Add libcrypto_utils.

This provides a tiny library implementing encode/decode functionality
for Android's custom RSA public key binary format. Keys are encoded
from and decoded to BoringSSL RSA key objects.

Change-Id: I55e5522d557e0e9f35927a87b6581f020ee34e7a

5 files changed, 437 insertions, 0 deletions

diff --git a/libcrypto_utils/Android.mk b/libcrypto_utils/Android.mk
new file mode 100644
index 000000000..5e9763fe5
--- /dev/null
+++ b/libcrypto_utils/Android.mk
@@ -0,0 +1,56 @@
+#
+# Copyright (C) 2016 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.
+#
+
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := libcrypto_utils
+LOCAL_SRC_FILES := android_pubkey.c
+LOCAL_CFLAGS := -Wall -Werror -Wextra -std=c99
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
+LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
+LOCAL_SHARED_LIBRARIES := libcrypto
+include $(BUILD_SHARED_LIBRARY)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := libcrypto_utils
+LOCAL_SRC_FILES := android_pubkey.c
+LOCAL_CFLAGS := -Wall -Werror -Wextra -std=c99
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
+LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
+LOCAL_SHARED_LIBRARIES := libcrypto-host
+include $(BUILD_HOST_SHARED_LIBRARY)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := libcrypto_utils_static
+LOCAL_SRC_FILES := android_pubkey.c
+LOCAL_CFLAGS := -Wall -Werror -Wextra -std=c99
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
+LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
+LOCAL_STATIC_LIBRARIES := libcrypto_static
+include $(BUILD_STATIC_LIBRARY)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := libcrypto_utils_static
+LOCAL_MODULE_HOST_OS := darwin linux windows
+LOCAL_SRC_FILES := android_pubkey.c
+LOCAL_CFLAGS := -Wall -Werror -Wextra -std=c99
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
+LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
+LOCAL_STATIC_LIBRARIES := libcrypto_static
+include $(BUILD_HOST_STATIC_LIBRARY)
+
+include $(call all-makefiles-under,$(LOCAL_PATH))
diff --git a/libcrypto_utils/android_pubkey.c b/libcrypto_utils/android_pubkey.c
new file mode 100644
index 000000000..9cd9aabe1
--- /dev/null
+++ b/libcrypto_utils/android_pubkey.c
@@ -0,0 +1,167 @@
+/*
+ * Copyright (C) 2016 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 <crypto_utils/android_pubkey.h>
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+// Better safe than sorry.
+#if (ANDROID_PUBKEY_MODULUS_SIZE % 4) != 0
+#error RSA modulus size must be multiple of the word size!
+#endif
+
+// Size of the RSA modulus in words.
+#define ANDROID_PUBKEY_MODULUS_SIZE_WORDS (ANDROID_PUBKEY_MODULUS_SIZE / 4)
+
+// This file implements encoding and decoding logic for Android's custom RSA
+// public key binary format. Public keys are stored as a sequence of
+// little-endian 32 bit words. Note that Android only supports little-endian
+// processors, so we don't do any byte order conversions when parsing the binary
+// struct.
+typedef struct RSAPublicKey {
+    // Modulus length. This must be ANDROID_PUBKEY_MODULUS_SIZE.
+    uint32_t modulus_size_words;
+
+    // Precomputed montgomery parameter: -1 / n[0] mod 2^32
+    uint32_t n0inv;
+
+    // RSA modulus as a little-endian array.
+    uint8_t modulus[ANDROID_PUBKEY_MODULUS_SIZE];
+
+    // Montgomery parameter R^2 as a little-endian array of little-endian words.
+    uint8_t rr[ANDROID_PUBKEY_MODULUS_SIZE];
+
+    // RSA modulus: 3 or 65537
+    uint32_t exponent;
+} RSAPublicKey;
+
+// Reverses byte order in |buffer|.
