コード例 #1
0
ファイル: decapsulate.c プロジェクト: 0x24bin/winexe-1
OM_uint32
_gsskrb5_decapsulate(OM_uint32 *minor_status,
			gss_buffer_t input_token_buffer,
			krb5_data *out_data,
			const void *type,
			gss_OID oid)
{
    u_char *p;
    OM_uint32 ret;

    p = input_token_buffer->value;
    ret = _gsskrb5_verify_header(&p,
				    input_token_buffer->length,
				    type,
				    oid);
    if (ret) {
	*minor_status = 0;
	return ret;
    }

    out_data->length = input_token_buffer->length -
	(p - (u_char *)input_token_buffer->value);
    out_data->data   = p;
    return GSS_S_COMPLETE;
}
コード例 #2
0
ファイル: verify_mic.c プロジェクト: Alexandr-Galko/samba
static OM_uint32
verify_mic_des
           (OM_uint32 * minor_status,
            const gsskrb5_ctx context_handle,
	    krb5_context context,
            const gss_buffer_t message_buffer,
            const gss_buffer_t token_buffer,
            gss_qop_t * qop_state,
	    krb5_keyblock *key,
	    char *type
	    )
{
  u_char *p;
  EVP_MD_CTX *md5;
  u_char hash[16], *seq;
  DES_key_schedule schedule;
  EVP_CIPHER_CTX des_ctx;
  DES_cblock zero;
  DES_cblock deskey;
  uint32_t seq_number;
  OM_uint32 ret;
  int cmp;

  p = token_buffer->value;
  ret = _gsskrb5_verify_header (&p,
				   token_buffer->length,
				   type,
				   GSS_KRB5_MECHANISM);
  if (ret)
      return ret;

  if (memcmp(p, "\x00\x00", 2) != 0)
      return GSS_S_BAD_SIG;
  p += 2;
  if (memcmp (p, "\xff\xff\xff\xff", 4) != 0)
    return GSS_S_BAD_MIC;
  p += 4;
  p += 16;

  /* verify checksum */
  md5 = EVP_MD_CTX_create();
  EVP_DigestInit_ex(md5, EVP_md5(), NULL);
  EVP_DigestUpdate(md5, p - 24, 8);
  EVP_DigestUpdate(md5, message_buffer->value, message_buffer->length);
  EVP_DigestFinal_ex(md5, hash, NULL);
  EVP_MD_CTX_destroy(md5);

  memset (&zero, 0, sizeof(zero));
  memcpy (&deskey, key->keyvalue.data, sizeof(deskey));

  DES_set_key_unchecked (&deskey, &schedule);
  DES_cbc_cksum ((void *)hash, (void *)hash, sizeof(hash),
		 &schedule, &zero);
  if (ct_memcmp (p - 8, hash, 8) != 0) {
    memset (deskey, 0, sizeof(deskey));
    memset (&schedule, 0, sizeof(schedule));
    return GSS_S_BAD_MIC;
  }

  /* verify sequence number */

  HEIMDAL_MUTEX_lock(&context_handle->ctx_id_mutex);

  p -= 16;

  EVP_CIPHER_CTX_init(&des_ctx);
  EVP_CipherInit_ex(&des_ctx, EVP_des_cbc(), NULL, key->keyvalue.data, hash, 0);
  EVP_Cipher(&des_ctx, p, p, 8);
  EVP_CIPHER_CTX_cleanup(&des_ctx);

  memset (deskey, 0, sizeof(deskey));
  memset (&schedule, 0, sizeof(schedule));

  seq = p;
  _gsskrb5_decode_om_uint32(seq, &seq_number);

  if (context_handle->more_flags & LOCAL)
      cmp = ct_memcmp(&seq[4], "\xff\xff\xff\xff", 4);
  else
      cmp = ct_memcmp(&seq[4], "\x00\x00\x00\x00", 4);

  if (cmp != 0) {
    HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
    return GSS_S_BAD_MIC;
  }

  ret = _gssapi_msg_order_check(context_handle->order, seq_number);
  if (ret) {
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return ret;
  }

  HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);

  return GSS_S_COMPLETE;
}
コード例 #3
0
ファイル: verify_mic.c プロジェクト: Alexandr-Galko/samba
static OM_uint32
verify_mic_des3
           (OM_uint32 * minor_status,
            const gsskrb5_ctx context_handle,
	    krb5_context context,
            const gss_buffer_t message_buffer,
            const gss_buffer_t token_buffer,
            gss_qop_t * qop_state,
	    krb5_keyblock *key,
	    char *type
	    )
{
  u_char *p;
  u_char *seq;
  uint32_t seq_number;
  OM_uint32 ret;
  krb5_crypto crypto;
  krb5_data seq_data;
  int cmp, docompat;
  Checksum csum;
  char *tmp;
  char ivec[8];

  p = token_buffer->value;
  ret = _gsskrb5_verify_header (&p,
				   token_buffer->length,
				   type,
				   GSS_KRB5_MECHANISM);
  if (ret)
      return ret;

  if (memcmp(p, "\x04\x00", 2) != 0) /* SGN_ALG = HMAC SHA1 DES3-KD */
      return GSS_S_BAD_SIG;
  p += 2;
  if (memcmp (p, "\xff\xff\xff\xff", 4) != 0)
    return GSS_S_BAD_MIC;
  p += 4;

  ret = krb5_crypto_init(context, key,
			 ETYPE_DES3_CBC_NONE, &crypto);
  if (ret){
      *minor_status = ret;
      return GSS_S_FAILURE;
  }

  /* verify sequence number */
  docompat = 0;
retry:
  if (docompat)
      memset(ivec, 0, 8);
  else
      memcpy(ivec, p + 8, 8);

  ret = krb5_decrypt_ivec (context,
			   crypto,
			   KRB5_KU_USAGE_SEQ,
			   p, 8, &seq_data, ivec);
  if (ret) {
      if (docompat++) {
	  krb5_crypto_destroy (context, crypto);
	  *minor_status = ret;
	  return GSS_S_FAILURE;
      } else
	  goto retry;
  }

  if (seq_data.length != 8) {
      krb5_data_free (&seq_data);
      if (docompat++) {
	  krb5_crypto_destroy (context, crypto);
	  return GSS_S_BAD_MIC;
      } else
	  goto retry;
  }

  HEIMDAL_MUTEX_lock(&context_handle->ctx_id_mutex);

  seq = seq_data.data;
  _gsskrb5_decode_om_uint32(seq, &seq_number);

  if (context_handle->more_flags & LOCAL)
      cmp = ct_memcmp(&seq[4], "\xff\xff\xff\xff", 4);
  else
      cmp = ct_memcmp(&seq[4], "\x00\x00\x00\x00", 4);

  krb5_data_free (&seq_data);
  if (cmp != 0) {
      krb5_crypto_destroy (context, crypto);
      *minor_status = 0;
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return GSS_S_BAD_MIC;
  }

  ret = _gssapi_msg_order_check(context_handle->order, seq_number);
  if (ret) {
      krb5_crypto_destroy (context, crypto);
      *minor_status = 0;
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return ret;
  }

  /* verify checksum */

  tmp = malloc (message_buffer->length + 8);
  if (tmp == NULL) {
      krb5_crypto_destroy (context, crypto);
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      *minor_status = ENOMEM;
      return GSS_S_FAILURE;
  }

  memcpy (tmp, p - 8, 8);
  memcpy (tmp + 8, message_buffer->value, message_buffer->length);

  csum.cksumtype = CKSUMTYPE_HMAC_SHA1_DES3;
  csum.checksum.length = 20;
  csum.checksum.data   = p + 8;

  ret = krb5_verify_checksum (context, crypto,
			      KRB5_KU_USAGE_SIGN,
			      tmp, message_buffer->length + 8,
			      &csum);
  free (tmp);
  if (ret) {
      krb5_crypto_destroy (context, crypto);
      *minor_status = ret;
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return GSS_S_BAD_MIC;
  }
  HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);

  krb5_crypto_destroy (context, crypto);
  return GSS_S_COMPLETE;
}
コード例 #4
0
OM_uint32
_gssapi_verify_mic_arcfour(OM_uint32 * minor_status,
			   const gsskrb5_ctx context_handle,
			   krb5_context context,
			   const gss_buffer_t message_buffer,
			   const gss_buffer_t token_buffer,
			   gss_qop_t * qop_state,
			   krb5_keyblock *key,
			   const char *type)
{
    krb5_error_code ret;
    uint32_t seq_number;
    OM_uint32 omret;
    u_char SND_SEQ[8], cksum_data[8], *p;
    char k6_data[16];
    int cmp;

    if (qop_state)
	*qop_state = 0;

    p = token_buffer->value;
    omret = _gsskrb5_verify_header (&p,
				       token_buffer->length,
				       type,
				       GSS_KRB5_MECHANISM);
    if (omret)
	return omret;

