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certtool(1) User Commands certtool(1)

NAME
certtool - GnuTLS certificate tool

SYNOPSIS
certtool [-flags] [-flag [value]] [--option-name[[=| ]value]]

All arguments must be options.

DESCRIPTION
Tool to parse and generate X.509 certificates, requests and private
keys. It can be used interactively or non interactively by specifying
the template command line option.

The tool accepts files or supported URIs via the --infile option. In
case PIN is required for URI access you can provide it using the envi-
ronment variables GNUTLS_PIN and GNUTLS_SO_PIN.

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.

--infile=file Input file.

--outfile=str Output file.

--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 docu-
mentation available at <https://www.gnu.org/software/coreutils/man-
ual/html_node/Date-input-formats.html> or locally via info '(coreutils)
date invocation'.

Certificate related options

-i, --certificate-info Print information on the given certificate.

--pubkey-info Print information on a public key.

The option combined with --load-request, --load-pubkey, --load-privkey
and --load-certificate will extract the public key of the object in
question.

-s, --generate-self-signed Generate a self-signed certificate.

-c, --generate-certificate Generate a signed certificate.

--generate-proxy Generates a proxy certificate.

-u, --update-certificate Update a signed certificate.

--fingerprint Print the fingerprint of the given certificate.

This is a simple hash of the DER encoding of the certificate. It can be
combined with the --hash parameter. However, it is recommended for
identification to use the key-id which depends only on the certifi-
cate's key.

--key-id Print the key ID of the given certificate.

This is a hash of the public key of the given certificate. It identi-
fies the key uniquely, remains the same on a certificate renewal and
depends only on signed fields of the certificate.

--certificate-pubkey Print certificate's public key.

This option is deprecated as a duplicate of --pubkey-info

NOTE: THIS OPTION IS DEPRECATED

--v1 Generate an X.509 version 1 certificate (with no extensions).

--sign-params=str Sign a certificate with a specific signature algo-
rithm.

This option can be combined with --generate-certificate, to sign the
certificate with a specific signature algorithm variant. The only op-
tion supported is 'RSA-PSS', and should be specified when the signer
does not have a certificate which is marked for RSA-PSS use only.

Certificate request related options

--crq-info Print information on the given certificate request.

-q, --generate-request Generate a PKCS #10 certificate request. This
option must not appear in combination with any of the following op-
tions: infile.

Will generate a PKCS #10 certificate request. To specify a private key
use --load-privkey.

--no-crq-extensions Do not use extensions in certificate requests.

PKCS#12 file related options

--p12-info Print information on a PKCS #12 structure.

This option will dump the contents and print the metadata of the pro-
vided PKCS #12 structure.

--p12-name=str The PKCS #12 friendly name to use.

The name to be used for the primary certificate and private key in a
PKCS #12 file.

--to-p12 Generate a PKCS #12 structure.

It requires a certificate, a private key and possibly a CA certificate
to be specified.

--pbmac1 Use PBMAC1 in a PKCS #12 structure.

Private key related options

-k, --key-info Print information on a private key.

--p8-info Print information on a PKCS #8 structure.

This option will print information about encrypted PKCS #8 structures.
That option does not require the decryption of the structure.

--to-rsa Convert an RSA-PSS key to raw RSA format.

It requires an RSA-PSS key as input and will output a raw RSA key. This
command is necessary for compatibility with applications that cannot
read RSA-PSS keys.

-p, --generate-privkey Generate a private key.

When generating RSA-PSS or RSA-OAEP private keys, the --hash option
will restrict the allowed hash for the key; For RSA-PSS keys the
--salt-size option is also acceptable.

--key-type=str Specify the key type to use on key generation.

This option can be combined with --generate-privkey, to specify the key
type to be generated. Valid options are, 'rsa', 'rsa-pss', 'rsa-oaep',
'dsa', 'ecdsa', 'ed25519, 'ed448', 'x25519', and 'x448'.'. When com-
bined with certificate generation it can be used to specify an RSA-PSS
certificate when an RSA key is given.

--bits=num Specify the number of bits for key generation. This option
takes an integer number as its argument.

--curve=str Specify the curve used for EC key generation.

