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- markus@cvs.openbsd.org 2002/03/14 16:56:33

Browse Source 
[auth-rh-rsa.c auth-rsa.c auth.h]
     split auth_rsa() for better readability and privsep; ok provos@
This commit is contained in:
Ben Lindstrom 2002-03-22 01:12:58 +00:00
parent abcb145b38
commit 9c8aefe750
4 changed files with 126 additions and 91 deletions
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5
ChangeLog
View File

@ -15,6 +15,9 @@
- markus@cvs.openbsd.org 2002/03/14 16:38:26
[sshd.c]
split out ssh1 session key decryption; ok provos@
- markus@cvs.openbsd.org 2002/03/14 16:56:33
[auth-rh-rsa.c auth-rsa.c auth.h]
split auth_rsa() for better readability and privsep; ok provos@
20020317
- (tim) [configure.ac] Assume path given with --with-pid-dir=PATH is wanted,
@ -7861,4 +7864,4 @@
- Wrote replacements for strlcpy and mkdtemp
- Released 1.0pre1
$Id: ChangeLog,v 1.1928 2002/03/22 01:10:21 mouring Exp $
$Id: ChangeLog,v 1.1929 2002/03/22 01:12:58 mouring Exp $

4
auth-rh-rsa.c
View File

@ -13,7 +13,7 @@
*/
#include "includes.h"
RCSID("$OpenBSD: auth-rh-rsa.c,v 1.29 2002/03/04 12:43:06 markus Exp $");
RCSID("$OpenBSD: auth-rh-rsa.c,v 1.30 2002/03/14 16:56:33 markus Exp $");
#include "packet.h"
#include "uidswap.h"
@ -63,7 +63,7 @@ auth_rhosts_rsa(struct passwd *pw, const char *client_user, Key *client_host_key
/* A matching host key was found and is known. */
/* Perform the challenge-response dialog with the client for the host key. */
if (!auth_rsa_challenge_dialog(client_host_key->rsa)) {
if (!auth_rsa_challenge_dialog(client_host_key)) {
log("Client on %.800s failed to respond correctly to host authentication.",
canonical_hostname);
return 0;

