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// SPDX-License-Identifier: GPL-2.0-or-later
/*******************************************************************************
* This file houses the main functions for the iSCSI CHAP support
*
* (c) Copyright 2007-2013 Datera, Inc.
*
* Author: Nicholas A. Bellinger <nab@linux-iscsi.org>
*
******************************************************************************/
#include <crypto/hash.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <target/iscsi/iscsi_target_core.h>
#include "iscsi_target_nego.h"
#include "iscsi_target_auth.h"
static char *chap_get_digest_name(const int digest_type)
{
switch (digest_type) {
case CHAP_DIGEST_MD5:
return "md5";
case CHAP_DIGEST_SHA1:
return "sha1";
case CHAP_DIGEST_SHA256:
return "sha256";
case CHAP_DIGEST_SHA3_256:
return "sha3-256";
default:
return NULL;
}
}
static int chap_gen_challenge(
struct iscsi_conn *conn,
int caller,
char *c_str,
unsigned int *c_len)
{
int ret;
unsigned char *challenge_asciihex;
struct iscsi_chap *chap = conn->auth_protocol;
challenge_asciihex = kzalloc(chap->challenge_len * 2 + 1, GFP_KERNEL);
if (!challenge_asciihex)
return -ENOMEM;
memset(chap->challenge, 0, MAX_CHAP_CHALLENGE_LEN);
ret = get_random_bytes_wait(chap->challenge, chap->challenge_len);
if (unlikely(ret))
goto out;
bin2hex(challenge_asciihex, chap->challenge,
chap->challenge_len);
/*
* Set CHAP_C, and copy the generated challenge into c_str.
*/
*c_len += sprintf(c_str + *c_len, "CHAP_C=0x%s", challenge_asciihex);
*c_len += 1;
pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client",
challenge_asciihex);
out:
kfree(challenge_asciihex);
return ret;
}
static int chap_test_algorithm(const char *name)
{
struct crypto_shash *tfm;
tfm = crypto_alloc_shash(name, 0, 0);
if (IS_ERR(tfm))
return -1;
crypto_free_shash(tfm);
return 0;
}
static int chap_check_algorithm(const char *a_str)
{
char *tmp, *orig, *token, *digest_name;
long digest_type;
int r = CHAP_DIGEST_UNKNOWN;
tmp = kstrdup(a_str, GFP_KERNEL);
if (!tmp) {
pr_err("Memory allocation failed for CHAP_A temporary buffer\n");
return CHAP_DIGEST_UNKNOWN;
}
orig = tmp;
token = strsep(&tmp, "=");
if (!token)
goto out;
if (strcmp(token, "CHAP_A")) {
pr_err("Unable to locate CHAP_A key\n");
goto out;
}
while (token) {
token = strsep(&tmp, ",");
if (!token)
goto out;
if (kstrtol(token, 10, &digest_type))
continue;
digest_name = chap_get_digest_name(digest_type);
if (!digest_name)
continue;
pr_debug("Selected %s Algorithm\n", digest_name);
if (chap_test_algorithm(digest_name) < 0) {
pr_err("failed to allocate %s algo\n", digest_name);
} else {
r = digest_type;
goto out;
}
}
out:
kfree(orig);
return r;
}
static void chap_close(struct iscsi_conn *conn)
{
kfree(conn->auth_protocol);
conn->auth_protocol = NULL;
}
static struct iscsi_chap *chap_server_open(
struct iscsi_conn *conn,
struct iscsi_node_auth *auth,
const char *a_str,
char *aic_str,
unsigned int *aic_len)
{
int digest_type;
struct iscsi_chap *chap;
if (!(auth->naf_flags & NAF_USERID_SET) ||
!(auth->naf_flags & NAF_PASSWORD_SET)) {
pr_err("CHAP user or password not set for"
" Initiator ACL\n");
return NULL;
}
conn->auth_protocol = kzalloc(sizeof(struct iscsi_chap), GFP_KERNEL);
if (!conn->auth_protocol)
return NULL;
chap = conn->auth_protocol;
digest_type = chap_check_algorithm(a_str);
switch (digest_type) {
case CHAP_DIGEST_MD5:
chap->digest_size = MD5_SIGNATURE_SIZE;
break;
case CHAP_DIGEST_SHA1:
chap->digest_size = SHA1_SIGNATURE_SIZE;
break;
case CHAP_DIGEST_SHA256:
chap->digest_size = SHA256_SIGNATURE_SIZE;
break;
case CHAP_DIGEST_SHA3_256:
chap->digest_size = SHA3_256_SIGNATURE_SIZE;
break;
case CHAP_DIGEST_UNKNOWN:
default:
pr_err("Unsupported CHAP_A value\n");
chap_close(conn);
return NULL;
}
chap->digest_name = chap_get_digest_name(digest_type);
/* Tie the challenge length to the digest size */
chap->challenge_len = chap->digest_size;
pr_debug("[server] Got CHAP_A=%d\n", digest_type);
*aic_len = sprintf(aic_str, "CHAP_A=%d", digest_type);
*aic_len += 1;
pr_debug("[server] Sending CHAP_A=%d\n", digest_type);
/*
* Set Identifier.