+static void reverse_bytes(uint8_t* buffer, size_t size) {
+  for (size_t i = 0; i < (size + 1) / 2; ++i) {
+    uint8_t tmp = buffer[i];
+    buffer[i] = buffer[size - i - 1];
+    buffer[size - i - 1] = tmp;
+  }
+}
+
+bool android_pubkey_decode(const uint8_t* key_buffer, size_t size, RSA** key) {
+  const RSAPublicKey* key_struct = (RSAPublicKey*)key_buffer;
+  bool ret = false;
+  uint8_t modulus_buffer[ANDROID_PUBKEY_MODULUS_SIZE];
+  RSA* new_key = RSA_new();
+  if (!new_key) {
+    goto cleanup;
+  }
+
+  // Check |size| is large enough and the modulus size is correct.
+  if (size < sizeof(RSAPublicKey)) {
+    goto cleanup;
+  }
+  if (key_struct->modulus_size_words != ANDROID_PUBKEY_MODULUS_SIZE_WORDS) {
+    goto cleanup;
+  }
+
+  // Convert the modulus to big-endian byte order as expected by BN_bin2bn.
+  memcpy(modulus_buffer, key_struct->modulus, sizeof(modulus_buffer));
+  reverse_bytes(modulus_buffer, sizeof(modulus_buffer));
+  new_key->n = BN_bin2bn(modulus_buffer, sizeof(modulus_buffer), NULL);
+  if (!new_key->n) {
+    goto cleanup;
+  }
+
+  // Read the exponent.
+  new_key->e = BN_new();
+  if (!new_key->e || !BN_set_word(new_key->e, key_struct->exponent)) {
+    goto cleanup;
+  }
+
+  // Note that we don't extract the montgomery parameters n0inv and rr from
+  // the RSAPublicKey structure. They assume a word size of 32 bits, but
+  // BoringSSL may use a word size of 64 bits internally, so we're lacking the
+  // top 32 bits of n0inv in general. For now, we just ignore the parameters
+  // and have BoringSSL recompute them internally. More sophisticated logic can
+  // be added here if/when we want the additional speedup from using the
+  // pre-computed montgomery parameters.
+
+  *key = new_key;
+  ret = true;
+
+cleanup:
+  if (!ret && new_key) {
+    RSA_free(new_key);
+  }
+  return ret;
+}
+
+static bool android_pubkey_encode_bignum(const BIGNUM* num, uint8_t* buffer) {
+  if (!BN_bn2bin_padded(buffer, ANDROID_PUBKEY_MODULUS_SIZE, num)) {
+    return false;
+  }
+
+  reverse_bytes(buffer, ANDROID_PUBKEY_MODULUS_SIZE);
+  return true;
+}
+
+bool android_pubkey_encode(const RSA* key, uint8_t* key_buffer, size_t size) {
+  RSAPublicKey* key_struct = (RSAPublicKey*)key_buffer;
+  bool ret = false;
+  BN_CTX* ctx = BN_CTX_new();
+  BIGNUM* r32 = BN_new();
+  BIGNUM* n0inv = BN_new();
+  BIGNUM* rr = BN_new();
+
+  if (sizeof(RSAPublicKey) > size ||
+      RSA_size(key) != ANDROID_PUBKEY_MODULUS_SIZE) {
+    goto cleanup;
+  }
+
+  // Store the modulus size.
+  key_struct->modulus_size_words = ANDROID_PUBKEY_MODULUS_SIZE_WORDS;
+
+  // Compute and store n0inv = -1 / N[0] mod 2^32.
+  if (!ctx || !r32 || !n0inv || !BN_set_bit(r32, 32) ||
+      !BN_mod(n0inv, key->n, r32, ctx) ||
+      !BN_mod_inverse(n0inv, n0inv, r32, ctx) || !BN_sub(n0inv, r32, n0inv)) {
+    goto cleanup;
+  }
+  key_struct->n0inv = (uint32_t)BN_get_word(n0inv);
+
+  // Store the modulus.
+  if (!android_pubkey_encode_bignum(key->n, key_struct->modulus)) {
+    goto cleanup;
+  }
+
+  // Compute and store rr = (2^(rsa_size)) ^ 2 mod N.
+  if (!ctx || !rr || !BN_set_bit(rr, ANDROID_PUBKEY_MODULUS_SIZE * 8) ||
+      !BN_mod_sqr(rr, rr, key->n, ctx) ||
+      !android_pubkey_encode_bignum(rr, key_struct->rr)) {
+    goto cleanup;
+  }
+
+  // Store the exponent.
