Refactor asn1_decoder functions into a class.

Test: mmma bootable/recovery
Test: recovery_unit_test passes.
Test: recovery_component_test passes.
Change-Id: If0bf25993158eaebeedff55ba4f4dd0f6e5f937d

4 files changed, 361 insertions, 410 deletions

diff --git a/asn1_decoder.cpp b/asn1_decoder.cpp
index ca4ee526..a9dfccc5 100644
--- a/asn1_decoder.cpp
+++ b/asn1_decoder.cpp
@@ -14,178 +14,145 @@
  * limitations under the License.
  */
 
-#include <malloc.h>
-#include <stdint.h>
-#include <string.h>
-
 #include "asn1_decoder.h"
 
+#include <stdint.h>
 
-typedef struct asn1_context {
-  size_t length;
-  const uint8_t* p;
-  int app_type;
-} asn1_context_t;
-
-
-static const int kMaskConstructed = 0xE0;
-static const int kMaskTag = 0x7F;
-static const int kMaskAppType = 0x1F;
-
-static const int kTagOctetString = 0x04;
-static const int kTagOid = 0x06;
-static const int kTagSequence = 0x30;
-static const int kTagSet = 0x31;
-static const int kTagConstructed = 0xA0;
-
-asn1_context_t* asn1_context_new(const uint8_t* buffer, size_t length) {
-    asn1_context_t* ctx = (asn1_context_t*) calloc(1, sizeof(asn1_context_t));
-    if (ctx == NULL) {
-        return NULL;
-    }
-    ctx->p = buffer;
-    ctx->length = length;
-    return ctx;
-}
-
-void asn1_context_free(asn1_context_t* ctx) {
-    free(ctx);
+int asn1_context::peek_byte() const {
+  if (length_ <= 0) {
+    return -1;
+  }
+  return *p_;
 }
 
-static inline int peek_byte(asn1_context_t* ctx) {
-    if (ctx->length <= 0) {
-        return -1;
-    }
-    return *ctx->p;
-}
+int asn1_context::get_byte() {
+  if (length_ <= 0) {
+    return -1;
+  }
 
-static inline int get_byte(asn1_context_t* ctx) {
-    if (ctx->length <= 0) {
-        return -1;
-    }
-    int byte = *ctx->p;
-    ctx->p++;
-    ctx->length--;
-    return byte;
+  int byte = *p_;
+  p_++;
+  length_--;
+  return byte;
 }
 
-static inline bool skip_bytes(asn1_context_t* ctx, size_t num_skip) {
-    if (ctx->length < num_skip) {
-        return false;
-    }
-    ctx->p += num_skip;
-    ctx->length -= num_skip;
-    return true;
+bool asn1_context::skip_bytes(size_t num_skip) {
+  if (length_ < num_skip) {
+    return false;
+  }
+  p_ += num_skip;
+  length_ -= num_skip;
+  return true;
 }
 
-static bool decode_length(asn1_context_t* ctx, size_t* out_len) {
-    int num_octets = get_byte(ctx);
-    if (num_octets == -1) {
-        return false;
-    }
-    if ((num_octets & 0x80) == 0x00) {
-        *out_len = num_octets;
-        return 1;
-    }
-    num_octets &= kMaskTag;
-    if ((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(ctx);
-        if (byte == -1) {
-            return false;
-        }
-        length <<= 8;
-        length += byte;
-    }
-    *out_len = length;
+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_t* asn1_constructed_get(asn1_context_t* ctx) {
-    int type = get_byte(ctx);
-    if (type == -1 || (type & kMaskConstructed) != kTagConstructed) {
-        return NULL;
-    }
-    size_t length;
-    if (!decode_length(ctx, &length) || length > ctx->length) {
-        return NULL;
-    }
-    asn1_context_t* app_ctx = asn1_context_new(ctx->p, length);
-    app_ctx->app_type = type & kMaskAppType;
-    return app_ctx;
+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_constructed_skip_all(asn1_context_t* ctx) {
-    int byte = peek_byte(ctx);
-    while (byte != -1 && (byte & kMaskConstructed) == kTagConstructed) {
-        skip_bytes(ctx, 1);
-        size_t length;
-        if (!decode_length(ctx, &length) || !skip_bytes(ctx, length)) {
-            return false;
-        }
-        byte = peek_byte(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;
     }
-    return byte != -1;
+    byte = peek_byte();
+  }
+  return byte != -1;
 }
 
