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libsstp.c
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/*
* SSToPer, Linux SSTP Client
* Christophe Alladoum < christophe __DOT__ alladoum __AT__ hsc __DOT__ fr>
* Herve Schauer Consultants (http://www.hsc.fr)
*
* GNU GENERAL PUBLIC LICENSE
* Version 2, June 1991
*
* 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 St, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#define _GNU_SOURCE 1
#define _POSIX_SOURCE 1
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <arpa/inet.h>
#include <sys/select.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <openssl/sha.h>
#include <openssl/md4.h>
#include <openssl/hmac.h>
#include <openssl/md4.h>
#ifdef HAS_GNUTLS
#include <gnutls/x509.h>
#include <gnutls/gnutls.h>
#else
#include <mbedtls/net.h>
#include <mbedtls/debug.h>
#include <mbedtls/ssl.h>
#include <mbedtls/entropy.h>
#include <mbedtls/ctr_drbg.h>
#include <mbedtls/error.h>
#include <mbedtls/certs.h>
#include "pem2der.h"
#endif
#include "libsstp.h"
#include "main.h"
#if defined __linux__
#include <pty.h>
#endif
/**
* SSTP I/O primitive for reading
*
* @param buf : buffer to read
* @param buflen : number of bytes to read
* @return size read if >0 or error if <0
*/
static ssize_t sstp_read(unsigned char *buf, size_t buflen)
{
ssize_t rbytes;
#ifdef HAS_GNUTLS
rbytes = gnutls_record_recv(tls, buf, buflen);
if (rbytes < 0)
xlog(LOG_ERROR, "sstp_read: %s\n", gnutls_strerror(rbytes));
#else
int do_loop = 1;
char msg[512] = {0,};
do {
rbytes = mbedtls_ssl_read(&tls, buf, buflen);
if (rbytes < 0)
{
mbedtls_strerror(rbytes, msg, sizeof(msg)-1);
xlog(LOG_ERROR, "sstp_read() failed: %d - %s\n", rbytes, msg);
return -1;
}
switch(rbytes)
{
case MBEDTLS_ERR_SSL_WANT_READ:
case MBEDTLS_ERR_SSL_WANT_WRITE:
continue;
case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
case 0:
do_loop = 0;
break;
default:
do_loop = 0;
break;
}
} while( do_loop );
#endif
if (cfg->verbose)
xlog(LOG_INFO, " <-- %lu bytes\n", rbytes);
return rbytes;
}
/**
* SSTP I/O primitive for writing
*
* @param buf : buffer to write
* @param buflen : number of bytes to write
* @return size written if >0 or error if <0
*/
static ssize_t sstp_write(unsigned char *buf, size_t buflen)
{
ssize_t sbytes;
#ifdef HAS_GNUTLS
sbytes = gnutls_record_send(tls, buf, buflen);
if (sbytes < 0){
xlog(LOG_ERROR, "sstp_write: %s\n", gnutls_strerror(sbytes));
return -1;
}
#else
char msg[512] = {0,};
sbytes = mbedtls_ssl_write(&tls, buf, buflen);
if (sbytes < 0)
{
if(sbytes != MBEDTLS_ERR_SSL_WANT_READ && sbytes != MBEDTLS_ERR_SSL_WANT_WRITE )
{
mbedtls_strerror(sbytes, msg, sizeof(msg)-1);
xlog(LOG_ERROR, "sstp_write() failed: %x: %s\n", sbytes, msg);
return -1;
}
}
#endif
if (cfg->verbose)
xlog(LOG_INFO, " --> %lu bytes\n", sbytes);
return sbytes;
}
/**
* Encapsulated data provided as argument inside a SSTP packet. SSTP packet type
* (control|data) should be specified throught `type` argument.