    if (memcmp(p, "\x11\x00", 2) != 0) /* SGN_ALG = HMAC MD5 ARCFOUR */
	return GSS_S_BAD_SIG;
    p += 2;
    if (memcmp (p, "\xff\xff\xff\xff", 4) != 0)
	return GSS_S_BAD_MIC;
    p += 4;

    ret = arcfour_mic_cksum(context,
			    key, KRB5_KU_USAGE_SIGN,
			    cksum_data, sizeof(cksum_data),
			    p - 8, 8,
			    message_buffer->value, message_buffer->length,
			    NULL, 0);
    if (ret) {
	*minor_status = ret;
	return GSS_S_FAILURE;
    }

    ret = arcfour_mic_key(context, key,
			  cksum_data, sizeof(cksum_data),
			  k6_data, sizeof(k6_data));
    if (ret) {
	*minor_status = ret;
	return GSS_S_FAILURE;
    }

    cmp = ct_memcmp(cksum_data, p + 8, 8);
    if (cmp) {
	*minor_status = 0;
	return GSS_S_BAD_MIC;
    }

    {
	EVP_CIPHER_CTX rc4_key;

	EVP_CIPHER_CTX_init(&rc4_key);
	EVP_CipherInit_ex(&rc4_key, EVP_rc4(), NULL, (void *)k6_data, NULL, 0);
	EVP_Cipher(&rc4_key, SND_SEQ, p, 8);
	EVP_CIPHER_CTX_cleanup(&rc4_key);

	memset(k6_data, 0, sizeof(k6_data));
    }

    _gss_mg_decode_be_uint32(SND_SEQ, &seq_number);

    if (context_handle->more_flags & LOCAL)
	cmp = memcmp(&SND_SEQ[4], "\xff\xff\xff\xff", 4);
    else
	cmp = memcmp(&SND_SEQ[4], "\x00\x00\x00\x00", 4);

    memset(SND_SEQ, 0, sizeof(SND_SEQ));
    if (cmp != 0) {
	*minor_status = 0;
	return GSS_S_BAD_MIC;
    }

    HEIMDAL_MUTEX_lock(&context_handle->ctx_id_mutex);
    omret = _gssapi_msg_order_check(context_handle->gk5c.order, seq_number);
    HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
    if (omret)
	return omret;

    *minor_status = 0;
    return GSS_S_COMPLETE;
}
コード例 #5
0
ファイル: unwrap.c プロジェクト: 2014-class/freerouter
static OM_uint32
unwrap_des
           (OM_uint32 * minor_status,
            const gsskrb5_ctx context_handle,
            const gss_buffer_t input_message_buffer,
            gss_buffer_t output_message_buffer,
            int * conf_state,
            gss_qop_t * qop_state,
	    krb5_keyblock *key
           )
{
  u_char *p, *seq;
  size_t len;
  MD5_CTX md5;
  u_char hash[16];
  DES_key_schedule schedule;
  DES_cblock deskey;
  DES_cblock zero;
  int i;
  uint32_t seq_number;
  size_t padlength;
  OM_uint32 ret;
  int cstate;
  int cmp;

  p = input_message_buffer->value;
  ret = _gsskrb5_verify_header (&p,
				   input_message_buffer->length,
				   "\x02\x01",
				   GSS_KRB5_MECHANISM);
  if (ret)
      return ret;

  if (memcmp (p, "\x00\x00", 2) != 0)
    return GSS_S_BAD_SIG;
  p += 2;
  if (memcmp (p, "\x00\x00", 2) == 0) {
      cstate = 1;
  } else if (memcmp (p, "\xFF\xFF", 2) == 0) {
      cstate = 0;
  } else
      return GSS_S_BAD_MIC;
  p += 2;
  if(conf_state != NULL)
      *conf_state = cstate;
  if (memcmp (p, "\xff\xff", 2) != 0)
    return GSS_S_DEFECTIVE_TOKEN;
  p += 2;
  p += 16;

  len = p - (u_char *)input_message_buffer->value;

  if(cstate) {
      /* decrypt data */
      memcpy (&deskey, key->keyvalue.data, sizeof(deskey));

      for (i = 0; i < sizeof(deskey); ++i)
	  deskey[i] ^= 0xf0;
      DES_set_key (&deskey, &schedule);
      memset (&zero, 0, sizeof(zero));
      DES_cbc_encrypt ((void *)p,
		       (void *)p,
		       input_message_buffer->length - len,
		       &schedule,
		       &zero,
		       DES_DECRYPT);
      
      memset (deskey, 0, sizeof(deskey));
      memset (&schedule, 0, sizeof(schedule));
  }
  /* check pad */
  ret = _gssapi_verify_pad(input_message_buffer, 
			   input_message_buffer->length - len,
			   &padlength);
  if (ret)
      return ret;

