Add public key and signature verification to browser-side API keys

content/common/experiments/api_key.cc

Index: content/common/experiments/api_key.cc
diff --git a/content/common/experiments/api_key.cc b/content/common/experiments/api_key.cc
index 09b607f5a523005feca5332e64728b2801dfb127..9bfd48ced3980bc97371cf613f5aeca49643e64d 100644
--- a/content/common/experiments/api_key.cc
+++ b/content/common/experiments/api_key.cc
@@ -5,6 +5,7 @@
 #include "content/common/experiments/api_key.h"
 
 #include <vector>
+#include <openssl/curve25519.h>
 
 #include "base/base64.h"
 #include "base/strings/string_number_conversions.h"
@@ -18,8 +19,19 @@ namespace content {
 
 namespace {
 
+// This is the default public key used for validating signatures.
+// TODO(iclelland): Move this to the embedder, and provide a mechanism to allow
+// for multiple signing keys. https://crbug.com/543220
+static const uint8_t kPublicKey[] = {
+    0x7c, 0xc4, 0xb8, 0x9a, 0x93, 0xba, 0x6e, 0xe2, 0xd0, 0xfd, 0x03,
+    0x1d, 0xfb, 0x32, 0x66, 0xc7, 0x3b, 0x72, 0xfd, 0x54, 0x3a, 0x07,
+    0x51, 0x14, 0x66, 0xaa, 0x02, 0x53, 0x4e, 0x33, 0xa1, 0x15,
+};
+static const size_t kPublicKeyLength = sizeof(kPublicKey);
+
 const char* kApiKeyFieldSeparator = "|";
-}
+
+}  // namespace
 
 ApiKey::~ApiKey() {}
 
@@ -30,6 +42,8 @@ scoped_ptr<ApiKey> ApiKey::Parse(const std::string& key_text) {
 
   // API Key should resemble:
   // signature|origin|api_name|expiry_timestamp
+  // TODO(iclelland): Add version code to API key format to identify key algo
+  // https://crbug.com/570684
   std::vector<std::string> parts =
       SplitString(key_text, kApiKeyFieldSeparator, base::KEEP_WHITESPACE,
                   base::SPLIT_WANT_ALL);
@@ -77,9 +91,7 @@ bool ApiKey::IsAppropriate(const std::string& origin,
 }
 
 bool ApiKey::IsValid(const base::Time& now) const {
-  // TODO(iclelland): Validate signature on key data here as well.
-  // https://crbug.com/543215
-  return ValidateDate(now);
+  return ValidateDate(now) && ValidateSignature(kPublicKey, kPublicKeyLength);
 }
 
 bool ApiKey::ValidateOrigin(const std::string& origin) const {
@@ -95,4 +107,27 @@ bool ApiKey::ValidateDate(const base::Time& now) const {
   return expiry_time > now;
 }
 
+bool ApiKey::ValidateSignature(const uint8_t* public_key,
+                               size_t public_key_length) const {
+  return ValidateSignature(signature_, data_, public_key, public_key_length);
+}
+
+// static
+bool ApiKey::ValidateSignature(const std::string& signature_text,
+                               const std::string& data,
+                               const uint8_t* public_key,
+                               size_t public_key_length) {

[chasej, 2016/01/11 16:11:25]

Remove the public_key_length parameter?  I don't see it used with the new
algorithm for signature validation.  That should allow the constant
kPublicKeyLength to be removed as well.

[iclelland, 2016/01/11 18:59:40]

No, it's a holdover from the previous (RSAPSS) code. Removed.

+  std::string signature;
+  // signature is base64-encoded
+  if (!base::Base64Decode(signature_text, &signature)) {
+    return false;
+  }
+
+  // TODO: verify signature length is 64
+  int result = ED25519_verify(
+      reinterpret_cast<const uint8_t*>(data.data()), data.length(),
+      reinterpret_cast<const uint8_t*>(signature.data()), public_key);
+  return (result != 0);
+}
+
 }  // namespace content