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Member "gnutls-3.3.13/doc/manpages/gnutls-cli.1" (25 Feb 2015, 14185 Bytes) of archive /linux/misc/gnutls-3.3.13.tar.gz:




gnutls-cli − GnuTLS client


gnutls-cli [−flags] [−flag [value]] [−−option-name[[=| ]value]] [hostname]

Operands and options may be intermixed. They will be reordered.


Simple client program to set up a TLS connection to some other computer. It sets up a TLS connection and forwards data from the standard input to the secured socket and vice versa.


−d number, −−debug=number

Enable debugging. This option takes an integer number as its argument. The value of number is constrained to being:

in the range 0 through 9999

Specifies the debug level.

−V, −−verbose

More verbose output. This option may appear an unlimited number of times.

−−tofu, − Fl −no−tofu

Enable trust on first use authentication. The no−tofu form will disable the option.

This option will, in addition to certificate authentication, perform authentication based on previously seen public keys, a model similar to SSH authentication. Note that when tofu is specified (PKI) and DANE authentication will become advisory to assist the public key acceptance process.

−−strict−tofu, − Fl −no−strict−tofu

Fail to connect if a known certificate has changed. The no−strict−tofu form will disable the option.

This option will perform authentication as with option −-tofu; however, while −-tofu asks whether to trust a changed public key, this option will fail in case of public key changes.

−−dane, − Fl −no−dane

Enable DANE certificate verification (DNSSEC). The no−dane form will disable the option.

This option will, in addition to certificate authentication using the trusted CAs, verify the server certificates using on the DANE information available via DNSSEC.

−−local−dns, − Fl −no−local−dns

Use the local DNS server for DNSSEC resolving. The no−local−dns form will disable the option.

This option will use the local DNS server for DNSSEC. This is disabled by default due to many servers not allowing DNSSEC.

−−ca−verification, − Fl −no−ca−verification

Disable CA certificate verification. The no−ca−verification form will disable the option. This option is enabled by default.

This option will disable CA certificate verification. It is to be used with the −-dane or −-tofu options.

−−ocsp, − Fl −no−ocsp

Enable OCSP certificate verification. The no−ocsp form will disable the option.

This option will enable verification of the peer’s certificate using ocsp

−r, −−resume

Establish a session and resume.

Connect, establish a session, reconnect and resume.

−e, −−rehandshake

Establish a session and rehandshake.

Connect, establish a session and rehandshake immediately.

−s, −−starttls

Connect, establish a plain session and start TLS.

The TLS session will be initiated when EOF or a SIGALRM is received.


This is an alias for the --starttls-proto option.


The application protocol to be used to obtain the server’s certificate (https, smtp, imap).

Specify the application layer protocol for STARTTLS. If the protocol is supported, gnutls-cli will proceed to the TLS negotiation.

−u, −−udp

Use DTLS (datagram TLS) over UDP.


Set MTU for datagram TLS. This option takes an integer number as its argument. The value of number is constrained to being:

in the range 0 through 17000


Send CR LF instead of LF.


Use DER format for certificates to read from.

−f, −−fingerprint

Send the openpgp fingerprint, instead of the key.


Print peer’s certificate in PEM format.


The minimum number of bits allowed for DH. This option takes an integer number as its argument.

This option sets the minimum number of bits allowed for a Diffie-Hellman key exchange. You may want to lower the default value if the peer sends a weak prime and you get an connection error with unacceptable prime.


Priorities string.

TLS algorithms and protocols to enable. You can use predefined sets of ciphersuites such as PERFORMANCE, NORMAL, PFS, SECURE128, SECURE256. The default is NORMAL.

Check the GnuTLS manual on section “Priority strings” for more information on the allowed keywords


Certificate file or PKCS #11 URL to use.


CRL file to use.


PGP Key file to use.


PGP Key ring file to use.


PGP Public Key (certificate) file to use.


X.509 key file or PKCS #11 URL to use.


X.509 Certificate file or PKCS #11 URL to use.


PGP subkey to use (hex or auto).


SRP username to use.


SRP password to use.


PSK username to use.


PSK key (in hex) to use.

−p string, −−port=string

The port or service to connect to.


Don’t abort program if server certificate can’t be validated.


Use length-hiding padding to prevent traffic analysis.

When possible (e.g., when using CBC ciphersuites), use length-hiding padding to prevent traffic analysis.


Benchmark individual ciphers.


Benchmark TLS key exchange methods.


Benchmark TLS ciphers.

−l, −−list

Print a list of the supported algorithms and modes. This option must not appear in combination with any of the following options: port.

Print a list of the supported algorithms and modes. If a priority string is given then only the enabled ciphersuites are shown.


