repository openssh.

commit 64bc121097f377142f1387ffb2df7592c49935af
Author: djm at openbsd.org <djm at openbsd.org>
Date:   Mon Jun 22 05:56:23 2020 +0000

    upstream: refactor ECDSA-SK verification a little ahead of adding
    
    support for FIDO webauthn signature verification support; ok markus@
    
    OpenBSD-Commit-ID: c9f478fd8e0c1bd17e511ce8694f010d8e32043e
---
 ssh-ecdsa-sk.c | 46 ++++++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 22 deletions(-)

diff --git a/ssh-ecdsa-sk.c b/ssh-ecdsa-sk.c
index 981d60d7..dcf605ba 100644
--- a/ssh-ecdsa-sk.c
+++ b/ssh-ecdsa-sk.c
@@ -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.
@@ -83,17 +83,24 @@ 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 ||
+	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, "sk-ecdsa-sha2-nistp256 at 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 (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
-		ret = SSH_ERR_KEY_TYPE_MISMATCH;
-		goto out;
-	}
 	if (sshbuf_len(b) != 0) {
 		ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
 		goto out;
@@ -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
@@ -123,13 +126,16 @@ 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
+	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 */
 
-	if (sshbuf_len(sigbuf) != 0) {
-		ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
-		goto out;
-	}
-
 	/* Reconstruct data that was supposedly signed */
 	if ((original_signed = sshbuf_new()) == NULL) {
 		ret = SSH_ERR_ALLOC_FAIL;
@@ -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

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