+  key_struct->exponent = (uint32_t)BN_get_word(key->e);
+
+  ret = true;
+
+cleanup:
+  BN_free(rr);
+  BN_free(n0inv);
+  BN_free(r32);
+  BN_CTX_free(ctx);
+  return ret;
+}
diff --git a/libcrypto_utils/include/crypto_utils/android_pubkey.h b/libcrypto_utils/include/crypto_utils/android_pubkey.h
new file mode 100644
index 000000000..1045eba0f
--- /dev/null
+++ b/libcrypto_utils/include/crypto_utils/android_pubkey.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#ifndef CRYPTO_UTILS_ANDROID_PUBKEY_H
+#define CRYPTO_UTILS_ANDROID_PUBKEY_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <openssl/rsa.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Size of an RSA modulus such as an encrypted block or a signature.
+#define ANDROID_PUBKEY_MODULUS_SIZE (2048 / 8)
+
+// Size of an encoded RSA key.
+#define ANDROID_PUBKEY_ENCODED_SIZE \
+  (3 * sizeof(uint32_t) + 2 * ANDROID_PUBKEY_MODULUS_SIZE)
+
+/* Allocates a new RSA |key| object, decodes a public RSA key stored in
+ * Android's custom binary format from |key_buffer| and sets the key parameters
+ * in |key|. |size| specifies the size of the key buffer and must be at least
+ * |ANDROID_PUBKEY_ENCODED_SIZE|. The resulting |*key| can be used with the
+ * standard BoringSSL API to perform public operations.
+ *
+ * Returns true if successful, in which case the caller receives ownership of
+ * the |*key| object, i.e. needs to call RSA_free() when done with it. If there
+ * is an error, |key| is left untouched and the return value will be false.
+ */
+bool android_pubkey_decode(const uint8_t* key_buffer, size_t size, RSA** key);
+
+/* Encodes |key| in the Android RSA public key binary format and stores the
+ * bytes in |key_buffer|. |key_buffer| should be of size at least
+ * |ANDROID_PUBKEY_ENCODED_SIZE|.
+ *
+ * Returns true if successful, false on error.
+ */
+bool android_pubkey_encode(const RSA* key, uint8_t* key_buffer, size_t size);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif  // CRYPTO_UTILS_ANDROID_PUBKEY_H
diff --git a/libcrypto_utils/tests/Android.mk b/libcrypto_utils/tests/Android.mk
new file mode 100644
index 000000000..dad82f70f
--- /dev/null
+++ b/libcrypto_utils/tests/Android.mk
@@ -0,0 +1,24 @@
+#
+# Copyright (C) 2016 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.
+#
+
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := libcrypto_utils_test
+LOCAL_SRC_FILES := android_pubkey_test.cpp
+LOCAL_CFLAGS := -Wall -Werror -Wextra -std=c++11
+LOCAL_SHARED_LIBRARIES := libcrypto_utils libcrypto-host
+include $(BUILD_HOST_NATIVE_TEST)
diff --git a/libcrypto_utils/tests/android_pubkey_test.cpp b/libcrypto_utils/tests/android_pubkey_test.cpp
new file mode 100644
index 000000000..f8c2e0cae
--- /dev/null
+++ b/libcrypto_utils/tests/android_pubkey_test.cpp
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2016 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 <crypto_utils/android_pubkey.h>
+
+#include <string.h>
+
+#include <memory>
+
+#include <openssl/obj_mac.h>
+#include <openssl/rsa.h>
+
+#include <gtest/gtest.h>
+
+// Test digest to verify.
+const uint8_t kDigest[] = {
+    0x31, 0x5f, 0x5b, 0xdb, 0x76, 0xd0, 0x78, 0xc4, 0x3b, 0x8a, 0xc0,
+    0x06, 0x4e, 0x4a, 0x01, 0x64, 0x61, 0x2b, 0x1f, 0xce, 0x77, 0xc8,
+    0x69, 0x34, 0x5b, 0xfc, 0x94, 0xc7, 0x58, 0x94, 0xed, 0xd3,
+};
+
+// 2048 RSA test key.
