David Zeuthen | 630de2a | 2020-05-11 14:04:54 -0400 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2020, The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #if !defined(EIC_INSIDE_LIBEIC_H) && !defined(EIC_COMPILATION) |
| 18 | #error "Never include this file directly, include libeic.h instead." |
| 19 | #endif |
| 20 | |
| 21 | #ifndef ANDROID_HARDWARE_IDENTITY_EIC_PRESENTATION_H |
| 22 | #define ANDROID_HARDWARE_IDENTITY_EIC_PRESENTATION_H |
| 23 | |
| 24 | #ifdef __cplusplus |
| 25 | extern "C" { |
| 26 | #endif |
| 27 | |
| 28 | #include "EicCbor.h" |
| 29 | |
| 30 | // The maximum size we support for public keys in reader certificates. |
| 31 | #define EIC_PRESENTATION_MAX_READER_PUBLIC_KEY_SIZE 65 |
| 32 | |
| 33 | typedef struct { |
| 34 | uint8_t storageKey[EIC_AES_128_KEY_SIZE]; |
| 35 | uint8_t credentialPrivateKey[EIC_P256_PRIV_KEY_SIZE]; |
| 36 | |
| 37 | uint8_t ephemeralPrivateKey[EIC_P256_PRIV_KEY_SIZE]; |
| 38 | |
| 39 | // The challenge generated with eicPresentationCreateAuthChallenge() |
| 40 | uint64_t authChallenge; |
| 41 | |
| 42 | // Set by eicPresentationSetAuthToken() and contains the fields |
| 43 | // from the passed in authToken and verificationToken. |
| 44 | // |
| 45 | uint64_t authTokenChallenge; |
| 46 | uint64_t authTokenSecureUserId; |
| 47 | uint64_t authTokenTimestamp; |
| 48 | uint64_t verificationTokenTimestamp; |
| 49 | |
| 50 | // The public key for the reader. |
| 51 | // |
| 52 | // (During the process of pushing reader certificates, this is also used to store |
| 53 | // the public key of the previously pushed certificate.) |
| 54 | // |
| 55 | uint8_t readerPublicKey[EIC_PRESENTATION_MAX_READER_PUBLIC_KEY_SIZE]; |
| 56 | size_t readerPublicKeySize; |
| 57 | |
| 58 | // This is set to true only if eicPresentationValidateRequestMessage() successfully |
| 59 | // validated the requestMessage. |
| 60 | // |
| 61 | // Why even record this? Because there's no requirement the HAL actually calls that |
| 62 | // function and we validate ACPs before it's called... so it's possible that a |
| 63 | // compromised HAL could trick us into marking ACPs as authorized while they in fact |
| 64 | // aren't. |
| 65 | bool requestMessageValidated; |
| 66 | bool buildCbor; |
| 67 | |
| 68 | // Set to true initialized as a test credential. |
| 69 | bool testCredential; |
| 70 | |
| 71 | // These are bitmasks indicating which of the possible 32 access control profiles are |
| 72 | // authorized. They are built up by eicPresentationValidateAccessControlProfile(). |
| 73 | // |
| 74 | uint32_t accessControlProfileMaskValidated; // True if the profile was validated. |
| 75 | uint32_t accessControlProfileMaskUsesReaderAuth; // True if the ACP is using reader auth |
| 76 | uint32_t accessControlProfileMaskFailedReaderAuth; // True if failed reader auth |
| 77 | uint32_t accessControlProfileMaskFailedUserAuth; // True if failed user auth |
| 78 | |
| 79 | // SHA-256 for AdditionalData, updated for each entry. |
| 80 | uint8_t additionalDataSha256[EIC_SHA256_DIGEST_SIZE]; |
| 81 | |
| 82 | size_t expectedCborSizeAtEnd; |
| 83 | EicCbor cbor; |
| 84 | } EicPresentation; |
| 85 | |
| 86 | bool eicPresentationInit(EicPresentation* ctx, bool testCredential, const char* docType, |
| 87 | const uint8_t encryptedCredentialKeys[80]); |
| 88 | |
| 89 | bool eicPresentationGenerateSigningKeyPair(EicPresentation* ctx, const char* docType, time_t now, |
