CFSSL is CloudFlare's SSL swiss army knife. It is both a command line tool and an HTTP API server for signing, verifying, and bundling SSL certificates. It requires Go 1.4 to build.
Note that certain linux distributions have certain algorithms removed (RHEL-based distributions in particular), so the golang from the official repositories will not work. Users of these distributions should install go manually to install CFSSL.
Installation requires a working Go
installation and a properly set GOPATH
.
$ go get -u github.com/cloudflare/cfssl/cmd/cfssl
will download and build the CFSSL tool, installing it in
$GOPATH/bin/cfssl
. To install the other utility programs that are in
this repo:
$ go get -u github.com/cloudflare/cfssl/cmd/...
This will download, build, and install cfssl
, cfssljson
, and
mkbundle
into $GOPATH/bin/
.
The command line tool takes a command to specify what operation it should carry out:
sign signs a certificate
bundle build a certificate bundle
genkey generate a private key and a certificate request
gencert generate a private key and a certificate
serve start the API server
version prints out the current version
selfsign generates a self-signed certificate
Use "cfssl [command] -help" to find out more about a command. The version command takes no arguments.
cfssl sign [-ca cert] [-ca-key key] [-hostname comma,separated,hostnames] csr [subject]
The csr is the client's certificate request. The -ca
and -ca-key
flags are the CA's certificate and private key, respectively. By
default, they are "ca.pem" and "ca_key.pem". The -hostname
is
a comma separated hostname list that overrides the DNS names and
IP address in the certificate SAN extension.
For example, assuming the CA's private key is in
/etc/ssl/private/cfssl_key.pem
and the CA's certificate is in
/etc/ssl/certs/cfssl.pem
, to sign the cloudflare.pem
certificate
for cloudflare.com:
cfssl sign -ca /etc/ssl/certs/cfssl.pem \
-ca-key /etc/ssl/private/cfssl_key.pem \
-hostname cloudflare.com ./cloudflare.pem
It is also possible to specify csr through '-csr' flag. By doing so, flag values take precedence and will overwrite the argument.
The subject is an optional file that contains subject information that should be used in place of the information from the CSR. It should be a JSON file with the type:
{
"CN": "example.com",
"names": [
{
"C": "US",
"L": "San Francisco",
"O": "Internet Widgets, Inc.",
"OU": "WWW",
"ST": "California"
}
]
}
cfssl bundle [-ca-bundle bundle] [-int-bundle bundle] \
[-metadata metadata_file] [-flavor bundle_flavor] \
-cert certificate_file [-key key_file]
The bundles are used for the root and intermediate certificate pools. In addition, platform metadata is specified through '-metadata' The bundle files, metadata file (and auxiliary files) can be found at cfssl_trust
Specify PEM-encoded client certificate and key through '-cert' and '-key' respectively. If key is specified, the bundle will be built and verified with the key. Otherwise the bundle will be built without a private key. Instead of file path, use '-' for reading certificate PEM from stdin. It is also acceptable the certificate file contains a (partial) certificate bundle.
Specify bundling flavor through '-flavor'. There are three flavors: 'optimal' to generate a bundle of shortest chain and most advanced cryptographic algorithms, 'ubiquitous' to generate a bundle of most widely acceptance across different browsers and OS platforms, and 'force' to find an acceptable bundle which is identical to the content of the input certificate file.
Alternatively, the client certificate can be pulled directly from a domain. It is also possible to connect to the remote address through '-ip'.