+const uint8_t kKey2048[ANDROID_PUBKEY_ENCODED_SIZE] = {
+    0x40, 0x00, 0x00, 0x00, 0x05, 0x75, 0x61, 0xd1, 0x33, 0xf0, 0x2d, 0x12,
+    0x45, 0xfb, 0xae, 0x07, 0x02, 0x15, 0x4f, 0x3a, 0x2b, 0xa3, 0xbc, 0x49,
+    0xbd, 0x14, 0x07, 0xa0, 0xc0, 0x9f, 0x0c, 0x52, 0x60, 0x77, 0x9f, 0xa2,
+    0x31, 0xd0, 0xa7, 0xfb, 0x7e, 0xde, 0xfb, 0xc9, 0x05, 0xc0, 0x97, 0xf7,
+    0x74, 0x99, 0xe6, 0xd1, 0x08, 0xa6, 0xc2, 0x59, 0x5a, 0xd8, 0x37, 0x1d,
+    0xe0, 0x48, 0x5e, 0x63, 0x44, 0x04, 0x8b, 0x05, 0x20, 0xf6, 0x25, 0x67,
+    0x38, 0xb2, 0xb6, 0xf9, 0xbe, 0xb6, 0x1d, 0x7f, 0x1b, 0x71, 0x8a, 0xeb,
+    0xb7, 0xf8, 0x01, 0xc1, 0x5e, 0xf7, 0xfe, 0x48, 0x08, 0x27, 0x0f, 0x27,
+    0x2a, 0x64, 0x1a, 0x43, 0x8d, 0xcf, 0x5a, 0x33, 0x5c, 0x18, 0xc5, 0xf4,
+    0xe7, 0xfe, 0xee, 0xd3, 0x12, 0x62, 0xad, 0x61, 0x78, 0x9a, 0x03, 0xb0,
+    0xaf, 0xab, 0x91, 0x57, 0x46, 0xbf, 0x18, 0xc6, 0xbc, 0x0c, 0x6b, 0x55,
+    0xcd, 0xda, 0xc4, 0xcc, 0x98, 0x46, 0x91, 0x99, 0xbc, 0xa3, 0xca, 0x6c,
+    0x86, 0xa6, 0x1c, 0x8f, 0xca, 0xf8, 0xf6, 0x8a, 0x00, 0x8e, 0x05, 0xd7,
+    0x13, 0x43, 0xe2, 0xf2, 0x1a, 0x13, 0xf3, 0x50, 0x13, 0xa4, 0xf2, 0x4e,
+    0x41, 0xb1, 0x36, 0x78, 0x55, 0x4c, 0x5e, 0x27, 0xc5, 0xc0, 0x4b, 0xd8,
+    0x93, 0xaa, 0x7e, 0xf0, 0x90, 0x08, 0x10, 0x26, 0x72, 0x6d, 0xb9, 0x21,
+    0xae, 0x4d, 0x01, 0x4b, 0x55, 0x1d, 0xe7, 0x1e, 0x5e, 0x31, 0x6e, 0x62,
+    0xd1, 0x33, 0x26, 0xcb, 0xdb, 0xfe, 0x72, 0x98, 0xc8, 0x06, 0x1c, 0x12,
+    0xdf, 0xfc, 0x74, 0xe5, 0x7a, 0x6f, 0xf5, 0xa3, 0x63, 0x08, 0xe3, 0x02,
+    0x68, 0x4d, 0x7c, 0x70, 0x05, 0xec, 0x95, 0x7e, 0x24, 0xa4, 0xbc, 0x4c,
+    0xcd, 0x39, 0x14, 0xb5, 0x2a, 0x8f, 0xc1, 0xe3, 0x4e, 0xfa, 0xf8, 0x70,
+    0x50, 0x8f, 0xd5, 0x8e, 0xc7, 0xb5, 0x32, 0x89, 0x4d, 0xbb, 0x6a, 0xc1,
