text: /*******************************************************************************
   * 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>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   ******************************************************************************/
  
  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/crypto.h>
  #include <linux/err.h>
  #include <linux/scatterlist.h>
  
  #include "iscsi_target_core.h"
  #include "iscsi_target_nego.h"
  #include "iscsi_target_auth.h"
  
  static int chap_string_to_hex(unsigned char *dst, unsigned char *src, int len)
  {
  	int j = DIV_ROUND_UP(len, 2), rc;
  
  	rc = hex2bin(dst, src, j);
  	if (rc < 0)
  		pr_debug("CHAP string contains non hex digit symbols\n");
  
  	dst[j] = '\0';
  	return j;
  }
  
  static void chap_binaryhex_to_asciihex(char *dst, char *src, int src_len)
  {
  	int i;
  
  	for (i = 0; i < src_len; i++) {
  		sprintf(&dst[i*2], "%02x", (int) src[i] & 0xff);
  	}
  }
  
  static void chap_gen_challenge(
  	struct iscsi_conn *conn,
  	int caller,
  	char *c_str,
  	unsigned int *c_len)
  {
  	unsigned char challenge_asciihex[CHAP_CHALLENGE_LENGTH * 2 + 1];
  	struct iscsi_chap *chap = conn->auth_protocol;
  
  	memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1);
  
  	get_random_bytes(chap->challenge, CHAP_CHALLENGE_LENGTH);
  	chap_binaryhex_to_asciihex(challenge_asciihex, chap->challenge,
  				CHAP_CHALLENGE_LENGTH);
  	/*
  	 * 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);
  }
  
  
  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)
  {
  	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;
  	/*
  	 * We only support MD5 MDA presently.
  	 */
  	if (strncmp(a_str, "CHAP_A=5", 8)) {
  		pr_err("CHAP_A is not MD5.\n");
  		return NULL;
  	}
  	pr_debug("[server] Got CHAP_A=5\n");
  	/*
  	 * Send back CHAP_A set to MD5.
  	 */
  	*aic_len = sprintf(aic_str, "CHAP_A=5");
  	*aic_len += 1;
  	chap->digest_type = CHAP_DIGEST_MD5;
  	pr_debug("[server] Sending CHAP_A=%d\n", chap->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.
  	 */
  	chap_gen_challenge(conn, 1, aic_str, aic_len);
  
  	return chap;
  }
  
  static void chap_close(struct iscsi_conn *conn)
  {
  	kfree(conn->auth_protocol);
  	conn->auth_protocol = NULL;
  }
  
  static int chap_server_compute_md5(
  	struct iscsi_conn *conn,
  	struct iscsi_node_auth *auth,
  	char *nr_in_ptr,
  	char *nr_out_ptr,
  	unsigned int *nr_out_len)
  {
  	char *endptr;
  	unsigned long id;
  	unsigned char id_as_uchar;
  	unsigned char digest[MD5_SIGNATURE_SIZE];
  	unsigned char type, response[MD5_SIGNATURE_SIZE * 2 + 2];
  	unsigned char identifier[10], *challenge = NULL;
  	unsigned char *challenge_binhex = NULL;
  	unsigned char client_digest[MD5_SIGNATURE_SIZE];
  	unsigned char server_digest[MD5_SIGNATURE_SIZE];
  	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_hash *tfm;
  	struct hash_desc desc;
  	struct scatterlist sg;
  	int auth_ret = -1, ret, challenge_len;
  
  	memset(identifier, 0, 10);
  	memset(chap_n, 0, MAX_CHAP_N_SIZE);
  	memset(chap_r, 0, MAX_RESPONSE_LENGTH);
  	memset(digest, 0, MD5_SIGNATURE_SIZE);
  	memset(response, 0, MD5_SIGNATURE_SIZE * 2 + 2);
  	memset(client_digest, 0, MD5_SIGNATURE_SIZE);
  	memset(server_digest, 0, MD5_SIGNATURE_SIZE);
  
  	challenge = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
  	if (!challenge) {
  		pr_err("Unable to allocate challenge buffer\n");
  		goto out;
  	}
  
  	challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
  	if (!challenge_binhex) {
  		pr_err("Unable to allocate challenge_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;
  	}
  
  	pr_debug("[server] Got CHAP_R=%s\n", chap_r);
  	chap_string_to_hex(client_digest, chap_r, strlen(chap_r));
  
  	tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
  	if (IS_ERR(tfm)) {
  		pr_err("Unable to allocate struct crypto_hash\n");
  		goto out;
  	}
  	desc.tfm = tfm;
  	desc.flags = 0;
  
