/*
 *  ntlm proxy support for OpenVPN
 *
 *  Copyright (C) 2004 William Preston
 *
 *  *NTLMv2 support and domain name parsing by Miroslav Zajic, Nextsoft s.r.o.*
 *
 *  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.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_MSC_VER)
#include "config-msvc.h"
#endif

#include "syshead.h"

#if NTLM

#include "common.h"
#include "buffer.h"
#include "misc.h"
#include "socket.h"
#include "fdmisc.h"
#include "proxy.h"
#include "ntlm.h"
#include "base64.h"
#include "crypto.h"

#include "memdbg.h"


/* 64bit datatype macros */
#ifdef _MSC_VER
/* MS compilers */
#define UINTEGER64 __int64
#define UINT64(c) c ## Ui64
#else
/* Non MS compilers */
#define UINTEGER64 unsigned long long
#define UINT64(c) c ## LL
#endif



static void
create_des_keys(const unsigned char *hash, unsigned char *key)
{
    key[0] = hash[0];
    key[1] = ((hash[0]&1)<<7)|(hash[1]>>1);
    key[2] = ((hash[1]&3)<<6)|(hash[2]>>2);
    key[3] = ((hash[2]&7)<<5)|(hash[3]>>3);
    key[4] = ((hash[3]&15)<<4)|(hash[4]>>4);
    key[5] = ((hash[4]&31)<<3)|(hash[5]>>5);
    key[6] = ((hash[5]&63)<<2)|(hash[6]>>6);
    key[7] = ((hash[6]&127)<<1);
    key_des_fixup(key, 8, 1);
}

static void
gen_md4_hash(const char *data, int data_len, char *result)
{
    /* result is 16 byte md4 hash */
    const md_kt_t *md4_kt = md_kt_get("MD4");
    char md[MD4_DIGEST_LENGTH];

    md_full(md4_kt, data, data_len, md);
    memcpy(result, md, MD4_DIGEST_LENGTH);
}

static void
gen_hmac_md5(const char *data, int data_len, const char *key, int key_len,char *result)
{
    const md_kt_t *md5_kt = md_kt_get("MD5");
    hmac_ctx_t *hmac_ctx = hmac_ctx_new();

    hmac_ctx_init(hmac_ctx, key, key_len, md5_kt);
    hmac_ctx_update(hmac_ctx, (const unsigned char *)data, data_len);
    hmac_ctx_final(hmac_ctx, (unsigned char *)result);
    hmac_ctx_cleanup(hmac_ctx);
    hmac_ctx_free(hmac_ctx);
}

static void
gen_timestamp(unsigned char *timestamp)
{
    /* Copies 8 bytes long timestamp into "timestamp" buffer.
     * Timestamp is Little-endian, 64-bit signed value representing the number of tenths of a microsecond since January 1, 1601.
     */

    UINTEGER64 timestamp_ull;

    timestamp_ull = openvpn_time(NULL);
    timestamp_ull = (timestamp_ull + UINT64(11644473600)) * UINT64(10000000);

    /* store little endian value */
    timestamp[0] = timestamp_ull & UINT64(0xFF);
    timestamp[1] = (timestamp_ull  >> 8)  & UINT64(0xFF);
    timestamp[2] = (timestamp_ull  >> 16) & UINT64(0xFF);
    timestamp[3] = (timestamp_ull  >> 24) & UINT64(0xFF);
    timestamp[4] = (timestamp_ull  >> 32) & UINT64(0xFF);
    timestamp[5] = (timestamp_ull  >> 40) & UINT64(0xFF);
    timestamp[6] = (timestamp_ull  >> 48) & UINT64(0xFF);
    timestamp[7] = (timestamp_ull  >> 56) & UINT64(0xFF);
}

static void
gen_nonce(unsigned char *nonce)
{
    /* Generates 8 random bytes to be used as client nonce */
    int i;

    for (i = 0; i<8; i++)
    {
        nonce[i] = (unsigned char)get_random();
    }
}

void
my_strupr(unsigned char *str)
{
    /* converts string to uppercase in place */

    while (*str)
    {
        *str = toupper(*str);
        str++;
    }
}

static int
unicodize(char *dst, const char *src)
{
    /* not really unicode... */
    int i = 0;
    do
    {
        dst[i++] = *src;
        dst[i++] = 0;
    }
    while (*src++);