204
auth-rsa.c
View File

@ -14,7 +14,7 @@
*/
#include "includes.h"
RCSID("$OpenBSD: auth-rsa.c,v 1.50 2001/12/28 14:50:54 markus Exp $");
RCSID("$OpenBSD: auth-rsa.c,v 1.51 2002/03/14 16:56:33 markus Exp $");
#include <openssl/rsa.h>
#include <openssl/md5.h>
@ -52,6 +52,51 @@ extern u_char session_id[16];
* description of the options.
*/
static BIGNUM *
auth_rsa_generate_challenge(Key *key)
{
BIGNUM *challenge;
BN_CTX *ctx;
if ((challenge = BN_new()) == NULL)
fatal("auth_rsa_generate_challenge: BN_new() failed");
/* Generate a random challenge. */
BN_rand(challenge, 256, 0, 0);
if ((ctx = BN_CTX_new()) == NULL)
fatal("auth_rsa_generate_challenge: BN_CTX_new() failed");
BN_mod(challenge, challenge, key->rsa->n, ctx);
BN_CTX_free(ctx);
return challenge;
}
static int
auth_rsa_verify_response(Key *key, BIGNUM *challenge, u_char response[16])
{
u_char buf[32], mdbuf[16];
MD5_CTX md;
int len;
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || len > 32)
fatal("auth_rsa_verify_response: bad challenge length %d", len);
memset(buf, 0, 32);
BN_bn2bin(challenge, buf + 32 - len);
MD5_Init(&md);
MD5_Update(&md, buf, 32);
MD5_Update(&md, session_id, 16);
MD5_Final(mdbuf, &md);
/* Verify that the response is the original challenge. */
if (memcmp(response, mdbuf, 16) != 0) {
/* Wrong answer. */
return (0);
}
/* Correct answer. */
return (1);
}
/*
* Performs the RSA authentication challenge-response dialog with the client,
* and returns true (non-zero) if the client gave the correct answer to
@ -59,29 +104,19 @@ extern u_char session_id[16];
*/
int
auth_rsa_challenge_dialog(RSA *pk)
auth_rsa_challenge_dialog(Key *key)
{
BIGNUM *challenge, *encrypted_challenge;
BN_CTX *ctx;
u_char buf[32], mdbuf[16], response[16];
MD5_CTX md;
u_int i;
int len;
u_char response[16];
int i, success;
if ((encrypted_challenge = BN_new()) == NULL)
fatal("auth_rsa_challenge_dialog: BN_new() failed");
if ((challenge = BN_new()) == NULL)
fatal("auth_rsa_challenge_dialog: BN_new() failed");
/* Generate a random challenge. */
BN_rand(challenge, 256, 0, 0);
if ((ctx = BN_CTX_new()) == NULL)
fatal("auth_rsa_challenge_dialog: BN_CTX_new() failed");
BN_mod(challenge, challenge, pk->n, ctx);
BN_CTX_free(ctx);
challenge = auth_rsa_generate_challenge(key);
/* Encrypt the challenge with the public key. */
rsa_public_encrypt(encrypted_challenge, challenge, pk);
rsa_public_encrypt(encrypted_challenge, challenge, key->rsa);
/* Send the encrypted challenge to the client. */
packet_start(SSH_SMSG_AUTH_RSA_CHALLENGE);
@ -96,48 +131,26 @@ auth_rsa_challenge_dialog(RSA *pk)
response[i] = packet_get_char();
packet_check_eom();
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || len > 32)
fatal("auth_rsa_challenge_dialog: bad challenge length %d", len);
memset(buf, 0, 32);
BN_bn2bin(challenge, buf + 32 - len);
MD5_Init(&md);
MD5_Update(&md, buf, 32);
MD5_Update(&md, session_id, 16);
MD5_Final(mdbuf, &md);
success = auth_rsa_verify_response(key, challenge, response);
BN_clear_free(challenge);
/* Verify that the response is the original challenge. */
if (memcmp(response, mdbuf, 16) != 0) {
/* Wrong answer. */
return 0;
}
/* Correct answer. */
return 1;
return (success);
}
/*
* Performs the RSA authentication dialog with the client. This returns
* 0 if the client could not be authenticated, and 1 if authentication was
* successful. This may exit if there is a serious protocol violation.
* check if there's user key matching client_n,
* return key if login is allowed, NULL otherwise
*/
int
auth_rsa(struct passwd *pw, BIGNUM *client_n)
static int
auth_rsa_key_allowed(struct passwd *pw, BIGNUM *client_n, Key **rkey)
{
char line[8192], *file;
int authenticated;
int allowed;
u_int bits;
FILE *f;
u_long linenum = 0;
struct stat st;
Key *key;
char *fp;
/* no user given */
if (pw == NULL)
return 0;
/* Temporarily use the user's uid. */
temporarily_use_uid(pw);
@ -151,29 +164,27 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n)
/* Restore the privileged uid. */
restore_uid();
xfree(file);
return 0;
return (NULL);
}
/* Open the file containing the authorized keys. */
f = fopen(file, "r");
if (!f) {
/* Restore the privileged uid. */
restore_uid();
packet_send_debug("Could not open %.900s for reading.", file);
packet_send_debug("If your home is on an NFS volume, it may need to be world-readable.");
xfree(file);
return 0;
return (NULL);
}
if (options.strict_modes &&
secure_filename(f, file, pw, line, sizeof(line)) != 0) {
xfree(file);
fclose(f);
log("Authentication refused: %s", line);
packet_send_debug("Authentication refused: %s", line);
restore_uid();
return 0;
return (NULL);
}
/* Flag indicating whether authentication has succeeded. */
authenticated = 0;
/* Flag indicating whether the key is allowed. */
allowed = 0;
key = key_new(KEY_RSA1);
@ -238,32 +249,8 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n)
if (!auth_parse_options(pw, options, file, linenum))
continue;
/* Perform the challenge-response dialog for this key. */
if (!auth_rsa_challenge_dialog(key->rsa)) {
/* Wrong response. */
verbose("Wrong response to RSA authentication challenge.");
packet_send_debug("Wrong response to RSA authentication challenge.");
/*
* Break out of the loop. Otherwise we might send
* another challenge and break the protocol.
*/
break;
}
/*
* Correct response. The client has been successfully
* authenticated. Note that we have not yet processed the
* options; this will be reset if the options cause the
* authentication to be rejected.
* Break out of the loop if authentication was successful;
* otherwise continue searching.
*/
authenticated = 1;
fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
verbose("Found matching %s key: %s",
key_type(key), fp);
xfree(fp);
/* break out, this key is allowed */
allowed = 1;
break;
}
@ -274,13 +261,58 @@ auth_rsa(struct passwd *pw, BIGNUM *client_n)
xfree(file);
fclose(f);
/* return key if allowed */
if (allowed && rkey != NULL)
*rkey = key;
else
key_free(key);
return (allowed);
}
/*
* Performs the RSA authentication dialog with the client. This returns
* 0 if the client could not be authenticated, and 1 if authentication was
* successful. This may exit if there is a serious protocol violation.
*/
int
auth_rsa(struct passwd *pw, BIGNUM *client_n)
{
Key *key;
char *fp;
/* no user given */
if (pw == NULL)
return 0;
if (auth_rsa_key_allowed(pw, client_n, &key) == 0) {
auth_clear_options();
return (0);
}
/* Perform the challenge-response dialog for this key. */
if (!auth_rsa_challenge_dialog(key)) {
/* Wrong response. */
verbose("Wrong response to RSA authentication challenge.");
packet_send_debug("Wrong response to RSA authentication challenge.");
/*
* Break out of the loop. Otherwise we might send
* another challenge and break the protocol.
*/
key_free(key);
return (0);
}
/*
* Correct response. The client has been successfully
* authenticated. Note that we have not yet processed the
* options; this will be reset if the options cause the
* authentication to be rejected.
*/
fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
verbose("Found matching %s key: %s",
key_type(key), fp);
xfree(fp);
key_free(key);
if (authenticated)
packet_send_debug("RSA authentication accepted.");
else
auth_clear_options();
/* Return authentication result. */
return authenticated;
packet_send_debug("RSA authentication accepted.");
return (1);
}

4
auth.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: auth.h,v 1.29 2002/03/04 17:27:39 stevesk Exp $ */
/* $OpenBSD: auth.h,v 1.30 2002/03/14 16:56:33 markus Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
@ -95,7 +95,7 @@ auth_rhosts2(struct passwd *, const char *, const char *, const char *);
int auth_rhosts_rsa(struct passwd *, const char *, Key *);
int auth_password(Authctxt *, const char *);
int auth_rsa(struct passwd *, BIGNUM *);
int auth_rsa_challenge_dialog(RSA *);
int auth_rsa_challenge_dialog(Key *);
#ifdef KRB4
#include <krb.h>