/*
 * vchat-client - alpha version
 * vchat-ssl.c - handling of SSL connection and X509 certificate
 * verification
 *
 * Copyright (C) 2007 Thorsten Schroeder <ths@berlin.ccc.de>
 *
 * This program is free software. It can be redistributed and/or modified,
 * provided that this copyright notice is kept intact. 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. In no event shall the copyright holder be liable for
 * any direct, indirect, incidental or special damages arising in any way out
 * of the use of this software. 
 *
 */

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

#include <openssl/err.h>
#include <openssl/ssl.h>
#include <openssl/bio.h>
#include <openssl/evp.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <openssl/conf.h>

#include "vchat.h"
#include "vchat-ssl.h"

char *vchat_ssl_version = "$Id$";

static int ignore_ssl;

#define VC_CTX_ERR_EXIT(se, cx) do { \
      snprintf(tmpstr, TMPSTRSIZE, "CREATE CTX: %s", \
            ERR_error_string (ERR_get_error (), NULL)); \
      writecf(FS_ERR, tmpstr); \
      if(se)  X509_STORE_free(se); \
      if(cx) SSL_CTX_free(cx); \
      return(0); \
   } while(0)

#define VC_SETCERT_ERR_EXIT(se, cx, err) do { \
      snprintf(tmpstr, TMPSTRSIZE, "CREATE CTX: %s", err); \
      writecf(FS_ERR, tmpstr); \
      if(se)  X509_STORE_free(se); \
      if(cx) SSL_CTX_free(cx); \
      return(NULL); \
   } while(0)

SSL_CTX * vc_create_sslctx( vc_x509store_t *vc_store )
{
   int                  i                 = 0;
   int                  n                 = 0;
   int                  flags             = 0;
   int                  r                 = 0;
   SSL_CTX              *ctx              = NULL;
   X509_STORE           *store            = NULL;
   vc_x509verify_cb_t   verify_callback   = NULL;

   if( !(ctx = SSL_CTX_new(SSLv3_method())) )
      VC_CTX_ERR_EXIT(store, ctx);

   if( !(store = vc_x509store_create(vc_store)) )
      VC_CTX_ERR_EXIT(store, ctx);

   SSL_CTX_set_cert_store(ctx, store);
   store = NULL;
   SSL_CTX_set_options(ctx, SSL_OP_ALL|SSL_OP_NO_SSLv2);
   SSL_CTX_set_cipher_list(ctx, "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH");

   SSL_CTX_set_verify_depth (ctx, 2);

   if( !(verify_callback = vc_store->callback) )
      verify_callback = vc_verify_callback;

   if( !(vc_store->flags & VC_X509S_SSL_VERIFY_MASK) ) {
      writecf(FS_DBG, tmpstr);
      flags = SSL_VERIFY_NONE;
   }
   else {
      if(vc_store->flags & VC_X509S_SSL_VERIFY_PEER)
         flags |= SSL_VERIFY_PEER;
      if(vc_store->flags & VC_X509S_SSL_VERIFY_FAIL_IF_NO_PEER_CERT)
         flags |= SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
      if(vc_store->flags & VC_X509S_SSL_VERIFY_CLIENT_ONCE)
         flags |= SSL_VERIFY_CLIENT_ONCE;
   }

   SSL_CTX_set_verify(ctx, flags, verify_callback);

   if(vc_store->flags & VC_X509S_USE_CERTIFICATE) {
      if(vc_store->use_certfile)
         SSL_CTX_use_certificate_chain_file(ctx, vc_store->use_certfile);
      else {
         SSL_CTX_use_certificate(ctx, 
               sk_X509_value(vc_store->use_certs, 0));
         for(i=0,n=sk_X509_num(vc_store->use_certs); i<n; i++)
            SSL_CTX_add_extra_chain_cert(ctx, 
                  sk_X509_value(vc_store->use_certs, i));
      }

      SSL_CTX_set_default_passwd_cb(ctx, vc_store->askpass_callback);

      if(vc_store->use_keyfile) {
         r=SSL_CTX_use_PrivateKey_file(ctx, vc_store->use_keyfile, 
               SSL_FILETYPE_PEM);
      } else if(vc_store->use_key)
            r=SSL_CTX_use_PrivateKey(ctx, vc_store->use_key);

      if(r!=1)
         VC_SETCERT_ERR_EXIT(store, ctx, "Load private key failed");

