From: djm <djm@openbsd.org>
Date: Mon, 7 Feb 2022 01:25:12 +0000 (+0000)
Subject: use libfido2 1.8.0+ fido_assert_set_clientdata() instead of manually
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=b4f4fe96fdc3285e7754238807aac259a49466c1;p=openbsd

use libfido2 1.8.0+ fido_assert_set_clientdata() instead of manually
hashing data outselves. Saves a fair bit of code and makes life easier
for some -portable platforms.
---

diff --git a/usr.bin/ssh/sk-usbhid.c b/usr.bin/ssh/sk-usbhid.c
index 6d629da7792..795a21d827d 100644
--- a/usr.bin/ssh/sk-usbhid.c
+++ b/usr.bin/ssh/sk-usbhid.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sk-usbhid.c,v 1.37 2021/12/07 22:06:45 djm Exp $ */
+/* $OpenBSD: sk-usbhid.c,v 1.38 2022/02/07 01:25:12 djm Exp $ */
 /*
  * Copyright (c) 2019 Markus Friedl
  * Copyright (c) 2020 Pedro Martelletto
@@ -22,7 +22,6 @@
 #include <stdio.h>
 #include <stddef.h>
 #include <stdarg.h>
-#include <sha2.h>
 #include <time.h>
 
 #ifdef WITH_OPENSSL
@@ -274,50 +273,22 @@ sk_touch_poll(struct sk_usbhid **skv, size_t nsk, int *touch, size_t *idx)
 	return 0;
 }
 
-/* Calculate SHA256(m) */
-static int
-sha256_mem(const void *m, size_t mlen, u_char *d, size_t dlen)
-{
-#ifdef WITH_OPENSSL
-	u_int mdlen;
-#else
-	SHA2_CTX ctx;
-#endif
-
-	if (dlen != 32)
-		return -1;
-#ifdef WITH_OPENSSL
-	mdlen = dlen;
-	if (!EVP_Digest(m, mlen, d, &mdlen, EVP_sha256(), NULL))
-		return -1;
-#else
-	SHA256Init(&ctx);
-	SHA256Update(&ctx, (const uint8_t *)m, mlen);
-	SHA256Final(d, &ctx);
-#endif
-	return 0;
-}
-
 /* Check if the specified key handle exists on a given sk. */
 static int
 sk_try(const struct sk_usbhid *sk, const char *application,
     const uint8_t *key_handle, size_t key_handle_len)
 {
 	fido_assert_t *assert = NULL;
-	/* generate an invalid signature on FIDO2 tokens */
-	const char *data = "";
-	uint8_t message[32];
 	int r = FIDO_ERR_INTERNAL;
+	uint8_t message[32];
 
-	if (sha256_mem(data, strlen(data), message, sizeof(message)) != 0) {
-		skdebug(__func__, "hash message failed");
-		goto out;
-	}
+	memset(message, '\0', sizeof(message));
 	if ((assert = fido_assert_new()) == NULL) {
 		skdebug(__func__, "fido_assert_new failed");
 		goto out;
 	}
-	if ((r = fido_assert_set_clientdata_hash(assert, message,
+	/* generate an invalid signature on FIDO2 tokens */
+	if ((r = fido_assert_set_clientdata(assert, message,
 	    sizeof(message))) != FIDO_OK) {
 		skdebug(__func__, "fido_assert_set_clientdata_hash: %s",
 		    fido_strerr(r));
@@ -687,7 +658,7 @@ sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
 {
 	fido_cred_t *cred = NULL;
 	const uint8_t *ptr;
-	uint8_t user_id[32], chall_hash[32];
+	uint8_t user_id[32];
 	struct sk_usbhid *sk = NULL;
 	struct sk_enroll_response *response = NULL;
 	size_t len;
@@ -741,14 +712,9 @@ sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
 		skdebug(__func__, "fido_cred_set_type: %s", fido_strerr(r));
 		goto out;
 	}
-	if (sha256_mem(challenge, challenge_len,
-	    chall_hash, sizeof(chall_hash)) != 0) {
-		skdebug(__func__, "hash challenge failed");
-		goto out;
-	}
-	if ((r = fido_cred_set_clientdata_hash(cred, chall_hash,
-	    sizeof(chall_hash))) != FIDO_OK) {
-		skdebug(__func__, "fido_cred_set_clientdata_hash: %s",
+	if ((r = fido_cred_set_clientdata(cred,
+	    challenge, challenge_len)) != FIDO_OK) {
+		skdebug(__func__, "fido_cred_set_clientdata: %s",
 		    fido_strerr(r));
 		goto out;
 	}
@@ -998,7 +964,6 @@ sk_sign(uint32_t alg, const uint8_t *data, size_t datalen,
 	char *device = NULL;
 	struct sk_usbhid *sk = NULL;
 	struct sk_sign_response *response = NULL;
-	uint8_t message[32];
 	int ret = SSH_SK_ERR_GENERAL, internal_uv;
 	int r;
 
@@ -1011,11 +976,6 @@ sk_sign(uint32_t alg, const uint8_t *data, size_t datalen,
 	*sign_response = NULL;
 	if (check_sign_load_resident_options(options, &device) != 0)
 		goto out; /* error already logged */
-	/* hash data to be signed before it goes to the security key */
-	if ((r = sha256_mem(data, datalen, message, sizeof(message))) != 0) {
-		skdebug(__func__, "hash message failed");
-		goto out;
-	}
 	if (device != NULL)
 		sk = sk_open(device);
 	else if (pin != NULL || (flags & SSH_SK_USER_VERIFICATION_REQD))
@@ -1031,9 +991,9 @@ sk_sign(uint32_t alg, const uint8_t *data, size_t datalen,
 		skdebug(__func__, "fido_assert_new failed");
 		goto out;
 	}
-	if ((r = fido_assert_set_clientdata_hash(assert, message,
-	    sizeof(message))) != FIDO_OK) {
-		skdebug(__func__, "fido_assert_set_clientdata_hash: %s",
+	if ((r = fido_assert_set_clientdata(assert,
+	    data, datalen)) != FIDO_OK)  {
+		skdebug(__func__, "fido_assert_set_clientdata: %s",
 		    fido_strerr(r));
 		goto out;
 	}
@@ -1086,7 +1046,6 @@ sk_sign(uint32_t alg, const uint8_t *data, size_t datalen,
 	response = NULL;
 	ret = 0;
  out:
-	explicit_bzero(message, sizeof(message));
 	free(device);
 	if (response != NULL) {
 		free(response->sig_r);