*
* @param type : set packet type (Control or Data)
* @param data : buffer to be sent
* @param data_length : `data` length
*/
void send_sstp_packet(uint8_t type, void* data, size_t data_length)
{
sstp_header_t sstp_header;
size_t total_length;
void *packet = NULL;
total_length = sizeof(sstp_header_t) + data_length;
memset(&sstp_header, 0, sizeof(sstp_header_t));
sstp_header.version = SSTP_VERSION;
sstp_header.reserved = type;
sstp_header.length = htons(total_length);
packet = xmalloc(total_length);
memcpy(packet, &sstp_header, sizeof(sstp_header_t));
memcpy(packet + sizeof(sstp_header_t), data, data_length);
sstp_write(packet, total_length);
xfree(packet);
}
/**
* Generic function to send an SSTP Data packet. Data to send is encapsulated
* inside an SSTP packet, and transmitted througth TLS session.
* As this function intercepts PPP packets, it is also used to detect PPP
* negociation success, and stores NT Response code inside client chap_ctx.
*
* @param data : buffer to be sent
* @param len : `data` length
*/
void send_sstp_data_packet(void* data, size_t len)
{
if ( ntohs(*((uint16_t*)data)) == 0xc223 )
{
uint8_t chap_handshake_code = *(uint8_t*)(data + 2);
/* if msg is PPP-CHAP response */
if (chap_handshake_code == 0x02 )
{
memcpy(chap_ctx, data+7, 49);
}
}
send_sstp_packet(SSTP_DATA_PACKET, data, len);
}
/**
* Generic function to send an SSTP control packet. As a control packet embeds one
* or many attributes, they also should be specified.
*
* @param msg_type : SSTP control message type
* @param attributes : pointer to the attributes buffer
* @param attribute_number : number of attributes inside buffer
* @param attributes_len : `attributes` length
*/
void send_sstp_control_packet(uint16_t msg_type, void* attributes,
uint16_t attribute_number, size_t attributes_len)
{
sstp_control_header_t control_header;
size_t control_length;
uint16_t i;
void *data, *data_ptr, *attr_ptr;
if (!attributes && attribute_number)
{
xlog(LOG_ERROR, "No attribute specified. Cannot send message.\n");
return;
}
control_length = sizeof(sstp_control_header_t) + attributes_len;
memset(&control_header, 0, sizeof(sstp_control_header_t));
/* setting control header */
control_header.message_type = htons(msg_type);
control_header.num_attributes = htons(attribute_number);
if (cfg->verbose > 2)
{
xlog(LOG_DEBUG, "\t-> Control packet\n");
xlog(LOG_DEBUG, "\t-> type: %s (%#.2x)\n",
control_messages_types_str[msg_type], msg_type);
xlog(LOG_DEBUG, "\t-> attribute number: %d\n", attribute_number);
xlog(LOG_DEBUG, "\t-> length: %d\n", control_length);
}
/* filling control with attributes */
data = xmalloc(control_length);
memcpy(data, &control_header, sizeof(sstp_control_header_t));
attr_ptr = attributes;
data_ptr = data + sizeof(sstp_control_header_t);
for (i=0; i<attribute_number; i++)
{
sstp_attribute_header_t* cur_attr = (sstp_attribute_header_t*)attr_ptr;
uint16_t plen = ntohs(cur_attr->packet_length);
if (cfg->verbose > 2)
{
xlog(LOG_DEBUG, "\t\t--> Attribute %d\n", i);
xlog(LOG_DEBUG, "\t\t--> type: %s (%x)\n",
attr_types_str[cur_attr->attribute_id], cur_attr->attribute_id);
xlog(LOG_DEBUG, "\t\t--> length: %d\n", plen);
}
memcpy(data_ptr, attr_ptr, plen);
attr_ptr += plen;
data_ptr += plen;
}
/* yield to lower */
send_sstp_packet(SSTP_CONTROL_PACKET, data, control_length);
xfree(data);
}
/**
* Generate an GUID identifier for the SSTP connection
*
* @param data : buffer to store guid
*/
static void generate_guid(char data[])
