Identity Credential: Switch default implementation to use libeic.

Introduce platform-neutral C library ("libeic") which can be used to
implement an Identity Credential Trusted Application/Applet in Secure
Hardware.

The libeic library is intentionally low-level, has no dependencies
(not even libc), uses very little run-time memory (less than 500 bytes
during a provisioning or presentation session), and doesn't
dynamically allocate any memory. Crypto routines are provided by the
library user through a simple crypto interface defined in EicOps.

Also provide an Android-side HAL implementation designed to
communicate with libeic running in Secure Hardware outside
Android. Abstract out communications between HAL and TA in a couple of
SecureHardwareProxy* classes which mimic libeic 1:1.

The default implementation of the HAL is a combination of the
aforementioned HAL using libeic in-process backed by BoringSSL for the
crypto bits.

Test: atest VtsHalIdentityTargetTest
Test: atest android.security.identity.cts
Bug: 170146643
Change-Id: I3bf43fa7fd9362f94023052591801f2094a04607

1 files changed, 290 insertions, 0 deletions

diff --git a/identity/aidl/default/libeic/EicProvisioning.c b/identity/aidl/default/libeic/EicProvisioning.c
new file mode 100644
index 0000000000..f16605cfad
--- /dev/null
+++ b/identity/aidl/default/libeic/EicProvisioning.c
@@ -0,0 +1,290 @@
+/*
+ * Copyright 2020, 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 "EicProvisioning.h"
+
+bool eicProvisioningInit(EicProvisioning* ctx, bool testCredential) {
+    eicMemSet(ctx, '\0', sizeof(EicProvisioning));
+    ctx->testCredential = testCredential;
+    if (!eicOpsRandom(ctx->storageKey, EIC_AES_128_KEY_SIZE)) {
+        return false;
+    }
+
+    return true;
+}
+
+bool eicProvisioningCreateCredentialKey(EicProvisioning* ctx, const uint8_t* challenge,
+                                        size_t challengeSize, const uint8_t* applicationId,
+                                        size_t applicationIdSize, uint8_t* publicKeyCert,
+                                        size_t* publicKeyCertSize) {
+    if (!eicOpsCreateCredentialKey(ctx->credentialPrivateKey, challenge, challengeSize,
+                                   applicationId, applicationIdSize, ctx->testCredential,
+                                   publicKeyCert, publicKeyCertSize)) {
+        return false;
+    }
+    return true;
+}
+
+bool eicProvisioningStartPersonalization(EicProvisioning* ctx, int accessControlProfileCount,
+                                         const int* entryCounts, size_t numEntryCounts,
+                                         const char* docType,
+                                         size_t expectedProofOfProvisioningSize) {
+    if (numEntryCounts >= EIC_MAX_NUM_NAMESPACES) {
+        return false;
+    }
+    if (accessControlProfileCount >= EIC_MAX_NUM_ACCESS_CONTROL_PROFILE_IDS) {
+        return false;
+    }
+
+    ctx->numEntryCounts = numEntryCounts;
+    if (numEntryCounts > EIC_MAX_NUM_NAMESPACES) {
+        return false;
+    }
+    for (size_t n = 0; n < numEntryCounts; n++) {
+        if (entryCounts[n] >= 256) {
+            return false;
+        }
+        ctx->entryCounts[n] = entryCounts[n];
+    }
+    ctx->curNamespace = -1;
+    ctx->curNamespaceNumProcessed = 0;
+
+    eicCborInit(&ctx->cbor, NULL, 0);
+
+    // What we're going to sign is the COSE ToBeSigned structure which
+    // looks like the following:
+    //
+    // Sig_structure = [
+    //   context : "Signature" / "Signature1" / "CounterSignature",
+    //   body_protected : empty_or_serialized_map,
+    //   ? sign_protected : empty_or_serialized_map,
+    //   external_aad : bstr,
+    //   payload : bstr
+    //  ]
+    //
+    eicCborAppendArray(&ctx->cbor, 4);
+    eicCborAppendString(&ctx->cbor, "Signature1");
+
+    // The COSE Encoded protected headers is just a single field with
+    // COSE_LABEL_ALG (1) -> COSE_ALG_ECSDA_256 (-7). For simplicitly we just
+    // hard-code the CBOR encoding:
+    static const uint8_t coseEncodedProtectedHeaders[] = {0xa1, 0x01, 0x26};
+    eicCborAppendByteString(&ctx->cbor, coseEncodedProtectedHeaders,
+                            sizeof(coseEncodedProtectedHeaders));
+
+    // We currently don't support Externally Supplied Data (RFC 8152 section 4.3)
