Add production GEEK validation code

Add the 2021 production Google Endpoint Encryption Key to the EEK
validation code.

The GEEK is a full COSE_Key, containing not only the pubkey, but
key type, algorithm, curve, and public key all in one blob.

Also switch to using string_view instead of vector so that we're not
using non-trivially constructed types in static variables. This allows
us to make the values constexpr, avoiding all heap use.

Lastly, compare both the pubkey and curve. This way we are certain
that we're not confusing one key type for another.

Test: libkeymint_remote_prov_support_test
Ignore-AOSP-First: No merge path to aosp, will manually merge
Bug: 191301285
Change-Id: Id90a5206a9a77dfed8547b2e7444a1fedd2edf18

1 files changed, 49 insertions, 10 deletions

diff --git a/android_keymaster/remote_provisioning_utils.cpp b/android_keymaster/remote_provisioning_utils.cpp
index 0e869fc..8cb635b 100644
--- a/android_keymaster/remote_provisioning_utils.cpp
+++ b/android_keymaster/remote_provisioning_utils.cpp
@@ -17,12 +17,14 @@
 #include "keymaster/cppcose/cppcose.h"
 #include <keymaster/logger.h>
 #include <keymaster/remote_provisioning_utils.h>
+#include <string_view>
 
 namespace keymaster {
 
 using cppcose::ALGORITHM;
 using cppcose::COSE_KEY;
 using cppcose::CoseKey;
+using cppcose::CoseKeyCurve;
 using cppcose::EC2;
 using cppcose::ECDH_ES_HKDF_256;
 using cppcose::ES256;
@@ -38,11 +40,27 @@ using cppcose::OCTET_KEY_PAIR;
 using cppcose::P256;
 using cppcose::verifyAndParseCoseSign1;
 
-// Hard-coded set of acceptable public keys that can act as roots of EEK chains.
-inline const std::vector<std::vector<uint8_t>> kAuthorizedEekRoots = {
-    {0x5c, 0xea, 0x4b, 0xd2, 0x31, 0x27, 0x15, 0x5e, 0x62, 0x94, 0x70,
-     0x53, 0x94, 0x43, 0x0f, 0x9a, 0x89, 0xd5, 0xc5, 0x0f, 0x82, 0x9b,
-     0xcd, 0x10, 0xe0, 0x79, 0xef, 0xf3, 0xfa, 0x40, 0xeb, 0x0a},
+using byte_view = std::basic_string_view<uint8_t>;
+
+struct KeyInfo {
+    CoseKeyCurve curve;
+    byte_view pubkey;
+    // Note: There's no need to include algorithm here, since it is assumed
+    //       that all root keys are EDDSA.
+
+    bool operator==(const KeyInfo& other) const {
+        return curve == other.curve && pubkey == other.pubkey;
+    }
+};
+
+// The production root signing key for Google Endpoint Encryption Key cert chains.
+inline constexpr uint8_t kGeekRoot[] = {
+    0x99, 0xB9, 0xEE, 0xDD, 0x5E, 0xE4, 0x52, 0xF6, 0x85, 0xC6, 0x4C, 0x62, 0xDC, 0x3E, 0x61, 0xAB,
+    0x57, 0x48, 0x7D, 0x75, 0x37, 0x29, 0xAD, 0x76, 0x80, 0x32, 0xD2, 0xB3, 0xCB, 0x63, 0x58, 0xD9};
+
+// Hard-coded set of acceptable public COSE_Keys that can act as roots of EEK chains.
+inline constexpr KeyInfo kAuthorizedEekRoots[] = {
+    {CoseKeyCurve::ED25519, byte_view(kGeekRoot, sizeof(kGeekRoot))},
 };
 
 StatusOr<std::pair<std::vector<uint8_t> /* EEK pub */, std::vector<uint8_t> /* EEK ID */>>
@@ -67,11 +85,32 @@ validateAndExtractEekPubAndId(bool testMode, const KeymasterBlob& endpointEncryp
         lastPubKey = *std::move(cosePubKey);
 
         // In prod mode the first pubkey should match a well-known Google public key.
-        if (!testMode && i == 0 &&
-            std::find(kAuthorizedEekRoots.begin(), kAuthorizedEekRoots.end(), lastPubKey) ==
-                kAuthorizedEekRoots.end()) {
-            LOG_E("Unrecognized root of EEK chain", 0);
-            return kStatusInvalidEek;
+        if (!testMode && i == 0) {
+            auto parsedPubKey = CoseKey::parse(lastPubKey);
+            if (!parsedPubKey) {
+                LOG_E("%s", parsedPubKey.moveMessage().c_str());
+                return kStatusFailed;
+            }
+
+            auto curve = parsedPubKey->getIntValue(CoseKey::CURVE);
+            if (!curve) {
+                LOG_E("Key is missing required label 'CURVE'", 0);
+                return kStatusInvalidEek;
+            }
+
+            auto rawPubKey = parsedPubKey->getBstrValue(CoseKey::PUBKEY_X);
+            if (!rawPubKey) {
+                LOG_E("Key is missing required label 'PUBKEY_X'", 0);
+                return kStatusInvalidEek;
+            }
+
+            KeyInfo matcher = {static_cast<CoseKeyCurve>(*curve),
+                               byte_view(rawPubKey->data(), rawPubKey->size())};
+            if (std::find(std::begin(kAuthorizedEekRoots), std::end(kAuthorizedEekRoots),
+                          matcher) == std::end(kAuthorizedEekRoots)) {
+                LOG_E("Unrecognized root of EEK chain", 0);
+                return kStatusInvalidEek;
+            }
         }
     }