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[App Check] Add failure reasons for App Attest error cases #11956

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merged 3 commits into from
Oct 19, 2023
Merged

[App Check] Add failure reasons for App Attest error cases #11956

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be8f840
Add error codes for App Attest failure cases
andrewheard Oct 17, 2023
fe1dfce
Revert public API changes, fix tests
andrewheard Oct 17, 2023
c9709ee
Add TODOs for FIRAppCheckErrorCodes
andrewheard Oct 19, 2023
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56 changes: 35 additions & 21 deletions FirebaseAppCheck/Sources/AppAttestProvider/FIRAppAttestProvider.m
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Original file line number Diff line number Diff line change
Expand Up @@ -280,16 +280,21 @@ - (void)getTokenWithCompletion:(void (^)(FIRAppCheckToken *_Nullable, NSError *_
do:^NSData *_Nullable {
return [FIRAppCheckCryptoUtils sha256HashFromData:challenge];
}]
.thenOn(
self.queue,
^FBLPromise<NSData *> *(NSData *challengeHash) {
return [FBLPromise onQueue:self.queue
wrapObjectOrErrorCompletion:^(FBLPromiseObjectOrErrorCompletion _Nonnull handler) {
[self.appAttestService attestKey:keyID
clientDataHash:challengeHash
completionHandler:handler];
}];
})
.thenOn(self.queue,
^FBLPromise<NSData *> *(NSData *challengeHash) {
return [FBLPromise onQueue:self.queue
wrapObjectOrErrorCompletion:^(
FBLPromiseObjectOrErrorCompletion _Nonnull handler) {
[self.appAttestService attestKey:keyID
clientDataHash:challengeHash
completionHandler:handler];
}]
.recoverOn(self.queue, ^id(NSError *error) {
return [FIRAppCheckErrorUtil appAttestAttestKeyFailedWithError:error
keyId:keyID
clientDataHash:challengeHash];
});
})
.thenOn(self.queue, ^FBLPromise<FIRAppAttestKeyAttestationResult *> *(NSData *attestation) {
FIRAppAttestKeyAttestationResult *result =
[[FIRAppAttestKeyAttestationResult alloc] initWithKeyID:keyID
Expand Down Expand Up @@ -391,17 +396,22 @@ - (void)getTokenWithCompletion:(void (^)(FIRAppCheckToken *_Nullable, NSError *_
// 1.2. Get the statement SHA256 hash.
return [FIRAppCheckCryptoUtils sha256HashFromData:[statementForAssertion copy]];
}]
.thenOn(
self.queue,
^FBLPromise<NSData *> *(NSData *statementHash) {
// 2. Generate App Attest assertion.
return [FBLPromise onQueue:self.queue
wrapObjectOrErrorCompletion:^(FBLPromiseObjectOrErrorCompletion _Nonnull handler) {
[self.appAttestService generateAssertion:keyID
clientDataHash:statementHash
completionHandler:handler];
}];
})
.thenOn(self.queue,
^FBLPromise<NSData *> *(NSData *statementHash) {
return [FBLPromise onQueue:self.queue
wrapObjectOrErrorCompletion:^(
FBLPromiseObjectOrErrorCompletion _Nonnull handler) {
[self.appAttestService generateAssertion:keyID
clientDataHash:statementHash
completionHandler:handler];
}]
.recoverOn(self.queue, ^id(NSError *error) {
return [FIRAppCheckErrorUtil
appAttestGenerateAssertionFailedWithError:error
keyId:keyID
clientDataHash:statementHash];
});
})
// 3. Compose the result object.
.thenOn(self.queue, ^FIRAppAttestAssertionData *(NSData *assertion) {
return [[FIRAppAttestAssertionData alloc] initWithChallenge:challenge
Expand Down Expand Up @@ -479,6 +489,10 @@ - (void)getTokenWithCompletion:(void (^)(FIRAppCheckToken *_Nullable, NSError *_
wrapObjectOrErrorCompletion:^(FBLPromiseObjectOrErrorCompletion _Nonnull handler) {
[self.appAttestService generateKeyWithCompletionHandler:handler];
}]
.recoverOn(self.queue,
^id(NSError *error) {
return [FIRAppCheckErrorUtil appAttestGenerateKeyFailedWithError:error];
})
.thenOn(self.queue, ^FBLPromise<NSString *> *(NSString *keyID) {
return [self.keyIDStorage setAppAttestKeyID:keyID];
});
Expand Down
12 changes: 12 additions & 0 deletions FirebaseAppCheck/Sources/Core/Errors/FIRAppCheckErrorUtil.h
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,18 @@ void FIRAppCheckSetErrorToPointer(NSError *error, NSError **pointer);

+ (NSError *)appAttestKeyIDNotFound;

// MARK: - App Attest Errors

+ (NSError *)appAttestGenerateKeyFailedWithError:(NSError *)error;

+ (NSError *)appAttestAttestKeyFailedWithError:(NSError *)error
keyId:(NSString *)keyId
clientDataHash:(NSData *)clientDataHash;

+ (NSError *)appAttestGenerateAssertionFailedWithError:(NSError *)error
keyId:(NSString *)keyId
clientDataHash:(NSData *)clientDataHash;

