tls_proxy_smtp.c

tls_proxy_smtp.c

// SSL/TLS 中继 SMTP 流量,由于Gmail证书精准识别,因此只能出此下策.

#include "mbedtls/build_info.h"
#include "mbedtls/platform.h"

#include <stdlib.h>
#include <string.h>

#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/x509.h"
#include "mbedtls/ssl.h"
#include "mbedtls/net_sockets.h"
#include "mbedtls/error.h"
#include "mbedtls/debug.h"
#include "test/certs.h"

#if defined(MBEDTLS_SSL_CACHE_C)
#include "mbedtls/ssl_cache.h"
#endif

#define DEBUG_LEVEL 0

// 没办法,为了和其他交互.
static mbedtls_ssl_context ssl_client;

static void debug( void *ctx, int level,
                      const char *file, int line,
                      const char *str )
{
    ((void) level);

    mbedtls_fprintf( (FILE *) ctx, "%s:%04d: %s", file, line, str );
    fflush(  (FILE *) ctx  );
}


int ssl_relayclient( int init_or_exit )
{
    int ret = 1, len;
    int exit_code = MBEDTLS_EXIT_FAILURE;
    static mbedtls_net_context server_fd;
    uint32_t flags;
    unsigned char buf[1024];
    const char *pers = "ssl_client";

    static mbedtls_entropy_context entropy;
    static mbedtls_ctr_drbg_context ctr_drbg;
    static mbedtls_ssl_config conf;
    static mbedtls_x509_crt cacert;

    if(init_or_exit){

#if defined(MBEDTLS_DEBUG_C)
    mbedtls_debug_set_threshold( DEBUG_LEVEL );
#endif

    /*
     * 0. Initialize the RNG and the session data
     */
    mbedtls_net_init( &server_fd );
    mbedtls_ssl_init( &ssl_client );
    mbedtls_ssl_config_init( &conf );
    mbedtls_x509_crt_init( &cacert );
    mbedtls_ctr_drbg_init( &ctr_drbg );

    mbedtls_printf( "\n  . Seeding the random number generator..." );
    fflush( stdout );

    mbedtls_entropy_init( &entropy );
    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
                               (const unsigned char *) pers,
                               strlen( pers ) ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
        for(;;);
    }

    mbedtls_printf( " ok\n" );

    /*
     * 1. Initialize certificates (反正也不验证,随便Load一个测试证书.)
     */
    mbedtls_printf( "  . Loading the CA root certificate ..." );
    fflush( stdout );

    ret = mbedtls_x509_crt_parse( &cacert, (const unsigned char *) mbedtls_test_cas_pem,
                          mbedtls_test_cas_pem_len );
    if( ret < 0 )
    {
        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", (unsigned int) -ret );
         for(;;);
    }

    mbedtls_printf( " ok (%d skipped)\n", ret );

    /*
     * 2. Start the connection
     */
    mbedtls_printf( "  . Connecting to tcp/%s:%d...", "smtp.gmail.com", 465 );
    fflush( stdout );

    if( ( ret = mbedtls_net_connect( &server_fd, "smtp.gmail.com",
                                         "465", MBEDTLS_NET_PROTO_TCP ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_net_connect returned %d\n\n", ret );
         for(;;);
    }

    mbedtls_printf( " ok\n" );

    /*
     * 3. Setup stuff
     */
    mbedtls_printf( "  . Setting up the SSL/TLS structure..." );
    fflush( stdout );

    if( ( ret = mbedtls_ssl_config_defaults( &conf,
                    MBEDTLS_SSL_IS_CLIENT,
                    MBEDTLS_SSL_TRANSPORT_STREAM,
                    MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned %d\n\n", ret );
         for(;;);
    }

    mbedtls_printf( " ok\n" );

    /* OPTIONAL is not optimal for security,
     * but makes interop easier in this simplified example */
    mbedtls_ssl_conf_authmode( &conf, MBEDTLS_SSL_VERIFY_OPTIONAL );
    mbedtls_ssl_conf_ca_chain( &conf, &cacert, NULL );
    mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
    mbedtls_ssl_conf_dbg( &conf, debug, stdout );
    mbedtls_ssl_conf_read_timeout( &conf, 1000 );

    if( ( ret = mbedtls_ssl_setup( &ssl_client, &conf ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned %d\n\n", ret );
         for(;;);
    }

    if( ( ret = mbedtls_ssl_set_hostname( &ssl_client, "smtp.gmail.com" ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ssl_set_hostname returned %d\n\n", ret );
         for(;;);
    }

    mbedtls_ssl_set_bio( &ssl_client, &server_fd, mbedtls_net_send, mbedtls_net_recv, mbedtls_net_recv_timeout );