{
uint32_t data1, data4;
uint16_t data2, data3;
struct timeval tv;
unsigned int seed;
gettimeofday(&tv, NULL);
seed = tv.tv_usec * tv.tv_sec;
seed ^= getpid();
memset(data, 0, 39);
srand (seed);
data1 = (rand() + 1) * (sizeof(uint32_t) * 8);
data2 = (rand() + 1) * (sizeof(uint16_t) * 8);
data3 = (rand() + 1) * (sizeof(uint16_t) * 8);
data4 = (rand() + 1) * (sizeof(uint32_t) * 8);
snprintf(data, 38, "{%.4X-%.2X-%.2X-%.4X}", data1, data2, data3, data4);
if (cfg->verbose > 2)
xlog(LOG_DEBUG, "Using GUID %s\n", data);
}
/**
* Change client state
*
* @param status : new status
*/
void set_client_status(uint8_t status)
{
if (ctx->state == status)
return;
if (cfg->verbose)
xlog(LOG_INFO, "status: %s (%#x) -> %s (%#x)\n",
client_status_str[ctx->state], ctx->state,
client_status_str[status], status);
ctx->state = status;
}
/**
* Header validation.
*
* @param header : sstp header to analyse
* @param recv_len : number of bytes received
* @return TRUE if valid, FALSE otherwise
*/
static int is_valid_header(sstp_header_t* header, ssize_t recv_len)
{
if (header->version != SSTP_VERSION)
{
if (cfg->verbose)
xlog(LOG_ERROR, "Invalid version (%#x)\n", header->version);
return FALSE;
}
if (header->reserved != SSTP_DATA_PACKET &&
header->reserved != SSTP_CONTROL_PACKET)
{
if (cfg->verbose)
xlog(LOG_ERROR, "Invalid packet type (%#x)\n", header->reserved);
return FALSE;
}
header->length = ntohs(header->length);
if (header->length > recv_len)
{
if ( header->reserved == SSTP_CONTROL_PACKET)
{
if (cfg->verbose > 2)
xlog(LOG_DEBUG, "Unmatching length: annonced %lu, received %lu\n",
header->length, recv_len);
return FALSE;
}
}
return TRUE;
}
/**
* Check whether received packet has Control flag raised.
*
* @param packet_header : received SSTP header
* @return TRUE if valid, FALSE otherwise
*/
static int is_control_packet(sstp_header_t* packet_header)
{
return (packet_header->reserved == SSTP_CONTROL_PACKET);
}
/**
* Send HTTP request to start a new SSTP connection.
*
* @return 0 if all good, negative value otherwise
*/
int https_session_negociation()
{
ssize_t rbytes;
unsigned char buf[1024] = {0, };
char guid[39] = {0, };
rbytes = -1;
/* Allocate SSTP session */
sess = (sstp_session_t*) xmalloc(sizeof(sstp_session_t));
generate_guid(guid);
rbytes = snprintf((char *)buf, 1024,
"SSTP_DUPLEX_POST %s HTTP/1.1\r\n"
"Host: %s\r\n"
"SSTPCORRELATIONID: %s\r\n"
"Content-Length: %llu\r\n"
"\r\n",
SSTP_HTTPS_RESOURCE,
cfg->server,
guid,
__UNSIGNED_LONG_LONG_MAX__);
if (cfg->verbose > 2)
xlog(LOG_DEBUG, "Sending: %lu bytes\n%s\n", rbytes, buf);
/* Start negociation */
if (sstp_write(buf, rbytes) < 0)
{
xlog(LOG_ERROR, "%s", "Failed to send the SSTP_DUPLEX_POST request\n");
return -1;
}
memset(buf, 0, 1024);
rbytes = sstp_read(buf, 1024);
if (rbytes < 0)
{
xlog(LOG_ERROR, "%s", "Failed to receive the SSTP_DUPLEX_POST response\n");
return -1;
}
if (rbytes == 0)
{
xlog(LOG_INFO, "Unexpected close notification from %s.\n", cfg->server);
return -1;
}
if (cfg->verbose)
{
if (cfg->verbose > 1)
xlog(LOG_DEBUG , "Received: %s\n", buf);
}
sess->rx_bytes += rbytes;
if (cfg->verbose > 2)
xlog(LOG_DEBUG, "Received: %lu bytes\n%s\n", rbytes, buf);
if (memcmp(buf, "HTTP/1.1 200", 12) && memcmp(buf, "HTTP/1.0 200", 12))
{
xlog(LOG_ERROR, "Incorrect HTTP response header\n");
if (cfg->verbose > 2)
{
buf[sizeof(buf)-1] = '\0';
xlog(LOG_DEBUG, "%s\n", buf);
}
return -1;
}
return 0;
}
/**
* Allocates and fills an attribute with specified data.