cfssl bundle [-ca-bundle bundle] [-int-bundle bundle] \
[-metadata metadata_file] [-flavor bundle_flavor] \
-domain domain_name [-ip ip_address]
The bundle output form should follow the example
{
"bundle": "CERT_BUNDLE_IN_PEM",
"crt": "LEAF_CERT_IN_PEM",
"crl_support": true,
"expires": "2015-12-31T23:59:59Z",
"hostnames": ["example.com"],
"issuer": "ISSUER CERT SUBJECT",
"key": "KEY_IN_PEM",
"key_size": 2048,
"key_type": "2048-bit RSA",
"ocsp": ["http://ocsp.example-ca.com"],
"ocsp_support": true,
"root": "ROOT_CA_CERT_IN_PEM",
"signature": "SHA1WithRSA",
"subject": "LEAF CERT SUBJECT",
"status": {
"rebundled": false,
"expiring_SKIs": [],
"untrusted_root_stores": [],
"messages": [],
"code": 0
}
}
cfssl genkey csrjson
To generate a private key and corresponding certificate request, specify the key request as a JSON file. This file should follow the form
{
"hosts": [
"example.com",
"www.example.com"
],
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "San Francisco",
"O": "Internet Widgets, Inc.",
"OU": "WWW",
"ST": "California"
}
]
}
cfssl genkey -initca csrjson | cfssljson -bare ca
To generate a self-signed root CA certificate, specify the key request as the JSON file in the same format as in 'genkey'. Three PEM-encoded entities will appear in the output: the private key, the csr, and the self-signed certificate.
cfssl gencert -remote=remote_server [-hostname=comma,separated,hostnames] csrjson
This is calls genkey, but has a remote CFSSL server sign and issue
a certificate. You may use -hostname
to override certificate SANs.
cfssl gencert -ca cert -ca-key key [-hostname=comma,separated,hostnames] csrjson
This is generates and issues a certificate and private key from a local CA
via a JSON request. You may use -hostname
to override certificate SANs.
CFSSL comes with an HTTP-based API server; the endpoints are
documented in doc/api.txt
. The server is started with the "serve"
command:
cfssl serve [-address address] [-ca cert] [-ca-bundle bundle] \
[-ca-key key] [-int-bundle bundle] [-port port] \
[-remote remote_server]
Address and port default to "127.0.0.1:8888". The -ca
and -ca-key
arguments should be the PEM-encoded certificate and private key to use
for signing; by default, they are "ca.pem" and "ca_key.pem". The
-ca-bundle
and -int-bundle
should be the certificate bundles used
for the root and intermediate certificate pools, respectively. These
default to "ca-bundle.crt" and "int-bundle." If the "remote" option is
provided, all signature operations will be forwarded to the remote CFSSL.
The amount of logging can be controlled with the -loglevel
option. This
comes before the serve command:
cfssl -loglevel 2 serve
The levels are:
-
- DEBUG
-
- INFO (this is the default level)
-
- WARNING
-
- ERROR
-
- CRITICAL
mkbundle
is used to build the root and intermediate bundles used in
verifying certificates. It can be installed with
go get -u github.com/cloudflare/cfssl/cmd/mkbundle
It takes a collection of certificates, checks for CRL revocation (OCSP
support is planned for the next release) and expired certificates, and
bundles them into one file. It takes directories of certificates and
certificate files (which may contain multiple certificates). For example,
if the directory intermediates
contains a number of intermediate
certificates,
mkbundle -f int-bundle.crt intermediates
will check those certificates and combine valid ones into a single
int-bundle.crt
file.
The -f
flag specifies an output name; -loglevel
specifies the verbosity
of the logging (using the same loglevels above), and -nw
controls the
number of revocation-checking workers.
Most of the output from cfssl
is in JSON. The cfssljson
will take
this output and split it out into separate key, certificate, CSR, and
bundle files as appropriate. The tool takes a single flag, -f
, that
specifies the input file, and an argument that specifies the base name for
the files produced. If the input filename is "-" (which is the default),
cfssljson
reads from standard input. It maps keys in the JSON file to
filenames in the following way:
- if there is a "cert" (or if not, if there's a "certificate") field, the file "basename.pem" will be produced.
- if there is a "key" (or if not, if there's a "private_key") field, the file "basename-key.pem" will be produced.
- if there is a "csr" (or if not, if there's a "certificate_request") field, the file "basename.csr" will be produced.
- if there is a "bundle" field, the file "basename-bundle.pem" will be producd.
Additional documentation can be found in the "doc/" directory:
api.txt
: documents the API endpointsbootstrap.txt
: a walkthrough from building the package to getting up and running