TLS 1.2 Cipher Suites not detected

[rebel313]

sslscan cannot detect correct Cipher Suites for TLS 1.2 even though it detects TLS 1.2 itself.

Version: 2.1.0 Windows 64-bit (Mingw)
OpenSSL 3.0.9 30 May 2023

SSL/TLS Protocols:
SSLv2 disabled
SSLv3 disabled
TLSv1.0 disabled
TLSv1.1 disabled
TLSv1.2 enabled
TLSv1.3 enabled

TLS Fallback SCSV:
Server supports TLS Fallback SCSV

TLS renegotiation:
Session renegotiation not supported

TLS Compression:
Compression disabled

Heartbleed:
TLSv1.3 not vulnerable to heartbleed
TLSv1.2 not vulnerable to heartbleed

Supported Server Cipher(s):
Preferred TLSv1.3 128 bits TLS_AES_128_GCM_SHA256 Curve 25519 DHE 253
Accepted TLSv1.3 256 bits TLS_AES_256_GCM_SHA384 Curve 25519 DHE 253
Accepted TLSv1.3 256 bits TLS_CHACHA20_POLY1305_SHA256 Curve 25519 DHE 253

Server Key Exchange Group(s):
TLSv1.3 128 bits secp256r1 (NIST P-256)
TLSv1.3 192 bits secp384r1 (NIST P-384)
TLSv1.3 260 bits secp521r1 (NIST P-521)
TLSv1.3 128 bits x25519
TLSv1.3 224 bits x448
TLSv1.2 128 bits secp256r1 (NIST P-256)
TLSv1.2 192 bits secp384r1 (NIST P-384)
TLSv1.2 260 bits secp521r1 (NIST P-521)
TLSv1.2 128 bits x25519
TLSv1.2 224 bits x448

I also tested it with sslyze-5.1.3
Here are the results:

TLS 1.2 Cipher Suites:
Attempted to connect using 156 cipher suites.

 The server accepted the following 26 cipher suites:
    TLS_RSA_WITH_AES_256_GCM_SHA384                   256
    TLS_RSA_WITH_AES_256_CCM_8                        128
    TLS_RSA_WITH_AES_256_CCM                          256
    TLS_RSA_WITH_AES_256_CBC_SHA256                   256
    TLS_RSA_WITH_AES_256_CBC_SHA                      256
    TLS_RSA_WITH_AES_128_GCM_SHA256                   128
    TLS_RSA_WITH_AES_128_CCM_8                        128
    TLS_RSA_WITH_AES_128_CCM                          128
    TLS_RSA_WITH_AES_128_CBC_SHA256                   128
    TLS_RSA_WITH_AES_128_CBC_SHA                      128
    TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384             256       ECDH: prime256v1 (256 bits)
    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384             256       ECDH: prime256v1 (256 bits)
    TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA                256       ECDH: prime256v1 (256 bits)
    TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256             128       ECDH: prime256v1 (256 bits)
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256             128       ECDH: prime256v1 (256 bits)
    TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA                128       ECDH: prime256v1 (256 bits)
    TLS_DHE_RSA_WITH_AES_256_GCM_SHA384               256       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_256_CCM_8                    256       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_256_CCM                      256       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_256_CBC_SHA256               256       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_256_CBC_SHA                  256       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_128_GCM_SHA256               128       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_128_CCM_8                    128       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_128_CCM                      128       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_128_CBC_SHA256               128       DH (2048 bits)
    TLS_DHE_RSA_WITH_AES_128_CBC_SHA                  128       DH (2048 bits)

 The group of cipher suites supported by the server has the following properties:
   Forward Secrecy                    OK - Supported
   Legacy RC4 Algorithm               OK - Not Supported

TLS 1.3 Cipher Suites:
Attempted to connect using 5 cipher suites.

 The server accepted the following 3 cipher suites:
    TLS_CHACHA20_POLY1305_SHA256                      256       ECDH: X25519 (253 bits)
    TLS_AES_256_GCM_SHA384                            256       ECDH: X25519 (253 bits)
    TLS_AES_128_GCM_SHA256                            128       ECDH: X25519 (253 bits)

Ciphers on the server:
ciphers = ECDHE-RSA-AES128-GCM-SHA256:ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS:!RSA-AES-128-CBC-SHA256:!RS
A-AES-128-GCM-SHA256:!RSA-AES-256-CBC-SHA256:!RSA-AES-256-GCM-SHA384:!DHE-RSA-3DES-EDE-CBC-SHA:!ECDHE-RSA-3DES-EDE-CBC-SHA:!RSA-3DES-EDE-CBC-SHA:!RSA-AES-128-CBC-SHA256:!RSA-AES-128-GCM-SHA25
6:!RSA-AES-256-CBC-SHA:!RSA-AES-256-CBC-SHA256:!RSA-AES-256-GCM-SHA384:!DES:!3DES

[jtesta]

What target host did you use? If we can reproduce this issue, then we can likely fix it quickly. Thanks!

[rebel313]

Hi, How can I send it in private? Thanks!

[jtesta]

My e-mail address is: jtesta at-sign positronsecurity dot com

[jtesta]

@rebel313 : I submitted a PR which fixes the problem against your target host; see #293. Thanks for reporting this problem!

[rbsec]

@jtesta fantastic work investigating and fixing this as always. It's amazing how many dodgy TLS implementations there out there, and the amount of hacky code needed to work around them...

Do you know what the server was that's behaving in this weird way?

[jtesta]

@jtesta fantastic work investigating and fixing this as always.

Sure thing!

Do you know what the server was that's behaving in this weird way?

No, I couldn't identify the software stack that was behaving this way, but perhaps @rebel313 might know how it was configured.

[rebel313]

@jtesta @rbsec Glad I could help. Thanks for fixing it. The software is https://www.stunnel.org

stunnel 5.69 on x86_64-pc-linux-gnu platform
Compiled/running with OpenSSL 1.1.1t 7 Feb 2023
Threading:PTHREAD Sockets:POLL,IPv6 TLS:ENGINE,OCSP,PSK,SNI

Configured for mTLS.

[rebel313]

@jtesta @rbsec I'm interested if mentioned stunnel is doing something in non-standard way? Could it cause some clients to behave strangely and cause some problems with SSL/TLS connections? Like Android apps perhaps? The project is open source so I thought the author could use your valuable input if stunnel is doing something hacky.

I'll be debugging soon some rare connection issues as I have "SSL_accept: ssl/statem/statem_srvr.c:1767: error:14209175:SSL routines:tls_early_post_process_client_hello:inappropriate fallback" problem. If I understand correctly it's connected with TLS_FALLBACK_SCSV. Not sure where problem lays now, maybe I'll discover more hacks.

Otherwise the issue is fixed and we can close the ticket. Thanks!