   }

   SSL_CTX_set_app_data(ctx, vc_store);
   return(ctx);
}

#define VC_CONNSSL_ERR_EXIT(_cx, cx, cn) do { \
      snprintf(tmpstr, TMPSTRSIZE, "[SSL ERROR] %s", \
            ERR_error_string (ERR_get_error (), NULL)); \
      writecf(FS_ERR, tmpstr); \
      if(cn)  BIO_free_all(cn); \
      if(*cx) SSL_CTX_free(*cx); \
      if(_cx) *cx = 0; \
      return(0); \
   } while(0)

BIO * vc_connect_ssl(char *host, int port, vc_x509store_t *vc_store,
      SSL_CTX **ctx)
{
   BIO *conn   = NULL;
   int _ctx    = 0;
   
   if(*ctx) {
      CRYPTO_add( &((*ctx)->references), 1, CRYPTO_LOCK_SSL_CTX );
      if( vc_store && vc_store != SSL_CTX_get_app_data(*ctx) ) {
         SSL_CTX_set_cert_store(*ctx, vc_x509store_create(vc_store));
         SSL_CTX_set_app_data(*ctx, vc_store);
      }
   } else {
      *ctx = vc_create_sslctx(vc_store);
      _ctx = 1;
   }

   if( !(conn = BIO_new_ssl_connect(*ctx)) )
      VC_CONNSSL_ERR_EXIT(_ctx, ctx, conn);

   BIO_set_conn_hostname(conn, host);
   BIO_set_conn_int_port(conn, &port);

   fflush(stdout);
   if(BIO_do_connect(conn) <= 0)
      VC_CONNSSL_ERR_EXIT(_ctx, ctx, conn);

   if(_ctx)
      SSL_CTX_free(*ctx);

   return(conn);
}

#define VC_CONN_ERR_EXIT(cn) do { \
      snprintf(tmpstr, TMPSTRSIZE, "[SSL ERROR] %s", \
            ERR_error_string(ERR_get_error(), NULL)); \
      if(ERR_get_error()) \
         writecf(FS_ERR, tmpstr); \
      if(cn)  BIO_free_all(cn); \
      return(NULL); \
   } while(0)

#define VC_VERIFICATION_ERR_EXIT(cn, err) do { \
      snprintf(tmpstr, TMPSTRSIZE, \
            "[SSL ERROR] certificate verify failed: %s", err); \
      writecf(FS_ERR, tmpstr); \
      if(cn && !ignore_ssl) { BIO_free_all(cn); return(NULL); } \
   } while(0)

BIO * vc_connect( char *host, int port, int use_ssl, 
      vc_x509store_t *vc_store, SSL_CTX **ctx)
{
   BIO *conn   = NULL;
   SSL *ssl    = NULL;

   if(use_ssl) {
      if( !(conn = vc_connect_ssl(host, port, vc_store, ctx)) )
         VC_CONN_ERR_EXIT(conn);


      BIO_get_ssl(conn, &ssl);
      if(!vc_verify_cert_hostname(SSL_get_peer_certificate(ssl), host))
         VC_VERIFICATION_ERR_EXIT(conn, "Hostname does not match!");

      return(conn);
   } 

   *ctx = 0;

   if( !(conn = BIO_new_connect(host)) )
      VC_CONN_ERR_EXIT(conn);

   BIO_set_conn_int_port(conn, &port);

   if(BIO_do_connect(conn) <= 0)
      VC_CONN_ERR_EXIT(conn);

   return(conn);
}

int vc_verify_cert_hostname(X509 *cert, char *host)
{
   
   int i          = 0;
   int j          = 0;
   int n          = 0;
   int extcount   = 0;
   int ok         = 0;