@end

NS_ASSUME_NONNULL_END
39 changes: 39 additions & 0 deletions FirebaseAppCheck/Sources/Core/Errors/FIRAppCheckErrorUtil.m
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Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,45 @@ + (NSError *)errorWithFailureReason:(NSString *)failureReason {
underlyingError:nil];
}

#pragma mark - App Attest

+ (NSError *)appAttestGenerateKeyFailedWithError:(NSError *)error {
NSString *failureReason = @"Failed to generate a new cryptographic key for use with the App "
@"Attest service (`generateKeyWithCompletionHandler:`).";
// TODO(#11967): Add a new error code for this case (e.g., FIRAppCheckAppAttestGenerateKeyFailed).
return [self appCheckErrorWithCode:FIRAppCheckErrorCodeUnknown
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failureReason:failureReason
underlyingError:error];
}

+ (NSError *)appAttestAttestKeyFailedWithError:(NSError *)error
keyId:(NSString *)keyId
clientDataHash:(NSData *)clientDataHash {
NSString *failureReason =
[NSString stringWithFormat:@"Failed to attest the validity of the generated cryptographic "
@"key (`attestKey:clientDataHash:completionHandler:`); "
@"keyId.length = %lu, clientDataHash.length = %lu",
keyId.length, clientDataHash.length];
// TODO(#11967): Add a new error code for this case (e.g., FIRAppCheckAppAttestAttestKeyFailed).
return [self appCheckErrorWithCode:FIRAppCheckErrorCodeUnknown
failureReason:failureReason
underlyingError:error];
}

+ (NSError *)appAttestGenerateAssertionFailedWithError:(NSError *)error
keyId:(NSString *)keyId
clientDataHash:(NSData *)clientDataHash {
NSString *failureReason = [NSString
stringWithFormat:@"Failed to create a block of data that demonstrates the legitimacy of the "
@"app instance (`generateAssertion:clientDataHash:completionHandler:`); "
@"keyId.length = %lu, clientDataHash.length = %lu.",
keyId.length, clientDataHash.length];
// TODO(#11967): Add error code for this case (e.g., FIRAppCheckAppAttestGenerateAssertionFailed).
return [self appCheckErrorWithCode:FIRAppCheckErrorCodeUnknown
failureReason:failureReason
underlyingError:error];
}

#pragma mark - Helpers

+ (NSError *)unknownErrorWithError:(NSError *)error {
Expand Down
14 changes: 11 additions & 3 deletions FirebaseAppCheck/Tests/Unit/AppAttestProvider/FIRAppAttestProviderTests.m
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Original file line number Diff line number Diff line change
Expand Up @@ -393,6 +393,10 @@ - (void)testGetToken_WhenUnregisteredKeyAndKeyAttestationError {
NSError *attestationError = [NSError errorWithDomain:@"testGetTokenWhenKeyAttestationError"
code:0
userInfo:nil];
NSError *expectedError =
[FIRAppCheckErrorUtil appAttestAttestKeyFailedWithError:attestationError
keyId:existingKeyID
clientDataHash:self.randomChallengeHash];
id attestCompletionArg = [OCMArg invokeBlockWithArgs:[NSNull null], attestationError, nil];
OCMExpect([self.mockAppAttestService attestKey:existingKeyID
clientDataHash:self.randomChallengeHash
Expand All @@ -411,7 +415,7 @@ - (void)testGetToken_WhenUnregisteredKeyAndKeyAttestationError {
[completionExpectation fulfill];

XCTAssertNil(token);
XCTAssertEqualObjects(error, attestationError);
XCTAssertEqualObjects(error, expectedError);
}];

[self waitForExpectations:@[ self.fakeBackoffWrapper.backoffExpectation, completionExpectation ]
Expand All @@ -422,7 +426,7 @@ - (void)testGetToken_WhenUnregisteredKeyAndKeyAttestationError {
[self verifyAllMocks];

// 9. Verify backoff error.
XCTAssertEqualObjects(self.fakeBackoffWrapper.operationError, attestationError);
XCTAssertEqualObjects(self.fakeBackoffWrapper.operationError, expectedError);
}

- (void)testGetToken_WhenUnregisteredKeyAndKeyAttestationExchangeError {
Expand Down Expand Up @@ -671,6 +675,10 @@ - (void)testGetToken_WhenKeyRegisteredAndGenerateAssertionError {
[NSError errorWithDomain:@"testGetToken_WhenKeyRegisteredAndGenerateAssertionError"
code:0
userInfo:nil];
NSError *expectedError =
[FIRAppCheckErrorUtil appAttestGenerateAssertionFailedWithError:generateAssertionError
keyId:existingKeyID
clientDataHash:self.randomChallengeHash];
id completionBlockArg = [OCMArg invokeBlockWithArgs:[NSNull null], generateAssertionError, nil];
OCMExpect([self.mockAppAttestService
generateAssertion:existingKeyID
Expand All @@ -690,7 +698,7 @@ - (void)testGetToken_WhenKeyRegisteredAndGenerateAssertionError {
[completionExpectation fulfill];

XCTAssertNil(token);
XCTAssertEqualObjects(error, generateAssertionError);
XCTAssertEqualObjects(error, expectedError);
}];

[self waitForExpectations:@[ completionExpectation ] timeout:0.5];
Expand Down
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