+    0xc1, 0xa2, 0x42, 0x57, 0x57, 0xbd, 0x2a, 0xdc, 0xa6, 0xfd, 0xc8, 0x86,
+    0x44, 0x6a, 0x03, 0x5d, 0x4d, 0x28, 0xe1, 0xde, 0xb4, 0xa9, 0xa5, 0x03,
+    0x61, 0x7a, 0x5f, 0xb1, 0x09, 0x17, 0x2b, 0x9c, 0xa2, 0x54, 0x28, 0xad,
+    0x34, 0xc9, 0x5f, 0x6c, 0x9f, 0xb8, 0xd2, 0xa9, 0x78, 0xa7, 0xaa, 0xb3,
+    0x11, 0x2f, 0x65, 0x9b, 0x4e, 0x67, 0x0c, 0xcc, 0x20, 0x36, 0xbf, 0x26,
+    0x2b, 0x4e, 0xc0, 0xd4, 0xbd, 0x22, 0x64, 0xc4, 0x1c, 0x56, 0x69, 0xdb,
+    0x5f, 0x89, 0xe1, 0x75, 0x68, 0x8d, 0x0e, 0xab, 0x1c, 0x10, 0x1a, 0xc0,
+    0x12, 0x5d, 0x6f, 0xbd, 0x09, 0xbb, 0x47, 0xcb, 0xe7, 0x34, 0xef, 0x56,
+    0xab, 0xea, 0xc3, 0xe9, 0x7f, 0x9a, 0x3d, 0xe9, 0x2d, 0x14, 0x61, 0x25,
+    0x37, 0x5c, 0x3b, 0x4b, 0xaf, 0x5a, 0x4b, 0xc8, 0x99, 0x1a, 0x32, 0x8f,
+    0x54, 0x07, 0xd3, 0x57, 0x8a, 0x3d, 0x2a, 0xf7, 0x9e, 0x7e, 0x92, 0x2a,
+    0x50, 0xe9, 0xd8, 0xdb, 0xd6, 0x03, 0xd3, 0x8e, 0x54, 0x32, 0xce, 0x87,
+    0x93, 0x92, 0xe7, 0x75, 0xe1, 0x6b, 0x78, 0x1a, 0x85, 0xc2, 0x46, 0xa1,
+    0x31, 0xbb, 0xc7, 0xb9, 0x1d, 0xd1, 0x71, 0xe0, 0xe2, 0x9b, 0x9c, 0x0d,
+    0xa3, 0xcf, 0x93, 0x4d, 0x87, 0x7b, 0x65, 0xd9, 0xda, 0x4c, 0xd9, 0x6a,
+    0xa6, 0x36, 0xc2, 0xc7, 0xe3, 0x33, 0xe2, 0xc3, 0x83, 0xd1, 0x72, 0x54,
+    0x30, 0x81, 0x5e, 0x34, 0x2c, 0x61, 0xee, 0xf4, 0x48, 0x97, 0xb6, 0xaa,
+    0x47, 0x6a, 0x05, 0x09, 0xd8, 0x4d, 0x90, 0xaf, 0xa8, 0x4e, 0x82, 0xe4,
+    0x8e, 0xb5, 0xe2, 0x65, 0x86, 0x67, 0xe9, 0x5b, 0x4b, 0x9a, 0x68, 0x08,
+    0x30, 0xf6, 0x25, 0x8b, 0x20, 0xda, 0x26, 0x6f, 0xbd, 0x0d, 0xa5, 0xd8,
+    0x6a, 0x7b, 0x01, 0x2f, 0xab, 0x7b, 0xb5, 0xfe, 0x62, 0x37, 0x2d, 0x94,
+    0x43, 0x2f, 0x4d, 0x16, 0x01, 0x00, 0x01, 0x00,
+};
+
+// 2048 bit RSA signature.