  	ret = crypto_hash_init(&desc);
  	if (ret < 0) {
  		pr_err("crypto_hash_init() failed\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  
  	sg_init_one(&sg, &chap->id, 1);
  	ret = crypto_hash_update(&desc, &sg, 1);
  	if (ret < 0) {
  		pr_err("crypto_hash_update() failed for id\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  
  	sg_init_one(&sg, &auth->password, strlen(auth->password));
  	ret = crypto_hash_update(&desc, &sg, strlen(auth->password));
  	if (ret < 0) {
  		pr_err("crypto_hash_update() failed for password\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  
  	sg_init_one(&sg, chap->challenge, CHAP_CHALLENGE_LENGTH);
  	ret = crypto_hash_update(&desc, &sg, CHAP_CHALLENGE_LENGTH);
  	if (ret < 0) {
  		pr_err("crypto_hash_update() failed for challenge\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  
  	ret = crypto_hash_final(&desc, server_digest);
  	if (ret < 0) {
  		pr_err("crypto_hash_final() failed for server digest\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  	crypto_free_hash(tfm);
  
  	chap_binaryhex_to_asciihex(response, server_digest, MD5_SIGNATURE_SIZE);
  	pr_debug("[server] MD5 Server Digest: %s\n", response);
  
  	if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
  		pr_debug("[server] MD5 Digests do not match!\n\n");
  		goto out;
  	} else
  		pr_debug("[server] MD5 Digests match, CHAP connetication"
  				" successful.\n\n");
  	/*
  	 * One way authentication has succeeded, return now if mutual
  	 * authentication is not enabled.
  	 */
  	if (!auth->authenticate_target) {
  		kfree(challenge);
  		kfree(challenge_binhex);
  		return 0;
  	}
  	/*
  	 * 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)
  		id = simple_strtoul(&identifier[2], &endptr, 0);
  	else
  		id = simple_strtoul(identifier, &endptr, 0);
  	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,
  			challenge, &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;
  	}
  	pr_debug("[server] Got CHAP_C=%s\n", challenge);
  	challenge_len = chap_string_to_hex(challenge_binhex, challenge,
  				strlen(challenge));
  	if (!challenge_len) {
  		pr_err("Unable to convert incoming challenge\n");
  		goto out;
  	}
  	/*
  	 * During mutual authentication, the CHAP_C generated by the
  	 * initiator must not match the original CHAP_C generated by
  	 * the target.
  	 */
  	if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) {
  		pr_err("initiator CHAP_C matches target CHAP_C, failing"
  		       " login attempt\n");
  		goto out;
  	}
  	/*
  	 * Generate CHAP_N and CHAP_R for mutual authentication.
  	 */
  	tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
  	if (IS_ERR(tfm)) {
  		pr_err("Unable to allocate struct crypto_hash\n");
  		goto out;
  	}
  	desc.tfm = tfm;
  	desc.flags = 0;
  
  	ret = crypto_hash_init(&desc);
  	if (ret < 0) {
  		pr_err("crypto_hash_init() failed\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  
  	/* To handle both endiannesses */
  	id_as_uchar = id;
  	sg_init_one(&sg, &id_as_uchar, 1);
  	ret = crypto_hash_update(&desc, &sg, 1);
  	if (ret < 0) {
  		pr_err("crypto_hash_update() failed for id\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  
  	sg_init_one(&sg, auth->password_mutual,
  				strlen(auth->password_mutual));
  	ret = crypto_hash_update(&desc, &sg, strlen(auth->password_mutual));
  	if (ret < 0) {
  		pr_err("crypto_hash_update() failed for"
  				" password_mutual\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  	/*
  	 * Convert received challenge to binary hex.
  	 */
  	sg_init_one(&sg, challenge_binhex, challenge_len);
  	ret = crypto_hash_update(&desc, &sg, challenge_len);
  	if (ret < 0) {
  		pr_err("crypto_hash_update() failed for ma challenge\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  
  	ret = crypto_hash_final(&desc, digest);
  	if (ret < 0) {
  		pr_err("crypto_hash_final() failed for ma digest\n");
  		crypto_free_hash(tfm);
  		goto out;
  	}
  	crypto_free_hash(tfm);
  	/*
  	 * 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.
  	 */
  	chap_binaryhex_to_asciihex(response, digest, MD5_SIGNATURE_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:
  	kfree(challenge);
  	kfree(challenge_binhex);
  	return auth_ret;
  }
  
  static int chap_got_response(
  	struct iscsi_conn *conn,
  	struct iscsi_node_auth *auth,
  	char *nr_in_ptr,
  	char *nr_out_ptr,
  	unsigned int *nr_out_len)
  {
  	struct iscsi_chap *chap = conn->auth_protocol;
  
  	switch (chap->digest_type) {
  	case CHAP_DIGEST_MD5:
  		if (chap_server_compute_md5(conn, auth, nr_in_ptr,
  				nr_out_ptr, nr_out_len) < 0)
  			return -1;
  		return 0;
  	default:
  		pr_err("Unknown CHAP digest type %d!\n",
  				chap->digest_type);
  		return -1;
  	}
  }
  
  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_got_response(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;
  }
  