   X509_NAME            *subj    = NULL;
   const char           *extstr  = NULL;
   CONF_VALUE           *nval    = NULL;
   unsigned char        *data    = NULL;
   X509_EXTENSION       *ext     = NULL;
   X509V3_EXT_METHOD    *meth    = NULL;
   STACK_OF(CONF_VALUE) *val     = NULL;

   char name[256];
   memset(&name, 0, sizeof(name));

   if((extcount = X509_get_ext_count(cert)) > 0) {
      
      for(i=0; !ok && i < extcount; i++) {
         
         meth = NULL;

         ext = X509_get_ext(cert, i);
         extstr = OBJ_nid2sn(OBJ_obj2nid(X509_EXTENSION_get_object(ext)));

         if(!strcasecmp(extstr, "subjectAltName")) {
            
            if( !(meth = X509V3_EXT_get(ext)) )
               break;

            if( !(meth->d2i) )
               break;
            
            data = ext->value->data;

            val = meth->i2v(meth, meth->d2i(0, &data, ext->value->length), 0);
            for( j=0, n=sk_CONF_VALUE_num(val); j<n; j++ ) {
               nval = sk_CONF_VALUE_value(val, j);
               if( !strcasecmp(nval->name, "DNS") && 
                     !strcasecmp(nval->value, host) ) {
                  ok = 1;
                  break;
               }
            } 
         }
      }
   }

   if( !ok && (subj = X509_get_subject_name(cert)) &&
         X509_NAME_get_text_by_NID(subj, NID_commonName, 
            name, sizeof(name)) > 0 ) {
      name[sizeof(name)-1] = '\0';
      if(!strcasecmp(name, host))
         ok = 1;
   }

   //printf("[*] vc_verify_cert_hostname() return: %d\n", ok);
   return(ok);
}

int vc_verify_cert(X509 *cert, vc_x509store_t *vc_store)
{
   int result           = -1;
   X509_STORE  *store   = NULL;
   X509_STORE_CTX *ctx  = NULL;

   if( !(store = vc_x509store_create(vc_store)) )
      return(result);

   if( (ctx = X509_STORE_CTX_new()) != 0 ) {
      if(X509_STORE_CTX_init(ctx, store, cert, 0) == 1)
         result = (X509_verify_cert(ctx) == 1);
      X509_STORE_CTX_free(ctx);
   }

   X509_STORE_free(store);
   return(result);
}

#define VC_STORE_ERR_EXIT(s) do { \
      fprintf(stderr, "[E] SSL_STORE: %s\n", ERR_error_string (ERR_get_error (), NULL)); \
      if(s)  X509_STORE_free(s); \
      return(0); \
   } while(0)

X509_STORE *vc_x509store_create(vc_x509store_t *vc_store)
{
   int i                = 0;
   int n                = 0;
   X509_STORE *store    = NULL;
   X509_LOOKUP *lookup  = NULL;

   store = X509_STORE_new();

   if(vc_store->callback)
      X509_STORE_set_verify_cb_func(store, vc_store->callback);
   else
      X509_STORE_set_verify_cb_func(store, vc_verify_callback);

   if( !(lookup = X509_STORE_add_lookup(store, X509_LOOKUP_file())) )
      VC_STORE_ERR_EXIT(store);

   if(!vc_store->cafile) {
      if( !(vc_store->flags & VC_X509S_NODEF_CAFILE) )
         X509_LOOKUP_load_file(lookup, 0, X509_FILETYPE_DEFAULT);
   } else if( !X509_LOOKUP_load_file(lookup, vc_store->cafile, 
            X509_FILETYPE_PEM) )
      VC_STORE_ERR_EXIT(store);

   if(vc_store->crlfile) {
      if( !X509_load_crl_file(lookup, vc_store->crlfile, 
               X509_FILETYPE_PEM) )
         VC_STORE_ERR_EXIT(store);

