xrdp/rdp/rdp_sec.c

/**
 * xrdp: A Remote Desktop Protocol server.
 *
 * Copyright (C) Jay Sorg 2004-2013
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * librdp secure layer
 */

#include "rdp.h"

static char g_pad_54[40] =
{
    54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54,
    54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54,
    54, 54, 54, 54, 54, 54, 54, 54
};

static char g_pad_92[48] =
{
    92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92,
    92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92,
    92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92
};

/*****************************************************************************/
struct rdp_sec *APP_CC
rdp_sec_create(struct rdp_rdp *owner)
{
    struct rdp_sec *self;

    self = (struct rdp_sec *)g_malloc(sizeof(struct rdp_sec), 1);
    self->rdp_layer = owner;
    make_stream(self->client_mcs_data);
    init_stream(self->client_mcs_data, 8192);
    make_stream(self->server_mcs_data);
    init_stream(self->server_mcs_data, 8192);
    self->mcs_layer = rdp_mcs_create(self, self->client_mcs_data,
                                     self->server_mcs_data);

    if (self->decrypt_rc4_info != NULL)
    {
        g_writeln("rdp_sec_create - decrypt_rc4_info already created !!!");
    }

    self->decrypt_rc4_info = ssl_rc4_info_create();

    if (self->encrypt_rc4_info != NULL)
    {
        g_writeln("rdp_sec_create - encrypt_rc4_info already created !!!");
    }

    self->encrypt_rc4_info = ssl_rc4_info_create();
    self->lic_layer = rdp_lic_create(self);
    return self;
}

/*****************************************************************************/
void APP_CC
rdp_sec_delete(struct rdp_sec *self)
{
    if (self == 0)
    {
        return;
    }

    rdp_lic_delete(self->lic_layer);
    rdp_mcs_delete(self->mcs_layer);
    free_stream(self->client_mcs_data);
    free_stream(self->server_mcs_data);
    ssl_rc4_info_delete(self->decrypt_rc4_info);
    ssl_rc4_info_delete(self->encrypt_rc4_info);
    g_free(self);
}

/*****************************************************************************/
/* Reduce key entropy from 64 to 40 bits */
static void APP_CC
rdp_sec_make_40bit(char *key)
{
    key[0] = 0xd1;
    key[1] = 0x26;
    key[2] = 0x9e;
}

/*****************************************************************************/
/* returns error */
/* update an encryption key */
static int APP_CC
rdp_sec_update(char *key, char *update_key, int key_len)
{
    char shasig[20];
    void *sha1_info;
    void *md5_info;
    void *rc4_info;

    sha1_info = ssl_sha1_info_create();
    md5_info = ssl_md5_info_create();
    rc4_info = ssl_rc4_info_create();
    ssl_sha1_clear(sha1_info);
    ssl_sha1_transform(sha1_info, update_key, key_len);
    ssl_sha1_transform(sha1_info, g_pad_54, 40);
    ssl_sha1_transform(sha1_info, key, key_len);
    ssl_sha1_complete(sha1_info, shasig);
    ssl_md5_clear(md5_info);
    ssl_md5_transform(md5_info, update_key, key_len);
    ssl_md5_transform(md5_info, g_pad_92, 48);
    ssl_md5_transform(md5_info, shasig, 20);
    ssl_md5_complete(md5_info, key);
    ssl_rc4_set_key(rc4_info, key, key_len);
    ssl_rc4_crypt(rc4_info, key, key_len);

    if (key_len == 8)
    {
        rdp_sec_make_40bit(key);
    }

    ssl_sha1_info_delete(sha1_info);
    ssl_md5_info_delete(md5_info);
    ssl_rc4_info_delete(rc4_info);
    return 0;
}

/*****************************************************************************/
static void APP_CC
rdp_sec_decrypt(struct rdp_sec *self, char *data, int len)
{
    if (self->decrypt_use_count == 4096)
    {
        rdp_sec_update(self->decrypt_key, self->decrypt_update_key,
                       self->rc4_key_len);
        ssl_rc4_set_key(self->decrypt_rc4_info, self->decrypt_key,
                        self->rc4_key_len);
        self->decrypt_use_count = 0;
    }

    ssl_rc4_crypt(self->decrypt_rc4_info, data, len);
    self->decrypt_use_count++;
}

/*****************************************************************************/
/* returns error */
int APP_CC
rdp_sec_recv(struct rdp_sec *self, struct stream *s, int *chan)
{
    int flags;