*/
chap->id = conn->tpg->tpg_chap_id++;
*aic_len += sprintf(aic_str + *aic_len, "CHAP_I=%d", chap->id);
*aic_len += 1;
pr_debug("[server] Sending CHAP_I=%d\n", chap->id);
/*
* Generate Challenge.
*/
if (chap_gen_challenge(conn, 1, aic_str, aic_len) < 0) {
chap_close(conn);
return NULL;
}
return chap;
}
static int chap_server_compute_hash(
struct iscsi_conn *conn,
struct iscsi_node_auth *auth,
char *nr_in_ptr,
char *nr_out_ptr,
unsigned int *nr_out_len)
{
unsigned long id;
unsigned char id_as_uchar;
unsigned char type;
unsigned char identifier[10], *initiatorchg = NULL;
unsigned char *initiatorchg_binhex = NULL;
unsigned char *digest = NULL;
unsigned char *response = NULL;
unsigned char *client_digest = NULL;
unsigned char *server_digest = NULL;
unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
size_t compare_len;
struct iscsi_chap *chap = conn->auth_protocol;
struct crypto_shash *tfm = NULL;
struct shash_desc *desc = NULL;
int auth_ret = -1, ret, initiatorchg_len;
digest = kzalloc(chap->digest_size, GFP_KERNEL);
if (!digest) {
pr_err("Unable to allocate the digest buffer\n");
goto out;
}
response = kzalloc(chap->digest_size * 2 + 2, GFP_KERNEL);
if (!response) {
pr_err("Unable to allocate the response buffer\n");
goto out;
}
client_digest = kzalloc(chap->digest_size, GFP_KERNEL);
if (!client_digest) {
pr_err("Unable to allocate the client_digest buffer\n");
goto out;
}
server_digest = kzalloc(chap->digest_size, GFP_KERNEL);
if (!server_digest) {
pr_err("Unable to allocate the server_digest buffer\n");
goto out;
}
memset(identifier, 0, 10);
memset(chap_n, 0, MAX_CHAP_N_SIZE);
memset(chap_r, 0, MAX_RESPONSE_LENGTH);
initiatorchg = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
if (!initiatorchg) {
pr_err("Unable to allocate challenge buffer\n");
goto out;
}
initiatorchg_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
if (!initiatorchg_binhex) {
pr_err("Unable to allocate initiatorchg_binhex buffer\n");
goto out;
}
/*
* Extract CHAP_N.
*/
if (extract_param(nr_in_ptr, "CHAP_N", MAX_CHAP_N_SIZE, chap_n,
&type) < 0) {
pr_err("Could not find CHAP_N.\n");
goto out;
}
if (type == HEX) {
pr_err("Could not find CHAP_N.\n");
goto out;
}
/* Include the terminating NULL in the compare */
compare_len = strlen(auth->userid) + 1;
if (strncmp(chap_n, auth->userid, compare_len) != 0) {
pr_err("CHAP_N values do not match!\n");
goto out;
}
pr_debug("[server] Got CHAP_N=%s\n", chap_n);
/*
* Extract CHAP_R.
*/
if (extract_param(nr_in_ptr, "CHAP_R", MAX_RESPONSE_LENGTH, chap_r,
&type) < 0) {
pr_err("Could not find CHAP_R.\n");
goto out;
}
if (type != HEX) {
pr_err("Could not find CHAP_R.\n");
goto out;
}
if (strlen(chap_r) != chap->digest_size * 2) {
pr_err("Malformed CHAP_R\n");
goto out;
}
if (hex2bin(client_digest, chap_r, chap->digest_size) < 0) {
pr_err("Malformed CHAP_R\n");
goto out;
}
pr_debug("[server] Got CHAP_R=%s\n", chap_r);
tfm = crypto_alloc_shash(chap->digest_name, 0, 0);
if (IS_ERR(tfm)) {
tfm = NULL;
pr_err("Unable to allocate struct crypto_shash\n");
goto out;
}
desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
if (!desc) {
pr_err("Unable to allocate struct shash_desc\n");
goto out;
}
desc->tfm = tfm;
ret = crypto_shash_init(desc);
if (ret < 0) {
pr_err("crypto_shash_init() failed\n");
goto out;
}
ret = crypto_shash_update(desc, &chap->id, 1);
if (ret < 0) {
pr_err("crypto_shash_update() failed for id\n");
goto out;
}
ret = crypto_shash_update(desc, (char *)&auth->password,
strlen(auth->password));
if (ret < 0) {
pr_err("crypto_shash_update() failed for password\n");
goto out;
}
ret = crypto_shash_finup(desc, chap->challenge,
chap->challenge_len, server_digest);
if (ret < 0) {
pr_err("crypto_shash_finup() failed for challenge\n");
goto out;
}
bin2hex(response, server_digest, chap->digest_size);
pr_debug("[server] %s Server Digest: %s\n",
chap->digest_name, response);
if (memcmp(server_digest, client_digest, chap->digest_size) != 0) {
pr_debug("[server] %s Digests do not match!\n\n",
chap->digest_name);
goto out;
} else
pr_debug("[server] %s Digests match, CHAP connection"
" successful.\n\n", chap->digest_name);
/*
* One way authentication has succeeded, return now if mutual
* authentication is not enabled.