-int asn1_constructed_type(asn1_context_t* ctx) {
-    return ctx->app_type;
+int asn1_context::asn1_constructed_type() const {
+  return app_type_;
 }
 
-asn1_context_t* asn1_sequence_get(asn1_context_t* ctx) {
-    if ((get_byte(ctx) & kMaskTag) != kTagSequence) {
-        return NULL;
-    }
-    size_t length;
-    if (!decode_length(ctx, &length) || length > ctx->length) {
-        return NULL;
-    }
-    return asn1_context_new(ctx->p, length);
+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_t* asn1_set_get(asn1_context_t* ctx) {
-    if ((get_byte(ctx) & kMaskTag) != kTagSet) {
-        return NULL;
-    }
-    size_t length;
-    if (!decode_length(ctx, &length) || length > ctx->length) {
-        return NULL;
-    }
-    return asn1_context_new(ctx->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_sequence_next(asn1_context_t* ctx) {
-    size_t length;
-    if (get_byte(ctx) == -1 || !decode_length(ctx, &length) || !skip_bytes(ctx, length)) {
-        return false;
-    }
-    return true;
+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_oid_get(asn1_context_t* ctx, const uint8_t** oid, size_t* length) {
-    if (get_byte(ctx) != kTagOid) {
-        return false;
-    }
-    if (!decode_length(ctx, length) || *length == 0 || *length > ctx->length) {
-        return false;
-    }
-    *oid = ctx->p;
-    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_octet_string_get(asn1_context_t* ctx, const uint8_t** octet_string, size_t* length) {
-    if (get_byte(ctx) != kTagOctetString) {
-        return false;
-    }
-    if (!decode_length(ctx, length) || *length == 0 || *length > ctx->length) {
-        return false;
-    }
-    *octet_string = ctx->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;
 }
diff --git a/asn1_decoder.h b/asn1_decoder.h
index fbd118f9..3e992115 100644
--- a/asn1_decoder.h
+++ b/asn1_decoder.h
@@ -14,23 +14,42 @@
  * limitations under the License.
  */
 
-
 #ifndef ASN1_DECODER_H_
 #define ASN1_DECODER_H_
 
 #include <stdint.h>
 
-typedef struct asn1_context asn1_context_t;
-
-asn1_context_t* asn1_context_new(const uint8_t* buffer, size_t length);
-void asn1_context_free(asn1_context_t* ctx);
-asn1_context_t* asn1_constructed_get(asn1_context_t* ctx);
-bool asn1_constructed_skip_all(asn1_context_t* ctx);
-int asn1_constructed_type(asn1_context_t* ctx);
-asn1_context_t* asn1_sequence_get(asn1_context_t* ctx);
-asn1_context_t* asn1_set_get(asn1_context_t* ctx);
-bool asn1_sequence_next(asn1_context_t* seq);
-bool asn1_oid_get(asn1_context_t* ctx, const uint8_t** oid, size_t* length);
-bool asn1_octet_string_get(asn1_context_t* ctx, const uint8_t** octet_string, size_t* length);
+class asn1_context {
+ public:
+  asn1_context(const uint8_t* buffer, size_t length) : p_(buffer), length_(length), app_type_(0) {}
+  int asn1_constructed_type() const;
+  asn1_context* asn1_constructed_get();
+  bool asn1_constructed_skip_all();
+  asn1_context* asn1_sequence_get();
+  asn1_context* asn1_set_get();
+  bool asn1_sequence_next();
+  bool asn1_oid_get(const uint8_t** oid, size_t* length);
+  bool asn1_octet_string_get(const uint8_t** octet_string, size_t* length);
+
+ private:
+  static constexpr int kMaskConstructed = 0xE0;
+  static constexpr int kMaskTag = 0x7F;
+  static constexpr int kMaskAppType = 0x1F;
+
+  static constexpr int kTagOctetString = 0x04;
+  static constexpr int kTagOid = 0x06;
+  static constexpr int kTagSequence = 0x30;
+  static constexpr int kTagSet = 0x31;
+  static constexpr int kTagConstructed = 0xA0;
+
+  int peek_byte() const;
+  int get_byte();
+  bool skip_bytes(size_t num_skip);
+  bool decode_length(size_t* out_len);
+
+  const uint8_t* p_;
+  size_t length_;
+  int app_type_;
+};
 
