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Diffstat (limited to 'uirdesktop/secure.c')
| -rw-r--r-- | uirdesktop/secure.c | 981 |
1 files changed, 981 insertions, 0 deletions
diff --git a/uirdesktop/secure.c b/uirdesktop/secure.c new file mode 100644 index 00000000..0d22ecc3 --- /dev/null +++ b/uirdesktop/secure.c @@ -0,0 +1,981 @@ +/* -*- c-basic-offset: 8 -*- + rdesktop: A Remote Desktop Protocol client. + Protocol services - RDP encryption and licensing + Copyright (C) Matthew Chapman 1999-2005 + + 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., 675 Mass Ave, Cambridge, MA 02139, USA. +*/ + +#include "rdesktop.h" + +#include <openssl/rc4.h> +#include <openssl/md5.h> +#include <openssl/sha.h> +#include <openssl/bn.h> +#include <openssl/x509v3.h> + +extern char g_hostname[16]; +extern int g_width; +extern int g_height; +extern unsigned int g_keylayout; +extern int g_keyboard_type; +extern int g_keyboard_subtype; +extern int g_keyboard_functionkeys; +extern BOOL g_encryption; +extern BOOL g_licence_issued; +extern BOOL g_use_rdp5; +extern BOOL g_console_session; +extern int g_server_depth; +extern uint16 mcs_userid; +extern VCHANNEL g_channels[]; +extern unsigned int g_num_channels; + +static int rc4_key_len; +static RC4_KEY rc4_decrypt_key; +static RC4_KEY rc4_encrypt_key; +static RSA *server_public_key; +static uint32 server_public_key_len; + +static uint8 sec_sign_key[16]; +static uint8 sec_decrypt_key[16]; +static uint8 sec_encrypt_key[16]; +static uint8 sec_decrypt_update_key[16]; +static uint8 sec_encrypt_update_key[16]; +static uint8 sec_crypted_random[SEC_MAX_MODULUS_SIZE]; + +uint16 g_server_rdp_version = 0; + +/* These values must be available to reset state - Session Directory */ +static int sec_encrypt_use_count = 0; +static int sec_decrypt_use_count = 0; + +/* + * I believe this is based on SSLv3 with the following differences: + * MAC algorithm (5.2.3.1) uses only 32-bit length in place of seq_num/type/length fields + * MAC algorithm uses SHA1 and MD5 for the two hash functions instead of one or other + * key_block algorithm (6.2.2) uses 'X', 'YY', 'ZZZ' instead of 'A', 'BB', 'CCC' + * key_block partitioning is different (16 bytes each: MAC secret, decrypt key, encrypt key) + * encryption/decryption keys updated every 4096 packets + * See http://wp.netscape.com/eng/ssl3/draft302.txt + */ + +/* + * 48-byte transformation used to generate master secret (6.1) and key material (6.2.2). + * Both SHA1 and MD5 algorithms are used. + */ +void +sec_hash_48(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2, uint8 salt) +{ + uint8 shasig[20]; + uint8 pad[4]; + SHA_CTX sha; + MD5_CTX md5; + int i; + + for (i = 0; i < 3; i++) + { + memset(pad, salt + i, i + 1); + + SHA1_Init(&sha); + SHA1_Update(&sha, pad, i + 1); + SHA1_Update(&sha, in, 48); + SHA1_Update(&sha, salt1, 32); + SHA1_Update(&sha, salt2, 32); + SHA1_Final(shasig, &sha); + + MD5_Init(&md5); + MD5_Update(&md5, in, 48); + MD5_Update(&md5, shasig, 20); + MD5_Final(&out[i * 16], &md5); + } +} + +/* + * 16-byte transformation used to generate export keys (6.2.2). + */ +void +sec_hash_16(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2) +{ + MD5_CTX md5; + + MD5_Init(&md5); + MD5_Update(&md5, in, 16); + MD5_Update(&md5, salt1, 32); + MD5_Update(&md5, salt2, 32); + MD5_Final(out, &md5); +} + +/* Reduce