--- sourceforge.net/trunk/rdesktop/secure.c 2003/01/28 11:36:02 295 +++ sourceforge.net/trunk/rdesktop/secure.c 2004/06/01 08:06:02 706 @@ -1,4 +1,4 @@ -/* +/* -*- c-basic-offset: 8 -*- rdesktop: A Remote Desktop Protocol client. Protocol services - RDP encryption and licensing Copyright (C) Matthew Chapman 1999-2002 @@ -25,6 +25,7 @@ #include #include #include +#include #else #include "crypto/rc4.h" #include "crypto/md5.h" @@ -33,15 +34,22 @@ #endif extern char hostname[16]; -extern int width; -extern int height; +extern int g_width; +extern int g_height; extern int keylayout; -extern BOOL encryption; -extern BOOL licence_issued; +extern BOOL g_encryption; +extern BOOL g_licence_issued; +extern BOOL g_use_rdp5; +extern BOOL g_console_session; +extern int g_server_bpp; +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 uint8 sec_sign_key[16]; static uint8 sec_decrypt_key[16]; @@ -50,9 +58,20 @@ static uint8 sec_encrypt_update_key[16]; static uint8 sec_crypted_random[SEC_MODULUS_SIZE]; +uint16 g_server_rdp_version = 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 + */ + /* - * General purpose 48-byte transformation, using two 32-byte salts (generally, - * a client and server salt) and a global salt value used for padding. + * 48-byte transformation used to generate master secret (6.1) and key material (6.2.2). * Both SHA1 and MD5 algorithms are used. */ void @@ -83,8 +102,7 @@ } /* - * Weaker 16-byte transformation, also using two 32-byte salts, but - * only using a single round of MD5. + * 16-byte transformation used to generate export keys (6.2.2). */ void sec_hash_16(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2) @@ -107,28 +125,28 @@ key[2] = 0x9e; } -/* Generate a session key and RC4 keys, given client and server randoms */ +/* Generate encryption 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_random, uint8 * server_random, int rc4_key_size) { - uint8 session_key[48]; - uint8 temp_hash[48]; - uint8 input[48]; - - /* Construct input data to hash */ - memcpy(input, client_key, 24); - memcpy(input + 24, server_key, 24); - - /* Generate session key - two rounds of sec_hash_48 */ - 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 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); + 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) { @@ -140,7 +158,7 @@ } 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; } @@ -177,7 +195,7 @@ buffer[3] = (value >> 24) & 0xff; } -/* Generate a signature hash, using a combination of SHA1 and MD5 */ +/* 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) { @@ -205,7 +223,7 @@ memcpy(signature, md5sig, siglen); } -/* Update an encryption key - similar to the signing process */ +/* Update an encryption key */ static void sec_update(uint8 * key, uint8 * update_key) { @@ -251,7 +269,7 @@ } /* Decrypt data using RC4 */ -static void +void sec_decrypt(uint8 * data, int length) { static int use_count; @@ -324,7 +342,7 @@ int hdrlen; STREAM s; - if (!licence_issued) + if (!g_licence_issued) hdrlen = (flags & SEC_ENCRYPT) ? 12 : 4; else hdrlen = (flags & SEC_ENCRYPT) ? 12 : 0; @@ -334,14 +352,14 @@ return s; } -/* Transmit secure transport packet */ +/* Transmit secure transport packet over specified channel */ void -sec_send(STREAM s, uint32 flags) +sec_send_to_channel(STREAM s, uint32 flags, uint16 channel) { 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) @@ -358,9 +376,18 @@ sec_encrypt(s->p + 8, datalen); } - mcs_send(s); + 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) @@ -384,16 +411,22 @@ sec_out_mcs_data(STREAM s) { int hostlen = 2 * strlen(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; - out_uint16_be(s, 5); /* unknown */ + /* 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, (158 | 0x8000)); /* remaining length */ + out_uint16_be(s, (length | 0x8000)); /* remaining length */ out_uint16_be(s, 8); /* length? */ out_uint16_be(s, 16); @@ -401,20 +434,20 @@ out_uint16_le(s, 0xc001); out_uint8(s, 0); - out_uint32_le(s, 0x61637544); /* "Duca" ?! */ - out_uint16_be(s, (144 | 0x8000)); /* remaining length */ + 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, 136); /* length */ - out_uint16_le(s, 1); + 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, width); - out_uint16_le(s, height); + 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, 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); @@ -424,14 +457,41 @@ out_uint32(s, 0); out_uint32_le(s, 12); out_uint8s(s, 64); /* reserved? 4 + 12 doublewords */ + out_uint16_le(s, 0xca01); /* colour depth? */ + out_uint16_le(s, 1); - out_uint16_le(s, 0xca01); - out_uint16(s, 0); + out_uint32(s, 0); + out_uint8(s, g_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, g_console_session ? 0xb : 9); + out_uint32(s, 0); /* Client encryption settings */ out_uint16_le(s, SEC_TAG_CLI_CRYPT); - out_uint16_le(s, 8); /* length */ - out_uint32_le(s, encryption ? 0x3 : 0); /* encryption supported, 128-bit supported */ + 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); } @@ -463,25 +523,54 @@ 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) { 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 encryptation */ + 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; } @@ -492,35 +581,129 @@ 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); + uint32 certcount; - next_tag = s->p + length; + DEBUG_RDP5(("We're going for the RDP5-style encryption\n")); + in_uint32_le(s, certcount); /* Number of certificates */ - switch (tag) + if (certcount < 2) { - case SEC_TAG_PUBKEY: - if (!sec_parse_public_key(s, modulus, exponent)) - return False; + error("Server didn't send enough X509 certificates\n"); + return False; + } - break; + 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")); + } - case SEC_TAG_KEYSIG: - /* Is this a Microsoft key that we just got? */ - /* Care factor: zero! */ - break; +#ifdef WITH_DEBUG_RDP5 + DEBUG_RDP5(("cert #%d (ignored):\n", certcount)); + X509_print_fp(stdout, ignorecert); +#endif + } - default: - unimpl("crypt tag 0x%x\n", tag); + /* 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; } - s->p = next_tag; - } + /* 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); + 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")); + return False; + } + return True; /* There's some garbage here we don't care about */ + } return s_check_end(s); } @@ -531,25 +714,72 @@ 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)) + { + DEBUG(("Failed to parse crypt info\n")); return; + } + DEBUG(("Generating client random\n")); /* Generate a client random, and hence determine encryption keys */ + /* 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_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, 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_bpp = 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 */ + in_uint8s(s, 21); /* header (T.124 ConferenceCreateResponse) */ in_uint8(s, len); if (len & 0x80) in_uint8(s, len); @@ -567,13 +797,19 @@ switch (tag) { case SEC_TAG_SRV_INFO: - case SEC_TAG_SRV_3: + 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); } @@ -587,25 +823,32 @@ 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 (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 & SEC_ENCRYPT) - { - in_uint8s(s, 8); /* signature */ - sec_decrypt(s->p, s->end - s->p); - } + if (channel != MCS_GLOBAL_CHANNEL) + { + channel_process(s, channel); + continue; } return s; @@ -616,20 +859,20 @@ /* 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); - if (encryption) + /* sec_process_mcs_data(&mcs_data); */ + if (g_encryption) sec_establish_key(); xfree(mcs_data.data); return True;