 #endif /* ASN1_DECODER_H_ */
diff --git a/tests/unit/asn1_decoder_test.cpp b/tests/unit/asn1_decoder_test.cpp
index 997639d8..b334a655 100644
--- a/tests/unit/asn1_decoder_test.cpp
+++ b/tests/unit/asn1_decoder_test.cpp
@@ -14,225 +14,188 @@
  * limitations under the License.
  */
 
-#define LOG_TAG "asn1_decoder_test"
+#include <stdint.h>
+
+#include <memory>
 
-#include <cutils/log.h>
 #include <gtest/gtest.h>
-#include <stdint.h>
-#include <unistd.h>
 
 #include "asn1_decoder.h"
 
-namespace android {
-
-class Asn1DecoderTest : public testing::Test {
-};
-
-TEST_F(Asn1DecoderTest, Empty_Failure) {
-    uint8_t empty[] = { };
-    asn1_context_t* ctx = asn1_context_new(empty, sizeof(empty));
-
-    EXPECT_EQ(NULL, asn1_constructed_get(ctx));
-    EXPECT_FALSE(asn1_constructed_skip_all(ctx));
-    EXPECT_EQ(0, asn1_constructed_type(ctx));
-    EXPECT_EQ(NULL, asn1_sequence_get(ctx));
-    EXPECT_EQ(NULL, asn1_set_get(ctx));
-    EXPECT_FALSE(asn1_sequence_next(ctx));
-
-    const uint8_t* junk;
-    size_t length;
-    EXPECT_FALSE(asn1_oid_get(ctx, &junk, &length));
-    EXPECT_FALSE(asn1_octet_string_get(ctx, &junk, &length));
-
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, ConstructedGet_TruncatedLength_Failure) {
-    uint8_t truncated[] = { 0xA0, 0x82, };
-    asn1_context_t* ctx = asn1_context_new(truncated, sizeof(truncated));
-    EXPECT_EQ(NULL, asn1_constructed_get(ctx));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, ConstructedGet_LengthTooBig_Failure) {
-    uint8_t truncated[] = { 0xA0, 0x8a, 0xA5, 0x5A, 0xA5, 0x5A,
-                            0xA5, 0x5A, 0xA5, 0x5A, 0xA5, 0x5A, };
-    asn1_context_t* ctx = asn1_context_new(truncated, sizeof(truncated));
-    EXPECT_EQ(NULL, asn1_constructed_get(ctx));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, ConstructedGet_TooSmallForChild_Failure) {
-    uint8_t data[] = { 0xA5, 0x02, 0x06, 0x01, 0x01, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    asn1_context_t* ptr = asn1_constructed_get(ctx);
-    ASSERT_NE((asn1_context_t*)NULL, ptr);
-    EXPECT_EQ(5, asn1_constructed_type(ptr));
-    const uint8_t* oid;
-    size_t length;
-    EXPECT_FALSE(asn1_oid_get(ptr, &oid, &length));
-    asn1_context_free(ptr);
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, ConstructedGet_Success) {
-    uint8_t data[] = { 0xA5, 0x03, 0x06, 0x01, 0x01, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    asn1_context_t* ptr = asn1_constructed_get(ctx);
-    ASSERT_NE((asn1_context_t*)NULL, ptr);
-    EXPECT_EQ(5, asn1_constructed_type(ptr));
-    const uint8_t* oid;
-    size_t length;
-    ASSERT_TRUE(asn1_oid_get(ptr, &oid, &length));
-    EXPECT_EQ(1U, length);
-    EXPECT_EQ(0x01U, *oid);
-    asn1_context_free(ptr);
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, ConstructedSkipAll_TruncatedLength_Failure) {
-    uint8_t truncated[] = { 0xA2, 0x82, };
-    asn1_context_t* ctx = asn1_context_new(truncated, sizeof(truncated));
-    EXPECT_FALSE(asn1_constructed_skip_all(ctx));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, ConstructedSkipAll_Success) {
-    uint8_t data[] = { 0xA0, 0x03, 0x02, 0x01, 0x01,
-                            0xA1, 0x03, 0x02, 0x01, 0x01,
-                            0x06, 0x01, 0xA5, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    ASSERT_TRUE(asn1_constructed_skip_all(ctx));
-    const uint8_t* oid;
-    size_t length;
-    ASSERT_TRUE(asn1_oid_get(ctx, &oid, &length));