key entropy from 64 to 40 bits */ +static void +sec_make_40bit(uint8 * key) +{ + key[0] = 0xd1; + key[1] = 0x26; + key[2] = 0x9e; +} + +/* Generate encryption keys given client and server randoms */ +static void +sec_generate_keys(uint8 * client_random, uint8 * server_random, int rc4_key_size) +{ + uint8 pre_master_secret[48]; + uint8 master_secret[48]; + uint8 key_block[48]; + + /* Construct pre-master secret */ + memcpy(pre_master_secret, client_random, 24); + memcpy(pre_master_secret + 24, server_random, 24); + + /* Generate master secret and then key material */ + sec_hash_48(master_secret, pre_master_secret, client_random, server_random, 'A'); + sec_hash_48(key_block, master_secret, client_random, server_random, 'X'); + + /* First 16 bytes of key material is MAC secret */ + memcpy(sec_sign_key, key_block, 16); + + /* Generate export keys from next two blocks of 16 bytes */ + sec_hash_16(sec_decrypt_key, &key_block[16], client_random, server_random); + sec_hash_16(sec_encrypt_key, &key_block[32], client_random, server_random); + + if (rc4_key_size == 1) + { + DEBUG(("40-bit encryption enabled\n")); + sec_make_40bit(sec_sign_key); + sec_make_40bit(sec_decrypt_key); + sec_make_40bit(sec_encrypt_key); + rc4_key_len = 8; + } + else + { + DEBUG(("rc_4_key_size == %d, 128-bit encryption enabled\n", rc4_key_size)); + rc4_key_len = 16; + } + + /* Save initial RC4 keys as update keys */ + memcpy(sec_decrypt_update_key, sec_decrypt_key, 16); + memcpy(sec_encrypt_update_key, sec_encrypt_key, 16); + + /* Initialise RC4 state arrays */ + RC4_set_key(&rc4_decrypt_key, rc4_key_len, sec_decrypt_key); + RC4_set_key(&rc4_encrypt_key, rc4_key_len, sec_encrypt_key); +} + +static uint8 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 uint8 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 +}; + +/* Output a uint32 into a buffer (little-endian) */ +void +buf_out_uint32(uint8 * buffer, uint32 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 +sec_sign(uint8 * signature, int siglen, uint8 * session_key, int keylen, uint8 * data, int datalen) +{ + uint8 shasig[20]; + uint8 md5sig[16]; + uint8 lenhdr[4]; + SHA_CTX sha; + MD5_CTX md5; + + buf_out_uint32(lenhdr, datalen); + + SHA1_Init(&sha); + SHA1_Update(&sha, session_key, keylen); + SHA1_Update(&sha, pad_54, 40); + SHA1_Update(&sha, lenhdr, 4); + SHA1_Update(&sha, data, datalen); + SHA1_Final(shasig, &sha); + + MD5_Init(&md5); + MD5_Update(&md5, session_key, keylen); + MD5_Update(&md5, pad_92, 48); + MD5_Update(&md5, shasig, 20); + MD5_Final(md5sig, &md5); + + memcpy(signature, md5sig, siglen); +} + +/* Update an encryption key */ +static void +sec_update(uint8 * key, uint8 * update_key) +{ + uint8 shasig[20]; + SHA_CTX sha; + MD5_CTX md5; + RC4_KEY update; + + SHA1_Init(&sha); + SHA1_Update(&sha, update_key, rc4_key_len); + SHA1_Update(&sha, pad_54, 40); + SHA1_Update(&sha, key, rc4_key_len); + SHA1_Final(shasig, &sha); + + MD5_Init(&md5); + MD5_Update(&md5, update_key, rc4_key_len); + MD5_Update(&md5, pad_92, 48); + MD5_Update(&md5, shasig, 20); + MD5_Final(key, &md5); + + RC4_set_key(&update, rc4_key_len, key); + RC4(&update, rc4_key_len, key, key); + + if (rc4_key_len == 8) + sec_make_40bit(key); +} + +/* Encrypt data using RC4 */ +static void +sec_encrypt(uint8 * data, int length) +{ + if (sec_encrypt_use_count == 4096) + { + sec_update(sec_encrypt_key, sec_encrypt_update_key); + RC4_set_key(&rc4_encrypt_key, rc4_key_len, sec_encrypt_key); + sec_encrypt_use_count = 0; + } + + RC4(&rc4_encrypt_key, length, data, data); + sec_encrypt_use_count++; +} + +/* Decrypt data using RC4 */ +void +sec_decrypt(uint8 * data, int length) +{ + if (sec_decrypt_use_count == 4096) + { + sec_update(sec_decrypt_key, sec_decrypt_update_key); + RC4_set_key(&rc4_decrypt_key, rc4_key_len, sec_decrypt_key); + sec_decrypt_use_count = 0; + } + + RC4(&rc4_decrypt_key, length, data, data); + sec_decrypt_use_count++; +} + +static void +reverse(uint8 * p, int len) +{ + int i, j; + uint8 temp; + + for (i = 0, j = len - 1; i < j; i++, j--) + { + temp = p[i]; + p[i] = p[j]; + p[j] = temp; + } +} + +/* Perform an RSA public key encryption operation */ +static void +sec_rsa_encrypt(uint8 * out, uint8 * in, int len, uint32 modulus_size, uint8 * modulus, uint8 * exponent) +{ + BN_CTX *ctx; + BIGNUM mod, exp, x, y; + uint8 inr[SEC_MAX_MODULUS_SIZE]; + int outlen; + + reverse(modulus, modulus_size); + reverse(exponent, SEC_EXPONENT_SIZE); + memcpy(inr, in, len); + reverse(inr, len); + + ctx = BN_CTX_new(); + BN_init(&mod); + BN_init(&exp); + BN_init(&x); + BN_init(&y); + + BN_bin2bn(modulus, modulus_size, &mod); + BN_bin2bn(exponent, SEC_EXPONENT_SIZE, &exp); + BN_bin2bn(inr, len, &x); + BN_mod_exp(&y, &x, &exp, &mod, ctx); + outlen = BN_bn2bin(&y, out); + reverse(out, outlen); + if (outlen < modulus_size) + memset(out + outlen, 0, modulus_size - outlen); + + BN_free(&y); + BN_clear_free(&x); + BN_free(&exp); + BN_free(&mod); + BN_CTX_free(ctx); +} + +/* Initialise secure transport packet */ +STREAM +sec_init(uint32 flags, int maxlen) +{ + int hdrlen; + STREAM s; + + if (!g_licence_issued) + hdrlen = (flags & SEC_ENCRYPT) ? 12 : 4; + else + hdrlen = (flags & SEC_ENCRYPT) ? 12 : 0; + s = mcs_init(maxlen + hdrlen); + s_push_layer(s, sec_hdr, hdrlen); + + return s; +} + +/* Transmit secure transport packet over specified channel */ +void +sec_send_to_channel(STREAM s, uint32 flags, uint16 channel) +{ + int datalen; + + s_pop_layer(s, sec_hdr); + if (!g_licence_issued || (flags & SEC_ENCRYPT)) + out_uint32_le(s, flags); + + if (flags & SEC_ENCRYPT) + { + flags &= ~SEC_ENCRYPT; + datalen = s->end - s->p - 8; + +#if WITH_DEBUG + DEBUG(("Sending encrypted packet:\n")); + hexdump(s->p + 8, datalen); +#endif + + sec_sign(s->p, 8, sec_sign_key, rc4_key_len, s->p + 8, datalen); + sec_encrypt(s->p + 8, datalen); + } + + mcs_send_to_channel(s, channel); +} + +/* Transmit secure transport packet */ + +void +sec_send(STREAM s, uint32 flags) +{ + sec_send_to_channel(s, flags, MCS_GLOBAL_CHANNEL); +} + + +/* Transfer the client random to the server */ +static void +sec_establish_key(void) +{ + uint32 length = server_public_key_len + SEC_PADDING_SIZE; + uint32 flags = SEC_CLIENT_RANDOM; + STREAM s; + + s = sec_init(flags, length+4); + + out_uint32_le(s, length); + out_uint8p(s, sec_crypted_random, server_public_key_len); + out_uint8s(s, SEC_PADDING_SIZE); + + s_mark_end(s); + sec_send(s, flags); +} + +/* Output connect initial data blob */ +static void +sec_out_mcs_data(STREAM s) +{ + int hostlen = 2 * strlen(g_hostname); + int length = 158 + 76 + 12 + 4; + unsigned int i; + + if (g_num_channels > 0) + length += g_num_channels * 12 + 8; + + if (hostlen > 30) + hostlen = 30; + + /* 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, g_use_rdp5 ? 