MQTT5 PKCS11 does not support TLS13

[flarno11]

Describe the bug

When using the MQTT5 client with PKCS11 and ECC certificates, the client seems to offer only TLS 1.2. If the same certificate is used without PKCS11, the client offers TLS 1.2 and TLS 1.3. If the IotSecurityPolicy TLS13_1_3_2022_10 is configured in IoT Core, the server rejects the connection directly after the Client Hello.

Expected Behavior

The offered TLS versions should be the same independent of whether PKCS11 is used or not.

Current Behavior

The server rejects the Client Hello when TLS 1.3 is enforced.

Reproduction Steps

1. Configure IoT Core with Security Policy TLS13_1_3_2022_10
2. Register custom Root CA with ECC certificates
3. Create Thing, register ECC client certificate
4. Run example https://github.com/aws/aws-iot-device-sdk-cpp-v2/blob/main/samples/mqtt/mqtt5_pkcs11/README.md with SoftHSM
5. Server rejects Client Hello with

TLSv1.2 Record Layer: Alert (Level: Fatal, Description: Protocol Version)
    Content Type: Alert (21)
    Version: TLS 1.2 (0x0303)
    Length: 2
    Alert Message
        Level: Fatal (2)
        Description: Protocol Version (70)

6. change policy to TLS13_1_2_2022_10
7. Server accepts Client Hello

Possible Solution

No response

Additional Information/Context

Client Hello with PKCS11:

TLSv1.2 Record Layer: Handshake Protocol: Client Hello
    Content Type: Handshake (22)
    Version: TLS 1.0 (0x0301)
    Length: 217
    Handshake Protocol: Client Hello
        Handshake Type: Client Hello (1)
        Length: 213
        Version: TLS 1.2 (0x0303)
        Random: xxx
        Session ID Length: 0
        Cipher Suites Length: 38
        Cipher Suites (19 suites)
        Compression Methods Length: 1
        Compression Methods (1 method)
        Extensions Length: 134
        Extension: supported_groups (len=6)
            Type: supported_groups (10)
            Length: 6
            Supported Groups List Length: 4
            Supported Groups (2 groups)
                Supported Group: secp256r1 (0x0017)
                Supported Group: secp384r1 (0x0018)
        Extension: signature_algorithms (len=22)
            Type: signature_algorithms (13)
            Length: 22
            Signature Hash Algorithms Length: 20
            Signature Hash Algorithms (10 algorithms)
        Extension: server_name (len=54) name=xxxx-ats.iot.eu-central-1.amazonaws.com
            Type: server_name (0)
            Length: 54
            Server Name Indication extension
        Extension: application_layer_protocol_negotiation (len=17)
            Type: application_layer_protocol_negotiation (16)
            Length: 17
            ALPN Extension Length: 15
            ALPN Protocol
                ALPN string length: 14
                ALPN Next Protocol: x-amzn-mqtt-ca
        Extension: status_request (len=5)
            Type: status_request (5)
            Length: 5
            Certificate Status Type: OCSP (1)
            Responder ID list Length: 0
            Request Extensions Length: 0
        Extension: ec_point_formats (len=2)
            Type: ec_point_formats (11)
            Length: 2
            EC point formats Length: 1
            Elliptic curves point formats (1)
        Extension: extended_master_secret (len=0)
            Type: extended_master_secret (23)
            Length: 0
...

Client Hello without PKCS11 (same client certificate, same version, same settings):

TLSv1.3 Record Layer: Handshake Protocol: Client Hello
    Content Type: Handshake (22)
    Version: TLS 1.0 (0x0301)
    Length: 361
    Handshake Protocol: Client Hello
        Handshake Type: Client Hello (1)
        Length: 357
        Version: TLS 1.2 (0x0303)
        Random: xxxx
        Session ID Length: 32
        Session ID: xxxx
        Cipher Suites Length: 48
        Cipher Suites (24 suites)
        Compression Methods Length: 1
        Compression Methods (1 method)
        Extensions Length: 236
        Extension: supported_versions (len=9) TLS 1.3, TLS 1.2, TLS 1.1, TLS 1.0
            Type: supported_versions (43)
            Length: 9
            Supported Versions length: 8
            Supported Version: TLS 1.3 (0x0304)
            Supported Version: TLS 1.2 (0x0303)
            Supported Version: TLS 1.1 (0x0302)
            Supported Version: TLS 1.0 (0x0301)
        Extension: supported_groups (len=8)
            Type: supported_groups (10)
            Length: 8
            Supported Groups List Length: 6
            Supported Groups (3 groups)
                Supported Group: secp256r1 (0x0017)
                Supported Group: x25519 (0x001d)
                Supported Group: secp384r1 (0x0018)
        Extension: key_share (len=71) secp256r1
            Type: key_share (51)
            Length: 71
            Key Share extension
        Extension: signature_algorithms (len=34)
            Type: signature_algorithms (13)
            Length: 34
            Signature Hash Algorithms Length: 32
            Signature Hash Algorithms (16 algorithms)
        Extension: server_name (len=54) name=xxxx-ats.iot.eu-central-1.amazonaws.com
            Type: server_name (0)
            Length: 54
            Server Name Indication extension
        Extension: application_layer_protocol_negotiation (len=17)
            Type: application_layer_protocol_negotiation (16)
            Length: 17
            ALPN Extension Length: 15
            ALPN Protocol
                ALPN string length: 14
                ALPN Next Protocol: x-amzn-mqtt-ca
        Extension: status_request (len=5)
            Type: status_request (5)
            Length: 5
            Certificate Status Type: OCSP (1)
            Responder ID list Length: 0
            Request Extensions Length: 0
        Extension: ec_point_formats (len=2)
            Type: ec_point_formats (11)
            Length: 2
            EC point formats Length: 1
            Elliptic curves point formats (1)
        Extension: extended_master_secret (len=0)
            Type: extended_master_secret (23)
            Length: 0
...

SDK version used

Latest main branch b8b7bc3

Environment details (OS name and version, etc.)

Ubuntu 22 LTS

[sfod]

Currently, TLS 1.3 is not supported with PKCS11, we explicitly forbid it in one of the upstream libraries.
I'll verify whether this is still the case. If so, we'll add a note to the sample readme.

[sfod]

So, I looked further into TLS 1.3 and PKCS11 problem - unfortunately, it's not trivial to support. I'll bring it to the team to review if this is a feature we want to add to our backlog. If you can describe your use case, this might be helpful.

[flarno11]

@sfod thank you for the fast investigation. It is not a must to have it right now for me, if you could document it accordingly it may also help others save a couple of hours of debugging.

Eventually I assume TLS 1.3 needs to be supported too.

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