*
* @param attribute_id : attribute code
* @param data : data to be inserted
* @param data_length : `data` length
* @return a pointer to the new attribute buffer
*/
void* create_attribute(uint8_t attribute_id, void* data, size_t data_length)
{
sstp_attribute_header_t attribute_header;
size_t attribute_length;
void* attribute;
if (!data) return NULL;
attribute_length = sizeof(sstp_attribute_header_t) + data_length;
attribute = xmalloc(attribute_length);
attribute_header.reserved = 0;
attribute_header.attribute_id = attribute_id;
attribute_header.packet_length = htons(attribute_length);
memcpy(attribute, &attribute_header, sizeof(sstp_attribute_header_t));
memcpy(attribute + sizeof(sstp_attribute_header_t), data, data_length);
return attribute;
}
/**
* Emits SSTP negociation request, ie Control message with
* ENCAPSULATED_PROTOCOL_ID attribute. Negociation timer is set up and state is
* changed.
*/
static void sstp_init()
{
uint16_t attribute_data;
void* attribute;
size_t attribute_len;
attribute_data = htons(SSTP_ENCAPSULATED_PROTOCOL_PPP);
attribute_len = sizeof(sstp_attribute_header_t) + sizeof(uint16_t);
attribute = create_attribute(SSTP_ATTRIB_ENCAPSULATED_PROTOCOL_ID,
(void*)&attribute_data, sizeof(uint16_t));
send_sstp_control_packet(SSTP_MSG_CALL_CONNECT_REQUEST, attribute,
1, attribute_len);
xfree(attribute);
alarm(ctx->negociation_timer.tv_sec);
ctx->flags |= NEGOCIATION_TIMER_RAISED;
set_client_status(CLIENT_CONNECT_REQUEST_SENT);
}
/**
* Print attribute information.
*
* @param data
* @param attr_len
*/
int attribute_status_info(void* data, uint16_t attr_len)
{
sstp_attribute_status_info_t* info;
uint8_t attribute_id;
uint32_t status;
int rbytes;
info = (sstp_attribute_status_info_t*) data;
attribute_id = info->attrib_id;
status = ntohl(info->status);
/* check attribute */
if (attribute_id > ATTRIB_STATUS_STATUS_INFO_NOT_SUPPORTED_IN_MSG)
{
xlog(LOG_ERROR, "Attribute id is not valid.\n");
return -1;
}
if (cfg->verbose > 2)
{
/* show attribute */
xlog(LOG_DEBUG, "\t\t--> attr_ref\t%s (%#.2x)\n", attr_types_str[attribute_id], attribute_id);
xlog(LOG_DEBUG, "\t\t--> status\t%s (%#.2x)\n", attrib_status_str[status], status);
}
if (ctx->state != CLIENT_CONNECT_REQUEST_SENT)
return 0;
/* attrib_value is at most 64 bytes (ie full attr len <= 64 + 12 bytes) */
rbytes = sizeof(sstp_attribute_header_t) + 2*sizeof(uint32_t);
while (rbytes < (64+12) && rbytes < attr_len)
{
uint32_t attrib_value;
attrib_value = ntohl(*((uint32_t*)data + rbytes));
if (cfg->verbose > 2)
xlog(LOG_DEBUG, "\t\t--> attribute value: %#.4x\n", attrib_value);
rbytes += sizeof(uint32_t);
}
return 0;
}
/**
* The main loop will be called right after the end of HTTPS negociation and
* - allocates SSTP client context regions
* - start an SSTP negociation
