[PATCH 08/13] iscsi-target: Add CHAP Authentication support using libcrypto

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

From: Nicholas Bellinger <nab@linux-iscsi.org>

This patch adds support for libcrypto md5 based iSCSI CHAP authentication
support for iscsi_target_mod.  This includes support for mutual and one-way
NodeACL authentication for SessionType=Normal and SessionType=Discovery
via /sys/kernel/config/target/iscsi.

Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
---
 drivers/target/iscsi/iscsi_target_auth.c |  490 ++++++++++++++++++++++++++++++
 drivers/target/iscsi/iscsi_target_auth.h |   31 ++
 2 files changed, 521 insertions(+), 0 deletions(-)
 create mode 100644 drivers/target/iscsi/iscsi_target_auth.c
 create mode 100644 drivers/target/iscsi/iscsi_target_auth.h

diff --git a/drivers/target/iscsi/iscsi_target_auth.c b/drivers/target/iscsi/iscsi_target_auth.c
new file mode 100644
index 0000000..11fd743
--- /dev/null
+++ b/drivers/target/iscsi/iscsi_target_auth.c
@@ -0,0 +1,490 @@
+/*******************************************************************************
+ * This file houses the main functions for the iSCSI CHAP support
+ *
+ * \u00a9 Copyright 2007-2011 RisingTide Systems LLC.
+ *
+ * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
+ *
+ * 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/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 unsigned char chap_asciihex_to_binaryhex(unsigned char val[2])
+{
+	unsigned char result = 0;
+	/*
+	 * MSB
+	 */
+	if ((val[0] >= 'a') && (val[0] <= 'f'))
+		result = ((val[0] - 'a' + 10) & 0xf) << 4;
+	else
+		if ((val[0] >= 'A') && (val[0] <= 'F'))
+			result = ((val[0] - 'A' + 10) & 0xf) << 4;
+		else /* digit */
+			result = ((val[0] - '0') & 0xf) << 4;
+	/*
+	 * LSB
+	 */
+	if ((val[1] >= 'a') && (val[1] <= 'f'))
+		result |= ((val[1] - 'a' + 10) & 0xf);
+	else
+		if ((val[1] >= 'A') && (val[1] <= 'F'))
+			result |= ((val[1] - 'A' + 10) & 0xf);
+		else /* digit */
+			result |= ((val[1] - '0') & 0xf);
+
+	return result;
+}
+
+static int chap_string_to_hex(unsigned char *dst, unsigned char *src, int len)
+{
+	int i, j = 0;
+
+	for (i = 0; i < len; i += 2) {
+		dst[j++] = (unsigned char) chap_asciihex_to_binaryhex(&src[i]);
+	}
+
+	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_set_random(char *data, int length)
+{
+	long r;
+	unsigned n;
+
+	while (length > 0) {
+		get_random_bytes(&r, sizeof(long));
+		r = r ^ (r >> 8);
+		r = r ^ (r >> 4);
+		n = r & 0x7;
+
+		get_random_bytes(&r, sizeof(long));
+		r = r ^ (r >> 8);
+		r = r ^ (r >> 5);
+		n = (n << 3) | (r & 0x7);
+
+		get_random_bytes(&r, sizeof(long));
+		r = r ^ (r >> 8);
+		r = r ^ (r >> 5);
+		n = (n << 2) | (r & 0x3);
+
+		*data++ = n;
+		length--;
+	}
+}
+
+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 = (struct iscsi_chap *) conn->auth_protocol;
+
+	memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1);
+
+	chap_set_random(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 = (struct iscsi_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 = ISCSI_TPG_C(conn)->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 char id, 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];
+	struct iscsi_chap *chap = (struct iscsi_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;
+	}
+
+	if (memcmp(chap_n, auth->userid, strlen(auth->userid)) != 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, (void *)&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, (void *)&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, (void *)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 = (unsigned char)simple_strtoul((char *)&identifier[2],
+					&endptr, 0);
+	else
+		id = (unsigned char)simple_strtoul(identifier, &endptr, 0);
+	/*
+	 * RFC 1994 says Identifier is no more than octet (8 bits).
+	 */
+	pr_debug("[server] Got CHAP_I=%d\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;
+	}
+	/*
+	 * 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;
+	}
+
+	sg_init_one(&sg, (void *)&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, (void *)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, (void *)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 = (struct iscsi_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 = (struct iscsi_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;
+}
diff --git a/drivers/target/iscsi/iscsi_target_auth.h b/drivers/target/iscsi/iscsi_target_auth.h
new file mode 100644
index 0000000..2f463c0
--- /dev/null
+++ b/drivers/target/iscsi/iscsi_target_auth.h
@@ -0,0 +1,31 @@
+#ifndef _ISCSI_CHAP_H_
+#define _ISCSI_CHAP_H_
+
+#define CHAP_DIGEST_MD5		5
+#define CHAP_DIGEST_SHA		6
+
+#define CHAP_CHALLENGE_LENGTH	16
+#define CHAP_CHALLENGE_STR_LEN	4096
+#define MAX_RESPONSE_LENGTH	64	/* sufficient for MD5 */
+#define	MAX_CHAP_N_SIZE		512
+
+#define MD5_SIGNATURE_SIZE	16	/* 16 bytes in a MD5 message digest */
+
+#define CHAP_STAGE_CLIENT_A	1
+#define CHAP_STAGE_SERVER_AIC	2
+#define CHAP_STAGE_CLIENT_NR	3
+#define CHAP_STAGE_CLIENT_NRIC	4
+#define CHAP_STAGE_SERVER_NR	5
+
+extern u32 chap_main_loop(struct iscsi_conn *, struct iscsi_node_auth *, char *, char *,
+				int *, int *);
+
+struct iscsi_chap {
+	unsigned char	digest_type;
+	unsigned char	id;
+	unsigned char	challenge[CHAP_CHALLENGE_LENGTH];
+	unsigned int	authenticate_target;
+	unsigned int	chap_state;
+} ____cacheline_aligned;
+
+#endif   /*** _ISCSI_CHAP_H_ ***/
-- 
1.7.6