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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXAMPLES | EXIT STATUS | SEE ALSO | AUTHORS | COPYRIGHT | BUGS | COLOPHON |
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gnutls-cli(1) User Commands gnutls-cli(1)
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 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.
--tofu, --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, --no-strict-tofu Fail to connect if a certificate
is unknown or a known certificate has changed. The no-strict-tofu
form will disable the option.
This option will perform authentication as with option --tofu;
however, no questions shall be asked whatsoever, neither to accept
an unknown certificate nor a changed one.
--dane, --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, --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, --no-ca-verification Enable CA certificate
verification. The no-ca-verification form will disable the
option. This option is enabled by default.
This option can be used to enable or disable CA certificate
verification. It is to be used with the --dane or --tofu options.
--ocsp, --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.
--earlydata=str Send early data on resumption from the specified
file.
-e, --rehandshake Establish a session and rehandshake.
Connect, establish a session and rehandshake immediately.
--sni-hostname=str Server's hostname for server name indication
extension.
Set explicitly the server name used in the TLS server name
indication extension. That is useful when testing with servers
setup on different DNS name than the intended. If not specified,
the provided hostname is used. Even with this option server
certificate verification still uses the hostname passed on the
main commandline. Use --verify-hostname to change this.
--verify-hostname=str Server's hostname to use for validation.
Set explicitly the server name to be used when validating the
server's certificate.
-s, --starttls Connect, establish a plain session and start TLS.
The TLS session will be initiated when EOF or a SIGALRM is
received.
--app-proto This is an alias for the --starttls-proto option.
--starttls-proto=str The application protocol to be used to obtain
the server's certificate (https, ftp, smtp, imap, ldap, xmpp,
lmtp, pop3, nntp, sieve, postgres). This option must not appear
in combination with any of the following options: starttls.
Specify the application layer protocol for STARTTLS. If the
protocol is supported, gnutls-cli will proceed to the TLS
negotiation.
--starttls-name=str The hostname presented to the application
protocol for STARTTLS (for smtp, xmpp, lmtp). This option must
not appear in combination with any of the following options:
starttls. This option must appear in combination with the
following options: starttls-proto.
Specify the hostname presented to the application protocol for
STARTTLS.
-u, --udp Use DTLS (datagram TLS) over UDP.
--mtu=num Set MTU for datagram TLS. This option takes an integer
number as its argument. The value of num is constrained to being:
in the range 0 through 17000
--crlf Send CR LF instead of LF.
--fastopen Enable TCP Fast Open.
--x509fmtder Use DER format for certificates to read from.
--print-cert Print peer's certificate in PEM format.
--save-cert=str Save the peer's certificate chain in the specified
file in PEM format.
--save-ocsp=str Save the peer's OCSP status response in the
provided file. This option must not appear in combination with
any of the following options: save-ocsp-multi.
--save-ocsp-multi=str Save all OCSP responses provided by the peer
in this file. This option must not appear in combination with any
of the following options: save-ocsp.
The file will contain a list of PEM encoded OCSP status responses
if any were provided by the peer, starting with the one for the
peer's server certificate.
--save-server-trace=str Save the server-side TLS message trace in
the provided file.
--save-client-trace=str Save the client-side TLS message trace in
the provided file.
--dh-bits=num 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.
--priority=str 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
--x509cafile=str Certificate file or PKCS #11 URL to use.
--x509crlfile=file CRL file to use.
--x509keyfile=str X.509 key file or PKCS #11 URL to use.
--x509certfile=str X.509 Certificate file or PKCS #11 URL to use.
This option must appear in combination with the following options:
x509keyfile.
--rawpkkeyfile=str Private key file (PKCS #8 or PKCS #12) or PKCS
#11 URL to use.
In order to instruct the application to negotiate raw public keys
one must enable the respective certificate types via the priority
strings (i.e. CTYPE-CLI-* and CTYPE-SRV-* flags).
Check the GnuTLS manual on section “Priority strings” for
more information on how to set certificate types.
--rawpkfile=str Raw public-key file to use. This option must
appear in combination with the following options: rawpkkeyfile.
In order to instruct the application to negotiate raw public keys
one must enable the respective certificate types via the priority
strings (i.e. CTYPE-CLI-* and CTYPE-SRV-* flags).
Check the GnuTLS manual on section “Priority strings” for
more information on how to set certificate types.
--srpusername=str SRP username to use.
--srppasswd=str SRP password to use.
--pskusername=str PSK username to use.
--pskkey=str PSK key (in hex) to use.
-p str, --port=str The port or service to connect to.
--insecure Don't abort program if server certificate can't be
validated.
--verify-allow-broken Allow broken algorithms, such as MD5 for
certificate verification.
--ranges Use length-hiding padding to prevent traffic analysis.
When possible (e.g., when using CBC ciphersuites), use
length-hiding padding to prevent traffic analysis.
NOTE: THIS OPTION IS DEPRECATED
--benchmark-ciphers Benchmark individual ciphers.
By default the benchmarked ciphers will utilize any capabilities
of the local CPU to improve performance. To test against the raw
software implementation set the environment variable
GNUTLS_CPUID_OVERRIDE to 0x1.
--benchmark-tls-kx Benchmark TLS key exchange methods.
--benchmark-tls-ciphers Benchmark TLS ciphers.
By default the benchmarked ciphers will utilize any capabilities
of the local CPU to improve performance. To test against the raw
software implementation set the environment variable
GNUTLS_CPUID_OVERRIDE to 0x1.
-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.
--priority-list Print a list of the supported priority strings.
Print a list of the supported priority strings. The ciphersuites
corresponding to each priority string can be examined using -l -p.
--noticket Don't allow session tickets.
