TLS connection fail: reset by server after sending Client Hello.

[Eskibear]

I use Adafruit WICED Feather to connect AzureIoTHub via cubipal.azure-devices.net:443, but fail the SSL handshake after sending Client Hello message.

Here is a list of cipher suites supported by Azure IoT

    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (0xc028) ECDH secp384r1 (eq. 7680 bits RSA) FS
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (0xc027) ECDH secp256r1 (eq. 3072 bits RSA) FS
    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (0xc014) ECDH secp384r1 (eq. 7680 bits RSA) FS
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (0xc013) ECDH secp256r1 (eq. 3072 bits RSA) FS
    TLS_RSA_WITH_AES_256_GCM_SHA384 (0x9d)
    TLS_RSA_WITH_AES_128_GCM_SHA256 (0x9c)
--> TLS_RSA_WITH_AES_256_CBC_SHA256 (0x3d)
    TLS_RSA_WITH_AES_128_CBC_SHA256 (0x3c)
    TLS_RSA_WITH_AES_256_CBC_SHA (0x35)
    TLS_RSA_WITH_AES_128_CBC_SHA (0x2f)
    TLS_RSA_WITH_3DES_EDE_CBC_SHA (0xa)

And following is the packet carrying Client Hello message.

Secure Sockets Layer
    SSL Record Layer: Handshake Protocol: Client Hello
        Content Type: Handshake (22)
        Version: TLS 1.2 (0x0303)
        Length: 93
        Handshake Protocol: Client Hello
            Handshake Type: Client Hello (1)
            Length: 89
            Version: TLS 1.2 (0x0303)
            Random
                GMT Unix Time: Feb 28, 2017 16:22:37.000000000 China Standard Time
                Random Bytes: ca70e95deba443f13e6a99cda89e8623bc9c6bffd622e610...
            Session ID Length: 0
            Cipher Suites Length: 24
            Cipher Suites (12 suites)
                Cipher Suite: TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 (0x006b)
                Cipher Suite: TLS_DHE_RSA_WITH_AES_256_CBC_SHA (0x0039)
                Cipher Suite: TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 (0x0067)
                Cipher Suite: TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x0033)
      ----->    Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA256 (0x003d)
                Cipher Suite: TLS_RSA_WITH_AES_256_CBC_SHA (0x0035)
                Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA256 (0x003c)
                Cipher Suite: TLS_RSA_WITH_AES_128_CBC_SHA (0x002f)
                Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA (0xc009)
                Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA (0xc00a)
                Cipher Suite: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 (0xc023)
                Cipher Suite: TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA (0xc004)
            Compression Methods Length: 1
            Compression Methods (1 method)
                Compression Method: null (0)
            Extensions Length: 24
            Extension: elliptic_curves
                Type: elliptic_curves (0x000a)
                Length: 4
                Elliptic Curves Length: 2
                Elliptic curves (1 curve)
                    Elliptic curve: secp256r1 (0x0017)
            Extension: ec_point_formats
                Type: ec_point_formats (0x000b)
                Length: 2
                EC point formats Length: 1
                Elliptic curves point formats (1)
                    EC point format: uncompressed (0)
            Extension: signature_algorithms
                Type: signature_algorithms (0x000d)
                Length: 6
                Signature Hash Algorithms Length: 4
                Signature Hash Algorithms (2 algorithms)
                    Signature Hash Algorithm: 0x0203
                        Signature Hash Algorithm Hash: SHA1 (2)
                        Signature Hash Algorithm Signature: ECDSA (3)
                    Signature Hash Algorithm: 0x0403
       ----->           Signature Hash Algorithm Hash: SHA256 (4)
       ----->           Signature Hash Algorithm Signature: ECDSA (3)

According to cipher suites in both client side and server side, the SSL negotiation should finally use TLS_RSA_WITH_AES_256_CBC_SHA256, but signature_algorithms extension doesn't contain RSA+SHA256. Since the common cipher suite doesn't match ECDSA+SHA1 or ECDSA+SHA256, the server terminate the negotiation.

I've done some experiments with openssl to support above assumption.

OpenSSL version:

$ openssl version
OpenSSL 1.0.2g  1 Mar 2016

For cipher suited supported by Adafruit WICED Feather, the cipher string is DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:AES256-SHA256:AES256-SHA:AES128-SHA256:AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA:ECDHE-ECDSA-AES128-SHA256:ECDH-ECDSA-AES128-SHA

Exp 1.

By using option -sigalgs <signature_algorithm>, we simulate the WICED using its signature_algorithm extension ECDSA+SHA1:ECDSA+SHA256.[Errno 104: connection reset by peer]

$ openssl s_client \
    -connect cubipal.azure-devices.net:443 \
    -cipher DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:AES256-SHA256:AES256-SHA:AES128-SHA256:AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA:ECDHE-ECDSA-AES128-SHA256:ECDH-ECDSA-AES128-SHA \
    -sigalgs ECDSA+SHA1:ECDSA+SHA256
CONNECTED(00000003)
write:errno=104
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 119 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : 0000
    Session-ID: 
    Session-ID-ctx: 
    Master-Key: 
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1488339212
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---

Exp 2.

Add RSA+SHA256 to signature_algorithm extension. [Successfully connected]

$ openssl s_client \
    -connect cubipal.azure-devices.net:443 \
    -cipher DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:AES256-SHA256:AES256-SHA:AES128-SHA256:AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA:ECDHE-ECDSA-AES128-SHA256:ECDH-ECDSA-AES128-SHA \
    -sigalgs ECDSA+SHA1:ECDSA+SHA256:RSA+SHA256 
CONNECTED(00000003)
depth=2 C = IE, O = Baltimore, OU = CyberTrust, CN = Baltimore CyberTrust Root
verify return:1
depth=1 C = US, ST = Washington, L = Redmond, O = Microsoft Corporation, OU = Microsoft IT, CN = Microsoft IT SSL SHA2
verify return:1
depth=0 CN = *.azure-devices.net
verify return:1
---
Certificate chain
 0 s:/CN=*.azure-devices.net
   i:/C=US/ST=Washington/L=Redmond/O=Microsoft Corporation/OU=Microsoft IT/CN=Microsoft IT SSL SHA2
 1 s:/C=US/ST=Washington/L=Redmond/O=Microsoft Corporation/OU=Microsoft IT/CN=Microsoft IT SSL SHA2
   i:/C=IE/O=Baltimore/OU=CyberTrust/CN=Baltimore CyberTrust Root
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=/CN=*.azure-devices.net
issuer=/C=US/ST=Washington/L=Redmond/O=Microsoft Corporation/OU=Microsoft IT/CN=Microsoft IT SSL SHA2
---
No client certificate CA names sent
---
SSL handshake has read 3266 bytes and written 495 bytes
---
New, TLSv1/SSLv3, Cipher is AES256-SHA256
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : AES256-SHA256
    Session-ID: F12200004B7B272FA59EE38A18CC8E016CEB35455E9AD6E6D5F680766224D560
    Session-ID-ctx: 
    Master-Key: 97F19F66232A3242AD08F66F3D67DBE595DB03035FEECAAC92BD273DE64AA0C894E6987008AC2515ADB7AE025DACF60D
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: 1488339228
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---
^C

It's not reasonable that the WICED Feather supports RSA SHA256 cipher suites but doesn't put RSA+SHA256 into Client Hello signature_algorithm extension. And personally I think it may be a firmware issue.

Here is a tcpdump .pcap file when WICED Feather tries to establish the SSL connection, FYI.

Could you help to take a further investigation and resolve this issue?
Thanks