    DEBUG((" in rdp_sec_recv"));

    if (rdp_mcs_recv(self->mcs_layer, s, chan) != 0)
    {
        DEBUG((" error in rdp_sec_recv, rdp_mcs_recv failed"));
        return 1;
    }

    in_uint32_le(s, flags);
    DEBUG((" rdp_sec_recv flags %8.8x", flags));

    if (flags & SEC_ENCRYPT) /* 0x08 */
    {
        in_uint8s(s, 8); /* signature */
        rdp_sec_decrypt(self, s->p, s->end - s->p);
    }

    if (flags & SEC_LICENCE_NEG) /* 0x80 */
    {
        DEBUG((" in rdp_sec_recv, got SEC_LICENCE_NEG"));
        rdp_lic_process(self->lic_layer, s);
        *chan = 0;
    }

    DEBUG((" out rdp_sec_recv"));
    return 0;
}

/*****************************************************************************/
/* prepare client mcs data to send in mcs layer */
static void APP_CC
rdp_sec_out_mcs_data(struct rdp_sec *self)
{
    struct stream *s;
    int hostlen;
    int length;

    s = self->client_mcs_data;
    init_stream(s, 512);
    self->rdp_layer->mod->hostname[15] = 0; /* limit length to 15 */
    hostlen = 2 * g_strlen(self->rdp_layer->mod->hostname);
    length = 158 + 76 + 12 + 4;
    /* Generic Conference Control (T.124) ConferenceCreateRequest */
    out_uint16_be(s, 5);
    out_uint16_be(s, 0x14);
    out_uint8(s, 0x7c);
    out_uint16_be(s, 1);
    out_uint16_be(s, (length | 0x8000)); /* remaining length */
    out_uint16_be(s, 8); /* length? */
    out_uint16_be(s, 16);
    out_uint8(s, 0);
    out_uint16_le(s, 0xc001);
    out_uint8(s, 0);
    out_uint32_le(s, 0x61637544); /* OEM ID: "Duca", as in Ducati. */
    out_uint16_be(s, ((length - 14) | 0x8000)); /* remaining length */
    /* Client information */
    out_uint16_le(s, SEC_TAG_CLI_INFO);
    out_uint16_le(s, 212); /* length */
    out_uint16_le(s, 1); /* RDP version. 1 == RDP4, 4 == RDP5. */
    out_uint16_le(s, 8);
    out_uint16_le(s, self->rdp_layer->mod->width);
    out_uint16_le(s, self->rdp_layer->mod->height);
    out_uint16_le(s, 0xca01);
    out_uint16_le(s, 0xaa03);
    out_uint32_le(s, self->rdp_layer->mod->keylayout);
    out_uint32_le(s, 2600); /* Client build */
    /* Unicode name of client, padded to 32 bytes */
    rdp_rdp_out_unistr(s, self->rdp_layer->mod->hostname);
    out_uint8s(s, 30 - hostlen);
    out_uint32_le(s, 4);
    out_uint32_le(s, 0);
    out_uint32_le(s, 12);
    out_uint8s(s, 64); /* reserved? 4 + 12 doublewords */
    out_uint16_le(s, 0xca01); /* color depth? */
    out_uint16_le(s, 1);
    out_uint32_le(s, 0);
    out_uint8(s, self->rdp_layer->mod->rdp_bpp);
    out_uint16_le(s, 0x0700);
    out_uint8(s, 0);
    out_uint32_le(s, 1);
    out_uint8s(s, 64); /* End of client info */
    out_uint16_le(s, SEC_TAG_CLI_4);
    out_uint16_le(s, 12);
    out_uint32_le(s, 9);
    out_uint32_le(s, 0);
    /* Client encryption settings */
    out_uint16_le(s, SEC_TAG_CLI_CRYPT);
    out_uint16_le(s, 12); /* length */
    /* encryption supported, 128-bit supported */
    out_uint32_le(s, 0x3);
    out_uint32_le(s, 0); /* Unknown */
    s_mark_end(s);
}

/*****************************************************************************/
/* Parse a public key structure */
/* returns boolean */
static int APP_CC
rdp_sec_parse_public_key(struct rdp_sec *self, struct stream *s,
                         char *modulus, char *exponent)
{
    int magic;
    int modulus_len;

    in_uint32_le(s, magic);

    if (magic != SEC_RSA_MAGIC)
    {
        return 0;
    }

    in_uint32_le(s, modulus_len);

    if (modulus_len != SEC_MODULUS_SIZE + SEC_PADDING_SIZE)
    {
        return 0;
    }

    in_uint8s(s, 8);
    in_uint8a(s, exponent, SEC_EXPONENT_SIZE);
    in_uint8a(s, modulus, SEC_MODULUS_SIZE);
    in_uint8s(s, SEC_PADDING_SIZE);
    return s_check(s);
}