  MD5_Init (&md5);
  MD5_Update (&md5, p - 24, 8);
  MD5_Update (&md5, p, input_message_buffer->length - len);
  MD5_Final (hash, &md5);

  memset (&zero, 0, sizeof(zero));
  memcpy (&deskey, key->keyvalue.data, sizeof(deskey));
  DES_set_key (&deskey, &schedule);
  DES_cbc_cksum ((void *)hash, (void *)hash, sizeof(hash),
		 &schedule, &zero);
  if (memcmp (p - 8, hash, 8) != 0)
    return GSS_S_BAD_MIC;

  /* verify sequence number */
  
  HEIMDAL_MUTEX_lock(&context_handle->ctx_id_mutex);

  p -= 16;
  DES_set_key (&deskey, &schedule);
  DES_cbc_encrypt ((void *)p, (void *)p, 8,
		   &schedule, (DES_cblock *)hash, DES_DECRYPT);

  memset (deskey, 0, sizeof(deskey));
  memset (&schedule, 0, sizeof(schedule));

  seq = p;
  _gsskrb5_decode_om_uint32(seq, &seq_number);

  if (context_handle->more_flags & LOCAL)
      cmp = memcmp(&seq[4], "\xff\xff\xff\xff", 4);
  else
      cmp = memcmp(&seq[4], "\x00\x00\x00\x00", 4);

  if (cmp != 0) {
    HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
    return GSS_S_BAD_MIC;
  }

  ret = _gssapi_msg_order_check(context_handle->order, seq_number);
  if (ret) {
    HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
    return ret;
  }

  HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);

  /* copy out data */

  output_message_buffer->length = input_message_buffer->length
    - len - padlength - 8;
  output_message_buffer->value  = malloc(output_message_buffer->length);
  if(output_message_buffer->length != 0 && output_message_buffer->value == NULL)
      return GSS_S_FAILURE;
  memcpy (output_message_buffer->value,
	  p + 24,
	  output_message_buffer->length);
  return GSS_S_COMPLETE;
}
コード例 #6
0
ファイル: unwrap.c プロジェクト: 2014-class/freerouter
static OM_uint32
unwrap_des3
           (OM_uint32 * minor_status,
            const gsskrb5_ctx context_handle,
	    krb5_context context,
            const gss_buffer_t input_message_buffer,
            gss_buffer_t output_message_buffer,
            int * conf_state,
            gss_qop_t * qop_state,
	    krb5_keyblock *key
           )
{
  u_char *p;
  size_t len;
  u_char *seq;
  krb5_data seq_data;
  u_char cksum[20];
  uint32_t seq_number;
  size_t padlength;
  OM_uint32 ret;
  int cstate;
  krb5_crypto crypto;
  Checksum csum;
  int cmp;

  p = input_message_buffer->value;
  ret = _gsskrb5_verify_header (&p,
				   input_message_buffer->length,
				   "\x02\x01",
				   GSS_KRB5_MECHANISM);
  if (ret)
      return ret;

  if (memcmp (p, "\x04\x00", 2) != 0) /* HMAC SHA1 DES3_KD */
    return GSS_S_BAD_SIG;
  p += 2;
  if (memcmp (p, "\x02\x00", 2) == 0) {
    cstate = 1;
  } else if (memcmp (p, "\xff\xff", 2) == 0) {
    cstate = 0;
  } else
    return GSS_S_BAD_MIC;
  p += 2;
  if(conf_state != NULL)
    *conf_state = cstate;
  if (memcmp (p, "\xff\xff", 2) != 0)
    return GSS_S_DEFECTIVE_TOKEN;
  p += 2;
  p += 28;

  len = p - (u_char *)input_message_buffer->value;

  if(cstate) {
      /* decrypt data */
      krb5_data tmp;

      ret = krb5_crypto_init(context, key,
			     ETYPE_DES3_CBC_NONE, &crypto);
      if (ret) {
	  *minor_status = ret;
	  return GSS_S_FAILURE;
      }
      ret = krb5_decrypt(context, crypto, KRB5_KU_USAGE_SEAL,
			 p, input_message_buffer->length - len, &tmp);
      krb5_crypto_destroy(context, crypto);
      if (ret) {
	  *minor_status = ret;
	  return GSS_S_FAILURE;
      }
      assert (tmp.length == input_message_buffer->length - len);

      memcpy (p, tmp.data, tmp.length);
      krb5_data_free(&tmp);
  }
  /* check pad */
  ret = _gssapi_verify_pad(input_message_buffer, 
			   input_message_buffer->length - len,
			   &padlength);
  if (ret)
      return ret;

