--- sourceforge.net/trunk/rdesktop/secure.c 2001/09/15 09:37:17 32 +++ sourceforge.net/trunk/rdesktop/secure.c 2003/05/30 21:44:06 380 @@ -1,7 +1,7 @@ -/* +/* -*- c-basic-offset: 8 -*- rdesktop: A Remote Desktop Protocol client. Protocol services - RDP encryption and licensing - Copyright (C) Matthew Chapman 1999-2001 + Copyright (C) Matthew Chapman 1999-2002 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 @@ -25,6 +25,7 @@ #include #include #include +#include #else #include "crypto/rc4.h" #include "crypto/md5.h" @@ -37,18 +38,23 @@ extern int height; extern int keylayout; extern BOOL encryption; -extern BOOL licence_issued; +extern BOOL g_licence_issued; +extern BOOL use_rdp5; +extern int server_bpp; static int rc4_key_len; static RC4_KEY rc4_decrypt_key; static RC4_KEY rc4_encrypt_key; +static RSA *server_public_key; -static uint8 sec_sign_key[8]; +static uint8 sec_sign_key[16]; static uint8 sec_decrypt_key[16]; static uint8 sec_encrypt_key[16]; -static uint8 sec_decrypt_update_key[8]; -static uint8 sec_encrypt_update_key[8]; -static uint8 sec_crypted_random[64]; +static uint8 sec_decrypt_update_key[16]; +static uint8 sec_encrypt_update_key[16]; +static uint8 sec_crypted_random[SEC_MODULUS_SIZE]; + +uint16 server_rdp_version = 0; /* * General purpose 48-byte transformation, using two 32-byte salts (generally, @@ -56,7 +62,7 @@ * Both SHA1 and MD5 algorithms are used. */ void -sec_hash_48(uint8 *out, uint8 *in, uint8 *salt1, uint8 *salt2, uint8 salt) +sec_hash_48(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2, uint8 salt) { uint8 shasig[20]; uint8 pad[4]; @@ -87,7 +93,7 @@ * only using a single round of MD5. */ void -sec_hash_16(uint8 *out, uint8 *in, uint8 *salt1, uint8 *salt2) +sec_hash_16(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2) { MD5_CTX md5; @@ -100,7 +106,7 @@ /* Reduce key entropy from 64 to 40 bits */ static void -sec_make_40bit(uint8 *key) +sec_make_40bit(uint8 * key) { key[0] = 0xd1; key[1] = 0x26; @@ -109,7 +115,7 @@ /* Generate a session key and RC4 keys, given client and server randoms */ static void -sec_generate_keys(uint8 *client_key, uint8 *server_key, int rc4_key_size) +sec_generate_keys(uint8 * client_key, uint8 * server_key, int rc4_key_size) { uint8 session_key[48]; uint8 temp_hash[48]; @@ -123,14 +129,12 @@ sec_hash_48(temp_hash, input, client_key, server_key, 65); sec_hash_48(session_key, temp_hash, client_key, server_key, 88); - /* Store first 8 bytes of session key, for generating signatures */ - memcpy(sec_sign_key, session_key, 8); + /* Store first 16 bytes of session key, for generating signatures */ + memcpy(sec_sign_key, session_key, 16); /* Generate RC4 keys */ - sec_hash_16(sec_decrypt_key, &session_key[16], client_key, - server_key); - sec_hash_16(sec_encrypt_key, &session_key[32], client_key, - server_key); + sec_hash_16(sec_decrypt_key, &session_key[16], client_key, server_key); + sec_hash_16(sec_encrypt_key, &session_key[32], client_key, server_key); if (rc4_key_size == 1) { @@ -142,13 +146,13 @@ } else { - DEBUG(("128-bit encryption enabled\n")); + DEBUG(("rc_4_key_size == %d, 128-bit encryption enabled\n", rc4_key_size)); rc4_key_len = 16; } - /* Store first 8 bytes of RC4 keys as update keys */ - memcpy(sec_decrypt_update_key, sec_decrypt_key, 8); - memcpy(sec_encrypt_update_key, sec_encrypt_key, 8); + /* 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); @@ -171,7 +175,7 @@ /* Output a uint32 into a buffer (little-endian) */ void -buf_out_uint32(uint8 *buffer, uint32 value) +buf_out_uint32(uint8 * buffer, uint32 value) { buffer[0] = (value) & 0xff; buffer[1] = (value >> 8) & 0xff; @@ -181,8 +185,7 @@ /* Generate a signature hash, using a combination of SHA1 and MD5 */ void -sec_sign(uint8 *signature, uint8 *session_key, int length, - uint8 *data, int datalen) +sec_sign(uint8 * signature, int siglen, uint8 * session_key, int keylen, uint8 * data, int datalen) { uint8 shasig[20]; uint8 md5sig[16]; @@ -193,24 +196,24 @@ buf_out_uint32(lenhdr, datalen); SHA1_Init(&sha); - SHA1_Update(&sha, session_key, length); + 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, length); + MD5_Update(&md5, session_key, keylen); MD5_Update(&md5, pad_92, 48); MD5_Update(&md5, shasig, 20); MD5_Final(md5sig, &md5); - memcpy(signature, md5sig, length); + memcpy(signature, md5sig, siglen); } /* Update an encryption key - similar to the signing process */ static void -sec_update(uint8 *key, uint8 *update_key) +sec_update(uint8 * key, uint8 * update_key) { uint8 shasig[20]; SHA_CTX sha; @@ -218,13 +221,13 @@ RC4_KEY update; SHA1_Init(&sha); - SHA1_Update(&sha, update_key, 8); + SHA1_Update(&sha, update_key, rc4_key_len); SHA1_Update(&sha, pad_54, 40); - SHA1_Update(&sha, key, 8); + SHA1_Update(&sha, key, rc4_key_len); SHA1_Final(shasig, &sha); MD5_Init(&md5); - MD5_Update(&md5, update_key, 8); + MD5_Update(&md5, update_key, rc4_key_len); MD5_Update(&md5, pad_92, 48); MD5_Update(&md5, shasig, 20); MD5_Final(key, &md5); @@ -238,7 +241,7 @@ /* Encrypt data using RC4 */ static void -sec_encrypt(uint8 *data, int length) +sec_encrypt(uint8 * data, int length) { static int use_count; @@ -254,8 +257,8 @@ } /* Decrypt data using RC4 */ -static void -sec_decrypt(uint8 *data, int length) +void +sec_decrypt(uint8 * data, int length) { static int use_count; @@ -271,12 +274,12 @@ } static void -reverse(uint8 *p, int len) +reverse(uint8 * p, int len) { int i, j; uint8 temp; - for (i = 0, j = len-1; i < j; i++, j--) + for (i = 0, j = len - 1; i < j; i++, j--) { temp = p[i]; p[i] = p[j]; @@ -286,10 +289,9 @@ /* Perform an RSA public key encryption operation */ static void -sec_rsa_encrypt(uint8 *out, uint8 *in, int len, - uint8 *modulus, uint8 *exponent) +sec_rsa_encrypt(uint8 * out, uint8 * in, int len, uint8 * modulus, uint8 * exponent) { - BN_CTX ctx; + BN_CTX *ctx; BIGNUM mod, exp, x, y; uint8 inr[SEC_MODULUS_SIZE]; int outlen; @@ -299,7 +301,7 @@ memcpy(inr, in, len); reverse(inr, len); - BN_CTX_init(&ctx); + ctx = BN_CTX_new(); BN_init(&mod); BN_init(&exp); BN_init(&x); @@ -308,17 +310,17 @@ BN_bin2bn(modulus, SEC_MODULUS_SIZE, &mod); BN_bin2bn(exponent, SEC_EXPONENT_SIZE, &exp); BN_bin2bn(inr, len, &x); - BN_mod_exp(&y, &x, &exp, &mod, &ctx); + BN_mod_exp(&y, &x, &exp, &mod, ctx); outlen = BN_bn2bin(&y, out); reverse(out, outlen); if (outlen < SEC_MODULUS_SIZE) - memset(out+outlen, 0, SEC_MODULUS_SIZE-outlen); + memset(out + outlen, 0, SEC_MODULUS_SIZE - outlen); BN_free(&y); BN_clear_free(&x); BN_free(&exp); BN_free(&mod); - BN_CTX_free(&ctx); + BN_CTX_free(ctx); } /* Initialise secure transport packet */ @@ -328,7 +330,7 @@ int hdrlen; STREAM s; - if (!licence_issued) + if (!g_licence_issued) hdrlen = (flags & SEC_ENCRYPT) ? 12 : 4; else hdrlen = (flags & SEC_ENCRYPT) ? 12 : 0; @@ -345,7 +347,7 @@ int datalen; s_pop_layer(s, sec_hdr); - if (!licence_issued || (flags & SEC_ENCRYPT)) + if (!g_licence_issued || (flags & SEC_ENCRYPT)) out_uint32_le(s, flags); if (flags & SEC_ENCRYPT) @@ -358,7 +360,7 @@ hexdump(s->p + 8, datalen); #endif - sec_sign(s->p, sec_sign_key, 8, s->p + 8, datalen); + sec_sign(s->p, 8, sec_sign_key, rc4_key_len, s->p + 8, datalen); sec_encrypt(s->p + 8, datalen); } @@ -367,7 +369,7 @@ /* Transfer the client random to the server */ static void -sec_establish_key() +sec_establish_key(void) { uint32 length = SEC_MODULUS_SIZE + SEC_PADDING_SIZE; uint32 flags = SEC_CLIENT_RANDOM; @@ -388,13 +390,17 @@ sec_out_mcs_data(STREAM s) { int hostlen = 2 * strlen(hostname); + int length = 158 + 76 + 12 + 4 + 20; + + if (hostlen > 30) + hostlen = 30; out_uint16_be(s, 5); /* unknown */ out_uint16_be(s, 0x14); out_uint8(s, 0x7c); out_uint16_be(s, 1); - out_uint16_be(s, (158 | 0x8000)); /* remaining length */ + out_uint16_be(s, (length | 0x8000)); /* remaining length */ out_uint16_be(s, 8); /* length? */ out_uint16_be(s, 16); @@ -403,19 +409,19 @@ out_uint8(s, 0); out_uint32_le(s, 0x61637544); /* "Duca" ?! */ - out_uint16_be(s, (144 | 0x8000)); /* remaining length */ + out_uint16_be(s, ((length - 14) | 0x8000)); /* remaining length */ /* Client information */ out_uint16_le(s, SEC_TAG_CLI_INFO); - out_uint16_le(s, 136); /* length */ - out_uint16_le(s, 1); + out_uint16_le(s, 212); /* length */ + out_uint16_le(s, use_rdp5 ? 4 : 1); /* RDP version. 1 == RDP4, 4 == RDP5. */ out_uint16_le(s, 8); out_uint16_le(s, width); out_uint16_le(s, height); out_uint16_le(s, 0xca01); out_uint16_le(s, 0xaa03); out_uint32_le(s, keylayout); - out_uint32_le(s, 419); /* client build? we are 419 compatible :-) */ + out_uint32_le(s, 2600); /* Client build. We are now 2600 compatible :-) */ /* Unicode name of client, padded to 32 bytes */ rdp_out_unistr(s, hostname, hostlen); @@ -426,19 +432,54 @@ out_uint32_le(s, 12); out_uint8s(s, 64); /* reserved? 4 + 12 doublewords */ - out_uint16(s, 0xca01); - out_uint16(s, 0); + switch (server_bpp) + { + case 8: + out_uint16_le(s, 0xca01); + break; + case 15: + out_uint16_le(s, 0xca02); + break; + case 16: + out_uint16_le(s, 0xca03); + break; + case 24: + out_uint16_le(s, 0xca04); + break; + } + out_uint16_le(s, 1); + + out_uint32(s, 0); + out_uint8(s, server_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(s, 0); /* Client encryption settings */ out_uint16_le(s, SEC_TAG_CLI_CRYPT); - out_uint16(s, 8); /* length */ - out_uint32_le(s, encryption ? 1 : 0); /* encryption enabled */ + out_uint16_le(s, 12); /* length */ + out_uint32_le(s, encryption ? 0x3 : 0); /* encryption supported, 128-bit supported */ + out_uint32(s, 0); /* Unknown */ + + out_uint16_le(s, SEC_TAG_CLI_CHANNELS); + out_uint16_le(s, 20); /* length */ + out_uint32_le(s, 1); /* number of virtual channels */ + out_uint8p(s, "cliprdr", 8); /* name padded to 8(?) */ + out_uint16(s, 0); + out_uint16_le(s, 0xc0a0); /* Flags. Rumours tell this is documented in MSDN. */ + s_mark_end(s); } /* Parse a public key structure */ static BOOL -sec_parse_public_key(STREAM s, uint8 **modulus, uint8 **exponent) +sec_parse_public_key(STREAM s, uint8 ** modulus, uint8 ** exponent) { uint32 magic, modulus_len; @@ -464,23 +505,54 @@ 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")); + 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 = (RSA *) epk->pkey.ptr; + + 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) +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\n", random_len); + error("random len %d, expected %d\n", random_len, SEC_RANDOM_SIZE); return False; } @@ -491,36 +563,97 @@ if (end > s->end) return False; - in_uint8s(s, 12); /* unknown */ + 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; - while (s->p < end) + 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 { - in_uint16_le(s, tag); - in_uint16_le(s, length); + DEBUG_RDP5(("We're going for the RDP5-style encryption\n")); + in_uint8s(s, 4); /* Number of certificates */ - next_tag = s->p + length; + /* Do da funky X.509 stuffy - switch (tag) + "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); + 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) { - case SEC_TAG_PUBKEY: - if (!sec_parse_public_key - (s, modulus, exponent)) - return False; + error("Couldn't load CA Certificate from server\n"); + return False; + } - break; + /* 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. + */ + + in_uint32_le(s, 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; + } - case SEC_TAG_KEYSIG: - /* Is this a Microsoft key that we just got? */ - /* Care factor: zero! */ - break; + in_uint8s(s, 16); /* Padding */ - default: - unimpl("crypt tag 0x%x\n", tag); - } + /* 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 */ - s->p = next_tag; + if (!sec_parse_x509_key(server_cert)) + { + DEBUG_RDP5(("Didn't parse X509 correctly\n")); + return False; + } + return True; /* There's some garbage here we don't care about */ } - return s_check_end(s); } @@ -531,26 +664,69 @@ uint8 *server_random, *modulus, *exponent; uint8 client_random[SEC_RANDOM_SIZE]; uint32 rc4_key_size; + uint8 inr[SEC_MODULUS_SIZE]; - if (!sec_parse_crypt_info(s, &rc4_key_size, &server_random, - &modulus, &exponent)) + 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")); + // This is what the MS client do: + memset(inr, 0, SEC_RANDOM_SIZE); + /* *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! + */ - /* Generate a client random, and hence determine encryption keys */ generate_random(client_random); - sec_rsa_encrypt(sec_crypted_random, client_random, - SEC_RANDOM_SIZE, modulus, exponent); + if (NULL != server_public_key) + { /* Which means we should use + RDP5-style encryption */ + + memcpy(inr + SEC_RANDOM_SIZE, client_random, SEC_RANDOM_SIZE); + reverse(inr + SEC_RANDOM_SIZE, SEC_RANDOM_SIZE); + + RSA_public_encrypt(SEC_MODULUS_SIZE, + inr, sec_crypted_random, server_public_key, RSA_NO_PADDING); + + reverse(sec_crypted_random, SEC_MODULUS_SIZE); + + } + else + { /* RDP4-style encryption */ + sec_rsa_encrypt(sec_crypted_random, + client_random, SEC_RANDOM_SIZE, modulus, exponent); + } sec_generate_keys(client_random, server_random, rc4_key_size); } -/* Process connect response data blob */ + +/* Process SRV_INFO, find RDP version supported by server */ static void +sec_process_srv_info(STREAM s) +{ + in_uint16_le(s, server_rdp_version); + DEBUG_RDP5(("Server RDP version is %d\n", server_rdp_version)); +} + + +/* Process connect response data blob */ +void sec_process_mcs_data(STREAM s) { uint16 tag, length; uint8 *next_tag; + uint8 len; - in_uint8s(s, 23); /* header */ + in_uint8s(s, 21); /* header (T.124 stuff, probably) */ + in_uint8(s, len); + if (len & 0x80) + in_uint8(s, len); while (s->p < s->end) { @@ -565,6 +741,9 @@ switch (tag) { case SEC_TAG_SRV_INFO: + sec_process_srv_info(s); + break; + case SEC_TAG_SRV_3: break; @@ -582,19 +761,23 @@ /* Receive secure transport packet */ STREAM -sec_recv() +sec_recv(void) { uint32 sec_flags; + uint16 channel; STREAM s; - while ((s = mcs_recv()) != NULL) + while ((s = mcs_recv(&channel)) != NULL) { - if (encryption || !licence_issued) + if (encryption || !g_licence_issued) { in_uint32_le(s, sec_flags); if (sec_flags & SEC_LICENCE_NEG) { + if (sec_flags & SEC_ENCRYPT) { + DEBUG_RDP5(("Encrypted license detected\n")); + } licence_process(s); continue; } @@ -606,7 +789,13 @@ } } - return s; + if (MCS_GLOBAL_CHANNEL == channel) + { + return s; + } + else + rdp5_process_channel(s, channel); + } return NULL; @@ -614,27 +803,28 @@ /* Establish a secure connection */ BOOL -sec_connect(char *server) +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 = xmalloc(mcs_data.size); + mcs_data.p = mcs_data.data = (uint8*)xmalloc(mcs_data.size); sec_out_mcs_data(&mcs_data); - if (!mcs_connect(server, &mcs_data)) + if (!mcs_connect(server, &mcs_data, username)) return False; - sec_process_mcs_data(&mcs_data); + // sec_process_mcs_data(&mcs_data); if (encryption) sec_establish_key(); + xfree(mcs_data.data); return True; } /* Disconnect a connection */ void -sec_disconnect() +sec_disconnect(void) { mcs_disconnect(); }