scep
is a Simple Certificate Enrollment Protocol server and client
Binary releases are available on the releases page.
To compile the SCEP client and server you will need a Go compiler as well as standard tools like git, make, etc.
- Clone the repository and get into the source directory:
git clone https://github.com/micromdm/scep.git && cd scep
- Compile the client and server binaries:
make
(for Windows:make win
)
The binaries will be compiled in the current directory and named after the architecture. I.e. scepclient-linux-amd64
and scepserver-linux-amd64
.
See Docker documentation below.
Minimal example for both server and client.
# SERVER:
# create a new CA
./scepserver-linux-amd64 ca -init
# start server
./scepserver-linux-amd64 -depot depot -port 2016 -challenge=secret
# SCEP request:
# in a separate terminal window, run a client
# note, if the client.key doesn't exist, the client will create a new rsa private key. Must be in PEM format.
./scepclient-linux-amd64 -private-key client.key -server-url=http://127.0.0.1:2016/scep -challenge=secret
# NDES request:
# note, this should point to an NDES server, scepserver does not provide NDES.
./scepclient-linux-amd64 -private-key client.key -server-url=https://scep.example.com:4321/certsrv/mscep/ -ca-fingerprint="e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
The default flags configure and run the scep server.
-depot
must be the path to a folder with ca.pem
and ca.key
files. If you don't already have a CA to use, you can create one using the ca
subcommand.
The scepserver provides one HTTP endpoint, /scep
, that facilitates the normal PKIOperation/Message parameters.
Server usage:
$ ./scepserver-linux-amd64 -help
-allowrenew string
do not allow renewal until n days before expiry, set to 0 to always allow (default "14")
-capass string
passwd for the ca.key
-challenge string
enforce a challenge password
-crtvalid string
validity for new client certificates in days (default "365")
-csrverifierexec string
will be passed the CSRs for verification
-debug
enable debug logging
-depot string
path to ca folder (default "depot")
-log-json
output JSON logs
-port string
port to listen on (default "8080")
-version
prints version information
usage: scep [<command>] [<args>]
ca <args> create/manage a CA
type <command> --help to see usage for each subcommand
Use the ca -init
subcommand to create a new CA and private key.
CA sub-command usage:
$ ./scepserver-linux-amd64 ca -help
Usage of ca:
-country string
country for CA cert (default "US")
-depot string
path to ca folder (default "depot")
-init
create a new CA
-key-password string
password to store rsa key
-keySize int
rsa key size (default 4096)
-common_name string
common name (CN) for CA cert (default "MICROMDM SCEP CA")
-organization string
organization for CA cert (default "scep-ca")
-organizational_unit string
organizational unit (OU) for CA cert (default "SCEP CA")
-years int
default CA years (default 10)
The -csrverifierexec
switch to the SCEP server allows for executing a command before a certificate is issued to verify the submitted CSR. Scripts exiting without errors (zero exit status) will proceed to certificate issuance, otherwise a SCEP error is generated to the client. For example if you wanted to just save the CSR this is a valid CSR verifier shell script:
#!/bin/sh
cat - > /tmp/scep.csr
$ ./scepclient-linux-amd64 -help
Usage of ./scepclient-linux-amd64:
-ca-fingerprint string
SHA-256 digest of CA certificate for NDES server. Note: Changed from MD5.
-certificate string
certificate path, if there is no key, scepclient will create one
-challenge string
enforce a challenge password
-cn string
common name for certificate (default "scepclient")
-country string
country code in certificate (default "US")
-debug
enable debug logging
-keySize int
rsa key size (default 2048)
-locality string
locality for certificate
-log-json
use JSON for log output
-organization string
organization for cert (default "scep-client")
-ou string
organizational unit for certificate (default "MDM")
-private-key string
private key path, if there is no key, scepclient will create one
-province string
province for certificate
-server-url string
SCEP server url
-version
prints version information
Note: Make sure to specify the desired endpoint in your -server-url
value (e.g. 'http://scep.groob.io:2016/scep'
)
To obtain a certificate through Network Device Enrollment Service (NDES), set -server-url
to a server that provides NDES.
This most likely uses the /certsrv/mscep
path. You will need to add the -ca-fingerprint
client argument during this request to specify which CA to use.
If you're not sure which SHA-256 hash (for a specific CA) to use, you can use the -debug
flag to print them out for the CAs returned from the SCEP server.
# first compile the Docker binaries
make docker
# build the image
docker build -t micromdm/scep:latest .
# create CA
docker run -it --rm -v /path/to/ca/folder:/depot micromdm/scep:latest ca -init
# run
docker run -it --rm -v /path/to/ca/folder:/depot -p 8080:8080 micromdm/scep:latest
You can import the scep endpoint into another Go project. For an example take a look at scepserver.go.
The SCEP server includes a built-in CA/certificate store. This is facilitated by the Depot
and CSRSigner
Go interfaces. This certificate storage to happen however you want. It also allows for swapping out the entire CA signer altogether or even using SCEP as a proxy for certificates.