* - handle receive packets
* - send packets
*/
void sstp_loop(pid_t pppd_pid)
{
fd_set rcv_fd;
int retcode;
uint16_t msg_type = 0;
gettimeofday(&sess->tv_start, NULL);
ctx = (sstp_context_t*) xmalloc(sizeof(sstp_context_t));
ctx->retry = SSTP_MAX_INIT_RETRY;
ctx->state = CLIENT_CALL_DISCONNECTED;
ctx->negociation_timer.tv_sec = SSTP_NEGOCIATION_TIMER;
ctx->hello_timer.tv_sec = SSTP_NEGOCIATION_TIMER;
ctx->pppd_pid = pppd_pid;
chap_ctx = (chap_context_t*) xmalloc(sizeof(chap_context_t));
/* start negociation */
sstp_init();
while(ctx->state != CLIENT_CALL_DISCONNECTED)
{
FD_ZERO(&rcv_fd);
if (ctx->pppd_pid > 0)
FD_SET(0, &rcv_fd);
FD_SET(sockfd, &rcv_fd);
retcode = select(sockfd + 1, &rcv_fd, NULL, NULL, NULL);
if ( retcode < 0 )
{
xlog(LOG_ERROR, "sstp_loop: %s\n", strerror(errno));
set_client_status(CLIENT_CALL_DISCONNECTED);
break;
}
if (ctx->pppd_pid > 0 && FD_ISSET(0, &rcv_fd))
{
unsigned char rbuffer[PPP_MAX_MRU];
ssize_t rbytes = -1;
memset(rbuffer, 0 , PPP_MAX_MRU);
rbytes = read(0, rbuffer, PPP_MAX_MRU);
if (rbytes > 0)
send_sstp_data_packet(rbuffer, rbytes);
}
if (FD_ISSET(sockfd, &rcv_fd))
{
unsigned char rbuffer[PPP_MAX_MRU];
ssize_t rbytes;
memset(rbuffer, 0 , PPP_MAX_MRU);
rbytes = sstp_read(rbuffer, PPP_MAX_MRU);
if (rbytes < 0)
retcode = rbytes;
else if (rbytes == 0)
{
if (cfg->verbose)
xlog(LOG_INFO, "sstp_loop: EOF\n");
}
else
{
if (cfg->verbose)
xlog(LOG_INFO,"<-- %lu bytes\n", rbytes);
sess->rx_bytes += rbytes;
retcode = sstp_decode(rbuffer, rbytes);
}
if (retcode < 0)
break;
}
}
if (ctx->pppd_pid > 0)
{
if (cfg->verbose)
xlog(LOG_INFO, "Waiting for %s process (PID:%d) to end\n",
cfg->pppd_path, ctx->pppd_pid);
kill(ctx->pppd_pid, SIGINT);
waitpid(ctx->pppd_pid, &retcode, 0);
if (retcode)
xlog(LOG_ERROR, "Failed to quit pppd, retcode %d\n", retcode);
}
msg_type = ctx->flags & REMOTE_DISCONNECTION ? SSTP_MSG_CALL_DISCONNECT_ACK : SSTP_MSG_CALL_DISCONNECT;
if (cfg->verbose)
xlog(LOG_INFO, "Sending %s message.\n", control_messages_types_str[msg_type]);
send_sstp_control_packet(msg_type, NULL, 0, 0);
gettimeofday(&sess->tv_end, NULL);
if (cfg->verbose)
{
unsigned int session_time = sess->tv_end.tv_sec - sess->tv_start.tv_sec;
xlog(LOG_INFO, "SSTP session duration: %lu sec\n", session_time);
xlog(LOG_INFO, "Sent %lu bytes (avg: %.2f B/s), received %lu bytes (avg: %.2f B/s)\n",
sess->rx_bytes,
(float)(sess->rx_bytes/session_time),
sess->tx_bytes,
(float)(sess->tx_bytes/session_time)
);
}
xfree(chap_ctx);
xfree(sess);
xfree(ctx);
}
/**
* This function is called by crypto_set_binding() and computes server certificate
* hash. Since certificate is provided as PEM format, it is first exported to DER
* binary format, hashed with context-defined algorithm, and stored inside client
* SSTP context.
