/*
 * 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 <readline/readline.h>

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

const char *vchat_ssl_version = "vchat-ssl.c      $Id$";

typedef int (*vc_x509verify_cb_t)(int, X509_STORE_CTX *);
struct vc_x509store_t {
   char                 *cafile;
   char                 *capath;
   char                 *crlfile;
   vc_x509verify_cb_t   callback;
   vc_askpass_cb_t      askpass_callback;
   STACK_OF(X509)       *certs;
   STACK_OF(X509_CRL)   *crls;
   char                 *use_certfile;
   STACK_OF(X509)       *use_certs;
   char                 *use_keyfile;
   EVP_PKEY             *use_key;
   int                  flags;
};

static void vc_cleanup_x509store(vc_x509store_t *); // Should not be static but is unused
static SSL_CTX * vc_create_sslctx( vc_x509store_t *vc_store );
static int vc_verify_callback(int, X509_STORE_CTX *);
static X509_STORE * vc_x509store_create(vc_x509store_t *);
static void vc_x509store_clearflags(vc_x509store_t *, int);
static void vc_x509store_setcafile(vc_x509store_t *, char *);
static void vc_x509store_setcapath(vc_x509store_t *, char *);
static void vc_x509store_setcrlfile(vc_x509store_t *, char *);
static void vc_x509store_addcert(vc_x509store_t *, X509 *);
static void vc_x509store_setcb(vc_x509store_t *, vc_x509verify_cb_t);

#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)

static 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;

   /* Explicitly use TLSv1 (or maybe later) */
   if( !(ctx = SSL_CTX_new(SSLv23_client_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;
   /* Disable some insecure protocols explicitly */
   SSL_CTX_set_options(ctx, SSL_OP_ALL | SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3);
   if (getstroption(CF_CIPHERSUITE))
     SSL_CTX_set_cipher_list(ctx, getstroption(CF_CIPHERSUITE));
   else
     SSL_CTX_set_cipher_list(ctx, "ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-SHA");

   SSL_CTX_set_verify_depth (ctx, getintoption(CF_VERIFYSSL));

   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 || !SSL_CTX_check_private_key(ctx))
         VC_SETCERT_ERR_EXIT(store, ctx, "Load private key failed");
   }

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

int vc_connect_ssl( BIO **conn, vc_x509store_t *vc_store )
{
  BIO *ssl_conn = NULL;
  SSL_CTX * ctx = vc_create_sslctx(vc_store);

  if( !ctx )
    return 1;

  ssl_conn = BIO_new_ssl(ctx, 1);
  SSL_CTX_free(ctx);

  if( ssl_conn ) {
    BIO_push( ssl_conn, *conn );
    *conn = ssl_conn;
    fflush(stdout);

    if( BIO_do_handshake( *conn ) > 0 ) {
      /* Show information about cipher used */
      const SSL *sslp = NULL;
      const SSL_CIPHER * cipher = NULL;

      /* Get cipher object */
      BIO_get_ssl(ssl_conn, &sslp);
      if (sslp)
        cipher = SSL_get_current_cipher(sslp);
      if (cipher) {
        char cipher_desc[TMPSTRSIZE];
        snprintf(tmpstr, TMPSTRSIZE, "[SSL CIPHER       ] %s", SSL_CIPHER_description(cipher, cipher_desc, TMPSTRSIZE));
        writecf(FS_SERV, tmpstr);
      } else {
        snprintf(tmpstr, TMPSTRSIZE, "[SSL ERROR        ] Cipher not known / SSL object can't be queried!");
        writecf(FS_ERR, tmpstr);
      }

      /* Accept being connected, _if_ verification passed */
      if (sslp) {
        long result = SSL_get_verify_result(sslp);
#if 1 == 1
        if (result == X509_V_OK) {
          return 0;
        } else if (getintoption(CF_IGNSSL)) {
          writecf(FS_ERR, "[SSL VERIFY ERROR ] FAILURE IGNORED!!!");
          return 0;
        }
#else
        /* show & verify fingerprint */
        if ((result == X509_V_OK) || getintoption(CF_IGNSSL)) {
          X509 *peercert = SSL_get_peer_certificate(sslp);

          /* FIXME: this IS bad code */
          char new_fingerprint[TMPSTRSIZE] = "";
          char old_fingerprint[TMPSTRSIZE] = "";
          FILE *fingerprint_file = NULL;

          unsigned int fingerprint_len;
          unsigned char fingerprint_bin[EVP_MAX_MD_SIZE];

