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Subject[RFC-v4 07/12] iscsi-target: Add CHAP Authentication support using libcrypto
Date
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 | 496 ++++++++++++++++++++++++++++++
drivers/target/iscsi/iscsi_target_auth.h | 32 ++
2 files changed, 528 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..077e631
--- /dev/null
+++ b/drivers/target/iscsi/iscsi_target_auth.c
@@ -0,0 +1,496 @@
+/*******************************************************************************
+ * This file houses the main functions for the iSCSI CHAP support
+ *
+ * © 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"
+
+#ifdef DEBUG_CHAP
+#define PRINT(x...) printk(KERN_INFO x)
+#else
+#define PRINT(x...)
+#endif
+
+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;
+
+ PRINT("[%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)) {
+ printk(KERN_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)) {
+ printk(KERN_ERR "CHAP_A is not MD5.\n");
+ return NULL;
+ }
+ PRINT("[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;
+ PRINT("[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;
+ PRINT("[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) {
+ printk(KERN_ERR "Unable to allocate challenge buffer\n");
+ goto out;
+ }
+
+ challenge_binhex = kzalloc(CHAP_CHALLENGE_STR_LEN, GFP_KERNEL);
+ if (!challenge_binhex) {
+ printk(KERN_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) {
+ printk(KERN_ERR "Could not find CHAP_N.\n");
+ goto out;
+ }
+ if (type == HEX) {
+ printk(KERN_ERR "Could not find CHAP_N.\n");
+ goto out;
+ }
+
+ if (memcmp(chap_n, auth->userid, strlen(auth->userid)) != 0) {
+ printk(KERN_ERR "CHAP_N values do not match!\n");
+ goto out;
+ }
+ PRINT("[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) {
+ printk(KERN_ERR "Could not find CHAP_R.\n");
+ goto out;
+ }
+ if (type != HEX) {
+ printk(KERN_ERR "Could not find CHAP_R.\n");
+ goto out;
+ }
+
+ PRINT("[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)) {
+ printk(KERN_ERR "Unable to allocate struct crypto_hash\n");
+ goto out;
+ }
+ desc.tfm = tfm;
+ desc.flags = 0;
+
+ ret = crypto_hash_init(&desc);
+ if (ret < 0) {
+ printk(KERN_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) {
+ printk(KERN_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) {
+ printk(KERN_ERR "crypto_hash_update() failed for password\n");
+ crypto_free_hash(tfm);
+ goto out;
+ }
+
+ sg_init_one(&sg, (void *)chap->challenge, strlen(chap->challenge));
+ ret = crypto_hash_update(&desc, &sg, strlen(chap->challenge));
+ if (ret < 0) {
+ printk(KERN_ERR "crypto_hash_update() failed for challenge\n");
+ crypto_free_hash(tfm);
+ goto out;
+ }
+
+ ret = crypto_hash_final(&desc, server_digest);
+ if (ret < 0) {
+ printk(KERN_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);
+ PRINT("[server] MD5 Server Digest: %s\n", response);
+
+ if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
+ PRINT("[server] MD5 Digests do not match!\n\n");
+ goto out;
+ } else
+ PRINT("[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) {
+ printk(KERN_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).
+ */
+ PRINT("[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) {
+ printk(KERN_ERR "Could not find CHAP_C.\n");
+ goto out;
+ }
+
+ if (type != HEX) {
+ printk(KERN_ERR "Could not find CHAP_C.\n");
+ goto out;
+ }
+ PRINT("[server] Got CHAP_C=%s\n", challenge);
+ challenge_len = chap_string_to_hex(challenge_binhex, challenge,
+ strlen(challenge));
+ if (!challenge_len) {
+ printk(KERN_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)) {
+ printk(KERN_ERR "Unable to allocate struct crypto_hash\n");
+ goto out;
+ }
+ desc.tfm = tfm;
+ desc.flags = 0;
+
+ ret = crypto_hash_init(&desc);
+ if (ret < 0) {
+ printk(KERN_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) {
+ printk(KERN_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) {
+ printk(KERN_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) {
+ printk(KERN_ERR "crypto_hash_update() failed for ma challenge\n");
+ crypto_free_hash(tfm);
+ goto out;
+ }
+
+ ret = crypto_hash_final(&desc, digest);
+ if (ret < 0) {
+ printk(KERN_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;
+ PRINT("[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;
+ PRINT("[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:
+ printk(KERN_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..17b042d
--- /dev/null
+++ b/drivers/target/iscsi/iscsi_target_auth.h
@@ -0,0 +1,32 @@
+#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 challenge_len;
+ unsigned int authenticate_target;
+ unsigned int chap_state;
+} ____cacheline_aligned;
+
+#endif /*** _ISCSI_CHAP_H_ ***/
--
1.7.4.1
--
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