Add flag to set cipher suite preferences on a TLS session (backport #1020) #1028
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* Add the definitions to set preferences which can't be set via the priority string * Extend open_stream_conenction_ext() to receive the new bit flag variable for setting cipher suite preferences on a TLS session * Forward the flag variable to set the TLS preferences or use NO_PRIORITY_FLAGS, as required for each case. * Catch the GNUTLS_E_DH_PRIME_UNACCEPTABLE error during the handshake and return -2 to allow caller functions to handle this especial case. * Handle the case GNUTLS_E_DH_PRIME_UNACCEPTABLE error. Retry with a lower prime bits number. For this, use the new bit flag variable. What: Currently, when the scanner opens a TLS session, cipher suite preferences can be set only via the priority string. Other preferences can be set via functions. This PR extends the open_stream_connection_ext() function to accept a flag which allows to set other preferences (e.g. the number of bits, for use in a Diffie-Hellman key exchange) Jira: SC-441 Why: nasl_builtin_find_service.c fails to detect SSL/TLS service because, in this particular case, the server sends a prime of 512 bits, and the client limit is 1008 (set with the NORMAL priority). This PR handles this error and set a new minimum (128) and retries to open the TLS connection. How: sudo openvas-nasl -X -B -d -i $PLUGINSPATH -t TARGET find_service.nasl --kb="Ports/tcp/443=1" --debug-tls=9 [19893] (1) FFDHE groups advertised, but server didn't support it; falling back to server's choice [19893] (2) Received a prime of 512 bits, limit is 1008 lib misc-Message: 03:36:31.165: replace key FindService/CnxTime1000/443 -> 45 lib misc-Message: 03:36:31.166: set key Transports/TCP/443 -> 1 lib misc-Message: 03:36:51.279: set key Services/unknown -> 443 With the PR: [19263] (1) FFDHE groups advertised, but server didn't support it; falling back to server's choice [19263] (2) Received a prime of 512 bits, limit is 1008 lib misc-Message: 03:19:20.218: [19263] gnutls_handshake: The Diffie-Hellman prime sent by the server is not acceptable (not long enough). [19263] (1) Note that the security level of the Diffie-Hellman key exchange has been lowered to 128 bits and this may allow decryption of the session data lib misc-Message: 03:37:38.525: replace key FindService/RwTime1000/443 -> 101 lib misc-Message: 03:37:38.525: replace key FindService/tcp/443/get_http -> HTTP/1.0 200 OK Date: Sat, 01 Jan 2011 00:00:53 GMT Server: Embedded HTTP Server. Connection: close Content-Length: 107 Last-Modified: Fri, 28 Feb 2014 14:53:02 GMT Content-Type: text/html <HTML><HEAD><meta http-equiv="refresh" content="0; URL=/scgi-bin/platform.cgi"></HEAD><BODY></BODY></HTML> lib misc-Message: 03:37:38.525: set key Services/www -> 443 lib misc-Message: 03:37:38.525: replace key Known/tcp/443 -> www lib misc-Message: 03:37:38.525: replace key www/banner/443 -> HTTP/1.0 200 OK Date: Sat, 01 Jan 2011 00:00:53 GMT Server: Embedded HTTP Server. Connection: close Content-Length: 107 Last-Modified: Fri, 28 Feb 2014 14:53:02 GMT Content-Type: text/html <HTML><HEAD><meta http-equiv="refresh" content="0; URL=/scgi-bin/platform.cgi"></HEAD><BODY></BODY></HTML> (cherry picked from commit 8186bb6)
ArnoStiefvater
approved these changes
Feb 8, 2022
jjnicola
approved these changes
Feb 8, 2022
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This is an automatic backport of pull request #1020 done by Mergify.
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