/*****************************************************************************/
/* Parse a crypto information structure */
/* returns boolean */
static int APP_CC
rdp_sec_parse_crypt_info(struct rdp_sec *self, struct stream *s,
                         char *modulus, char *exponent)
{
    int random_len;
    int rsa_info_len;
    int flags;
    int tag;
    int length;
    char *next_tag;
    char *end;

    in_uint32_le(s, self->rc4_key_size); /* 1 = 40-bit, 2 = 128-bit */
    in_uint32_le(s, self->crypt_level); /* 1 = low, 2 = medium, 3 = high */

    if (self->crypt_level == 0) /* no encryption */
    {
        return 0;
    }

    in_uint32_le(s, random_len);
    in_uint32_le(s, rsa_info_len);

    if (random_len != SEC_RANDOM_SIZE)
    {
        return 0;
    }

    in_uint8a(s, self->server_random, random_len);
    /* RSA info */
    end = s->p + rsa_info_len;

    if (end > s->end)
    {
        return 0;
    }

    in_uint32_le(s, flags); /* 1 = RDP4-style, 0x80000002 = X.509 */

    if (flags & 1)
    {
        in_uint8s(s, 8); /* unknown */

        while (s->p < end)
        {
            in_uint16_le(s, tag);
            in_uint16_le(s, length);
            next_tag = s->p + length;
            DEBUG((" rdp_sec_parse_crypt_info tag %d length %d", tag, length));

            switch (tag)
            {
                case SEC_TAG_PUBKEY:

                    if (!rdp_sec_parse_public_key(self, s, modulus, exponent))
                    {
                        return 0;
                    }

                    break;
                case SEC_TAG_KEYSIG:
                    break;
                default:
                    break;
            }

            s->p = next_tag;
        }
    }
    else
    {
        /* todo */
        return 0;
    }

    return s_check_end(s);
}

/*****************************************************************************/
static void APP_CC
rdp_sec_rsa_op(char *out, char *in, char *mod, char *exp)
{
    ssl_mod_exp(out, SEC_MODULUS_SIZE, /* 64 */
                in, SEC_RANDOM_SIZE, /* 32 */
                mod, SEC_MODULUS_SIZE, /* 64 */
                exp, SEC_EXPONENT_SIZE); /* 4 */
}

/*****************************************************************************/
void APP_CC
rdp_sec_hash_48(char *out, char *in, char *salt1, char *salt2, int salt)
{
    int i;
    void *sha1_info;
    void *md5_info;
    char pad[4];
    char sha1_sig[20];
    char md5_sig[16];

    sha1_info = ssl_sha1_info_create();
    md5_info = ssl_md5_info_create();

    for (i = 0; i < 3; i++)
    {
        g_memset(pad, salt + i, 4);
        ssl_sha1_clear(sha1_info);
        ssl_sha1_transform(sha1_info, pad, i + 1);
        ssl_sha1_transform(sha1_info, in, 48);
        ssl_sha1_transform(sha1_info, salt1, 32);
        ssl_sha1_transform(sha1_info, salt2, 32);
        ssl_sha1_complete(sha1_info, sha1_sig);
        ssl_md5_clear(md5_info);
        ssl_md5_transform(md5_info, in, 48);
        ssl_md5_transform(md5_info, sha1_sig, 20);
        ssl_md5_complete(md5_info, md5_sig);
        g_memcpy(out + i * 16, md5_sig, 16);
    }

    ssl_sha1_info_delete(sha1_info);
    ssl_md5_info_delete(md5_info);
}

/*****************************************************************************/
void APP_CC
rdp_sec_hash_16(char *out, char *in, char *salt1, char *salt2)
{
    void *md5_info;

    md5_info = ssl_md5_info_create();
    ssl_md5_clear(md5_info);
    ssl_md5_transform(md5_info, in, 16);
    ssl_md5_transform(md5_info, salt1, 32);
    ssl_md5_transform(md5_info, salt2, 32);
    ssl_md5_complete(md5_info, out);
    ssl_md5_info_delete(md5_info);
}