  /* verify sequence number */
  
  HEIMDAL_MUTEX_lock(&context_handle->ctx_id_mutex);

  p -= 28;

  ret = krb5_crypto_init(context, key,
			 ETYPE_DES3_CBC_NONE, &crypto);
  if (ret) {
      *minor_status = ret;
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return GSS_S_FAILURE;
  }
  {
      DES_cblock ivec;

      memcpy(&ivec, p + 8, 8);
      ret = krb5_decrypt_ivec (context,
			       crypto,
			       KRB5_KU_USAGE_SEQ,
			       p, 8, &seq_data,
			       &ivec);
  }
  krb5_crypto_destroy (context, crypto);
  if (ret) {
      *minor_status = ret;
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return GSS_S_FAILURE;
  }
  if (seq_data.length != 8) {
      krb5_data_free (&seq_data);
      *minor_status = 0;
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return GSS_S_BAD_MIC;
  }

  seq = seq_data.data;
  _gsskrb5_decode_om_uint32(seq, &seq_number);

  if (context_handle->more_flags & LOCAL)
      cmp = memcmp(&seq[4], "\xff\xff\xff\xff", 4);
  else
      cmp = memcmp(&seq[4], "\x00\x00\x00\x00", 4);
  
  krb5_data_free (&seq_data);
  if (cmp != 0) {
      *minor_status = 0;
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return GSS_S_BAD_MIC;
  }

  ret = _gssapi_msg_order_check(context_handle->order, seq_number);
  if (ret) {
      *minor_status = 0;
      HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
      return ret;
  }

  HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);

  /* verify checksum */

  memcpy (cksum, p + 8, 20);

  memcpy (p + 20, p - 8, 8);

  csum.cksumtype = CKSUMTYPE_HMAC_SHA1_DES3;
  csum.checksum.length = 20;
  csum.checksum.data   = cksum;

  ret = krb5_crypto_init(context, key, 0, &crypto);
  if (ret) {
      *minor_status = ret;
      return GSS_S_FAILURE;
  }

  ret = krb5_verify_checksum (context, crypto,
			      KRB5_KU_USAGE_SIGN,
			      p + 20,
			      input_message_buffer->length - len + 8,
			      &csum);
  krb5_crypto_destroy (context, crypto);
  if (ret) {
      *minor_status = ret;
      return GSS_S_FAILURE;
  }

  /* copy out data */

  output_message_buffer->length = input_message_buffer->length
    - len - padlength - 8;
  output_message_buffer->value  = malloc(output_message_buffer->length);
  if(output_message_buffer->length != 0 && output_message_buffer->value == NULL)
      return GSS_S_FAILURE;
  memcpy (output_message_buffer->value,
	  p + 36,
	  output_message_buffer->length);
  return GSS_S_COMPLETE;
}
コード例 #7
0
ファイル: unwrap.c プロジェクト: FreeBSDFoundation/freebsd
static OM_uint32
unwrap_des
           (OM_uint32 * minor_status,
            const gsskrb5_ctx context_handle,
            const gss_buffer_t input_message_buffer,
            gss_buffer_t output_message_buffer,
            int * conf_state,
            gss_qop_t * qop_state,
	    krb5_keyblock *key
           )
{
  u_char *p, *seq;
  size_t len;
  EVP_MD_CTX *md5;
  u_char hash[16];
  EVP_CIPHER_CTX *des_ctx;
  DES_key_schedule schedule;
  DES_cblock deskey;
  DES_cblock zero;
  size_t i;
  uint32_t seq_number;
  size_t padlength;
  OM_uint32 ret;
  int cstate;
  int cmp;
  int token_len;

  if (IS_DCE_STYLE(context_handle)) {
     token_len = 22 + 8 + 15; /* 45 */
  } else {
     token_len = input_message_buffer->length;
  }

  p = input_message_buffer->value;
  ret = _gsskrb5_verify_header (&p,
				   token_len,
				   "\x02\x01",
				   GSS_KRB5_MECHANISM);
  if (ret)
      return ret;

