1 files changed, 156 insertions, 0 deletions
diff --git a/otautil/asn1_decoder.cpp b/otautil/asn1_decoder.cpp
new file mode 100644
index 000000000..2d81a6e13
--- /dev/null
+++ b/otautil/asn1_decoder.cpp
@@ -0,0 +1,156 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "private/asn1_decoder.h"
+
+int asn1_context::peek_byte() const {
+  if (length_ == 0) {
+    return -1;
+  }
+  return *p_;
+}
+
+int asn1_context::get_byte() {
+  if (length_ == 0) {
+    return -1;
+  }
+
+  int byte = *p_;
+  p_++;
+  length_--;
+  return byte;
+}
+
+bool asn1_context::skip_bytes(size_t num_skip) {
+  if (length_ < num_skip) {
+    return false;
+  }
+  p_ += num_skip;
+  length_ -= num_skip;
+  return true;
+}
+
+bool asn1_context::decode_length(size_t* out_len) {
+  int num_octets = get_byte();
+  if (num_octets == -1) {
+    return false;
+  }
+  if ((num_octets & 0x80) == 0x00) {
+    *out_len = num_octets;
+    return true;
+  }
+  num_octets &= kMaskTag;
+  if (static_cast<size_t>(num_octets) >= sizeof(size_t)) {
+    return false;
+  }
+  size_t length = 0;
+  for (int i = 0; i < num_octets; ++i) {
+    int byte = get_byte();
+    if (byte == -1) {
+      return false;
+    }
+    length <<= 8;
+    length += byte;
+  }
+  *out_len = length;
+  return true;
+}
+
+/**
+ * Returns the constructed type and advances the pointer. E.g. A0 -> 0
+ */
+asn1_context* asn1_context::asn1_constructed_get() {
+  int type = get_byte();
+  if (type == -1 || (type & kMaskConstructed) != kTagConstructed) {
+    return nullptr;
+  }
+  size_t length;
+  if (!decode_length(&length) || length > length_) {
+    return nullptr;
+  }
+  asn1_context* app_ctx = new asn1_context(p_, length);
+  app_ctx->app_type_ = type & kMaskAppType;
+  return app_ctx;
+}
+
+bool asn1_context::asn1_constructed_skip_all() {
+  int byte = peek_byte();
+  while (byte != -1 && (byte & kMaskConstructed) == kTagConstructed) {
+    skip_bytes(1);
+    size_t length;
+    if (!decode_length(&length) || !skip_bytes(length)) {
+      return false;
+    }
+    byte = peek_byte();
+  }
+  return byte != -1;
+}
+
+int asn1_context::asn1_constructed_type() const {
+  return app_type_;
+}
+
+asn1_context* asn1_context::asn1_sequence_get() {
+  if ((get_byte() & kMaskTag) != kTagSequence) {
+    return nullptr;
+  }
+  size_t length;
+  if (!decode_length(&length) || length > length_) {
+    return nullptr;
+  }
+  return new asn1_context(p_, length);
+}
+
+asn1_context* asn1_context::asn1_set_get() {
+  if ((get_byte() & kMaskTag) != kTagSet) {
+    return nullptr;
+  }
+  size_t length;
+  if (!decode_length(&length) || length > length_) {
+    return nullptr;
+  }
+  return new asn1_context(p_, length);
+}
+
+bool asn1_context::asn1_sequence_next() {
+  size_t length;
+  if (get_byte() == -1 || !decode_length(&length) || !skip_bytes(length)) {
+    return false;
+  }
+  return true;
+}
+
+bool asn1_context::asn1_oid_get(const uint8_t** oid, size_t* length) {
+  if (get_byte() != kTagOid) {
+    return false;
+  }
+  if (!decode_length(length) || *length == 0 || *length > length_) {
+    return false;
+  }
+  *oid = p_;
+  return true;
+}
+
+bool asn1_context::asn1_octet_string_get(const uint8_t** octet_string, size_t* length) {
+  if (get_byte() != kTagOctetString) {
+    return false;
+  }
+  if (!decode_length(length) || *length == 0 || *length > length_) {
+    return false;
+  }
+  *octet_string = p_;
+  return true;
+}