    return i;
}

static void
add_security_buffer(int sb_offset, void *data, int length, unsigned char *msg_buf, int *msg_bufpos)
{
    /* Adds security buffer data to a message and sets security buffer's offset and length */
    msg_buf[sb_offset] = (unsigned char)length;
    msg_buf[sb_offset + 2] = msg_buf[sb_offset];
    msg_buf[sb_offset + 4] = (unsigned char)(*msg_bufpos & 0xff);
    msg_buf[sb_offset + 5] = (unsigned char)((*msg_bufpos >> 8) & 0xff);
    memcpy(&msg_buf[*msg_bufpos], data, msg_buf[sb_offset]);
    *msg_bufpos += length;
}

const char *
ntlm_phase_1(const struct http_proxy_info *p, struct gc_arena *gc)
{
    struct buffer out = alloc_buf_gc(96, gc);
    /* try a minimal NTLM handshake
     *
     * http://davenport.sourceforge.net/ntlm.html
     *
     * This message contains only the NTLMSSP signature,
     * the NTLM message type,
     * and the minimal set of flags (Negotiate NTLM and Negotiate OEM).
     *
     */
    buf_printf(&out, "%s", "TlRMTVNTUAABAAAAAgIAAA==");
    return (BSTR(&out));
}

const char *
ntlm_phase_3(const struct http_proxy_info *p, const char *phase_2, struct gc_arena *gc)
{
    /* NTLM handshake
     *
     * http://davenport.sourceforge.net/ntlm.html
     *
     */

    char pwbuf[sizeof(p->up.password) * 2]; /* for unicode password */
    unsigned char buf2[128]; /* decoded reply from proxy */
    unsigned char phase3[464];

    char md4_hash[MD4_DIGEST_LENGTH+5];
    char challenge[8], ntlm_response[24];
    int i, ret_val;

    char ntlmv2_response[144];
    char userdomain_u[256];     /* for uppercase unicode username and domain */
    char userdomain[128];       /* the same as previous but ascii */
    char ntlmv2_hash[MD5_DIGEST_LENGTH];
    char ntlmv2_hmacmd5[16];
    char *ntlmv2_blob = ntlmv2_response + 16;     /* inside ntlmv2_response, length: 128 */
    int ntlmv2_blob_size = 0;
    int phase3_bufpos = 0x40;     /* offset to next security buffer data to be added */
    size_t len;

    char domain[128];
    char username[128];
    char *separator;

    bool ntlmv2_enabled = (p->auth_method == HTTP_AUTH_NTLM2);

    CLEAR(buf2);

    ASSERT(strlen(p->up.username) > 0);
    ASSERT(strlen(p->up.password) > 0);

    /* username parsing */
    separator = strchr(p->up.username, '\\');
    if (separator == NULL)
    {
        strncpy(username, p->up.username, sizeof(username)-1);
        username[sizeof(username)-1] = 0;
        domain[0] = 0;
    }
    else
    {
        strncpy(username, separator+1, sizeof(username)-1);
        username[sizeof(username)-1] = 0;
        len = separator - p->up.username;
        if (len > sizeof(domain) - 1)
        {
            len = sizeof(domain) - 1;
        }
        strncpy(domain, p->up.username,  len);
        domain[len] = 0;
    }


    /* fill 1st 16 bytes with md4 hash, disregard terminating null */
    gen_md4_hash(pwbuf, unicodize(pwbuf, p->up.password) - 2, md4_hash);

    /* pad to 21 bytes */
    memset(md4_hash + MD4_DIGEST_LENGTH, 0, 5);

    ret_val = openvpn_base64_decode( phase_2, (void *)buf2, -1);
    if (ret_val < 0)
    {
        return NULL;
    }

    /* we can be sure that phase_2 is less than 128
     * therefore buf2 needs to be (3/4 * 128) */

    /* extract the challenge from bytes 24-31 */
    for (i = 0; i<8; i++)
    {
        challenge[i] = buf2[i+24];
    }

    if (ntlmv2_enabled)      /* Generate NTLMv2 response */
    {
        int tib_len;

        /* NTLMv2 hash */
        my_strupr((unsigned char *)strcpy(userdomain, username));
        if (strlen(username) + strlen(domain) < sizeof(userdomain))
        {
            strcat(userdomain, domain);
        }
        else
        {
            msg(M_INFO, "Warning: Username or domain too long");
        }
        unicodize(userdomain_u, userdomain);
        gen_hmac_md5(userdomain_u, 2 * strlen(userdomain), md4_hash, MD5_DIGEST_LENGTH, ntlmv2_hash);