    /*
     * 4. Handshake
     */
    mbedtls_printf( "  . Performing the SSL/TLS handshake..." );
    fflush( stdout );

    while( ( ret = mbedtls_ssl_handshake( &ssl_client ) ) != 0 )
    {
        if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE )
        {
            mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", (unsigned int) -ret );
             for(;;);
        }
    }

    mbedtls_printf( " ok\n" );
}else{

    mbedtls_net_free( &server_fd );

    mbedtls_x509_crt_free( &cacert );
    mbedtls_ssl_free( &ssl_client );
    mbedtls_ssl_config_free( &conf );
    mbedtls_ctr_drbg_free( &ctr_drbg );
    mbedtls_entropy_free( &entropy );
}
}


int main( void )
{
    int ret, len;
    mbedtls_net_context listen_fd, client_fd;
    unsigned char buf[1024];
    const char *pers = "ssl_server";

    mbedtls_entropy_context entropy;
    mbedtls_ctr_drbg_context ctr_drbg;
    mbedtls_ssl_context ssl;
    mbedtls_ssl_config conf;
    mbedtls_x509_crt srvcert;
    mbedtls_pk_context pkey;
#if defined(MBEDTLS_SSL_CACHE_C)
    mbedtls_ssl_cache_context cache;
#endif

    mbedtls_net_init( &listen_fd );
    mbedtls_net_init( &client_fd );
    mbedtls_ssl_init( &ssl );
    mbedtls_ssl_config_init( &conf );
#if defined(MBEDTLS_SSL_CACHE_C)
    mbedtls_ssl_cache_init( &cache );
#endif
    mbedtls_x509_crt_init( &srvcert );
    mbedtls_pk_init( &pkey );
    mbedtls_entropy_init( &entropy );
    mbedtls_ctr_drbg_init( &ctr_drbg );

#if defined(MBEDTLS_DEBUG_C)
    mbedtls_debug_set_threshold( DEBUG_LEVEL );
#endif

    /*
     * 1. Seed the RNG
     */
    mbedtls_printf( "  . Seeding the random number generator..." );
    fflush( stdout );

    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
                               (const unsigned char *) pers,
                               strlen( pers ) ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
         for(;;);
    }

    mbedtls_printf( " ok\n" );

    /*
     * 2. Load the certificates and private RSA key
     */
    mbedtls_printf( "\n  . Loading the server cert. and key..." );
    fflush( stdout );

    /*
     * This demonstration program uses embedded test certificates.
     * Instead, you may want to use mbedtls_x509_crt_parse_file() to read the
     * server and CA certificates, as well as mbedtls_pk_parse_keyfile().
     */
    ret = mbedtls_x509_crt_parse_file( &srvcert,  "/etc/letsencrypt/live/lax-01.taterli.cyou/fullchain.pem" );
    if( ret != 0 )
    {
        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned %d\n\n", ret );
         for(;;);  
    }

    ret = mbedtls_x509_crt_parse_file( &srvcert, "/etc/letsencrypt/live/lax-01.taterli.cyou/fullchain.pem" );
    if( ret != 0 )
    {
        mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned %d\n\n", ret );
         for(;;);
    }

    ret =  mbedtls_pk_parse_keyfile( &pkey, "/etc/letsencrypt/live/lax-01.taterli.cyou/privkey.pem", NULL,mbedtls_ctr_drbg_random, &ctr_drbg);
    if( ret != 0 )
    {
        mbedtls_printf( " failed\n  !  mbedtls_pk_parse_key returned %d\n\n", ret );
         for(;;);
    }

    mbedtls_printf( " ok\n" );

    /*
     * 3. Setup the listening TCP socket
     */
    mbedtls_printf( "  . Bind on https://0.0.0.0:465/ ..." );
    fflush( stdout );

    if( ( ret = mbedtls_net_bind( &listen_fd, NULL, "465", MBEDTLS_NET_PROTO_TCP ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_net_bind returned %d\n\n", ret );
         for(;;);
    }

    mbedtls_printf( " ok\n" );

    /*
     * 4. Setup stuff
     */
    mbedtls_printf( "  . Setting up the SSL data...." );
    fflush( stdout );

    if( ( ret = mbedtls_ssl_config_defaults( &conf,
                    MBEDTLS_SSL_IS_SERVER,
                    MBEDTLS_SSL_TRANSPORT_STREAM,
                    MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned %d\n\n", ret );
         for(;;);
    }

    mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
    mbedtls_ssl_conf_dbg( &conf, debug, stdout );

#if defined(MBEDTLS_SSL_CACHE_C)
    mbedtls_ssl_conf_session_cache( &conf, &cache,
                                   mbedtls_ssl_cache_get,
                                   mbedtls_ssl_cache_set );
#endif

    mbedtls_ssl_conf_ca_chain( &conf, srvcert.next, NULL );
    if( ( ret = mbedtls_ssl_conf_own_cert( &conf, &srvcert, &pkey ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ssl_conf_own_cert returned %d\n\n", ret );
         for(;;);
    }

    if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned %d\n\n", ret );
         for(;;);
    }

    mbedtls_printf( " ok\n" );

reset:
#ifdef MBEDTLS_ERROR_C
    if( ret != 0 )
    {
        char error_buf[100];
        mbedtls_strerror( ret, error_buf, 100 );
        mbedtls_printf("Last error was: %d - %s\n\n", ret, error_buf );
    }
#endif

    mbedtls_net_free( &client_fd );

    mbedtls_ssl_session_reset( &ssl );

