Hey there, I am working on a multiplatform project...

# kotlin-native

[Cyrille QUÉMIN]

Hey there, I am working on a multiplatform project (android and iOS) and currently dealing with crypto operation on iOS.
Thanks to @olonho I managed create an RSA key via SecKeyCreateRandomKey and `CFBridgingRetain`:

val privateKeyRef = SecKeyCreateRandomKey(cfKeyGenerationAttributes, error.ptr)
println("Key generated: ${CFBridgingRelease(privateKeyRef)} ")

This works nicely. When I try to retrieve my key at later date I have either crashes or the key is not found.
I suspect this is due to how I define the application data string tag in my dictionary:

CFDictionaryAddValue(cfKeyGenerationAttributes,kSecAttrApplicationTag,CFBridgingRetain(keyAlias.wcstr.ptr))

I tried few combination but I never seem to be able to retrieve the key that is successfully created: it is either crashing or saying that the key is not found.
What is the proper way to pass a string to the dictionary and overall to Kotlin Native for Object C?

[olonho]

Hmm, the way how you use retain operation on raw string pointer (.wcstr.ptr) look wrong - this operation returns pointer to C style string, so reference counter operations doesn’t make sense

[Cyrille QUÉMIN]

Sorry that was the last of my attempt

[Cyrille QUÉMIN]

I tried with, without, with cstr instead. MAybe I should try to cast a Kotlin String into a NString?

[olonho]

Please post the whole code

[Cyrille QUÉMIN]

RSA generation:

val cfKeyGenerationAttributes = CFDictionaryCreateMutable(null, 0, null, null)
CFDictionaryAddValue(cfKeyGenerationAttributes, kSecAttrKeyType, kSecAttrKeyTypeRSA)
CFDictionaryAddValue(cfKeyGenerationAttributes, kSecAttrKeySizeInBits, CFBridgingRetain(NSNumber(int = rsaSpec.keyLength)))
CFDictionaryAddValue(cfKeyGenerationAttributes, kSecAttrIsPermanent, CFBridgingRetain(shouldBePersisted))
CFDictionaryAddValue(cfKeyGenerationAttributes, kSecAttrApplicationTag, keyAlias.cstr)

val error = alloc<CFErrorRefVar>()
val privateKeyRef = SecKeyCreateRandomKey(cfKeyGenerationAttributes, error.ptr)
println("Private Key generated: ${CFBridgingRelease(privateKeyRef)} ")

val publicKeySecRef = SecKeyCopyPublicKey(privateKeyRef)
println("Public Key generated: ${CFBridgingRelease(publicKeySecRef)} ")

RSA retrieval:

val cfKeyQueryAttributes = CFDictionaryCreateMutable(null, 0, null, null)
CFDictionaryAddValue(cfKeyQueryAttributes, kSecClass, kSecClassKey)
CFDictionaryAddValue(cfKeyQueryAttributes, kSecAttrKeyType, kSecAttrKeyTypeRSA)
CFDictionaryAddValue(cfKeyQueryAttributes, kSecAttrApplicationTag, keyAlias.cstr)
CFDictionaryAddValue(cfKeyQueryAttributes, kSecReturnRef, CFBridgingRetain(true))

val secKeyRef = alloc<CFTypeRefVar>()
val status = SecItemCopyMatching(cfKeyQueryAttributes, secKeyRef.ptr)
val errMsg = CFBridgingRelease(SecCopyErrorMessageString(status, null))
println("status is: ${errMsg!!}")

This produces a segmentation fault
Everytime, every attempt, the error is when SecItemCopyMatching is called. Generation displays the messages

I did several different attempts where I change how the alias is used for both generation and retrieval:
- with val cfString: CFStringRef = CFBridgingRetain(keyAlias)!!.reinterpret() SecItemCopyMatching produces: No keychain is available. You may need to restart your computer.
- with CFBridgingRetain(keyAlias.cstr) SecItemCopyMatching produces One or more parameters passed to a function were not valid

[svyatoslav.scherbina]

CFBridgingRetain(keyAlias) seems to be correct.
Have you tried writing the same code in Swift?

[Cyrille QUÉMIN]

Does that work for you?

[Cyrille QUÉMIN]

I haven't tried in Swift yet. maybe I should do that

[svyatoslav.scherbina]

I haven’t tried, but this seems to be correct according to framework documentation and Kotlin/Native rules for importing Objective-C.

[Cyrille QUÉMIN]

I have chatted with some iOS people and they say that for keychain related unit test they need attached the unit test to a host Application (something you can do through XCode)

[Cyrille QUÉMIN]

Do you know if there will be a way to generate the framework and attach it to an host app ?