Disable the request of receiving of session tickets under TLS1.2
or earlier
--srtp-profiles=str Offer SRTP profiles.
--alpn=str 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.
--compress-cert=str Compress certificate. This option may appear
an unlimited number of times.
This option sets a supported compression method for certificate
compression.
-b, --heartbeat Activate heartbeat support.
--recordsize=num The maximum record size to advertise. This
option takes an integer number as its argument. The value of num
is constrained to being:
in the range 0 through 4096
--disable-sni Do not send a Server Name Indication (SNI).
--disable-extensions Disable all the TLS extensions.
This option disables all TLS extensions. Deprecated option. Use
the priority string.
NOTE: THIS OPTION IS DEPRECATED
--single-key-share Send a single key share under TLS1.3.
This option switches the default mode of sending multiple key
shares, to send a single one (the top one).
--post-handshake-auth Enable post-handshake authentication under
TLS1.3.
This option enables post-handshake authentication when under
TLS1.3.
--inline-commands 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, rekey1 (local rekey), rekey (rekey on both peers) and
renegotiate.
--inline-commands-prefix=str 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
--provider=file Specify the PKCS #11 provider library.
This will override the default options in /etc/gnutls/pkcs11.conf
--fips140-mode Reports the status of the FIPS140-2 mode in gnutls
library.
--list-config Reports the configuration of the library.
--logfile=str Redirect informational messages to a specific file.
Redirect informational messages to a specific file. The file may
be /dev/null also to make the gnutls client quiet to use it in
piped server connections where only the server communication may
appear on stdout.
--keymatexport=str Label used for exporting keying material.
--keymatexportsize=num Size of the exported keying material. This
option takes an integer number as its argument.
--waitresumption Block waiting for the resumption data under
TLS1.3.
This option makes the client to block waiting for the resumption
data under TLS1.3. The option has effect only when --resume is
provided.
--ca-auto-retrieve, --no-ca-auto-retrieve Enable automatic
retrieval of missing CA certificates. The no-ca-auto-retrieve
form will disable the option.
This option enables the client to automatically retrieve the
missing intermediate CA certificates in the certificate chain,
based on the Authority Information Access (AIA) extension.
--attime=timestamp Perform validation at the timestamp instead of
the system time.
timestamp is an instance in time encoded as Unix time or in a
human
readable timestring such as "29 Feb 2004", "2004-02-29". Full
documentation available at
<https://www.gnu.org/software/coreutils/manual/html_node/Date-input-formats.html>
or locally via info '(coreutils) date invocation'.
-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.
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 '127.0.0.1:5556'...
- PSK authentication.
- Version: TLS1.1
- Key Exchange: PSK
- Cipher: AES-128-CBC
- MAC: SHA1
- 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.
Connecting using raw public-key authentication
To connect to a server using raw public-key authentication,
you need to enable the option to negotiate raw public-keys
via the priority strings such as in the example below.
$ ./gnutls-cli -p 5556 localhost --priority NORMAL:-CTYPE-CLI-ALL:+CTYPE-CLI-RAWPK --rawpkkeyfile cli.key.pem --rawpkfile cli.rawpk.pem
Processed 1 client raw public key pair...
Resolving 'localhost'...
Connecting to '127.0.0.1:5556'...
- Successfully sent 1 certificate(s) to server.
- Server has requested a certificate.
- Certificate type: X.509
- Got a certificate list of 1 certificates.
- Certificate[0] info:
- skipped
- Description: (TLS1.3-Raw Public Key-X.509)-(ECDHE-SECP256R1)-(RSA-PSS-RSAE-SHA256)-(AES-256-GCM)
- Options:
- Handshake was completed
- Simple Client Mode:
Connecting to STARTTLS services
You could also use the client to connect to services with
starttls capability.
$ gnutls-cli --starttls-proto smtp --port 25 localhost
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 TLS1.2
TLS_ECDHE_ECDSA_AES_256_GCM_SHA384 0xc0, 0x2e TLS1.2
TLS_ECDHE_RSA_AES_256_GCM_SHA384 0xc0, 0x30 TLS1.2
TLS_DHE_RSA_AES_256_CBC_SHA256 0x00, 0x6b TLS1.2
TLS_DHE_DSS_AES_256_CBC_SHA256 0x00, 0x6a TLS1.2
TLS_RSA_AES_256_CBC_SHA256 0x00, 0x3d TLS1.2
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
PK-signatures: SIGN-RSA-SHA384, SIGN-ECDSA-SHA384, SIGN-RSA-SHA512, SIGN-ECDSA-SHA512
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;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
$ MYCERT="pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test;object=client;type=cert"
$ MYKEY="pkcs11:model=PKCS15;manufacturer=MyMan;serial=1234;token=Test;object=client;type=private"
$ export MYCERT MYKEY
$ gnutls-cli www.example.com --x509keyfile $MYKEY --x509certfile $MYCERT
Notice that the private key only differs from the
certificate in the type.
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.
gnutls-cli-debug(1), gnutls-serv(1)
Copyright (C) 2020-2023 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 page is part of the GnuTLS (GnuTLS Transport Layer Security
Library) project. Information about the project can be found at
⟨http://www.gnutls.org/⟩. If you have a bug report for this
manual page, send it to bugs@gnutls.org. This page was obtained
from the tarball fetched from
⟨https://www.gnupg.org/ftp/gcrypt/gnutls/⟩ on 2025-08-11. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
3.8.10 09 Jul 2025 gnutls-cli(1)
Pages that refer to this page: gnutls-cli-debug(1), gnutls-serv(1), ldap.conf(5), lloadd.conf(5), slapd.conf(5), slapd-config(5)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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