      X509_STORE_set_flags( store, 
            X509_V_FLAG_CRL_CHECK | X509_V_FLAG_CRL_CHECK_ALL );
   }
   
   if( !(lookup = X509_STORE_add_lookup(store, X509_LOOKUP_hash_dir())) )
      VC_STORE_ERR_EXIT(store);

   if( !vc_store->capath ) {
      if( !(vc_store->flags & VC_X509S_NODEF_CAPATH) )
         X509_LOOKUP_add_dir(lookup, 0, X509_FILETYPE_DEFAULT);
   } else if( !X509_LOOKUP_add_dir(lookup, vc_store->capath, 
            X509_FILETYPE_PEM) )
      VC_STORE_ERR_EXIT(store);

   for( i=0, n=sk_X509_num(vc_store->certs); i<n; i++)
      if( !X509_STORE_add_cert(store, sk_X509_value(vc_store->certs, i)) )
         VC_STORE_ERR_EXIT(store);

   for( i=0, n=sk_X509_CRL_num(vc_store->crls); i<n; i++)
      if( !X509_STORE_add_crl(store, 
               sk_X509_CRL_value(vc_store->crls, i)) ) 
         VC_STORE_ERR_EXIT(store);

   return(store);
}

int vc_verify_callback(int ok, X509_STORE_CTX *store)
{
   if(!ok) {
      /* XXX handle action/abort */
      if(!ignore_ssl)
         snprintf(tmpstr, TMPSTRSIZE, "[SSL ERROR] %s", 
               X509_verify_cert_error_string(store->error));
      else
         snprintf(tmpstr, TMPSTRSIZE, "[SSL ERROR] %s (ignored)", 
               X509_verify_cert_error_string(store->error));

      writecf(FS_ERR, tmpstr);
      ok = ignore_ssl;
   }
   return(ok);
}

void vc_x509store_setflags(vc_x509store_t *store, int flags)
{
   store->flags |= flags;
}

void vc_x509store_setignssl(vc_x509store_t *store, int ignore)
{
   store->ignore_ssl |= ignore;
   ignore_ssl = ignore;
}

void vc_x509store_clearflags(vc_x509store_t *store, int flags)
{
   store->flags &= ~flags;
}

void vc_x509store_setcb(vc_x509store_t *store, 
      vc_x509verify_cb_t callback)
{
   store->callback = callback;
}

void vc_x509store_set_pkeycb(vc_x509store_t *store, 
      vc_askpass_cb_t callback)
{
   store->askpass_callback = callback;
}

void vc_x509store_addcert(vc_x509store_t *store, X509 *cert)
{
   sk_X509_push(store->certs, cert);
}

void vc_x509store_setcafile(vc_x509store_t *store, char *file) 
{
   if( store->cafile) free(store->cafile);
   store->cafile = ( file ? strdup(file) : 0 );
}

void vc_x509store_setcapath(vc_x509store_t *store, char *path) 
{
   if( store->capath) free(store->capath);
   store->capath = ( path ? strdup(path) : 0 );
}

void vc_x509store_setcrlfile(vc_x509store_t *store, char *file) 
{
   if( store->crlfile) free(store->crlfile);
   store->crlfile = ( file ? strdup(file) : 0 );
}

void vc_x509store_setkeyfile(vc_x509store_t *store, char *file) 
{
   if( store->use_keyfile) free(store->use_keyfile);
   store->use_keyfile = ( file ? strdup(file) : 0 );
}

void vc_x509store_setcertfile(vc_x509store_t *store, char *file) 
{
   if( store->use_certfile) free(store->use_certfile);
   store->use_certfile = ( file ? strdup(file) : 0 );
}


void vc_init_x509store(vc_x509store_t *s)
{
   s->cafile         = NULL;
   s->capath         = NULL;
   s->crlfile        = NULL;
   s->callback       = NULL;
   s->askpass_callback = NULL;
   s->certs          = sk_X509_new_null();
   s->crls           = sk_X509_CRL_new_null();
   s->use_certfile   = NULL;
   s->use_certs      = sk_X509_new_null();
   s->use_keyfile    = NULL;
   s->use_key        = NULL;
   s->flags          = 0;
   s->ignore_ssl     = 0;
}

void vc_cleanup_x509store(vc_x509store_t *s)
{
   if(s->cafile)        free(s->cafile);
   if(s->capath)        free(s->capath);
   if(s->crlfile)       free(s->crlfile);
   if(s->use_certfile)  free(s->use_certfile);
   if(s->use_keyfile)   free(s->use_keyfile);
   if(s->use_key)       free(s->use_key);
   sk_X509_free(s->certs);
   sk_X509_free(s->crls);
   sk_X509_free(s->use_certs);
   s->ignore_ssl     = 0;
}