*
* @return 0 if all good, negative value otherwise
*/
int crypto_set_certhash()
{
int val,i;
unsigned char dst[32] = {0, };
unsigned char* (*HASH)();
/* export certificate to DER format */
#ifdef HAS_GNUTLS
unsigned char buffer[8192] = {0, };
size_t buffer_len = sizeof(buffer);
val = gnutls_x509_crt_export (certificate, GNUTLS_X509_FMT_DER, buffer, &buffer_len);
if (val != GNUTLS_E_SUCCESS)
{
xlog(LOG_ERROR, "crypto_set_certhash: fail to export certificate\n");
if (val == GNUTLS_E_SHORT_MEMORY_BUFFER)
xlog(LOG_ERROR, "Missing memory (expected %d)\n", buffer_len);
return -1;
}
#else
unsigned char *ibuf;
unsigned char obuf[8192] = {0, };
size_t ibuflen, obuflen;
if(cfg->verbose > 1)
xlog(LOG_DEBUG, "[polarssl] converting '%s' PEM -> DER format\n", cfg->ca_file);
if (load_file(cfg->ca_file, (unsigned char **)&ibuf, &ibuflen) < 0)
{
xlog(LOG_ERROR, "Failed to load '%s': %d - %s\n", cfg->ca_file, errno, strerror(errno));
return -1;
}
if (convert_pem_to_der(ibuf, ibuflen, obuf, &obuflen) < 0)
{
xlog(LOG_ERROR, "Failed to convert '%s' to DER\n", cfg->ca_file);
xfree(ibuf);
return -1;
}
xfree(ibuf);
if(cfg->verbose > 2)
xlog(LOG_DEBUG, "Converted '%s' PEM=%d bytes -> DER=%d bytes\n", cfg->ca_file, ibuflen, obuflen);
#endif
/* select hash algorithm */
if (ctx->hash_algorithm == CERT_HASH_PROTOCOL_SHA256)
{
val = SHA256_HASH_LEN;
HASH = &SHA256;
}
else
{
val = SHA1_HASH_LEN;
HASH = &SHA1;
}
/* compute hash */
#ifdef HAS_GNUTLS
HASH(buffer, buffer_len, dst);
#else
HASH(obuf, obuflen, dst);
#endif
/* move hash to client context variable */
for(i=0; i<8; i++) ctx->certhash[i] = *(uint32_t*)(dst+(i*4));
return 0;
}
/**
* On receiving a binding request, this function is triggered to prepare
* cryptographic properties. It selects strongest negociated hash algorithm,
* stores Nonce into client SSTP context, invoke certhash(), and changes client
* state.
