michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=8 sts=2 et sw=2 tw=80: */
michael@0: /* Copyright 2013 Mozilla Foundation
michael@0:  *
michael@0:  * Licensed under the Apache License, Version 2.0 (the "License");
michael@0:  * you may not use this file except in compliance with the License.
michael@0:  * You may obtain a copy of the License at
michael@0:  *
michael@0:  *     http://www.apache.org/licenses/LICENSE-2.0
michael@0:  *
michael@0:  * Unless required by applicable law or agreed to in writing, software
michael@0:  * distributed under the License is distributed on an "AS IS" BASIS,
michael@0:  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
michael@0:  * See the License for the specific language governing permissions and
michael@0:  * limitations under the License.
michael@0:  */
michael@0: 
michael@0: #include "pkixder.h"
michael@0: 
michael@0: namespace mozilla { namespace pkix { namespace der {
michael@0: 
michael@0: // not inline
michael@0: Result
michael@0: Fail(PRErrorCode errorCode)
michael@0: {
michael@0:   PR_SetError(errorCode, 0);
michael@0:   return Failure;
michael@0: }
michael@0: 
michael@0: // Too complicated to be inline
michael@0: Result
michael@0: ExpectTagAndGetLength(Input& input, uint8_t expectedTag, uint16_t& length)
michael@0: {
michael@0:   PR_ASSERT((expectedTag & 0x1F) != 0x1F); // high tag number form not allowed
michael@0: 
michael@0:   uint8_t tag;
michael@0:   if (input.Read(tag) != Success) {
michael@0:     return Failure;
michael@0:   }
michael@0: 
michael@0:   if (tag != expectedTag) {
michael@0:     return Fail(SEC_ERROR_BAD_DER);
michael@0:   }
michael@0: 
michael@0:   // The short form of length is a single byte with the high order bit set
michael@0:   // to zero. The long form of length is one byte with the high order bit
michael@0:   // set, followed by N bytes, where N is encoded in the lowest 7 bits of
michael@0:   // the first byte.
michael@0:   uint8_t length1;
michael@0:   if (input.Read(length1) != Success) {
michael@0:     return Failure;
michael@0:   }
michael@0:   if (!(length1 & 0x80)) {
michael@0:     length = length1;
michael@0:   } else if (length1 == 0x81) {
michael@0:     uint8_t length2;
michael@0:     if (input.Read(length2) != Success) {
michael@0:       return Failure;
michael@0:     }
michael@0:     if (length2 < 128) {
michael@0:       // Not shortest possible encoding
michael@0:       return Fail(SEC_ERROR_BAD_DER);
michael@0:     }
michael@0:     length = length2;
michael@0:   } else if (length1 == 0x82) {
michael@0:     if (input.Read(length) != Success) {
michael@0:       return Failure;
michael@0:     }
michael@0:     if (length < 256) {
michael@0:       // Not shortest possible encoding
michael@0:       return Fail(SEC_ERROR_BAD_DER);
michael@0:     }
michael@0:   } else {
michael@0:     // We don't support lengths larger than 2^16 - 1.
michael@0:     return Fail(SEC_ERROR_BAD_DER);
michael@0:   }
michael@0: 
michael@0:   // Ensure the input is long enough for the length it says it has.
michael@0:   return input.EnsureLength(length);
michael@0: }
michael@0: 
michael@0: } } } // namespace mozilla::pkix::der