  if (memcmp (p, "\x00\x00", 2) != 0)
    return GSS_S_BAD_SIG;
  p += 2;
  if (memcmp (p, "\x00\x00", 2) == 0) {
      cstate = 1;
  } else if (memcmp (p, "\xFF\xFF", 2) == 0) {
      cstate = 0;
  } else
      return GSS_S_BAD_MIC;
  p += 2;
  if(conf_state != NULL)
      *conf_state = cstate;
  if (memcmp (p, "\xff\xff", 2) != 0)
    return GSS_S_DEFECTIVE_TOKEN;
  p += 2;
  p += 16;

  len = p - (u_char *)input_message_buffer->value;

  if(cstate) {
      /* decrypt data */
      memcpy (&deskey, key->keyvalue.data, sizeof(deskey));
      memset (&zero, 0, sizeof(zero));

      for (i = 0; i < sizeof(deskey); ++i)
	  deskey[i] ^= 0xf0;


      des_ctx = EVP_CIPHER_CTX_new();
      if (des_ctx == NULL) {
	  memset (deskey, 0, sizeof(deskey));
	  *minor_status = ENOMEM;
	  return GSS_S_FAILURE;
      }
      EVP_CipherInit_ex(des_ctx, EVP_des_cbc(), NULL, deskey, zero, 0);
      EVP_Cipher(des_ctx, p, p, input_message_buffer->length - len);
      EVP_CIPHER_CTX_free(des_ctx);

      memset (deskey, 0, sizeof(deskey));
  }

  if (IS_DCE_STYLE(context_handle)) {
    padlength = 0;
  } else {
    /* check pad */
    ret = _gssapi_verify_pad(input_message_buffer,
			     input_message_buffer->length - len,
			     &padlength);
    if (ret)
        return ret;
  }

  md5 = EVP_MD_CTX_create();
  EVP_DigestInit_ex(md5, EVP_md5(), NULL);
  EVP_DigestUpdate(md5, p - 24, 8);
  EVP_DigestUpdate(md5, p, input_message_buffer->length - len);
  EVP_DigestFinal_ex(md5, hash, NULL);
  EVP_MD_CTX_destroy(md5);

  memset (&zero, 0, sizeof(zero));
  memcpy (&deskey, key->keyvalue.data, sizeof(deskey));
  DES_set_key_unchecked (&deskey, &schedule);
  DES_cbc_cksum ((void *)hash, (void *)hash, sizeof(hash),
		 &schedule, &zero);
  if (ct_memcmp (p - 8, hash, 8) != 0) {
    memset (deskey, 0, sizeof(deskey));
    memset (&schedule, 0, sizeof(schedule));
    return GSS_S_BAD_MIC;
  }

  /* verify sequence number */

  des_ctx = EVP_CIPHER_CTX_new();
  if (des_ctx == NULL) {
    memset (deskey, 0, sizeof(deskey));
    memset (&schedule, 0, sizeof(schedule));
    *minor_status = ENOMEM;
    return GSS_S_FAILURE;
  }

  HEIMDAL_MUTEX_lock(&context_handle->ctx_id_mutex);

  p -= 16;

  EVP_CipherInit_ex(des_ctx, EVP_des_cbc(), NULL, key->keyvalue.data, hash, 0);
  EVP_Cipher(des_ctx, p, p, 8);
  EVP_CIPHER_CTX_free(des_ctx);

  memset (deskey, 0, sizeof(deskey));
  memset (&schedule, 0, sizeof(schedule));

  seq = p;
  _gsskrb5_decode_om_uint32(seq, &seq_number);

  if (context_handle->more_flags & LOCAL)
      cmp = ct_memcmp(&seq[4], "\xff\xff\xff\xff", 4);
  else
      cmp = ct_memcmp(&seq[4], "\x00\x00\x00\x00", 4);

  if (cmp != 0) {
    HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
    return GSS_S_BAD_MIC;
  }

  ret = _gssapi_msg_order_check(context_handle->order, seq_number);
  if (ret) {
    HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);
    return ret;
  }

  HEIMDAL_MUTEX_unlock(&context_handle->ctx_id_mutex);

  /* copy out data */

  output_message_buffer->length = input_message_buffer->length
    - len - padlength - 8;
  output_message_buffer->value  = malloc(output_message_buffer->length);
  if(output_message_buffer->length != 0 && output_message_buffer->value == NULL)
      return GSS_S_FAILURE;
  memcpy (output_message_buffer->value,
	  p + 24,
	  output_message_buffer->length);
  return GSS_S_COMPLETE;
}