Supported values are secp192r1, secp224r1, secp256r1, secp384r1 and
secp521r1.

--sec-param=security parameter Specify the security level [low, legacy,
medium, high, ultra].

This is alternative to the bits option.

--to-p8 Convert a given key to a PKCS #8 structure.

This needs to be combined with --load-privkey.

-8, --pkcs8 Use PKCS #8 format for private keys.

--provable Generate a private key or parameters from a seed using a
provable method.

This will use the FIPS PUB186-4 algorithms (i.e., Shawe-Taylor) for
provable key generation. When specified the private keys or parameters
will be generated from a seed, and can be later validated with --ver-
ify-provable-privkey to be correctly generated from the seed. You may
specify --seed or allow GnuTLS to generate one (recommended). This op-
tion can be combined with --generate-privkey or --generate-dh-params.

That option applies to RSA and DSA keys. On the DSA keys the PQG para-
meters are generated using the seed, and on RSA the two primes.

--verify-provable-privkey Verify a private key generated from a seed
using a provable method.

This will use the FIPS-186-4 algorithms for provable key generation.
You may specify --seed or use the seed stored in the private key struc-
ture.

--seed=str When generating a private key use the given hex-encoded
seed.

The seed acts as a security parameter for the private key, and thus a
seed size which corresponds to the security level of the private key
should be provided (e.g., 256-bits seed).

CRL related options

-l, --crl-info Print information on the given CRL structure.

--generate-crl Generate a CRL.

This option generates a Certificate Revocation List. When combined with
--load-crl it would use the loaded CRL as base for the generated (i.e.,
all revoked certificates in the base will be copied to the new CRL).
To add new certificates to the CRL use --load-certificate.

--verify-crl Verify a Certificate Revocation List using a trusted list.
This option must appear in combination with the following options:
load-ca-certificate.

The trusted certificate list must be loaded with --load-ca-certificate.

Certificate verification related options

-e, --verify-chain Verify a PEM encoded certificate chain.

Verifies the validity of a certificate chain. That is, an ordered set
of certificates where each one is the issuer of the previous, and the
first is the end-certificate to be validated. In a proper chain the
last certificate is a self signed one. It can be combined with --ver-
ify-purpose or --verify-hostname.

--verify Verify a PEM encoded certificate (chain) against a trusted
set.

The trusted certificate list can be loaded with --load-ca-certificate.
If no certificate list is provided, then the system's trusted certifi-
cate list is used. Note that during verification multiple paths may be
explored. On a successful verification the successful path will be the
last one. It can be combined with --verify-purpose or --verify-host-
name.

--verify-hostname=str Specify a hostname to be used for certificate
chain verification.

This is to be combined with one of the verify certificate options.

--verify-email=str Specify a email to be used for certificate chain
verification. This option must not appear in combination with any of
the following options: verify-hostname.

This is to be combined with one of the verify certificate options.

--verify-purpose=str Specify a purpose OID to be used for certificate
chain verification.

This object identifier restricts the purpose of the certificates to be
verified. Example purposes are 1.3.6.1.5.5.7.3.1 (TLS WWW),
1.3.6.1.5.5.7.3.4 (EMAIL) etc. Note that a CA certificate without a
purpose set (extended key usage) is valid for any purpose.

--verify-allow-broken Allow broken algorithms, such as MD5 for verifi-
cation.

This can be combined with --p7-verify, --verify or --verify-chain.

--verify-profile=str Specify a security level profile to be used for
verification.

This option can be used to specify a certificate verification profile.
Certificate
verification profiles correspond to the security level. This should
be one of
'none', 'very weak', 'low', 'legacy', 'medium', 'high', 'ultra',
'future'. Note that by default no profile is applied, unless one is
set
as minimum in the gnutls configuration file.

PKCS#7 structure options

--p7-generate Generate a PKCS #7 structure.

This option generates a PKCS #7 certificate container structure. To add
certificates in the structure use --load-certificate and --load-crl.

--p7-sign Signs using a PKCS #7 structure.