-    EXPECT_EQ(1U, length);
-    EXPECT_EQ(0xA5U, *oid);
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, SequenceGet_TruncatedLength_Failure) {
-    uint8_t truncated[] = { 0x30, 0x82, };
-    asn1_context_t* ctx = asn1_context_new(truncated, sizeof(truncated));
-    EXPECT_EQ(NULL, asn1_sequence_get(ctx));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, SequenceGet_TooSmallForChild_Failure) {
-    uint8_t data[] = { 0x30, 0x02, 0x06, 0x01, 0x01, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    asn1_context_t* ptr = asn1_sequence_get(ctx);
-    ASSERT_NE((asn1_context_t*)NULL, ptr);
-    const uint8_t* oid;
-    size_t length;
-    EXPECT_FALSE(asn1_oid_get(ptr, &oid, &length));
-    asn1_context_free(ptr);
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, SequenceGet_Success) {
-    uint8_t data[] = { 0x30, 0x03, 0x06, 0x01, 0x01, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    asn1_context_t* ptr = asn1_sequence_get(ctx);
-    ASSERT_NE((asn1_context_t*)NULL, ptr);
-    const uint8_t* oid;
-    size_t length;
-    ASSERT_TRUE(asn1_oid_get(ptr, &oid, &length));
-    EXPECT_EQ(1U, length);
-    EXPECT_EQ(0x01U, *oid);
-    asn1_context_free(ptr);
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, SetGet_TruncatedLength_Failure) {
-    uint8_t truncated[] = { 0x31, 0x82, };
-    asn1_context_t* ctx = asn1_context_new(truncated, sizeof(truncated));
-    EXPECT_EQ(NULL, asn1_set_get(ctx));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, SetGet_TooSmallForChild_Failure) {
-    uint8_t data[] = { 0x31, 0x02, 0x06, 0x01, 0x01, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    asn1_context_t* ptr = asn1_set_get(ctx);
-    ASSERT_NE((asn1_context_t*)NULL, ptr);
-    const uint8_t* oid;
-    size_t length;
-    EXPECT_FALSE(asn1_oid_get(ptr, &oid, &length));
-    asn1_context_free(ptr);
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, SetGet_Success) {
-    uint8_t data[] = { 0x31, 0x03, 0x06, 0x01, 0xBA, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    asn1_context_t* ptr = asn1_set_get(ctx);
-    ASSERT_NE((asn1_context_t*)NULL, ptr);
-    const uint8_t* oid;
-    size_t length;
-    ASSERT_TRUE(asn1_oid_get(ptr, &oid, &length));
-    EXPECT_EQ(1U, length);
-    EXPECT_EQ(0xBAU, *oid);
-    asn1_context_free(ptr);
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, OidGet_LengthZero_Failure) {
-    uint8_t data[] = { 0x06, 0x00, 0x01, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    const uint8_t* oid;
-    size_t length;
-    EXPECT_FALSE(asn1_oid_get(ctx, &oid, &length));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, OidGet_TooSmall_Failure) {
-    uint8_t data[] = { 0x06, 0x01, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    const uint8_t* oid;
-    size_t length;
-    EXPECT_FALSE(asn1_oid_get(ctx, &oid, &length));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, OidGet_Success) {
-    uint8_t data[] = { 0x06, 0x01, 0x99, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    const uint8_t* oid;
-    size_t length;
-    ASSERT_TRUE(asn1_oid_get(ctx, &oid, &length));
-    EXPECT_EQ(1U, length);
-    EXPECT_EQ(0x99U, *oid);
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, OctetStringGet_LengthZero_Failure) {
-    uint8_t data[] = { 0x04, 0x00, 0x55, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    const uint8_t* string;
-    size_t length;
