-flag [value]] [
--option-name[[=| ]value]] [hostname]
Operands and options may be intermixed. They will be reordered.
TLS debug client. It sets up multiple TLS connections to a server and queries its capabilities. It was created to assist in debugging GnuTLS, but it might be useful to extract a TLS server's capabilities. It connects to a TLS server, performs tests and print the server's capabilities. If called with the `-V' parameter more checks will be performed. Can be used to check for servers with special needs or bugs.
- -d num, --debug=num
Enable debugging. This option takes an integer number as its argument. The value of num is constrained to being:
in the range 0 through 9999
Specifies the debug level.
- -V, --verbose
More verbose output.
- -p num, --port=num
The port to connect to. This option takes an integer number as its argument. The value of num is constrained to being:
in the range 0 through 65536
This is an alias for the --starttls-proto option.
The application protocol to be used to obtain the server's certificate (https, ftp, smtp, imap, ldap, xmpp, lmtp, pop3, nntp, sieve, postgres).
Specify the application layer protocol for STARTTLS. If the protocol is supported, gnutls-cli will proceed to the TLS negotiation.
- -v arg, --version=arg
Output version of program and exit. The default mode is `v', a simple version. The `c' mode will print copyright information and `n' will print the full copyright notice.
- -h, --help
Display usage information and exit.
- -!, --more-help
Pass the extended usage information through a pager.
$ gnutls-cli-debug localhost GnuTLS debug client 3.5.0 Checking localhost:443 for SSL 3.0 (RFC6101) support... yes whether we need to disable TLS 1.2... no whether we need to disable TLS 1.1... no whether we need to disable TLS 1.0... no whether %NO_EXTENSIONS is required... no whether %COMPAT is required... no for TLS 1.0 (RFC2246) support... yes for TLS 1.1 (RFC4346) support... yes for TLS 1.2 (RFC5246) support... yes fallback from TLS 1.6 to... TLS1.2 for RFC7507 inappropriate fallback... yes for HTTPS server name... Local for certificate chain order... sorted for safe renegotiation (RFC5746) support... yes for Safe renegotiation support (SCSV)... no for encrypt-then-MAC (RFC7366) support... no for ext master secret (RFC7627) support... no for heartbeat (RFC6520) support... no for version rollback bug in RSA PMS... dunno for version rollback bug in Client Hello... no whether the server ignores the RSA PMS version... yes whether small records (512 bytes) are tolerated on handshake... yes whether cipher suites not in SSL 3.0 spec are accepted... yes whether a bogus TLS record version in the client hello is accepted... yes whether the server understands TLS closure alerts... partially whether the server supports session resumption... yes for anonymous authentication support... no for ephemeral Diffie-Hellman support... no for ephemeral EC Diffie-Hellman support... yes ephemeral EC Diffie-Hellman group info... SECP256R1 for AES-128-GCM cipher (RFC5288) support... yes for AES-128-CCM cipher (RFC6655) support... no for AES-128-CCM-8 cipher (RFC6655) support... no for AES-128-CBC cipher (RFC3268) support... yes for CAMELLIA-128-GCM cipher (RFC6367) support... no for CAMELLIA-128-CBC cipher (RFC5932) support... no for 3DES-CBC cipher (RFC2246) support... yes for ARCFOUR 128 cipher (RFC2246) support... yes for MD5 MAC support... yes for SHA1 MAC support... yes for SHA256 MAC support... yes for ZLIB compression support... no for max record size (RFC6066) support... no for OCSP status response (RFC6066) support... no for OpenPGP authentication (RFC6091) support... no
You could also use the client to debug services with starttls capability.
$ gnutls-cli-debug --starttls-proto smtp --port 25 localhost
One of the following exit values will be returned:
- 0 (EXIT_SUCCESS)
Successful program execution.
- 1 (EXIT_FAILURE)
The operation failed or the command syntax was not valid.
Copyright (C) 2020-2021 Free Software Foundation, and others all rights reserved. This program is released under the terms of the GNU General Public License, version 3 or later
Please send bug reports to: email@example.com
gnutls-cli(1), gnutls-serv(1), psktool(1), srptool(1).