    /*
     * 3. Wait until a client connects
     */
    mbedtls_printf( "  . Waiting for a remote connection ..." );
    fflush( stdout );

    if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
                                    NULL, 0, NULL ) ) != 0 )
    {
        mbedtls_printf( " failed\n  ! mbedtls_net_accept returned %d\n\n", ret );
         for(;;);
    }

    mbedtls_ssl_set_bio( &ssl, &client_fd, mbedtls_net_send, mbedtls_net_recv, NULL );

    mbedtls_printf( " ok\n" );

    /*
     * 5. Handshake
     */
    mbedtls_printf( "  . Performing the SSL/TLS handshake..." );
    fflush( stdout );

    while( ( ret = mbedtls_ssl_handshake( &ssl ) ) != 0 )
    {
        if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE )
        {
            mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned %d\n\n", ret );
            goto reset;
        }
    }

    mbedtls_printf( " ok\n" );


// 这里开始建立到另一边的TCP SSL链接,并修改部分数据

    ssl_relayclient(1); // 初始化客户端

    do
    {
        // 第一圈,从远端的送到客户端
        len = sizeof( buf ) - 1;
        memset( buf, 0, sizeof( buf ) );
        ret = mbedtls_ssl_read( &ssl_client, buf, len ); /* 会从对面服务器获取数据 */

        if( ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY )
            break;

        if(ret > 0){
            // 假定成功(事实上要判断ret)
            len = ret;
            mbedtls_printf( " %d bytes read\n\n%s", len, (char *) buf );

            mbedtls_printf( "  > Write to client:" );
            fflush( stdout );

            // 这里针对地处理(比如替换GMIAL特征)
            
            while( ( ret = mbedtls_ssl_write( &ssl, buf, len ) ) <= 0 )
            {
                if( ret == MBEDTLS_ERR_NET_CONN_RESET )
                {
                    mbedtls_printf( " failed\n  ! peer closed the connection\n\n" );
                    goto reset;
                }

                if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE )
                {
                    mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned %d\n\n", ret );
                    for(;;);
                }
            }

            len = ret;
            mbedtls_printf( " %d bytes written\n\n%s\n", len, (char *) buf );
        }

        // 第二圈,从客户端的送到远端.
        len = sizeof( buf ) - 1;
        memset( buf, 0, sizeof( buf ) );
        ret = mbedtls_ssl_read( &ssl, buf, len ); /* 会从对面服务器获取数据 */

        // 假定成功(事实上要判断ret)

        if( ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY )
            break;

        len = ret;
        mbedtls_printf( " %d bytes read\n\n%s", ret, (char *) buf );

        mbedtls_printf( "  > Read from client:" );
        fflush( stdout );

        while( ( ret = mbedtls_ssl_write( &ssl_client, buf, len ) ) <= 0 )
        {
            if( ret == MBEDTLS_ERR_NET_CONN_RESET )
            {
                mbedtls_printf( " failed\n  ! peer closed the connection\n\n" );
                goto reset;
            }

            if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE )
            {
                mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned %d\n\n", ret );
                for(;;);
            }
        }

        len = ret;
        mbedtls_printf( " %d bytes read\n\n%s\n", len, (char *) buf );


    }
    while( 1 );
    mbedtls_printf( "  . Closing the connection..." );

    mbedtls_ssl_close_notify( &ssl_client );
    ssl_relayclient(0); // 取消客户端的初始化
    while( ( ret = mbedtls_ssl_close_notify( &ssl ) ) < 0 )
    {
        if( ret != MBEDTLS_ERR_SSL_WANT_READ &&
            ret != MBEDTLS_ERR_SSL_WANT_WRITE )
        {
            mbedtls_printf( " failed\n  ! mbedtls_ssl_close_notify returned %d\n\n", ret );
            goto reset;
        }
    }

    mbedtls_printf( " ok\n" );

    ret = 0;
    goto reset;

#ifdef MBEDTLS_ERROR_C
    if( ret != 0 )
    {
        char error_buf[100];
        mbedtls_strerror( ret, error_buf, 100 );
        mbedtls_printf("Last error was: %d - %s\n\n", ret, error_buf );
    }
#endif

    mbedtls_net_free( &client_fd );
    mbedtls_net_free( &listen_fd );

    mbedtls_x509_crt_free( &srvcert );
    mbedtls_pk_free( &pkey );
    mbedtls_ssl_free( &ssl );
    mbedtls_ssl_config_free( &conf );
#if defined(MBEDTLS_SSL_CACHE_C)
    mbedtls_ssl_cache_free( &cache );
#endif
    mbedtls_ctr_drbg_free( &ctr_drbg );
    mbedtls_entropy_free( &entropy );

    mbedtls_exit( ret );
}