+    // so external_aad is the empty bstr
+    static const uint8_t externalAad[0] = {};
+    eicCborAppendByteString(&ctx->cbor, externalAad, sizeof(externalAad));
+
+    // For the payload, the _encoded_ form follows here. We handle this by simply
+    // opening a bstr, and then writing the CBOR. This requires us to know the
+    // size of said bstr, ahead of time.
+    eicCborBegin(&ctx->cbor, EIC_CBOR_MAJOR_TYPE_BYTE_STRING, expectedProofOfProvisioningSize);
+    ctx->expectedCborSizeAtEnd = expectedProofOfProvisioningSize + ctx->cbor.size;
+
+    eicCborAppendArray(&ctx->cbor, 5);
+    eicCborAppendString(&ctx->cbor, "ProofOfProvisioning");
+    eicCborAppendString(&ctx->cbor, docType);
+
+    eicCborAppendArray(&ctx->cbor, accessControlProfileCount);
+
+    return true;
+}
+
+bool eicProvisioningAddAccessControlProfile(EicProvisioning* ctx, int id,
+                                            const uint8_t* readerCertificate,
+                                            size_t readerCertificateSize,
+                                            bool userAuthenticationRequired, uint64_t timeoutMillis,
+                                            uint64_t secureUserId, uint8_t outMac[28]) {
+    uint8_t cborBuffer[EIC_MAX_CBOR_SIZE_FOR_ACCESS_CONTROL_PROFILE];
+    EicCbor cborBuilder;
+
+    eicCborInit(&cborBuilder, cborBuffer, EIC_MAX_CBOR_SIZE_FOR_ACCESS_CONTROL_PROFILE);
+
+    if (!eicCborCalcAccessControl(&cborBuilder, id, readerCertificate, readerCertificateSize,
+                                  userAuthenticationRequired, timeoutMillis, secureUserId)) {
+        return false;
+    }
+
+    // Calculate and return MAC
+    uint8_t nonce[12];
+    if (!eicOpsRandom(nonce, 12)) {
+        return false;
+    }
+    if (!eicOpsEncryptAes128Gcm(ctx->storageKey, nonce, NULL, 0, cborBuilder.buffer,
+                                cborBuilder.size, outMac)) {
+        return false;
+    }
+
+    // The ACP CBOR in the provisioning receipt doesn't include secureUserId so build
+    // it again.
+    eicCborInit(&cborBuilder, cborBuffer, EIC_MAX_CBOR_SIZE_FOR_ACCESS_CONTROL_PROFILE);
+    if (!eicCborCalcAccessControl(&cborBuilder, id, readerCertificate, readerCertificateSize,
+                                  userAuthenticationRequired, timeoutMillis,
+                                  0 /* secureUserId */)) {
+        return false;
+    }
+
+    // Append the CBOR from the local builder to the digester.
+    eicCborAppend(&ctx->cbor, cborBuilder.buffer, cborBuilder.size);
+
+    return true;
+}
+
+bool eicProvisioningBeginAddEntry(EicProvisioning* ctx, const int* accessControlProfileIds,
+                                  size_t numAccessControlProfileIds, const char* nameSpace,
+                                  const char* name, uint64_t entrySize, uint8_t* scratchSpace,
+                                  size_t scratchSpaceSize) {
+    uint8_t* additionalDataCbor = scratchSpace;
+    const size_t additionalDataCborBufSize = scratchSpaceSize;
+    size_t additionalDataCborSize;
+
+    // We'll need to calc and store a digest of additionalData to check that it's the same
+    // additionalData being passed in for every eicProvisioningAddEntryValue() call...
+    if (!eicCborCalcEntryAdditionalData(accessControlProfileIds, numAccessControlProfileIds,
+                                        nameSpace, name, additionalDataCbor,
+                                        additionalDataCborBufSize, &additionalDataCborSize,
+                                        ctx->additionalDataSha256)) {
+        return false;
+    }
+
+    if (ctx->curNamespace == -1) {
+        ctx->curNamespace = 0;
+        ctx->curNamespaceNumProcessed = 0;
+        // Opens the main map: { * Namespace => [ + Entry ] }
+        eicCborAppendMap(&ctx->cbor, ctx->numEntryCounts);
+        eicCborAppendString(&ctx->cbor, nameSpace);
+        // Opens the per-namespace array: [ + Entry ]
+        eicCborAppendArray(&ctx->cbor, ctx->entryCounts[ctx->curNamespace]);
+    }
+
+    if (ctx->curNamespaceNumProcessed == ctx->entryCounts[ctx->curNamespace]) {
+        ctx->curNamespace += 1;
+        ctx->curNamespaceNumProcessed = 0;
+        eicCborAppendString(&ctx->cbor, nameSpace);
+        // Opens the per-namespace array: [ + Entry ]