This option generates a PKCS #7 structure containing a signature for
the provided data from infile. The data are stored within the struc-
ture. The signer certificate has to be specified using --load-certifi-
cate and --load-privkey. The input to --load-certificate can be a list
of certificates. In case of a list, the first certificate is used for
signing and the other certificates are included in the structure.

--p7-detached-sign Signs using a detached PKCS #7 structure.

This option generates a PKCS #7 structure containing a signature for
the provided data from infile. The signer certificate has to be speci-
fied using --load-certificate and --load-privkey. The input to
--load-certificate can be a list of certificates. In case of a list,
the first certificate is used for signing and the other certificates
are included in the structure.

--p7-include-cert, --no-p7-include-cert The signer's certificate will
be included in the cert list. The no-p7-include-cert form will disable
the option. This option is enabled by default.

This options works with --p7-sign or --p7-detached-sign and will in-
clude or exclude the signer's certificate into the generated signature.

--p7-time, --no-p7-time Will include a timestamp in the PKCS #7 struc-
ture. The no-p7-time form will disable the option.

This option will include a timestamp in the generated signature

--p7-show-data, --no-p7-show-data Will show the embedded data in the
PKCS #7 structure. The no-p7-show-data form will disable the option.

This option can be combined with --p7-verify or --p7-info and will dis-
play the embedded signed data in the PKCS #7 structure.

--p7-info Print information on a PKCS #7 structure.

--p7-verify Verify the provided PKCS #7 structure.

This option verifies the signed PKCS #7 structure. The certificate list
to use for verification can be specified with --load-ca-certificate.
When no certificate list is provided, then the system's certificate
list is used. Alternatively a direct signer can be provided using
--load-certificate. A key purpose can be enforced with the --ver-
ify-purpose option, and the --load-data option will utilize detached
data.

--smime-to-p7 Convert S/MIME to PKCS #7 structure.

Other options

--generate-dh-params Generate PKCS #3 encoded Diffie-Hellman parame-
ters.

The will generate random parameters to be used with Diffie-Hellman key
exchange. The output parameters will be in PKCS #3 format. Note that it
is recommended to use the --get-dh-params option instead.

NOTE: THIS OPTION IS DEPRECATED

--get-dh-params List the included PKCS #3 encoded Diffie-Hellman para-
meters.

Returns stored DH parameters in GnuTLS. Those parameters returned are
defined in RFC7919, and can be considered standard parameters for a TLS
key exchange. This option is provided for old applications which re-
quire DH parameters to be specified; modern GnuTLS applications should
not require them.

--dh-info Print information PKCS #3 encoded Diffie-Hellman parameters.

--load-privkey=str Loads a private key file.

This can be either a file or a PKCS #11 URL

--load-pubkey=str Loads a public key file.

This can be either a file or a PKCS #11 URL

--load-request=str Loads a certificate request file.

This option can be used with a file

--load-certificate=str Loads a certificate file.

This option can be used with a file

--load-ca-privkey=str Loads the certificate authority's private key
file.

This can be either a file or a PKCS #11 URL

--load-ca-certificate=str Loads the certificate authority's certificate
file.

This can be either a file or a PKCS #11 URL

--load-crl=str Loads the provided CRL.

This option can be used with a file

--load-data=str Loads auxiliary data.

This option can be used with a file

--password=str Password to use.

You can use this option to specify the password in the command line in-
stead of reading it from the tty. Note, that the command line arguments
are available for view in others in the system. Specifying password as
'' is the same as specifying no password.

--null-password Enforce a NULL password.

This option enforces a NULL password. This is different than the empty
or no password in schemas like PKCS #8.

--empty-password Enforce an empty password.

This option enforces an empty password. This is different than the NULL
or no password in schemas like PKCS #8.

--hex-numbers Print big number in an easier format to parse.

--cprint In certain operations it prints the information in C-friendly
format.

In certain operations it prints the information in C-friendly format,
suitable for including into C programs.

--rsa Generate RSA key.

When combined with --generate-privkey generates an RSA private key.

NOTE: THIS OPTION IS DEPRECATED

--dsa Generate DSA key.

When combined with --generate-privkey generates a DSA private key.

NOTE: THIS OPTION IS DEPRECATED

--ecc Generate ECC (ECDSA) key.