          /* show basic information about peer cert */
          snprintf(tmpstr, TMPSTRSIZE, "[SSL SUBJECT      ] %s", X509_NAME_oneline(X509_get_subject_name(peercert),0,0));
          writecf(FS_SERV, tmpstr);
          snprintf(tmpstr, TMPSTRSIZE, "[SSL ISSUER       ] %s", X509_NAME_oneline(X509_get_issuer_name(peercert),0,0));
          writecf(FS_SERV, tmpstr);

          /* calculate fingerprint */
          if (X509_digest(peercert,EVP_sha1(),fingerprint_bin,&fingerprint_len)) {
            char shorttmpstr[3] = "XX";
            int j;
            for (j=0; j<(int)fingerprint_len; j++) {
              if (j)
                strncat(new_fingerprint, ":", TMPSTRSIZE);
              snprintf(shorttmpstr, 3, "%02X", fingerprint_bin[j]);
              strncat(new_fingerprint, shorttmpstr, TMPSTRSIZE);
            }
            snprintf(tmpstr, TMPSTRSIZE, "[SSL FINGERPRINT  ] from server: %s", new_fingerprint);
            writecf(FS_SERV, tmpstr);
          }

          // we don't need the peercert anymore
          X509_free(peercert);

          fingerprint_file = fopen(tilde_expand(getstroption(CF_FINGERPRINT)), "r");
          if (fingerprint_file) {
            fgets(old_fingerprint, TMPSTRSIZE, fingerprint_file);
            fclose(fingerprint_file);

            /* verify fingerprint matches stored version */
            if (!strncmp(new_fingerprint, old_fingerprint, TMPSTRSIZE))
              return 0;
            else {
              snprintf(tmpstr, TMPSTRSIZE, "[SSL FINGERPRINT  ] from %s: %s", getstroption(CF_FINGERPRINT), old_fingerprint);
              writecf(FS_ERR, tmpstr);
              writecf(FS_ERR, "[SSL CONNECT ERROR] Fingerprint mismatch! Server cert updated?");
              return 1;
            }
          } else {
            /* FIXME: there might be other errors than missing file */
            fingerprint_file = fopen(tilde_expand(getstroption(CF_FINGERPRINT)), "w");
            if (!fingerprint_file) {
              snprintf (tmpstr, TMPSTRSIZE, "Can't write fingerprint file, %s.", strerror(errno));
              writecf(FS_ERR, tmpstr);
            } else {
              fputs(new_fingerprint, fingerprint_file);
              fclose(fingerprint_file);
              writecf(FS_SERV, "Stored fingerprint.");
              return 0;
            }
          }
        }
#endif
      }
    }
  }

  snprintf(tmpstr, TMPSTRSIZE, "[SSL CONNECT ERROR] %s", ERR_error_string (ERR_get_error (), NULL));
  writecf(FS_ERR, tmpstr);

  return 1;
}

#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) {
      snprintf(tmpstr, TMPSTRSIZE, "[SSL VERIFY ERROR ] %s",
               X509_verify_cert_error_string(store->error));
      writecf(FS_ERR, tmpstr);
   }
   return (ok | getintoption(CF_IGNSSL));
}

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

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)
{
   free(store->cafile);
   store->cafile = ( file ? strdup(file) : 0 );
}

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

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

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

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


vc_x509store_t *vc_init_x509store()
{
   vc_x509store_t *s = malloc(sizeof(vc_x509store_t));
   if (s) {

       static int sslinit;
       if( !sslinit++ ) {
           SSL_library_init ();
           SSL_load_error_strings();
       }

       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;
   }
   return s;
}

void vc_cleanup_x509store(vc_x509store_t *s)
{
   free(s->cafile);
   free(s->capath);
   free(s->crlfile);
   free(s->use_certfile);
   free(s->use_keyfile);
   free(s->use_key);
   sk_X509_free(s->certs);
   sk_X509_CRL_free(s->crls);
   sk_X509_free(s->use_certs);
}

const char *vchat_ssl_version_external = "OpenSSL implementation; version unknown";
void vchat_ssl_get_version_external()
{
   char tmpstr[TMPSTRSIZE];
   snprintf(tmpstr, TMPSTRSIZE, "%s with %s", SSLeay_version(SSLEAY_VERSION), SSLeay_version(SSLEAY_CFLAGS));
   vchat_ssl_version_external = strdup(tmpstr);
}