// 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 <crypto/utils.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/hex.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 iscsit_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 iscsit_conn *conn)
{
        kfree(conn->auth_protocol);
        conn->auth_protocol = NULL;
}

static struct iscsi_chap *chap_server_open(
        struct iscsit_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_obj(struct iscsi_chap);
        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 const char base64_lookup_table[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static int chap_base64_decode(u8 *dst, const char *src, size_t len)
{
        int i, bits = 0, ac = 0;
        const char *p;
        u8 *cp = dst;

        for (i = 0; i < len; i++) {
                if (src[i] == '=')
                        return cp - dst;

                p = strchr(base64_lookup_table, src[i]);
                if (p == NULL || src[i] == 0)
                        return -2;

                ac <<= 6;
                ac += (p - base64_lookup_table);
                bits += 6;
                if (bits >= 8) {
                        *cp++ = (ac >> (bits - 8)) & 0xff;
                        ac &= ~(BIT(16) - BIT(bits - 8));
                        bits -= 8;
                }
        }
        if (ac)
                return -1;

        return cp - dst;
}

static int chap_server_compute_hash(
        struct iscsit_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;
        }

        switch (type) {
        case HEX:
                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: invalid HEX\n");
                        goto out;
                }
                break;
        case BASE64: {
                size_t r_len = strlen(chap_r);

                while (r_len > 0 && chap_r[r_len - 1] == '=')
                        r_len--;
                if (r_len > DIV_ROUND_UP(chap->digest_size * 4, 3)) {
                        pr_err("Malformed CHAP_R: base64 payload too long\n");
                        goto out;
                }
                if (chap_base64_decode(client_digest, chap_r, strlen(chap_r)) !=
                    chap->digest_size) {
                        pr_err("Malformed CHAP_R: invalid BASE64\n");
                        goto out;
                }
                break;
        }
        default:
                pr_err("Could not find 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 (crypto_memneq(server_digest, client_digest, chap->digest_size)) {
                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.
         */
        ret = extract_param(nr_in_ptr, "CHAP_I", 10, identifier, &type);
        if (ret == -ENOENT) {
                pr_debug("Could not find CHAP_I. Initiator uses One way authentication.\n");
                auth_ret = 0;
                goto out;
        }
        if (ret < 0) {
                pr_err("Could not find CHAP_I.\n");
                goto out;
        }

        if (type == HEX)
                ret = kstrtoul(identifier, 16, &id);
        else if (type == DECIMAL)
                ret = kstrtoul(identifier, 10, &id);
        else
                ret = -EINVAL;

        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;
        }

        switch (type) {
        case HEX:
                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: invalid HEX\n");
                        goto out;
                }
                break;
        case BASE64:
                /*
                 * No overflow check needed: initiatorchg_binhex is
                 * CHAP_CHALLENGE_STR_LEN bytes and extract_param() caps
                 * initiatorchg at CHAP_CHALLENGE_STR_LEN characters, so
                 * the decoded output is at most DIV_ROUND_UP(
                 * (CHAP_CHALLENGE_STR_LEN - 1) * 3, 4) bytes, which is
                 * less than CHAP_CHALLENGE_STR_LEN.
                 */
                initiatorchg_len = chap_base64_decode(initiatorchg_binhex,
                                                      initiatorchg,
                                                      strlen(initiatorchg));
                if (initiatorchg_len < 0) {
                        pr_err("Malformed CHAP_C: invalid BASE64\n");
                        goto out;
                }
                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;
                }
                break;
        default:
                pr_err("Could not find 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:
        kfree_sensitive(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 iscsit_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;
}