When combined with --generate-privkey generates an elliptic curve pri-
vate key to be used with ECDSA.

NOTE: THIS OPTION IS DEPRECATED

--ecdsa This is an alias for the --ecc option.

NOTE: THIS OPTION IS DEPRECATED

--hash=str Hash algorithm to use for signing.

Available hash functions are SHA1, RMD160, SHA256, SHA384, SHA512,
SHA3-224, SHA3-256, SHA3-384, SHA3-512.

--salt-size=num Specify the RSA-PSS key default salt size. This option
takes an integer number as its argument.

Typical keys shouldn't set or restrict this option.

--label=str Specify the RSA-OAEP label, encoded in hexadecimal.

Typical keys shouldn't set or restrict this option.

--inder, --no-inder Use DER format for input certificates, private
keys, and DH parameters . The no-inder form will disable the option.

The input files will be assumed to be in DER or RAW format. Unlike op-
tions that in PEM input would allow multiple input data (e.g. multiple
certificates), when reading in DER format a single data structure is
read.

--inraw This is an alias for the --inder option.

--outder, --no-outder Use DER format for output certificates, private
keys, and DH parameters. The no-outder form will disable the option.

The output will be in DER or RAW format.

--outraw This is an alias for the --outder option.

--disable-quick-random No effect.

NOTE: THIS OPTION IS DEPRECATED

--template=str Template file to use for non-interactive operation.

--stdout-info Print information to stdout instead of stderr.

--ask-pass Enable interaction for entering password when in batch mode.

This option will enable interaction to enter password when in batch
mode. That is useful when the template option has been specified.

--pkcs-cipher=cipher Cipher to use for PKCS #8 and #12 operations.

Cipher may be one of 3des, 3des-pkcs12, aes-128, aes-192, aes-256,
rc2-40, arcfour.

--provider=str Specify the PKCS #11 provider library.

This will override the default options in /usr/lo-
cal/etc/gnutls/pkcs11.conf

--text, --no-text Output textual information before PEM-encoded cer-
tificates, private keys, etc. The no-text form will disable the op-
tion. This option is enabled by default.

Output textual information before PEM-encoded data

-v arg, --version=arg Output version of program and exit. The default
mode is `v', a simple version. The `c' mode will print copyright in-
formation 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.

FILES
Certtool's template file format
A template file can be used to avoid the interactive questions
of certtool. Initially create a file named 'cert.cfg' that con-
tains the information about the certificate. The template can be
used as below:

$ certtool --generate-certificate --load-privkey key.pem --template cert.cfg --outfile cert.pem --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem

An example certtool template file that can be used to generate a
certificate request or a self signed certificate follows.

# X.509 Certificate options
#
# DN options

# The organization of the subject.
organization = "Koko inc."

# The organizational unit of the subject.
unit = "sleeping dept."

# The locality of the subject.
# locality =

# The state of the certificate owner.
state = "Attiki"

# The country of the subject. Two letter code.
country = GR

# The common name of the certificate owner.
cn = "Cindy Lauper"

# A user id of the certificate owner.
#uid = "clauper"

# Set domain components
#dc = "name"
#dc = "domain"

# If the supported DN OIDs are not adequate you can set
# any OID here.
# For example set the X.520 Title and the X.520 Pseudonym
# by using OID and string pairs.
#dn_oid = "2.5.4.12 Dr."
#dn_oid = "2.5.4.65 jackal"

# This is deprecated and should not be used in new
# certificates.
# pkcs9_email = "none@none.org"

# An alternative way to set the certificate's distinguished name directly
# is with the "dn" option. The attribute names allowed are:
# C (country), street, O (organization), OU (unit), title, CN (common name),
# L (locality), ST (state), placeOfBirth, gender, countryOfCitizenship,
# countryOfResidence, serialNumber, telephoneNumber, surName, initials,
# generationQualifier, givenName, pseudonym, dnQualifier, postalCode, name,
# businessCategory, DC, UID, jurisdictionOfIncorporationLocalityName,
# jurisdictionOfIncorporationStateOrProvinceName,
# jurisdictionOfIncorporationCountryName, XmppAddr, and numeric OIDs.

