Amplify ios signin with custom flow - ios

Question

I am trying to implement a custom signin flow using amplify ios library and cognito.
The flow is based on this passwordless implementation https://github.com/mobilequickie/amplify-passwordless-sms-auth/tree/68152489152e1fc4c3185f4e5e3383639bdc8285, it works great on web, but I can't make it work on ios, I get the following error:
-------Sign In response---------
failure(AuthError: Incorrect username or password.
Recovery suggestion: Check whether the given values are correct and the user is authorized to perform the operation.)
Please find below the relevant code:
public init(_ secureService: SecureServiceProtocol) {
self.secureService = secureService
self.token = secureService.get(tokenKey)
self.authModel = secureService.get(authKey, type: AuthModel.self)
do {
let url = Bundle.main.url(forResource: "amplifyconfiguration", withExtension: "json")!
let configuration = try AmplifyConfiguration(configurationFile: url)
try Amplify.add(plugin: AWSCognitoAuthPlugin())
try Amplify.configure(configuration)
if authModel != nil {
self.retrieveAuthData { _ in }
}
} catch {
L.log(type: .error, message: error.localizedDescription)
print(error)
print(error.asAFError)
}
}
public func accessWith(_ phone: String, callback: #escaping AuthResultCallback) {
print(phone)
Amplify.Auth.signIn(username: phone) { result in
print("-------Sign In response---------")
print(result)
}
}
configuration
{
"auth": {
"plugins": {
"awsCognitoAuthPlugin": {
"IdentityManager": {
"Default": {}
},
"CredentialsProvider": {
"CognitoIdentity": {
"Default": {}
}
},
"CognitoUserPool": {
"Default": {
"Region": "eu-west-2",
"PoolId": "eu-west-2xxxxxx",
"AppClientId": "5vmjioxxxxxxxxxx"
}
}
},
"Auth": {
"Default": {
"authenticationFlowType": "CUSTOM_AUTH"
}
}
}
}
}

Answer 1

I have been facing the same issue and found this
The root cause for our issue was that the iOS Amplify library always sends an initial ChallengeName of SRP_A to the Cognito signIn call. However, the example "Define Auth Challenge trigger" is explicitly coded to fail any authentication calls where the ChallengeName is not CUSTOM_CHALLENGE.
So you need to port that same behavior with these lambdas. Because the Define lambda looks for the CUSTOM_CHALLENGE ChallengeName and fails requests that have a different ChallngeName, the logic is incompatible with the iOS Amplify libraries as-is, since they initially send SRP_A.
I was able to work around this by modifying the Define Auth Challenge lambda to respond with the CUSTOM_CHALLENGE name instead of failing outright, and that seems to have fixed up the iOS side.
You can use the lambda's from here