+const uint8_t kSignature2048[ANDROID_PUBKEY_MODULUS_SIZE] = {
+    0x3a, 0x11, 0x84, 0x40, 0xc1, 0x2f, 0x13, 0x8c, 0xde, 0xb0, 0xc3, 0x89,
+    0x8a, 0x63, 0xb2, 0x50, 0x93, 0x58, 0xc0, 0x0c, 0xb7, 0x08, 0xe7, 0x6c,
+    0x52, 0x87, 0x4e, 0x78, 0x89, 0xa3, 0x9a, 0x47, 0xeb, 0x11, 0x57, 0xbc,
+    0xb3, 0x97, 0xf8, 0x34, 0xf1, 0xf7, 0xbf, 0x3a, 0xfa, 0x1c, 0x6b, 0xdc,
+    0xd1, 0x02, 0xde, 0x9a, 0x0d, 0x72, 0xe7, 0x19, 0x63, 0x81, 0x46, 0x68,
+    0x1e, 0x63, 0x64, 0xc6, 0x59, 0xe7, 0x7c, 0x39, 0xed, 0x32, 0xd2, 0xd1,
+    0xd5, 0x1f, 0x13, 0x9b, 0x52, 0xdf, 0x34, 0xa3, 0xc0, 0xc4, 0x9a, 0x63,
+    0x9b, 0x9c, 0xbe, 0x22, 0xc8, 0xd8, 0x14, 0x2f, 0x4c, 0x78, 0x36, 0xdb,
+    0x16, 0x41, 0x67, 0xc1, 0x21, 0x8a, 0x73, 0xb2, 0xe5, 0xb0, 0xd3, 0x80,
+    0x91, 0x7a, 0xbf, 0xf9, 0x59, 0x4a, 0x4d, 0x78, 0x45, 0x44, 0xa1, 0x52,
+    0x86, 0x29, 0x48, 0x4d, 0xf0, 0x5d, 0xf2, 0x55, 0xa7, 0xcd, 0xc5, 0x2b,
+    0x7b, 0xe0, 0xb1, 0xf6, 0x2a, 0xd5, 0x61, 0xba, 0x1e, 0x1e, 0x3a, 0xf0,
+    0x55, 0xbc, 0x8c, 0x44, 0x41, 0xfc, 0xb8, 0x8c, 0x76, 0xbf, 0x80, 0x58,
+    0x82, 0x35, 0x4b, 0x0c, 0xfd, 0xef, 0xd5, 0x70, 0xd1, 0x64, 0xcb, 0x46,
+    0x58, 0x37, 0xbc, 0xa9, 0x7d, 0xd4, 0x70, 0xac, 0xce, 0xec, 0xca, 0x48,
+    0xcb, 0x0a, 0x40, 0x77, 0x04, 0x59, 0xca, 0x9c, 0x7d, 0x1a, 0x0b, 0xf0,
+    0xb5, 0xdd, 0xde, 0x71, 0x18, 0xb8, 0xef, 0x90, 0x2a, 0x09, 0x42, 0x39,
+    0x74, 0xff, 0x45, 0xa1, 0x39, 0x17, 0x50, 0x89, 0xa6, 0x5f, 0xbc, 0x9c,
+    0x0c, 0x9b, 0x47, 0x25, 0x79, 0x3e, 0xe3, 0xaa, 0xaf, 0xbe, 0x73, 0x6b,
+    0xcb, 0xe7, 0x35, 0xc1, 0x27, 0x09, 0xcd, 0xeb, 0xd7, 0xcf, 0x63, 0x83,
+    0x64, 0x8c, 0x45, 0x1c, 0x1d, 0x58, 0xcc, 0xd2, 0xf8, 0x2b, 0x4c, 0x4e,
+    0x14, 0x89, 0x2d, 0x70,
+};
+
+struct AndroidPubkeyTest : public ::testing::Test {
+  void SetUp() override {
+    RSA* new_key = nullptr;
+    ASSERT_TRUE(android_pubkey_decode(kKey2048, sizeof(kKey2048), &new_key));
+    key_.reset(new_key);
+  }
+
+  std::unique_ptr<RSA, void(*)(RSA*)> key_ = {nullptr, RSA_free};
+};
+
+TEST_F(AndroidPubkeyTest, Decode) {
+  // Make sure the decoded key successfully verifies a valid signature.
+  EXPECT_TRUE(RSA_verify(NID_sha256, kDigest, sizeof(kDigest), kSignature2048,
+                         sizeof(kSignature2048), key_.get()));
+}
+
+TEST_F(AndroidPubkeyTest, Encode) {
+  uint8_t key_data[ANDROID_PUBKEY_ENCODED_SIZE];
+  ASSERT_TRUE(android_pubkey_encode(key_.get(), key_data, sizeof(key_data)));
+  ASSERT_EQ(0, memcmp(kKey2048, key_data, sizeof(kKey2048)));
+}