#dn = "cn = Nikos,st = New Something,C=GR,surName=Mavrogiannopoulos,2.5.4.9=Arkadias"

# The serial number of the certificate
# The value is in decimal (i.e. 1963) or hex (i.e. 0x07ab).
# Comment the field for a random serial number.
serial = 007

# In how many days, counting from today, this certificate will expire.
# Use -1 if there is no expiration date.
expiration_days = 700

# Alternatively you may set concrete dates and time. The GNU date string
# formats are accepted. See:
# https://www.gnu.org/software/tar/manual/html_node/Date-input-formats.html

#activation_date = "2004-02-29 16:21:42"
#expiration_date = "2025-02-29 16:24:41"

# X.509 v3 extensions

# A dnsname in case of a WWW server.
#dns_name = "www.none.org"
#dns_name = "www.morethanone.org"

# An othername defined by an OID and a hex encoded string
#other_name = "1.3.6.1.5.2.2 302ca00d1b0b56414e5245494e2e4f5247a11b3019a006020400000002a10f300d1b047269636b1b0561646d696e"
#other_name_utf8 = "1.2.4.5.6 A UTF8 string"
#other_name_octet = "1.2.4.5.6 A string that will be encoded as ASN.1 octet string"

# Allows writing an XmppAddr Identifier
#xmpp_name = juliet@im.example.com

# Names used in PKINIT
#krb5_principal = user@REALM.COM
#krb5_principal = HTTP/user@REALM.COM

# A subject alternative name URI
#uri = "https://www.example.com"

# An IP address in case of a server.
#ip_address = "192.168.1.1"

# An email in case of a person
email = "none@none.org"

# TLS feature (rfc7633) extension. That can is used to indicate mandatory TLS
# extension features to be provided by the server. In practice this is used
# to require the Status Request (extid: 5) extension from the server. That is,
# to require the server holding this certificate to provide a stapled OCSP response.
# You can have multiple lines for multiple TLS features.

# To ask for OCSP status request use:
#tls_feature = 5

# Challenge password used in certificate requests
challenge_password = 123456

# Password when encrypting a private key
#password = secret

# An URL that has CRLs (certificate revocation lists)
# available. Needed in CA certificates.
#crl_dist_points = "https://www.getcrl.crl/getcrl/"

# Whether this is a CA certificate or not
#ca

# Subject Unique ID (in hex)
#subject_unique_id = 00153224

# Issuer Unique ID (in hex)
#issuer_unique_id = 00153225

#### Key usage

# The following key usage flags are used by CAs and end certificates

# Whether this certificate will be used to sign data (needed
# in TLS DHE ciphersuites). This is the digitalSignature flag
# in RFC5280 terminology.
signing_key

# Whether this certificate will be used to encrypt data (needed
# in TLS RSA ciphersuites). Note that it is preferred to use different
# keys for encryption and signing. This is the keyEncipherment flag
# in RFC5280 terminology.
encryption_key

# Whether this key will be used to sign other certificates. The
# keyCertSign flag in RFC5280 terminology.
#cert_signing_key

# Whether this key will be used to sign CRLs. The
# cRLSign flag in RFC5280 terminology.
#crl_signing_key

# The keyAgreement flag of RFC5280. Its purpose is loosely
# defined. Not use it unless required by a protocol.
#key_agreement

# The dataEncipherment flag of RFC5280. Its purpose is loosely
# defined. Not use it unless required by a protocol.
#data_encipherment

# The nonRepudiation flag of RFC5280. Its purpose is loosely
# defined. Not use it unless required by a protocol.
#non_repudiation

#### Extended key usage (key purposes)

# The following extensions are used in an end certificate
# to clarify its purpose. Some CAs also use it to indicate
# the types of certificates they are purposed to sign.