Don’t allow session tickets.


Offer SRTP profiles.


Application layer protocol. This option may appear an unlimited number of times.

This option will set and enable the Application Layer Protocol Negotiation (ALPN) in the TLS protocol.

−b, −−heartbeat

Activate heartbeat support.


The maximum record size to advertize. This option takes an integer number as its argument. The value of number is constrained to being:

in the range 0 through 4096


Do not send a Server Name Indication (SNI).


Disable all the TLS extensions.

This option disables all TLS extensions. Deprecated option. Use the priority string.


Inline commands of the form ^<cmd>^.

Enable inline commands of the form ^<cmd>^. The inline commands are expected to be in a line by themselves. The available commands are: resume and renegotiate.


Change the default delimiter for inline commands..

Change the default delimiter (^) used for inline commands. The delimiter is expected to be a single US-ASCII character (octets 0 − 127). This option is only relevant if inline commands are enabled via the inline-commands option


Specify the PKCS #11 provider library.

This will override the default options in /etc/gnutls/pkcs11.conf


Reports the status of the FIPS140-2 mode in gnutls library.

−h, −−help

Display usage information and exit.

−!, −−more-help

Pass the extended usage information through a pager.

−v [{v|c|n −−version [{v|c|n}]}]

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.


Connecting using PSK authentication
To connect to a server using PSK authentication, you need to enable the choice of PSK by using a cipher priority parameter such as in the example below.

$ ./gnutls−cli −p 5556 localhost −−pskusername psk_identity −−pskkey 88f3824b3e5659f52d00e959bacab954b6540344 −−priority NORMAL:−KX−ALL:+ECDHE−PSK:+DHE−PSK:+PSK
Resolving ’localhost’...
Connecting to ’’...
- PSK authentication.
- Version: TLS1.1
- Key Exchange: PSK
- Cipher: AES−128−CBC
- Compression: NULL
- Handshake was completed
- Simple Client Mode:

By keeping the −−pskusername parameter and removing the −−pskkey parameter, it will query only for the password during the handshake.

Listing ciphersuites in a priority string
To list the ciphersuites in a priority string:

$ ./gnutls−cli −−priority SECURE192 −l
Cipher suites for SECURE192

TLS_ECDHE_ECDSA_AES_256_CBC_SHA384 0xc0, 0x24


TLS_ECDHE_ECDSA_AES_256_GCM_SHA384 0xc0, 0x2e


TLS_ECDHE_RSA_AES_256_GCM_SHA384 0xc0, 0x30


TLS_DHE_RSA_AES_256_CBC_SHA256 0x00, 0x6b


TLS_DHE_DSS_AES_256_CBC_SHA256 0x00, 0x6a


TLS_RSA_AES_256_CBC_SHA256 0x00, 0x3d


Certificate types: CTYPE−X.509
Protocols: VERS−TLS1.2, VERS−TLS1.1, VERS−TLS1.0, VERS−SSL3.0, VERS−DTLS1.0
Compression: COMP−NULL
Elliptic curves: CURVE−SECP384R1, CURVE−SECP521R1

Connecting using a PKCS #11 token
To connect to a server using a certificate and a private key present in a PKCS #11 token you need to substitute the PKCS 11 URLs in the x509certfile and x509keyfile parameters.

Those can be found using "p11tool −−list−tokens" and then listing all the objects in the needed token, and using the appropriate.

$ p11tool −−list−tokens

Token 0:
URL: pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test
Label: Test
Manufacturer: EnterSafe
Model: PKCS15
Serial: 1234

$ p11tool −−login −−list−certs "pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test"

Object 0:
URL: pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test;object=client;object−type=cert
Type: X.509 Certificate
Label: client
ID: 2a:97:0d:58:d1:51:3c:23:07:ae:4e:0d:72:26:03:7d:99:06:02:6a

$ export MYCERT="pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test;object=client;object−type=cert"
$ export MYKEY="pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test;object=client;object−type=private"

$ gnutls−cli www.example.com −−x509keyfile $MYKEY −−x509certfile MYCERT

Notice that the private key only differs from the certificate in the object−type.


One of the following exit values will be returned:

Successful program execution.


The operation failed or the command syntax was not valid.


libopts had an internal operational error. Please report it to autogen-users@lists.sourceforge.net. Thank you.


gnutls−cli−debug(1), gnutls−serv(1)


Nikos Mavrogiannopoulos, Simon Josefsson and others; see /usr/share/doc/gnutls/AUTHORS for a complete list.


Copyright (C) 2000-2015 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: bugs@gnutls.org


This manual page was AutoGen-erated from the gnutls-cli option definitions.