+        eicCborAppendArray(&ctx->cbor, ctx->entryCounts[ctx->curNamespace]);
+    }
+
+    eicCborAppendMap(&ctx->cbor, 3);
+    eicCborAppendString(&ctx->cbor, "name");
+    eicCborAppendString(&ctx->cbor, name);
+
+    ctx->curEntrySize = entrySize;
+    ctx->curEntryNumBytesReceived = 0;
+
+    eicCborAppendString(&ctx->cbor, "value");
+
+    ctx->curNamespaceNumProcessed += 1;
+    return true;
+}
+
+bool eicProvisioningAddEntryValue(EicProvisioning* ctx, const int* accessControlProfileIds,
+                                  size_t numAccessControlProfileIds, const char* nameSpace,
+                                  const char* name, const uint8_t* content, size_t contentSize,
+                                  uint8_t* outEncryptedContent, uint8_t* scratchSpace,
+                                  size_t scratchSpaceSize) {
+    uint8_t* additionalDataCbor = scratchSpace;
+    const size_t additionalDataCborBufSize = scratchSpaceSize;
+    size_t additionalDataCborSize;
+
+    uint8_t calculatedSha256[EIC_SHA256_DIGEST_SIZE];
+    if (!eicCborCalcEntryAdditionalData(accessControlProfileIds, numAccessControlProfileIds,
+                                        nameSpace, name, additionalDataCbor,
+                                        additionalDataCborBufSize, &additionalDataCborSize,
+                                        calculatedSha256)) {
+        return false;
+    }
+    if (eicCryptoMemCmp(calculatedSha256, ctx->additionalDataSha256, EIC_SHA256_DIGEST_SIZE) != 0) {
+        eicDebug("SHA-256 mismatch of additionalData");
+        return false;
+    }
+
+    eicCborAppend(&ctx->cbor, content, contentSize);
+
+    uint8_t nonce[12];
+    if (!eicOpsRandom(nonce, 12)) {
+        return false;
+    }
+    if (!eicOpsEncryptAes128Gcm(ctx->storageKey, nonce, content, contentSize, additionalDataCbor,
+                                additionalDataCborSize, outEncryptedContent)) {
+        return false;
+    }
+
+    // If done with this entry, close the map
+    ctx->curEntryNumBytesReceived += contentSize;
+    if (ctx->curEntryNumBytesReceived == ctx->curEntrySize) {
+        eicCborAppendString(&ctx->cbor, "accessControlProfiles");
+        eicCborAppendArray(&ctx->cbor, numAccessControlProfileIds);
+        for (size_t n = 0; n < numAccessControlProfileIds; n++) {
+            eicCborAppendNumber(&ctx->cbor, accessControlProfileIds[n]);
+        }
+    }
+    return true;
+}
+
+bool eicProvisioningFinishAddingEntries(
+        EicProvisioning* ctx, uint8_t signatureOfToBeSigned[EIC_ECDSA_P256_SIGNATURE_SIZE]) {
+    uint8_t cborSha256[EIC_SHA256_DIGEST_SIZE];
+
+    eicCborAppendBool(&ctx->cbor, ctx->testCredential);
+    eicCborFinal(&ctx->cbor, cborSha256);
+
+    // This verifies that the correct expectedProofOfProvisioningSize value was
+    // passed in at eicStartPersonalization() time.
+    if (ctx->cbor.size != ctx->expectedCborSizeAtEnd) {
+        eicDebug("CBOR size is %zd, was expecting %zd", ctx->cbor.size, ctx->expectedCborSizeAtEnd);
+        return false;
+    }
+
+    if (!eicOpsEcDsa(ctx->credentialPrivateKey, cborSha256, signatureOfToBeSigned)) {
+        eicDebug("Error signing proofOfProvisioning");
+        return false;
+    }
+
+    return true;
+}
+
+bool eicProvisioningFinishGetCredentialData(EicProvisioning* ctx, const char* docType,
+                                            uint8_t encryptedCredentialKeys[80]) {
+    EicCbor cbor;
+    uint8_t cborBuf[52];
+
+    eicCborInit(&cbor, cborBuf, sizeof(cborBuf));
+    eicCborAppendArray(&cbor, 2);
+    eicCborAppendByteString(&cbor, ctx->storageKey, EIC_AES_128_KEY_SIZE);
+    eicCborAppendByteString(&cbor, ctx->credentialPrivateKey, EIC_P256_PRIV_KEY_SIZE);
+    if (cbor.size > sizeof(cborBuf)) {
+        eicDebug("Exceeded buffer size");
+        return false;
+    }
+
+    uint8_t nonce[12];
+    if (!eicOpsRandom(nonce, 12)) {
+        eicDebug("Error getting random");
+        return false;
+    }
+    if (!eicOpsEncryptAes128Gcm(
+                eicOpsGetHardwareBoundKey(ctx->testCredential), nonce, cborBuf, cbor.size,
+                // DocType is the additionalAuthenticatedData
+                (const uint8_t*)docType, eicStrLen(docType), encryptedCredentialKeys)) {
+        eicDebug("Error encrypting CredentialKeys");
+        return false;
+    }
+
+    return true;
+}