# Whether this certificate will be used for a TLS client;
# this sets the id-kp-clientAuth (1.3.6.1.5.5.7.3.2) of
# extended key usage.
#tls_www_client

# Whether this certificate will be used for a TLS server;
# this sets the id-kp-serverAuth (1.3.6.1.5.5.7.3.1) of
# extended key usage.
#tls_www_server

# Whether this key will be used to sign code. This sets the
# id-kp-codeSigning (1.3.6.1.5.5.7.3.3) of extended key usage
# extension.
#code_signing_key

# Whether this key will be used to sign OCSP data. This sets the
# id-kp-OCSPSigning (1.3.6.1.5.5.7.3.9) of extended key usage extension.
#ocsp_signing_key

# Whether this key will be used for time stamping. This sets the
# id-kp-timeStamping (1.3.6.1.5.5.7.3.8) of extended key usage extension.
#time_stamping_key

# Whether this key will be used for email protection. This sets the
# id-kp-emailProtection (1.3.6.1.5.5.7.3.4) of extended key usage extension.
#email_protection_key

# Whether this key will be used for IPsec IKE operations (1.3.6.1.5.5.7.3.17).
#ipsec_ike_key

## adding custom key purpose OIDs

# for microsoft smart card logon
# key_purpose_oid = 1.3.6.1.4.1.311.20.2.2

# for email protection
# key_purpose_oid = 1.3.6.1.5.5.7.3.4

# for any purpose (must not be used in intermediate CA certificates)
# key_purpose_oid = 2.5.29.37.0

### end of key purpose OIDs

### Adding arbitrary extensions
# This requires to provide the extension OIDs, as well as the extension data in
# hex format. The following two options are available since GnuTLS 3.5.3.
#add_extension = "1.2.3.4 0x0AAB01ACFE"

# As above but encode the data as an octet string
#add_extension = "1.2.3.4 octet_string(0x0AAB01ACFE)"

# For portability critical extensions shouldn't be set to certificates.
#add_critical_extension = "5.6.7.8 0x1AAB01ACFE"

# When generating a certificate from a certificate
# request, then honor the extensions stored in the request
# and store them in the real certificate.
#honor_crq_extensions

# Alternatively only specific extensions can be copied.
#honor_crq_ext = 2.5.29.17
#honor_crq_ext = 2.5.29.15

# Path length constraint. Sets the maximum number of
# certificates that can be used to certify this certificate.
# (i.e. the certificate chain length)
#path_len = -1
#path_len = 2

# OCSP URI
# ocsp_uri = https://my.ocsp.server/ocsp

# CA issuers URI
# ca_issuers_uri = https://my.ca.issuer

# Certificate policies
#policy1 = 1.3.6.1.4.1.5484.1.10.99.1.0
#policy1_txt = "This is a long policy to summarize"
#policy1_url = https://www.example.com/a-policy-to-read

#policy2 = 1.3.6.1.4.1.5484.1.10.99.1.1
#policy2_txt = "This is a short policy"
#policy2_url = https://www.example.com/another-policy-to-read

# The number of additional certificates that may appear in a
# path before the anyPolicy is no longer acceptable.
#inhibit_anypolicy_skip_certs 1

# Name constraints

# DNS
#nc_permit_dns = example.com
#nc_exclude_dns = test.example.com

# EMAIL
#nc_permit_email = "nmav@ex.net"

# Exclude subdomains of example.com
#nc_exclude_email = .example.com

# Exclude all e-mail addresses of example.com
#nc_exclude_email = example.com

# IP
#nc_permit_ip = 192.168.0.0/16
#nc_exclude_ip = 192.168.5.0/24
#nc_permit_ip = fc0a:eef2:e7e7:a56e::/64

# Options for proxy certificates
#proxy_policy_language = 1.3.6.1.5.5.7.21.1

# Options for generating a CRL

# The number of days the next CRL update will be due.
# next CRL update will be in 43 days
#crl_next_update = 43

# this is the 5th CRL by this CA
# The value is in decimal (i.e. 1963) or hex (i.e. 0x07ab).
# Comment the field for a time-based number.
# Time-based CRL numbers generated in GnuTLS 3.6.3 and later
# are significantly larger than those generated in previous
# versions. Since CRL numbers need to be monotonic, you need
# to specify the CRL number here manually if you intend to
# downgrade to an earlier version than 3.6.3 after publishing
# the CRL as it is not possible to specify CRL numbers greater
# than 2**63-2 using hex notation in those versions.
#crl_number = 5

# Specify the update dates more precisely.
#crl_this_update_date = "2004-02-29 16:21:42"
#crl_next_update_date = "2025-02-29 16:24:41"

# The date that the certificates will be made seen as
# being revoked.
#crl_revocation_date = "2025-02-29 16:24:41"

EXAMPLES
Generating private keys
To create an RSA private key, run:
$ certtool --generate-privkey --outfile key.pem --rsa

To create a DSA or elliptic curves (ECDSA) private key use the above
command combined with 'dsa' or 'ecc' options.