/*****************************************************************************/
static int APP_CC
rdp_sec_generate_keys(struct rdp_sec *self)
{
    char session_key[48];
    char temp_hash[48];
    char input[48];

    g_memcpy(input, self->client_random, 24);
    g_memcpy(input + 24, self->server_random, 24);
    rdp_sec_hash_48(temp_hash, input, self->client_random,
                    self->server_random, 65);
    rdp_sec_hash_48(session_key, temp_hash, self->client_random,
                    self->server_random, 88);
    g_memcpy(self->sign_key, session_key, 16);
    rdp_sec_hash_16(self->decrypt_key, session_key + 16, self->client_random,
                    self->server_random);
    rdp_sec_hash_16(self->encrypt_key, session_key + 32, self->client_random,
                    self->server_random);
    DEBUG((" rdp_sec_generate_keys, rc4_key_size is %d", self->rc4_key_size));
    DEBUG((" rdp_sec_generate_keys, crypt_level is %d", self->crypt_level));

    if (self->rc4_key_size == 1)
    {
        rdp_sec_make_40bit(self->sign_key);
        rdp_sec_make_40bit(self->encrypt_key);
        rdp_sec_make_40bit(self->decrypt_key);
        self->rc4_key_len = 8;
    }
    else
    {
        self->rc4_key_len = 16;
    }

    g_memcpy(self->decrypt_update_key, self->decrypt_key, 16);
    g_memcpy(self->encrypt_update_key, self->encrypt_key, 16);
    ssl_rc4_set_key(self->decrypt_rc4_info, self->decrypt_key, self->rc4_key_len);
    ssl_rc4_set_key(self->encrypt_rc4_info, self->encrypt_key, self->rc4_key_len);
    return 0;
}

/*****************************************************************************/
/* Process crypto information blob */
static void APP_CC
rdp_sec_process_crypt_info(struct rdp_sec *self, struct stream *s)
{
    char modulus[64];
    char exponent[64];

    g_memset(modulus, 0, sizeof(modulus));
    g_memset(exponent, 0, sizeof(exponent));

    if (!rdp_sec_parse_crypt_info(self, s, modulus, exponent))
    {
        DEBUG((" error in rdp_sec_process_crypt_info"));
        return;
    }

    /* Generate a client random, and determine encryption keys */
    g_random(self->client_random, 32);
    rdp_sec_rsa_op(self->client_crypt_random, self->client_random,
                   modulus, exponent);
    rdp_sec_generate_keys(self);
}

/*****************************************************************************/
/* Process connect response data blob */
static void APP_CC
rdp_sec_process_mcs_data(struct rdp_sec *self)
{
    int tag;
    int length;
    int len;
    char *next_tag;
    struct stream *s;

    s = self->server_mcs_data;
    s->p = s->data;
    in_uint8s(s, 21); /* header (T.124 ConferenceCreateResponse) */
    in_uint8(s, len);

    if (len & 0x80)
    {
        in_uint8(s, len);
    }

    while (s->p < s->end)
    {
        in_uint16_le(s, tag);
        in_uint16_le(s, length);
        DEBUG((" rdp_sec_process_mcs_data tag %d length %d", tag, length));

        if (length <= 4)
        {
            return;
        }

        next_tag = (s->p + length) - 4;

        switch (tag)
        {
            case SEC_TAG_SRV_INFO:
                //rdp_sec_process_srv_info(self, s);
                break;
            case SEC_TAG_SRV_CRYPT:
                rdp_sec_process_crypt_info(self, s);
                break;
            case SEC_TAG_SRV_CHANNELS:
                break;
            default:
                break;
        }

        s->p = next_tag;
    }
}

/*****************************************************************************/
/* Transfer the client random to the server */
/* returns error */
static int APP_CC
rdp_sec_establish_key(struct rdp_sec *self)
{
    int length;
    int flags;
    struct stream *s;

    DEBUG((" sending client random"));
    make_stream(s);
    init_stream(s, 8192);
    length = SEC_MODULUS_SIZE + SEC_PADDING_SIZE;
    flags = SEC_CLIENT_RANDOM;

    if (rdp_sec_init(self, s, flags) != 0)
    {
        free_stream(s);
        return 1;
    }

    out_uint32_le(s, length);
    out_uint8p(s, self->client_crypt_random, SEC_MODULUS_SIZE);
    out_uint8s(s, SEC_PADDING_SIZE);
    s_mark_end(s);

    if (rdp_sec_send(self, s, flags) != 0)
    {
        free_stream(s);
        return 1;
    }