        /* NTLMv2 Blob */
        memset(ntlmv2_blob, 0, 128);                        /* Clear blob buffer */
        ntlmv2_blob[0x00] = 1;                              /* Signature */
        ntlmv2_blob[0x01] = 1;                              /* Signature */
        ntlmv2_blob[0x04] = 0;                              /* Reserved */
        gen_timestamp((unsigned char *)&ntlmv2_blob[0x08]);                  /* 64-bit Timestamp */
        gen_nonce((unsigned char *)&ntlmv2_blob[0x10]);                      /* 64-bit Client Nonce */
        ntlmv2_blob[0x18] = 0;                              /* Unknown, zero should work */

        /* Add target information block to the blob */
        if (( *((long *)&buf2[0x14]) & 0x00800000) == 0x00800000)          /* Check for Target Information block */
        {
            tib_len = buf2[0x28];            /* Get Target Information block size */
            if (tib_len > 96)
            {
                tib_len = 96;
            }
            {
                char *tib_ptr;
                int tib_pos = buf2[0x2c];
                if (tib_pos + tib_len > sizeof(buf2))
                {
                    return NULL;
                }
                tib_ptr = buf2 + tib_pos;                               /* Get Target Information block pointer */
                memcpy(&ntlmv2_blob[0x1c], tib_ptr, tib_len);           /* Copy Target Information block into the blob */
            }
        }
        else
        {
            tib_len = 0;
        }

        ntlmv2_blob[0x1c + tib_len] = 0;                    /* Unknown, zero works */

        /* Get blob length */
        ntlmv2_blob_size = 0x20 + tib_len;

        /* Add challenge from message 2 */
        memcpy(&ntlmv2_response[8], challenge, 8);

        /* hmac-md5 */
        gen_hmac_md5(&ntlmv2_response[8], ntlmv2_blob_size + 8, ntlmv2_hash, MD5_DIGEST_LENGTH, ntlmv2_hmacmd5);

        /* Add hmac-md5 result to the blob */
        memcpy(ntlmv2_response, ntlmv2_hmacmd5, MD5_DIGEST_LENGTH);         /* Note: This overwrites challenge previously written at ntlmv2_response[8..15] */

    }
    else         /* Generate NTLM response */
    {
        unsigned char key1[DES_KEY_LENGTH], key2[DES_KEY_LENGTH], key3[DES_KEY_LENGTH];

        create_des_keys((unsigned char *)md4_hash, key1);
        cipher_des_encrypt_ecb(key1, challenge, ntlm_response);

        create_des_keys((unsigned char *)&(md4_hash[DES_KEY_LENGTH-1]), key2);
        cipher_des_encrypt_ecb(key2, challenge, &ntlm_response[DES_KEY_LENGTH]);

        create_des_keys((unsigned char *)&(md4_hash[2*(DES_KEY_LENGTH-1)]), key3);
        cipher_des_encrypt_ecb(key3, challenge, &ntlm_response[DES_KEY_LENGTH*2]);
    }


    memset(phase3, 0, sizeof(phase3));       /* clear reply */

    strcpy((char *)phase3, "NTLMSSP\0");      /* signature */
    phase3[8] = 3;     /* type 3 */

    if (ntlmv2_enabled)      /* NTLMv2 response */
    {
        add_security_buffer(0x14, ntlmv2_response, ntlmv2_blob_size + 16, phase3, &phase3_bufpos);
    }
    else       /* NTLM response */
    {
        add_security_buffer(0x14, ntlm_response, 24, phase3, &phase3_bufpos);
    }

    /* username in ascii */
    add_security_buffer(0x24, username, strlen(username), phase3, &phase3_bufpos);

    /* Set domain. If <domain> is empty, default domain will be used (i.e. proxy's domain) */
    add_security_buffer(0x1c, domain, strlen(domain), phase3, &phase3_bufpos);


    /* other security buffers will be empty */
    phase3[0x10] = phase3_bufpos;     /* lm not used */
    phase3[0x30] = phase3_bufpos;     /* no workstation name supplied */
    phase3[0x38] = phase3_bufpos;     /* no session key */

    /* flags */
    phase3[0x3c] = 0x02; /* negotiate oem */
    phase3[0x3d] = 0x02; /* negotiate ntlm */

    return ((const char *)make_base64_string2((unsigned char *)phase3, phase3_bufpos, gc));
}

#else  /* if NTLM */
static void
dummy(void)
{
}
#endif /* if NTLM */
