iscsi_target_auth.c

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/*******************************************************************************
 * 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 <[email protected]>
 *
 * 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_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 = 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 = 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 long id;
    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];
    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;
    }

    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, &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;
    }
    /*
     * 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, &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_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;
}