4 : 1); /* RDP version. 1 == RDP4, 4 == RDP5. */ + out_uint16_le(s, 8); + out_uint16_le(s, g_width); + out_uint16_le(s, g_height); + out_uint16_le(s, 0xca01); + out_uint16_le(s, 0xaa03); + out_uint32_le(s, g_keylayout); + out_uint32_le(s, 2600); /* Client build. We are now 2600 compatible :-) */ + + /* Unicode name of client, padded to 32 bytes */ + rdp_out_unistr(s, g_hostname, hostlen); + out_uint8s(s, 30 - hostlen); + + /* See + http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wceddk40/html/cxtsksupportingremotedesktopprotocol.asp */ + out_uint32_le(s, g_keyboard_type); + out_uint32_le(s, g_keyboard_subtype); + out_uint32_le(s, g_keyboard_functionkeys); + out_uint8s(s, 64); /* reserved? 4 + 12 doublewords */ + out_uint16_le(s, 0xca01); /* colour depth? */ + out_uint16_le(s, 1); + + out_uint32(s, 0); + out_uint8(s, g_server_depth); + 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, g_console_session ? 0xb : 9); + out_uint32(s, 0); + + /* Client encryption settings */ + out_uint16_le(s, SEC_TAG_CLI_CRYPT); + out_uint16_le(s, 12); /* length */ + out_uint32_le(s, g_encryption ? 0x3 : 0); /* encryption supported, 128-bit supported */ + out_uint32(s, 0); /* Unknown */ + + DEBUG_RDP5(("g_num_channels is %d\n", g_num_channels)); + if (g_num_channels > 0) + { + out_uint16_le(s, SEC_TAG_CLI_CHANNELS); + out_uint16_le(s, g_num_channels * 12 + 8); /* length */ + out_uint32_le(s, g_num_channels); /* number of virtual channels */ + for (i = 0; i < g_num_channels; i++) + { + DEBUG_RDP5(("Requesting channel %s\n", g_channels[i].name)); + out_uint8a(s, g_channels[i].name, 8); + out_uint32_be(s, g_channels[i].flags); + } + } + + s_mark_end(s); +} + +/* Parse a public key structure */ +static BOOL +sec_parse_public_key(STREAM s, uint8 ** modulus, uint8 ** exponent) +{ + uint32 magic, modulus_len; + + in_uint32_le(s, magic); + if (magic != SEC_RSA_MAGIC) + { + error("RSA magic 0x%x\n", magic); + return False; + } + + in_uint32_le(s, modulus_len); + modulus_len -= SEC_PADDING_SIZE; + if ((modulus_len < 64) || (modulus_len > SEC_MAX_MODULUS_SIZE)) + { + error("Bad server public key size (%u bits)\n", modulus_len*8); + return False; + } + + in_uint8s(s, 8); /* modulus_bits, unknown */ + in_uint8p(s, *exponent, SEC_EXPONENT_SIZE); + in_uint8p(s, *modulus, modulus_len); + in_uint8s(s, SEC_PADDING_SIZE); + server_public_key_len = modulus_len; + + return s_check(s); +} + +static BOOL +sec_parse_x509_key(X509 * cert) +{ + EVP_PKEY *epk = NULL; + /* By some reason, Microsoft sets the OID of the Public RSA key to + the oid for "MD5 with RSA Encryption" instead of "RSA Encryption" + + Kudos to Richard Levitte for the following (. intiutive .) + lines of code that resets the OID and let's us extract the key. */ + if (OBJ_obj2nid(cert->cert_info->key->algor->algorithm) == NID_md5WithRSAEncryption) + { + DEBUG_RDP5(("Re-setting algorithm type to RSA in server certificate\n")); + ASN1_OBJECT_free(cert->cert_info->key->algor->algorithm); + cert->cert_info->key->algor->algorithm = OBJ_nid2obj(NID_rsaEncryption); + } + epk = X509_get_pubkey(cert); + if (NULL == epk) + { + error("Failed to extract public key from certificate\n"); + return False; + } + + server_public_key = RSAPublicKey_dup((RSA *) epk->pkey.ptr); + EVP_PKEY_free(epk); + + server_public_key_len = RSA_size(server_public_key); + if ((server_public_key_len < 64) || (server_public_key_len > SEC_MAX_MODULUS_SIZE)) + { + error("Bad server public key size (%u bits)\n", server_public_key_len*8); + return False; + } + + return True; +} + + +/* Parse a crypto information structure */ +static BOOL +sec_parse_crypt_info(STREAM s, uint32 * rc4_key_size, + uint8 ** server_random, uint8 ** modulus, uint8 ** exponent) +{ + uint32 crypt_level, random_len, rsa_info_len; + uint32 cacert_len, cert_len, flags; + X509 *cacert, *server_cert; + uint16 tag, length; + uint8 *next_tag, *end; + + in_uint32_le(s, *rc4_key_size); /* 1 = 40-bit, 2 = 128-bit */ + in_uint32_le(s, crypt_level); /* 1 = low, 2 = medium, 3 = high */ + if (crypt_level == 0) /* no encryption */ + return False; + in_uint32_le(s, random_len); + in_uint32_le(s, rsa_info_len); + + if (random_len != SEC_RANDOM_SIZE) + { + error("random len %d, expected %d\n", random_len, SEC_RANDOM_SIZE); + return False; + } + + in_uint8p(s, *server_random, random_len); + + /* RSA info */ + end = s->p + rsa_info_len; + if (end > s->end) + return False; + + in_uint32_le(s, flags); /* 1 = RDP4-style, 0x80000002 = X.509 */ + if (flags & 1) + { + DEBUG_RDP5(("We're going for the RDP4-style encryption\n")); + in_uint8s(s, 8); /* unknown */ + + while (s->p < end) + { + in_uint16_le(s, tag); + in_uint16_le(s, length); + + next_tag = s->p + length; + + switch (tag) + { + case SEC_TAG_PUBKEY: + if (!sec_parse_public_key(s, modulus, exponent)) + return False; + DEBUG_RDP5(("Got Public key, RDP4-style\n")); + + break; + + case SEC_TAG_KEYSIG: + /* Is this a Microsoft key that we just got? */ + /* Care factor: zero! */ + /* Actually, it would probably be a good idea to check if the public key is signed with this key, and then store this + key as a known key of the hostname. This would prevent some MITM-attacks. */ + break; + + default: + unimpl("crypt tag 0x%x\n", tag); + } + + s->p = next_tag; + } + } + else + { + uint32 certcount; + + DEBUG_RDP5(("We're going for the RDP5-style encryption\n")); + in_uint32_le(s, certcount); /* Number of certificates */ + + if (certcount < 2) + { + error("Server didn't send enough X509 certificates\n"); + return False; + } + + for (; certcount > 2; certcount--) + { /* ignore all the certificates between the root and the signing CA */ + uint32 ignorelen; + X509 *ignorecert; + + DEBUG_RDP5(("Ignored certs left: %d\n", certcount)); + + in_uint32_le(s, ignorelen); + DEBUG_RDP5(("Ignored Certificate length is %d\n", ignorelen)); + ignorecert = d2i_X509(NULL, &(s->p), ignorelen); + + if (ignorecert == NULL) + { /* XXX: error out? */ + DEBUG_RDP5(("got a bad cert: this will probably screw up the rest of the communication\n")); + } + +#ifdef WITH_DEBUG_RDP5 + DEBUG_RDP5(("cert #%d (ignored):\n", certcount)); + X509_print_fp(stdout, ignorecert); +#endif + } + + /* Do da funky X.509 stuffy + + "How did I find out about this? I looked up and saw a + bright light and when I came to I had a scar on my forehead + and knew about X.500" + - Peter Gutman in a early version of + http://www.cs.auckland.ac.nz/~pgut001/pubs/x509guide.txt + */ + + in_uint32_le(s, cacert_len); + DEBUG_RDP5(("CA Certificate length is %d\n", cacert_len)); + cacert = d2i_X509(NULL, &(s->p), cacert_len); + /* Note: We don't need to move s->p here - d2i_X509 is + "kind" enough to do it for us */ + if (NULL == cacert) + { + error("Couldn't load CA Certificate from server\n"); + return False; + } + + /* Currently, we don't use the CA Certificate. + FIXME: + *) Verify the server certificate (server_cert) with the + CA certificate. + *) Store the CA Certificate with the hostname of the + server we are connecting to as key, and compare it + when we connect the next time, in order to prevent + MITM-attacks. + */ + + X509_free(cacert); + + in_uint32_le(s, cert_len); + DEBUG_RDP5(("Certificate length is %d\n", cert_len)); + server_cert = d2i_X509(NULL, &(s->p), cert_len); + if (NULL == server_cert) + { + error("Couldn't load Certificate from server\n"); + return False; + } + + in_uint8s(s, 16); /* Padding */ + + /* Note: Verifying the server certificate must be done here, + before sec_parse_public_key since we'll have to apply + serious violence to the key after this */ + + if (!sec_parse_x509_key(server_cert)) + { + DEBUG_RDP5(("Didn't parse X509 correctly\n")); + X509_free(server_cert); + return False; + } + X509_free(server_cert); + return True; /* There's some garbage here we don't care about */ + } + return s_check_end(s); +} + +/* Process crypto information blob */ +static void +sec_process_crypt_info(STREAM s) +{ + uint8 *server_random, *modulus, *exponent; + uint8 client_random[SEC_RANDOM_SIZE]; + uint32 rc4_key_size; + + if (!sec_parse_crypt_info(s, &rc4_key_size, &server_random, &modulus, &exponent)) + { + DEBUG(("Failed to parse crypt info\n")); + return; + } + + DEBUG(("Generating client random\n")); + generate_random(client_random); + + if (NULL != server_public_key) + { /* Which means we should use + RDP5-style encryption */ + uint8 inr[SEC_MAX_MODULUS_SIZE]; + uint32 padding_len = server_public_key_len - SEC_RANDOM_SIZE; + + /* This is what the MS client do: */ + memset(inr, 0, padding_len); + /* *ARIGL!* Plaintext attack, anyone? + I tried doing: + generate_random(inr); + ..but that generates connection errors now and then (yes, + "now and then". Something like 0 to 3 attempts needed before a + successful connection. Nice. Not! + */ + memcpy(inr + padding_len, client_random, SEC_RANDOM_SIZE); + reverse(inr + padding_len, SEC_RANDOM_SIZE); + + RSA_public_encrypt(server_public_key_len, + inr, sec_crypted_random, server_public_key, RSA_NO_PADDING); + + reverse(sec_crypted_random, server_public_key_len); + + RSA_free(server_public_key); + server_public_key = NULL; + } + else + { /* RDP4-style encryption */ + sec_rsa_encrypt(sec_crypted_random, + client_random, SEC_RANDOM_SIZE, server_public_key_len, modulus, exponent); + } + sec_generate_keys(client_random, server_random, rc4_key_size); +} + + +/* Process SRV_INFO, find RDP version supported by server */ +static void +sec_process_srv_info(STREAM s) +{ + in_uint16_le(s, g_server_rdp_version); + DEBUG_RDP5(("Server RDP version is %d\n", g_server_rdp_version)); + if (1 == g_server_rdp_version) + { + g_use_rdp5 = 0; + g_server_depth = 8; + } +} + + +/* Process connect response data blob */ +void +sec_process_mcs_data(STREAM s) +{ + uint16 tag, length; + uint8 *next_tag; + uint8 len; + + 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); + + if (length <= 