*/
if (!auth->authenticate_target) {
auth_ret = 0;
goto out;
}
/*
* Get CHAP_I.
*/
if (extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type) < 0) {
pr_err("Could not find CHAP_I.\n");
goto out;
}
if (type == HEX)
ret = kstrtoul(&identifier[2], 0, &id);
else
ret = kstrtoul(identifier, 0, &id);
if (ret < 0) {
pr_err("kstrtoul() failed for CHAP identifier: %d\n", ret);
goto out;
}
if (id > 255) {
pr_err("chap identifier: %lu greater than 255\n", id);
goto out;
}
/*
* RFC 1994 says Identifier is no more than octet (8 bits).
*/
pr_debug("[server] Got CHAP_I=%lu\n", id);
/*
* Get CHAP_C.
*/
if (extract_param(nr_in_ptr, "CHAP_C", CHAP_CHALLENGE_STR_LEN,
initiatorchg, &type) < 0) {
pr_err("Could not find CHAP_C.\n");
goto out;
}
if (type != HEX) {
pr_err("Could not find CHAP_C.\n");
goto out;
}
initiatorchg_len = DIV_ROUND_UP(strlen(initiatorchg), 2);
if (!initiatorchg_len) {
pr_err("Unable to convert incoming challenge\n");
goto out;
}
if (initiatorchg_len > 1024) {
pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
goto out;
}
if (hex2bin(initiatorchg_binhex, initiatorchg, initiatorchg_len) < 0) {
pr_err("Malformed CHAP_C\n");
goto out;
}
pr_debug("[server] Got CHAP_C=%s\n", initiatorchg);
/*
* During mutual authentication, the CHAP_C generated by the
* initiator must not match the original CHAP_C generated by
* the target.
*/
if (initiatorchg_len == chap->challenge_len &&
!memcmp(initiatorchg_binhex, chap->challenge,
initiatorchg_len)) {
pr_err("initiator CHAP_C matches target CHAP_C, failing"
" login attempt\n");
goto out;
}
/*
* Generate CHAP_N and CHAP_R for mutual authentication.
*/
ret = crypto_shash_init(desc);
if (ret < 0) {
pr_err("crypto_shash_init() failed\n");
goto out;
}
/* To handle both endiannesses */
id_as_uchar = id;
ret = crypto_shash_update(desc, &id_as_uchar, 1);
if (ret < 0) {
pr_err("crypto_shash_update() failed for id\n");
goto out;
}
ret = crypto_shash_update(desc, auth->password_mutual,
strlen(auth->password_mutual));
if (ret < 0) {
pr_err("crypto_shash_update() failed for"
" password_mutual\n");
goto out;
}
/*
* Convert received challenge to binary hex.
*/
ret = crypto_shash_finup(desc, initiatorchg_binhex, initiatorchg_len,
digest);
if (ret < 0) {
pr_err("crypto_shash_finup() failed for ma challenge\n");
goto out;
}
/*
* Generate CHAP_N and CHAP_R.
*/
*nr_out_len = sprintf(nr_out_ptr, "CHAP_N=%s", auth->userid_mutual);
*nr_out_len += 1;
pr_debug("[server] Sending CHAP_N=%s\n", auth->userid_mutual);
/*
* Convert response from binary hex to ascii hext.
*/
bin2hex(response, digest, chap->digest_size);
*nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
response);
*nr_out_len += 1;
pr_debug("[server] Sending CHAP_R=0x%s\n", response);
auth_ret = 0;
out:
kzfree(desc);
if (tfm)
crypto_free_shash(tfm);
kfree(initiatorchg);
kfree(initiatorchg_binhex);
kfree(digest);
kfree(response);
kfree(server_digest);
kfree(client_digest);
return auth_ret;
}
u32 chap_main_loop(
struct iscsi_conn *conn,
struct iscsi_node_auth *auth,
char *in_text,
char *out_text,
int *in_len,
int *out_len)
{
struct iscsi_chap *chap = conn->auth_protocol;
if (!chap) {
chap = chap_server_open(conn, auth, in_text, out_text, out_len);
if (!chap)
return 2;
chap->chap_state = CHAP_STAGE_SERVER_AIC;
return 0;
} else if (chap->chap_state == CHAP_STAGE_SERVER_AIC) {
convert_null_to_semi(in_text, *in_len);
if (chap_server_compute_hash(conn, auth, in_text, out_text,
out_len) < 0) {
chap_close(conn);
return 2;
}
if (auth->authenticate_target)
chap->chap_state = CHAP_STAGE_SERVER_NR;
else
*out_len = 0;
chap_close(conn);
return 1;
}
return 2;
}