-    ASSERT_FALSE(asn1_octet_string_get(ctx, &string, &length));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, OctetStringGet_TooSmall_Failure) {
-    uint8_t data[] = { 0x04, 0x01, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    const uint8_t* string;
-    size_t length;
-    ASSERT_FALSE(asn1_octet_string_get(ctx, &string, &length));
-    asn1_context_free(ctx);
-}
-
-TEST_F(Asn1DecoderTest, OctetStringGet_Success) {
-    uint8_t data[] = { 0x04, 0x01, 0xAA, };
-    asn1_context_t* ctx = asn1_context_new(data, sizeof(data));
-    const uint8_t* string;
-    size_t length;
-    ASSERT_TRUE(asn1_octet_string_get(ctx, &string, &length));
-    EXPECT_EQ(1U, length);
-    EXPECT_EQ(0xAAU, *string);
-    asn1_context_free(ctx);
-}
-
-} // namespace android
+TEST(Asn1DecoderTest, Empty_Failure) {
+  uint8_t empty[] = {};
+  asn1_context ctx(empty, sizeof(empty));
+
+  ASSERT_EQ(nullptr, ctx.asn1_constructed_get());
+  ASSERT_FALSE(ctx.asn1_constructed_skip_all());
+  ASSERT_EQ(0, ctx.asn1_constructed_type());
+  ASSERT_EQ(nullptr, ctx.asn1_sequence_get());
+  ASSERT_EQ(nullptr, ctx.asn1_set_get());
+  ASSERT_FALSE(ctx.asn1_sequence_next());
+
+  const uint8_t* junk;
+  size_t length;
+  ASSERT_FALSE(ctx.asn1_oid_get(&junk, &length));
+  ASSERT_FALSE(ctx.asn1_octet_string_get(&junk, &length));
+}
+
+TEST(Asn1DecoderTest, ConstructedGet_TruncatedLength_Failure) {
+  uint8_t truncated[] = { 0xA0, 0x82 };
+  asn1_context ctx(truncated, sizeof(truncated));
+  ASSERT_EQ(nullptr, ctx.asn1_constructed_get());
+}
+
+TEST(Asn1DecoderTest, ConstructedGet_LengthTooBig_Failure) {
+  uint8_t truncated[] = { 0xA0, 0x8a, 0xA5, 0x5A, 0xA5, 0x5A, 0xA5, 0x5A, 0xA5, 0x5A, 0xA5, 0x5A };
+  asn1_context ctx(truncated, sizeof(truncated));
+  ASSERT_EQ(nullptr, ctx.asn1_constructed_get());
+}
+
+TEST(Asn1DecoderTest, ConstructedGet_TooSmallForChild_Failure) {
+  uint8_t data[] = { 0xA5, 0x02, 0x06, 0x01, 0x01 };
+  asn1_context ctx(data, sizeof(data));
+  std::unique_ptr<asn1_context> ptr(ctx.asn1_constructed_get());
+  ASSERT_NE(nullptr, ptr);
+  ASSERT_EQ(5, ptr->asn1_constructed_type());
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_FALSE(ptr->asn1_oid_get(&oid, &length));
+}
+
+TEST(Asn1DecoderTest, ConstructedGet_Success) {
+  uint8_t data[] = { 0xA5, 0x03, 0x06, 0x01, 0x01 };
+  asn1_context ctx(data, sizeof(data));
+  std::unique_ptr<asn1_context> ptr(ctx.asn1_constructed_get());
+  ASSERT_NE(nullptr, ptr);
+  ASSERT_EQ(5, ptr->asn1_constructed_type());
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_TRUE(ptr->asn1_oid_get(&oid, &length));
+  ASSERT_EQ(1U, length);
+  ASSERT_EQ(0x01U, *oid);
+}
+
+TEST(Asn1DecoderTest, ConstructedSkipAll_TruncatedLength_Failure) {
+  uint8_t truncated[] = { 0xA2, 0x82 };
+  asn1_context ctx(truncated, sizeof(truncated));
+  ASSERT_FALSE(ctx.asn1_constructed_skip_all());
+}
+
+TEST(Asn1DecoderTest, ConstructedSkipAll_Success) {
+  uint8_t data[] = { 0xA0, 0x03, 0x02, 0x01, 0x01, 0xA1, 0x03, 0x02, 0x01, 0x01, 0x06, 0x01, 0xA5 };
+  asn1_context ctx(data, sizeof(data));
+  ASSERT_TRUE(ctx.asn1_constructed_skip_all());
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_TRUE(ctx.asn1_oid_get(&oid, &length));
+  ASSERT_EQ(1U, length);
+  ASSERT_EQ(0xA5U, *oid);
+}
+
+TEST(Asn1DecoderTest, SequenceGet_TruncatedLength_Failure) {
+  uint8_t truncated[] = { 0x30, 0x82 };
+  asn1_context ctx(truncated, sizeof(truncated));
+  ASSERT_EQ(nullptr, ctx.asn1_sequence_get());