4) + return; + + next_tag = s->p + length - 4; + + switch (tag) + { + case SEC_TAG_SRV_INFO: + sec_process_srv_info(s); + break; + + case SEC_TAG_SRV_CRYPT: + sec_process_crypt_info(s); + break; + + case SEC_TAG_SRV_CHANNELS: + /* FIXME: We should parse this information and + use it to map RDP5 channels to MCS + channels */ + break; + + default: + unimpl("response tag 0x%x\n", tag); + } + + s->p = next_tag; + } +} + +/* Receive secure transport packet */ +STREAM +sec_recv(uint8 * rdpver) +{ + uint32 sec_flags; + uint16 channel; + STREAM s; + + while ((s = mcs_recv(&channel, rdpver)) != NULL) + { + if (rdpver != NULL) + { + if (*rdpver != 3) + { + if (*rdpver & 0x80) + { + in_uint8s(s, 8); /* signature */ + sec_decrypt(s->p, s->end - s->p); + } + return s; + } + } + if (g_encryption || !g_licence_issued) + { + in_uint32_le(s, sec_flags); + + if (sec_flags & SEC_ENCRYPT) + { + in_uint8s(s, 8); /* signature */ + sec_decrypt(s->p, s->end - s->p); + } + + if (sec_flags & SEC_LICENCE_NEG) + { + licence_process(s); + continue; + } + + if (sec_flags & 0x0400) /* SEC_REDIRECT_ENCRYPT */ + { + uint8 swapbyte; + + in_uint8s(s, 8); /* signature */ + sec_decrypt(s->p, s->end - s->p); + + /* Check for a redirect packet, starts with 00 04 */ + if (s->p[0] == 0 && s->p[1] == 4) + { + /* for some reason the PDU and the length seem to be swapped. + This isn't good, but we're going to do a byte for byte + swap. So the first foure value appear as: 00 04 XX YY, + where XX YY is the little endian length. We're going to + use 04 00 as the PDU type, so after our swap this will look + like: XX YY 04 00 */ + swapbyte = s->p[0]; + s->p[0] = s->p[2]; + s->p[2] = swapbyte; + + swapbyte = s->p[1]; + s->p[1] = s->p[3]; + s->p[3] = swapbyte; + + swapbyte = s->p[2]; + s->p[2] = s->p[3]; + s->p[3] = swapbyte; + } +#ifdef WITH_DEBUG + /* warning! this debug statement will show passwords in the clear! */ + hexdump(s->p, s->end - s->p); +#endif + } + + } + + if (channel != MCS_GLOBAL_CHANNEL) + { + channel_process(s, channel); + *rdpver = 0xff; + return s; + } + + return s; + } + + return NULL; +} + +/* Establish a secure connection */ +BOOL +sec_connect(char *server, char *username) +{ + struct stream mcs_data; + + /* We exchange some RDP data during the MCS-Connect */ + mcs_data.size = 512; + mcs_data.p = mcs_data.data = (uint8 *) xmalloc(mcs_data.size); + sec_out_mcs_data(&mcs_data); + + if (!mcs_connect(server, &mcs_data, username)) + return False; + + /* sec_process_mcs_data(&mcs_data); */ + if (g_encryption) + sec_establish_key(); + xfree(mcs_data.data); + return True; +} + +/* Establish a secure connection */ +BOOL +sec_reconnect(char *server) +{ + struct stream mcs_data; + + /* We exchange some RDP data during the MCS-Connect */ + mcs_data.size = 512; + mcs_data.p = mcs_data.data = (uint8 *) xmalloc(mcs_data.size); + sec_out_mcs_data(&mcs_data); + + if (!mcs_reconnect(server, &mcs_data)) + return False; + + /* sec_process_mcs_data(&mcs_data); */ + if (g_encryption) + sec_establish_key(); + xfree(mcs_data.data); + return True; +} + +/* Disconnect a connection */ +void +sec_disconnect(void) +{ + mcs_disconnect(); +} + +/* reset the state of the sec layer */ +void +sec_reset_state(void) +{ + g_server_rdp_version = 0; + sec_encrypt_use_count = 0; + sec_decrypt_use_count = 0; + mcs_reset_state(); +} |