gnutls-cli - GnuTLS client

NAME SYNOPSIS DESCRIPTION OPTIONS EXAMPLES EXIT STATUS SEE ALSO AUTHORS COPYRIGHT BUGS

SYNOPSIS

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

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

DESCRIPTION

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.

OPTIONS

−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.

−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 ˆ<cmd>ˆ.

Enable inline commands of the form ˆ<cmd>ˆ. 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 (ˆ) 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.

EXAMPLES

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.