+}
+
+TEST(Asn1DecoderTest, SequenceGet_TooSmallForChild_Failure) {
+  uint8_t data[] = { 0x30, 0x02, 0x06, 0x01, 0x01 };
+  asn1_context ctx(data, sizeof(data));
+  std::unique_ptr<asn1_context> ptr(ctx.asn1_sequence_get());
+  ASSERT_NE(nullptr, ptr);
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_FALSE(ptr->asn1_oid_get(&oid, &length));
+}
+
+TEST(Asn1DecoderTest, SequenceGet_Success) {
+  uint8_t data[] = { 0x30, 0x03, 0x06, 0x01, 0x01 };
+  asn1_context ctx(data, sizeof(data));
+  std::unique_ptr<asn1_context> ptr(ctx.asn1_sequence_get());
+  ASSERT_NE(nullptr, ptr);
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_TRUE(ptr->asn1_oid_get(&oid, &length));
+  ASSERT_EQ(1U, length);
+  ASSERT_EQ(0x01U, *oid);
+}
+
+TEST(Asn1DecoderTest, SetGet_TruncatedLength_Failure) {
+  uint8_t truncated[] = { 0x31, 0x82 };
+  asn1_context ctx(truncated, sizeof(truncated));
+  ASSERT_EQ(nullptr, ctx.asn1_set_get());
+}
+
+TEST(Asn1DecoderTest, SetGet_TooSmallForChild_Failure) {
+  uint8_t data[] = { 0x31, 0x02, 0x06, 0x01, 0x01 };
+  asn1_context ctx(data, sizeof(data));
+  std::unique_ptr<asn1_context> ptr(ctx.asn1_set_get());
+  ASSERT_NE(nullptr, ptr);
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_FALSE(ptr->asn1_oid_get(&oid, &length));
+}
+
+TEST(Asn1DecoderTest, SetGet_Success) {
+  uint8_t data[] = { 0x31, 0x03, 0x06, 0x01, 0xBA };
+  asn1_context ctx(data, sizeof(data));
+  std::unique_ptr<asn1_context> ptr(ctx.asn1_set_get());
+  ASSERT_NE(nullptr, ptr);
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_TRUE(ptr->asn1_oid_get(&oid, &length));
+  ASSERT_EQ(1U, length);
+  ASSERT_EQ(0xBAU, *oid);
+}
+
+TEST(Asn1DecoderTest, OidGet_LengthZero_Failure) {
+  uint8_t data[] = { 0x06, 0x00, 0x01 };
+  asn1_context ctx(data, sizeof(data));
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_FALSE(ctx.asn1_oid_get(&oid, &length));
+}
+
+TEST(Asn1DecoderTest, OidGet_TooSmall_Failure) {
+  uint8_t data[] = { 0x06, 0x01 };
+  asn1_context ctx(data, sizeof(data));
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_FALSE(ctx.asn1_oid_get(&oid, &length));
+}
+
+TEST(Asn1DecoderTest, OidGet_Success) {
+  uint8_t data[] = { 0x06, 0x01, 0x99 };
+  asn1_context ctx(data, sizeof(data));
+  const uint8_t* oid;
+  size_t length;
+  ASSERT_TRUE(ctx.asn1_oid_get(&oid, &length));
+  ASSERT_EQ(1U, length);
+  ASSERT_EQ(0x99U, *oid);
+}
+
+TEST(Asn1DecoderTest, OctetStringGet_LengthZero_Failure) {
+  uint8_t data[] = { 0x04, 0x00, 0x55 };
+  asn1_context ctx(data, sizeof(data));
+  const uint8_t* string;
+  size_t length;
+  ASSERT_FALSE(ctx.asn1_octet_string_get(&string, &length));
+}
+
+TEST(Asn1DecoderTest, OctetStringGet_TooSmall_Failure) {
+  uint8_t data[] = { 0x04, 0x01 };
+  asn1_context ctx(data, sizeof(data));
+  const uint8_t* string;
+  size_t length;
+  ASSERT_FALSE(ctx.asn1_octet_string_get(&string, &length));
+}
+
+TEST(Asn1DecoderTest, OctetStringGet_Success) {
+  uint8_t data[] = { 0x04, 0x01, 0xAA };
+  asn1_context ctx(data, sizeof(data));
+  const uint8_t* string;
+  size_t length;
+  ASSERT_TRUE(ctx.asn1_octet_string_get(&string, &length));
+  ASSERT_EQ(1U, length);
+  ASSERT_EQ(0xAAU, *string);
+}
diff --git a/verifier.cpp b/verifier.cpp
index fa344d74..e9d540cd 100644
--- a/verifier.cpp
+++ b/verifier.cpp
@@ -66,48 +66,50 @@ static bool read_pkcs7(const uint8_t* pkcs7_der, size_t pkcs7_der_len,
   CHECK(sig_der != nullptr);
   sig_der->clear();
 