| 90 | uint8_t* publicKeyCert, size_t* publicKeyCertSize, |
| 91 | uint8_t signingKeyBlob[60]); |
| 92 | |
| 93 | // Create an ephemeral key-pair. |
| 94 | // |
| 95 | // The private key is stored in |ctx->ephemeralPrivateKey| and also returned in |
| 96 | // |ephemeralPrivateKey|. |
| 97 | // |
| 98 | bool eicPresentationCreateEphemeralKeyPair(EicPresentation* ctx, |
| 99 | uint8_t ephemeralPrivateKey[EIC_P256_PRIV_KEY_SIZE]); |
| 100 | |
| 101 | // Returns a non-zero challenge in |authChallenge|. |
| 102 | bool eicPresentationCreateAuthChallenge(EicPresentation* ctx, uint64_t* authChallenge); |
| 103 | |
| 104 | // Starts retrieveing entries. |
| 105 | // |
| 106 | bool eicPresentationStartRetrieveEntries(EicPresentation* ctx); |
| 107 | |
| 108 | // Sets the auth-token. |
| 109 | bool eicPresentationSetAuthToken(EicPresentation* ctx, uint64_t challenge, uint64_t secureUserId, |
| 110 | uint64_t authenticatorId, int hardwareAuthenticatorType, |
| 111 | uint64_t timeStamp, const uint8_t* mac, size_t macSize, |
| 112 | uint64_t verificationTokenChallenge, |
| 113 | uint64_t verificationTokenTimeStamp, |
| 114 | int verificationTokenSecurityLevel, |
| 115 | const uint8_t* verificationTokenMac, |
| 116 | size_t verificationTokenMacSize); |
| 117 | |
| 118 | // Function to push certificates in the reader certificate chain. |
| 119 | // |
| 120 | // This should start with the root certificate (e.g. the last in the chain) and |
| 121 | // continue up the chain, ending with the certificate for the reader. |
| 122 | // |
| 123 | // Calls to this function should be interleaved with calls to the |
| 124 | // eicPresentationValidateAccessControlProfile() function, see below. |
| 125 | // |
| 126 | bool eicPresentationPushReaderCert(EicPresentation* ctx, const uint8_t* certX509, |
| 127 | size_t certX509Size); |
| 128 | |
| 129 | // Checks an access control profile. |
| 130 | // |
| 131 | // Returns false if an error occurred while checking the profile (e.g. MAC doesn't check out). |
| 132 | // |
| 133 | // Returns in |accessGranted| whether access is granted. |
| 134 | // |
| 135 | // If |readerCertificate| is non-empty and the public key of one of those |
| 136 | // certificates appear in the chain presented by the reader, this function must |
| 137 | // be called after pushing that certificate using |
| 138 | // eicPresentationPushReaderCert(). |
| 139 | // |
| 140 | bool eicPresentationValidateAccessControlProfile(EicPresentation* ctx, int id, |
| 141 | const uint8_t* readerCertificate, |
| 142 | size_t readerCertificateSize, |
| 143 | bool userAuthenticationRequired, int timeoutMillis, |
| 144 | uint64_t secureUserId, const uint8_t mac[28], |
| 145 | bool* accessGranted); |
| 146 | |
| 147 | // Validates that the given requestMessage is signed by the public key in the |
| 148 | // certificate last set with eicPresentationPushReaderCert(). |
| 149 | // |
| 150 | // The format of the signature is the same encoding as the 'signature' field of |
| 151 | // COSE_Sign1 - that is, it's the R and S integers both with the same length as |
| 152 | // the key-size. |
| 153 | // |
| 154 | // Must be called after eicPresentationPushReaderCert() have been used to push |
| 155 | // the final certificate. Which is the certificate of the reader itself. |
| 156 | // |
| 157 | bool eicPresentationValidateRequestMessage(EicPresentation* ctx, const uint8_t* sessionTranscript, |
| 158 | size_t sessionTranscriptSize, |