    free_stream(s);
    return 0;
}

/*****************************************************************************/
/* Establish a secure connection */
int APP_CC
rdp_sec_connect(struct rdp_sec *self, char *ip, char *port)
{
    DEBUG((" in rdp_sec_connect"));
    rdp_sec_out_mcs_data(self);

    if (rdp_mcs_connect(self->mcs_layer, ip, port) != 0)
    {
        DEBUG((" out rdp_sec_connect error rdp_mcs_connect failed"));
        return 1;
    }

    rdp_sec_process_mcs_data(self);

    if (rdp_sec_establish_key(self) != 0)
    {
        DEBUG((" out rdp_sec_connect error rdp_sec_establish_key failed"));
        return 1;
    }

    DEBUG((" out rdp_sec_connect"));
    return 0;
}

/*****************************************************************************/
/* returns error */
int APP_CC
rdp_sec_init(struct rdp_sec *self, struct stream *s, int flags)
{
    if (rdp_mcs_init(self->mcs_layer, s) != 0)
    {
        return 1;
    }

    if (flags & SEC_ENCRYPT)
    {
        s_push_layer(s, sec_hdr, 12);
    }
    else
    {
        s_push_layer(s, sec_hdr, 4);
    }

    return 0;
}

/*****************************************************************************/
/* Output a uint32 into a buffer (little-endian) */
void APP_CC
rdp_sec_buf_out_uint32(char *buffer, int value)
{
    buffer[0] = value & 0xff;
    buffer[1] = (value >> 8) & 0xff;
    buffer[2] = (value >> 16) & 0xff;
    buffer[3] = (value >> 24) & 0xff;
}

/*****************************************************************************/
/* Generate a MAC hash (5.2.3.1), using a combination of SHA1 and MD5 */
void APP_CC
rdp_sec_sign(char *signature, int siglen, char *session_key, int keylen,
             char *data, int datalen)
{
    char shasig[20];
    char md5sig[16];
    char lenhdr[4];
    void *sha1_context;
    void *md5_context;

    rdp_sec_buf_out_uint32(lenhdr, datalen);
    sha1_context = ssl_sha1_info_create();
    ssl_sha1_clear(sha1_context);
    ssl_sha1_transform(sha1_context, session_key, keylen);
    ssl_sha1_transform(sha1_context, g_pad_54, 40);
    ssl_sha1_transform(sha1_context, lenhdr, 4);
    ssl_sha1_transform(sha1_context, data, datalen);
    ssl_sha1_complete(sha1_context, shasig);
    ssl_sha1_info_delete(sha1_context);
    md5_context = ssl_md5_info_create();
    ssl_md5_clear(md5_context);
    ssl_md5_transform(md5_context, session_key, keylen);
    ssl_md5_transform(md5_context, g_pad_92, 48);
    ssl_md5_transform(md5_context, shasig, 20);
    ssl_md5_complete(md5_context, md5sig);
    ssl_md5_info_delete(md5_context);
    g_memcpy(signature, md5sig, siglen);
}

/*****************************************************************************/
/* Encrypt data using RC4 */
static void APP_CC
rdp_sec_encrypt(struct rdp_sec *self, char *data, int length)
{
    if (self->encrypt_use_count == 4096)
    {
        rdp_sec_update(self->encrypt_key, self->encrypt_update_key,
                       self->rc4_key_len);
        ssl_rc4_set_key(self->encrypt_rc4_info, self->encrypt_key,
                        self->rc4_key_len);
        self->encrypt_use_count = 0;
    }

    ssl_rc4_crypt(self->encrypt_rc4_info, data, length);
    self->encrypt_use_count++;
}

/*****************************************************************************/
/* returns error */
int APP_CC
rdp_sec_send(struct rdp_sec *self, struct stream *s, int flags)
{
    int datalen;

    DEBUG((" in rdp_sec_send flags %8.8x", flags));
    s_pop_layer(s, sec_hdr);
    out_uint32_le(s, flags);

    if (flags & SEC_ENCRYPT)
    {
        datalen = (s->end - s->p) - 8;
        rdp_sec_sign(s->p, 8, self->sign_key, self->rc4_key_len, s->p + 8,
                     datalen);
        rdp_sec_encrypt(self, s->p + 8, datalen);
    }

    if (rdp_mcs_send(self->mcs_layer, s) != 0)
    {
        DEBUG((" out rdp_sec_send, rdp_mcs_send failed"));
        return 1;
    }

    DEBUG((" out rdp_sec_send"));
    return 0;
}