59 lines
4.0 KiB
Markdown
59 lines
4.0 KiB
Markdown
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# Fuzzers for libkeymaster4support
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## Plugin Design Considerations
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The fuzzer plugins for libkeymaster4support are designed based on the understanding of the
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source code and try to achieve the following:
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##### Maximize code coverage
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The configuration parameters are not hardcoded, but instead selected based on
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incoming data. This ensures more code paths are reached by the fuzzers.
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libkeymaster4support supports the following parameters:
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1. Security Level (parameter name: `securityLevel`)
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2. Ec Curve (parameter name: `ecCurve`)
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3. Padding Mode (parameter name: `paddingMode`)
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4. Digest (parameter name: `digest`)
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5. Tag (parameter name: `tag`)
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| Parameter| Valid Values| Configured Value|
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|------------- |-------------| ----- |
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| `securityLevel` | 0.`SecurityLevel::SOFTWARE` 1.`SecurityLevel::TRUSTED_ENVIRONMENT` 2.`SecurityLevel::STRONGBOX`| Value obtained from FuzzedDataProvider|
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| `ecCurve` | 0.`EcCurve::P_224` 1.`EcCurve::P_256` 2.`EcCurve::P_384` 3. `EcCurve::P_521`| Value obtained from FuzzedDataProvider|
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| `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|
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| `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|
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| `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|
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This also ensures that the plugins are always deterministic for any given input.
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##### Maximize utilization of input data
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The plugins feed the entire input data to the module.
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This ensures that the plugins tolerate any kind of input (empty, huge,
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malformed, etc) and dont `exit()` on any input and thereby increasing the
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chance of identifying vulnerabilities.
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## Build
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This describes steps to build keymaster4_attestation_fuzzer, keymaster4_authSet_fuzzer and keymaster4_utils_fuzzer binaries
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### Android
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#### Steps to build
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Build the fuzzer
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```
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$ mm -j$(nproc) keymaster4_attestation_fuzzer
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$ mm -j$(nproc) keymaster4_authSet_fuzzer
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$ mm -j$(nproc) keymaster4_utils_fuzzer
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```
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#### Steps to run
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To run on device
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```
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$ adb sync data
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$ adb shell /data/fuzz/${TARGET_ARCH}/keymaster4_attestation_fuzzer/keymaster4_attestation_fuzzer
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$ adb shell /data/fuzz/${TARGET_ARCH}/keymaster4_authSet_fuzzer/keymaster4_authSet_fuzzer
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$ adb shell /data/fuzz/${TARGET_ARCH}/keymaster4_utils_fuzzer/keymaster4_utils_fuzzer
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```
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## References:
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* http://llvm.org/docs/LibFuzzer.html
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* https://github.com/google/oss-fuzz
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