-  asn1_context_t* ctx = asn1_context_new(pkcs7_der, pkcs7_der_len);
-  if (ctx == NULL) {
+  asn1_context ctx(pkcs7_der, pkcs7_der_len);
+
+  std::unique_ptr<asn1_context> pkcs7_seq(ctx.asn1_sequence_get());
+  if (pkcs7_seq == nullptr || !pkcs7_seq->asn1_sequence_next()) {
     return false;
   }
 
-  asn1_context_t* pkcs7_seq = asn1_sequence_get(ctx);
-  if (pkcs7_seq != NULL && asn1_sequence_next(pkcs7_seq)) {
-    asn1_context_t *signed_data_app = asn1_constructed_get(pkcs7_seq);
-    if (signed_data_app != NULL) {
-      asn1_context_t* signed_data_seq = asn1_sequence_get(signed_data_app);
-      if (signed_data_seq != NULL
-          && asn1_sequence_next(signed_data_seq)
-          && asn1_sequence_next(signed_data_seq)
-          && asn1_sequence_next(signed_data_seq)
-          && asn1_constructed_skip_all(signed_data_seq)) {
-        asn1_context_t *sig_set = asn1_set_get(signed_data_seq);
-        if (sig_set != NULL) {
-          asn1_context_t* sig_seq = asn1_sequence_get(sig_set);
-          if (sig_seq != NULL
-              && asn1_sequence_next(sig_seq)
-              && asn1_sequence_next(sig_seq)
-              && asn1_sequence_next(sig_seq)
-              && asn1_sequence_next(sig_seq)) {
-            const uint8_t* sig_der_ptr;
-            size_t sig_der_length;
-            if (asn1_octet_string_get(sig_seq, &sig_der_ptr, &sig_der_length)) {
-              sig_der->resize(sig_der_length);
-              std::copy(sig_der_ptr, sig_der_ptr + sig_der_length, sig_der->begin());
-            }
-            asn1_context_free(sig_seq);
-          }
-          asn1_context_free(sig_set);
-        }
-        asn1_context_free(signed_data_seq);
-      }
-      asn1_context_free(signed_data_app);
-    }
-    asn1_context_free(pkcs7_seq);
+  std::unique_ptr<asn1_context> signed_data_app(pkcs7_seq->asn1_constructed_get());
+  if (signed_data_app == nullptr) {
+    return false;
+  }
+
+  std::unique_ptr<asn1_context> signed_data_seq(signed_data_app->asn1_sequence_get());
+  if (signed_data_seq == nullptr ||
+      !signed_data_seq->asn1_sequence_next() ||
+      !signed_data_seq->asn1_sequence_next() ||
+      !signed_data_seq->asn1_sequence_next() ||
+      !signed_data_seq->asn1_constructed_skip_all()) {
+    return false;
+  }
+
+  std::unique_ptr<asn1_context> sig_set(signed_data_seq->asn1_set_get());
+  if (sig_set == nullptr) {
+    return false;
+  }
+
+  std::unique_ptr<asn1_context> sig_seq(sig_set->asn1_sequence_get());
+  if (sig_seq == nullptr ||
+      !sig_seq->asn1_sequence_next() ||
+      !sig_seq->asn1_sequence_next() ||
+      !sig_seq->asn1_sequence_next() ||
+      !sig_seq->asn1_sequence_next()) {
+    return false;
+  }
+
+  const uint8_t* sig_der_ptr;
+  size_t sig_der_length;
+  if (!sig_seq->asn1_octet_string_get(&sig_der_ptr, &sig_der_length)) {
+    return false;
   }
-  asn1_context_free(ctx);
 
-  return !sig_der->empty();
+  sig_der->resize(sig_der_length);
+  std::copy(sig_der_ptr, sig_der_ptr + sig_der_length, sig_der->begin());
+  return true;
 }
 
 /*