1# Fuzzers for libkeymaster4support
2
3## Plugin Design Considerations
4The fuzzer plugins for libkeymaster4support are designed based on the understanding of the
5source code and try to achieve the following:
6
7##### Maximize code coverage
8The configuration parameters are not hardcoded, but instead selected based on
9incoming data. This ensures more code paths are reached by the fuzzers.
10
11libkeymaster4support supports the following parameters:
121. Security Level (parameter name: `securityLevel`)
132. Ec Curve (parameter name: `ecCurve`)
143. Padding Mode (parameter name: `paddingMode`)
154. Digest (parameter name: `digest`)
165. Tag (parameter name: `tag`)
17
18| Parameter| Valid Values| Configured Value|
19|------------- |-------------| ----- |
20| `securityLevel` | 0.`SecurityLevel::SOFTWARE` 1.`SecurityLevel::TRUSTED_ENVIRONMENT` 2.`SecurityLevel::STRONGBOX`| Value obtained from FuzzedDataProvider|
21| `ecCurve` | 0.`EcCurve::P_224` 1.`EcCurve::P_256` 2.`EcCurve::P_384` 3. `EcCurve::P_521`| Value obtained from FuzzedDataProvider|
22| `paddingMode` | 0.`PaddingMode::NONE` 1.`PaddingMode::RSA_OAEP` 2.`PaddingMode::RSA_PSS` 3. `PaddingMode::RSA_PKCS1_1_5_ENCRYPT` 4.`PaddingMode::RSA_PKCS1_1_5_SIGN` 5.`PaddingMode::PKCS7`| Value obtained from FuzzedDataProvider|
23| `digest` | 1. `Digest::NONE` 2.`Digest::MD5` 3.`Digest::SHA1` 4.`Digest::SHA_2_224` 5.`Digest::SHA_2_256` 6.`Digest::SHA_2_384`  7.`Digest::SHA_2_512`| Value obtained from FuzzedDataProvider|
24| `tag` | 1. `Tag::INVALID` 2.`Tag::PURPOSE` 3.`Tag::ALGORITHM` 4.`Tag::KEY_SIZE` 5.`Tag::BLOCK_MODE` 6.`Tag::DIGEST` 7.`Tag::PADDING` 8.`Tag::CALLER_NONCE` 9.`Tag::MIN_MAC_LENGTH` 10.`Tag::EC_CURVE` 11.`Tag::RSA_PUBLIC_EXPONENT` 12.`Tag::INCLUDE_UNIQUE_ID` 13. `Tag::BLOB_USAGE_REQUIREMENTS` 14.`Tag::BOOTLOADER_ONLY` 15.`Tag::ROLLBACK_RESISTANCE` 16.`Tag::HARDWARE_TYPE` 17.`Tag::ACTIVE_DATETIME` 18. `Tag::ORIGINATION_EXPIRE_DATETIME` 19.`Tag::USAGE_EXPIRE_DATETIME` 20.`Tag::MIN_SECONDS_BETWEEN_OPS` 21.`Tag::MAX_USES_PER_BOOT` 22.`Tag::USER_ID` 23.` Tag::USER_SECURE_ID` 24.`Tag::NO_AUTH_REQUIRED` 25.`Tag::USER_AUTH_TYPE` 26.`Tag::AUTH_TIMEOUT` 27.`Tag::ALLOW_WHILE_ON_BODY` 28.`Tag::TRUSTED_USER_PRESENCE_REQUIRED` 29.`Tag::TRUSTED_CONFIRMATION_REQUIRED` 30.`Tag::UNLOCKED_DEVICE_REQUIRED` 31.`Tag::APPLICATION_ID` 32.`Tag::APPLICATION_DATA` 33.`Tag::CREATION_DATETIME` 34.`Tag::ORIGIN` 35.`Tag::ROOT_OF_TRUST` 36.`Tag::OS_VERSION` 37.`Tag::OS_PATCHLEVEL` 38.`Tag::UNIQUE_ID` 39.`Tag::ATTESTATION_CHALLENGE` 40.`Tag::ATTESTATION_APPLICATION_ID` 41.`Tag::ATTESTATION_ID_BRAND` 42.`Tag::ATTESTATION_ID_DEVICE` 43.`Tag::ATTESTATION_ID_PRODUCT` 44.`Tag::ATTESTATION_ID_SERIAL` 45.`Tag::ATTESTATION_ID_IMEI` 46.`Tag::ATTESTATION_ID_MEID` 47.`Tag::ATTESTATION_ID_MANUFACTURER` 48.`Tag::ATTESTATION_ID_MODEL` 49.`Tag::VENDOR_PATCHLEVEL` 50.`Tag::BOOT_PATCHLEVEL` 51.`Tag::ASSOCIATED_DATA` 52.`Tag::NONCE` 53.`Tag::MAC_LENGTH` 54.`Tag::RESET_SINCE_ID_ROTATION` 55.`Tag::CONFIRMATION_TOKEN`| Value obtained from FuzzedDataProvider|
25
26This also ensures that the plugins are always deterministic for any given input.
27
28##### Maximize utilization of input data
29The plugins feed the entire input data to the module.
30This ensures that the plugins tolerate any kind of input (empty, huge,
31malformed, etc) and dont `exit()` on any input and thereby increasing the
32chance of identifying vulnerabilities.
33
34## Build
35
36This describes steps to build keymaster4_attestation_fuzzer, keymaster4_authSet_fuzzer and keymaster4_utils_fuzzer binaries
37
38### Android
39
40#### Steps to build
41Build the fuzzer
42```
43  $ mm -j$(nproc) keymaster4_attestation_fuzzer
44  $ mm -j$(nproc) keymaster4_authSet_fuzzer
45  $ mm -j$(nproc) keymaster4_utils_fuzzer
46```
47#### Steps to run
48To run on device
49```
50  $ adb sync data
51  $ adb shell /data/fuzz/${TARGET_ARCH}/keymaster4_attestation_fuzzer/keymaster4_attestation_fuzzer
52  $ adb shell /data/fuzz/${TARGET_ARCH}/keymaster4_authSet_fuzzer/keymaster4_authSet_fuzzer
53  $ adb shell /data/fuzz/${TARGET_ARCH}/keymaster4_utils_fuzzer/keymaster4_utils_fuzzer
54```
55
56## References:
57 * http://llvm.org/docs/LibFuzzer.html
58 * https://github.com/google/oss-fuzz
59