| 159 | const uint8_t* requestMessage, size_t requestMessageSize, |
| 160 | int coseSignAlg, |
| 161 | const uint8_t* readerSignatureOfToBeSigned, |
| 162 | size_t readerSignatureOfToBeSignedSize); |
| 163 | |
| 164 | typedef enum { |
| 165 | // Returned if access is granted. |
| 166 | EIC_ACCESS_CHECK_RESULT_OK, |
| 167 | |
| 168 | // Returned if an error occurred checking for access. |
| 169 | EIC_ACCESS_CHECK_RESULT_FAILED, |
| 170 | |
| 171 | // Returned if access was denied because item is configured without any |
| 172 | // access control profiles. |
| 173 | EIC_ACCESS_CHECK_RESULT_NO_ACCESS_CONTROL_PROFILES, |
| 174 | |
| 175 | // Returned if access was denied because of user authentication. |
| 176 | EIC_ACCESS_CHECK_RESULT_USER_AUTHENTICATION_FAILED, |
| 177 | |
| 178 | // Returned if access was denied because of reader authentication. |
| 179 | EIC_ACCESS_CHECK_RESULT_READER_AUTHENTICATION_FAILED, |
| 180 | } EicAccessCheckResult; |
| 181 | |
| 182 | // Passes enough information to calculate the MACing key |
| 183 | // |
| 184 | bool eicPresentationCalcMacKey(EicPresentation* ctx, const uint8_t* sessionTranscript, |
| 185 | size_t sessionTranscriptSize, |
| 186 | const uint8_t readerEphemeralPublicKey[EIC_P256_PUB_KEY_SIZE], |
| 187 | const uint8_t signingKeyBlob[60], const char* docType, |
| 188 | unsigned int numNamespacesWithValues, |
| 189 | size_t expectedDeviceNamespacesSize); |
| 190 | |
| 191 | // The scratchSpace should be set to a buffer at least 512 bytes (ideally 1024 |
| 192 | // bytes, the bigger the better). It's done this way to avoid allocating stack |
| 193 | // space. |
| 194 | // |
| 195 | EicAccessCheckResult eicPresentationStartRetrieveEntryValue( |
| 196 | EicPresentation* ctx, const char* nameSpace, const char* name, |
| 197 | unsigned int newNamespaceNumEntries, int32_t entrySize, const int* accessControlProfileIds, |
| 198 | size_t numAccessControlProfileIds, uint8_t* scratchSpace, size_t scratchSpaceSize); |
| 199 | |
| 200 | // Note: |content| must be big enough to hold |encryptedContentSize| - 28 bytes. |
| 201 | // |
| 202 | // The scratchSpace should be set to a buffer at least 512 bytes. It's done this way to |
| 203 | // avoid allocating stack space. |
| 204 | // |
| 205 | bool eicPresentationRetrieveEntryValue(EicPresentation* ctx, const uint8_t* encryptedContent, |
| 206 | size_t encryptedContentSize, uint8_t* content, |
| 207 | const char* nameSpace, const char* name, |
| 208 | const int* accessControlProfileIds, |
| 209 | size_t numAccessControlProfileIds, uint8_t* scratchSpace, |
| 210 | size_t scratchSpaceSize); |
| 211 | |
| 212 | // Returns the HMAC-SHA256 of |ToBeMaced| as per RFC 8051 "6.3. How to Compute |
| 213 | // and Verify a MAC". |
| 214 | bool eicPresentationFinishRetrieval(EicPresentation* ctx, uint8_t* digestToBeMaced, |
| 215 | size_t* digestToBeMacedSize); |
| 216 | |
| 217 | // The data returned in |signatureOfToBeSigned| contains the ECDSA signature of |
| 218 | // the ToBeSigned CBOR from RFC 8051 "4.4. Signing and Verification Process" |
| 219 | // where content is set to the ProofOfDeletion CBOR. |
| 220 | // |
| 221 | bool eicPresentationDeleteCredential(EicPresentation* ctx, const char* docType, |
| 222 | size_t proofOfDeletionCborSize, |
| 223 | uint8_t signatureOfToBeSigned[EIC_ECDSA_P256_SIGNATURE_SIZE]); |
| 224 | |
| 225 | #ifdef __cplusplus |
| 226 | } |
| 227 | #endif |
| 228 | |
| 229 | #endif // ANDROID_HARDWARE_IDENTITY_EIC_PRESENTATION_H |