*
* @param data : pointer to crypto binding request packet
* @return 0 if all good, negative value otherwise
*/
int crypto_set_binding(void* data)
{
sstp_attribute_crypto_bind_req_t* req;
/* Validating client state */
if (ctx->state != CLIENT_CONNECT_REQUEST_SENT)
{
xlog(LOG_ERROR, "Incorrect message for this state\n");
if (cfg->verbose)
{
xlog(LOG_ERROR, "Current state: %#x. Expected %#x\n",
ctx->state, CLIENT_CONNECT_REQUEST_SENT);
}
return -1;
}
/* Disable negociation timer */
alarm(0);
ctx->flags &= ~NEGOCIATION_TIMER_RAISED;
/* Setting crypto properties */
req = (sstp_attribute_crypto_bind_req_t*) data;
/* Setting hash algorithm type (SHA1 or SHA256) */
switch(req->hash_bitmask)
{
case CERT_HASH_PROTOCOL_SHA256:
ctx->hash_algorithm = CERT_HASH_PROTOCOL_SHA256;
break;
case CERT_HASH_PROTOCOL_SHA1:
ctx->hash_algorithm = CERT_HASH_PROTOCOL_SHA1;
break;
default:
xlog(LOG_ERROR, "Unknown hash algorithm %#x\n", req->hash_bitmask);
return -1;
}
memcpy(ctx->nonce, req->nonce, sizeof(uint32_t) * 8);
/* compute ca file hash with chosen algorithm */
if (crypto_set_certhash() < 0)
return -1;
/* change client state */
set_client_status(CLIENT_CONNECT_ACK_RECEIVED);
return 0;
}
/**
* Defines Compound Mac value and store its value into SSTP client context.
*
* @return 0 on SUCCESS, < 0 on ERROR
*/
int crypto_set_cmac()
{
uint16_t hash_len;
unsigned char Call_Connected_buffer[112];
uint8_t hlak[32];
uint8_t *cmac, *cmk;
uint8_t msg[32];
uint8_t PasswordHash[MD4_DIGEST_LENGTH];
uint8_t PasswordHashHash[MD4_DIGEST_LENGTH];
uint8_t NT_Response[24];
uint8_t Master_Key[16];
uint8_t Master_Send_Key[16];
uint8_t Master_Receive_Key[16];
uint8_t* ptr = NULL;
unsigned char Call_Connected_header[16] =
{
0x10, 0x01, 0x00, 0x70, 0x00, 0x04, 0x00, 0x01,
0x00, 0x03, 0x00, 0x68, 0x00, 0x00, 0x00, 0x02
};
memset(hlak, 0, 32);
memset(PasswordHash, 0, MD4_DIGEST_LENGTH);
memset(PasswordHashHash, 0, MD4_DIGEST_LENGTH);
memset(NT_Response, 0, 24);
memset(Call_Connected_buffer, 0, 112);
/* Crypto super fun time */
/* Setting HLAK */
NtPasswordHash( PasswordHash, (const uint8_t *)cfg->password, strlen(cfg->password) );
HashNtPasswordHash( PasswordHashHash, PasswordHash );
memcpy( NT_Response, chap_ctx->response_nt_response, 24 );
GetMasterKey( Master_Key, PasswordHashHash, NT_Response );
GetAsymmetricStartKey( Master_Send_Key, Master_Key, 16, TRUE, TRUE );
GetAsymmetricStartKey( Master_Receive_Key, Master_Key, 16, FALSE, TRUE );
/*
* Specification bug:
* "For MS-CHAPv2, SSTP Client HLAK = MasterSendKey | MasterReceiveKey"
* whereas implementation SHOULD be done like
* For MS-CHAPv2, SSTP Client HLAK = MasterReceiveKey | MasterSendKey
*/
memcpy(hlak, Master_Receive_Key, 16*sizeof(uint8_t));
memcpy(hlak+16, Master_Send_Key, 16*sizeof(uint8_t));
/*
* Computing CMAC:
* CMac computation occurs in 2 times:
* T1 - CMK computation : CMK = HMAC-SHA(key= hlak, msg= SEED|LEN|0x01)
* T2 - CMac computation: CMac= HMAC-SHA(key= CMK, msg= SSTP_CALL_CONNECTED_MSG_ZEROED)
*
* Where SSTP_CALL_CONNECTED_MSG_ZEROED is SSTP_CALL_CONNECTED_MSG with CMAC field
* filled with 0 (zero)
*/
ptr = msg;
memcpy(ptr, SSTP_SEED_PREFIX, strlen(SSTP_SEED_PREFIX));
ptr += strlen(SSTP_SEED_PREFIX);
/* T1 */
/*
* To generate the Compound MAC Key (CMK), implementations MUST use the HLAK, MUST use the
* PRF+ seed value as the input to a PRF+ operation, and MUST generate 32 bytes.