Generating certificate requests
To create a certificate request (needed when the certificate is issued
by another party), run:
certtool --generate-request --load-privkey key.pem --outfile request.pem

If the private key is stored in a smart card you can generate a request
by specifying the private key object URL.
$ ./certtool --generate-request --load-privkey "pkcs11:..." --load-pubkey "pkcs11:..." --outfile request.pem

Generating a self-signed certificate
To create a self signed certificate, use the command:
$ certtool --generate-privkey --outfile ca-key.pem
$ certtool --generate-self-signed --load-privkey ca-key.pem --outfile ca-cert.pem

Note that a self-signed certificate usually belongs to a certificate
authority, that signs other certificates.

Generating a certificate
To generate a certificate using the previous request, use the command:
$ certtool --generate-certificate --load-request request.pem --outfile cert.pem --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem

To generate a certificate using the private key only, use the command:
$ certtool --generate-certificate --load-privkey key.pem --outfile cert.pem --load-ca-certificate ca-cert.pem --load-ca-privkey ca-key.pem

Certificate information
To view the certificate information, use:
$ certtool --certificate-info --infile cert.pem

Changing the certificate format
To convert the certificate from PEM to DER format, use:
$ certtool --certificate-info --infile cert.pem --outder --outfile cert.der

PKCS #12 structure generation
To generate a PKCS #12 structure using the previous key and certifi-
cate, use the command:
$ certtool --load-certificate cert.pem --load-privkey key.pem --to-p12 --outder --outfile key.p12

Some tools (reportedly web browsers) have problems with that file be-
cause it does not contain the CA certificate for the certificate. To
work around that problem in the tool, you can use the --load-ca-cer-
tificate parameter as follows:

$ certtool --load-ca-certificate ca.pem --load-certificate cert.pem --load-privkey key.pem --to-p12 --outder --outfile key.p12

Obtaining Diffie-Hellman parameters
To obtain the RFC7919 parameters for Diffie-Hellman key exchange, use
the command:
$ certtool --get-dh-params --outfile dh.pem --sec-param medium

Verifying a certificate
To verify a certificate in a file against the system's CA trust store
use the following command:
$ certtool --verify --infile cert.pem

It is also possible to simulate hostname verification with the follow-
ing options:
$ certtool --verify --verify-hostname www.example.com --infile cert.pem

Proxy certificate generation
Proxy certificate can be used to delegate your credential to a tempo-
rary, typically short-lived, certificate. To create one from the pre-
viously created certificate, first create a temporary key and then gen-
erate a proxy certificate for it, using the commands:

$ certtool --generate-privkey > proxy-key.pem
$ certtool --generate-proxy --load-ca-privkey key.pem --load-privkey proxy-key.pem --load-certificate cert.pem --outfile proxy-cert.pem

Certificate revocation list generation
To create an empty Certificate Revocation List (CRL) do:

$ certtool --generate-crl --load-ca-privkey x509-ca-key.pem --load-ca-certificate x509-ca.pem

To create a CRL that contains some revoked certificates, place the cer-
tificates in a file and use --load-certificate as follows:

$ certtool --generate-crl --load-ca-privkey x509-ca-key.pem --load-ca-certificate x509-ca.pem --load-certificate revoked-certs.pem

To verify a Certificate Revocation List (CRL) do:

$ certtool --verify-crl --load-ca-certificate x509-ca.pem < crl.pem

EXIT STATUS
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.

SEE ALSO
p11tool (1), psktool (1), srptool (1)

BUGS
Please send bug reports to: bugs@gnutls.org

3.8.9 08 Feb 2025 certtool(1)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=certtool&sektion=1&manpath=FreeBSD+Ports+14.3.quarterly>

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