*/
hash_len = (ctx->hash_algorithm==CERT_HASH_PROTOCOL_SHA1) ? SHA1_HASH_LEN : SHA256_HASH_LEN;
memcpy(ptr, &hash_len, sizeof(uint16_t)); ptr += sizeof(uint16_t);
*ptr = 0x01; ptr ++;
if ( (cmk = sstp_hmac(hlak, msg, 32)) == NULL)
return -1;
/* T2 */
/*
* "[...] the Compound MAC MUST be constructed from the entire 112 bytes of the Call Connected
* message(section 2.2.11) with the Compound MAC field and Padding field zeroed out."
*/
ptr = Call_Connected_buffer;
memcpy(ptr, Call_Connected_header, 16); ptr+= 16;
memcpy(ptr, ctx->nonce, 32); ptr += 32;
memcpy(ptr, ctx->certhash, 32); ptr += 32;
if ( !(cmac = sstp_hmac(cmk, Call_Connected_buffer, 112)) )
return -1;
memcpy(ctx->cmk, cmk, 32);
memcpy(ctx->cmac, cmac, 32);
xfree(cmk);
xfree(cmac);
/* Verbose output displays brief crypto information */
#ifdef DEBUG
if (cfg->verbose > 2)
{
int i=0;
char dbg_msg[MAX_LINE_LENGTH];
/* display hash algorithm */
xlog(LOG_DEBUG, "[Crypto debug] %-20s\t%s (%#2x)\n",
"Hash algorithm", crypto_req_attrs_str[ctx->hash_algorithm], ctx->hash_algorithm);
/* display nonce sent by server for authentication */
memset(dbg_msg, 0, MAX_LINE_LENGTH);
for (i=0; i<8; i++) snprintf(dbg_msg+(i*8), 9, "%8x", ntohl(ctx->nonce[i]));
xlog(LOG_DEBUG, "[Crypto debug] %-20s\t0x%s\n", "Nonce", dbg_msg);
/* display certificate hash */
memset(dbg_msg, 0, MAX_LINE_LENGTH);
for(i=0; i<8; i++) snprintf(dbg_msg+(i*8), 9, "%8x", ntohl(ctx->certhash[i]));
xlog(LOG_DEBUG, "[Crypto debug] %-20s\t0x%s\n", "CA Hash", dbg_msg);
/* display T1 message */
memset(dbg_msg, 0, MAX_LINE_LENGTH);
for (i=0; i<32; i++) snprintf(dbg_msg+i,3, "%2x", msg[i]);
xlog(LOG_DEBUG, "[Crypto debug] %-20s\t0x%s\n", "T1 msg", dbg_msg);
/* display user's password hashed with MD4 */
memset(dbg_msg, 0, MAX_LINE_LENGTH);
for (i=0; i<MD4_DIGEST_LENGTH; i++) snprintf(dbg_msg+i, 3, "%2x", PasswordHash[i]);
xlog(LOG_DEBUG, "[Crypto debug] %-20s\t0x%s\n", "H(Password)", dbg_msg);
/* display user's password hash hashed with MD4 */
memset(dbg_msg, 0, MAX_LINE_LENGTH);
for (i=0; i<MD4_DIGEST_LENGTH; i++) snprintf(dbg_msg+i, 3, "%2x", PasswordHashHash[i]);
xlog(LOG_DEBUG, "[Crypto debug] %-20s\t0x%s\n", "H(H(Password))", dbg_msg);
/* display NT Authentication Response code */