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HSM-PKCS11.md

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HSM/PKCS#11 Support

Ghostunnel has support for loading private keys from PKCS#11 modules, which should work with any hardware security module that exposes a PKCS#11 interface. An easy way to test the PKCS#11 interface for development purposes is with SoftHSM. Note that CGO is required in order for PKCS#11 support to work (see CROSS-COMPILE for instructions to cross-compile with CGO enabled).

To import the server test key into SoftHSM, for example:

softhsm2-util --init-token \
    --slot 0 \
    --label ghostunnel-server \
    --so-pin 1234 \
    --pin 1234

softhsm2-util --id 01 \
    --token ghostunnel-server \
    --label ghostunnel-server \
    --import test-keys/server-pkcs8.pem \
    --so-pin 1234 \
    --pin 1234

To launch ghostunnel with the SoftHSM-backed PKCS11 key (on macOS):

ghostunnel server \
    --cert test-keys/server-cert.pem \
    --pkcs11-module /usr/local/Cellar/softhsm/2.4.0/lib/softhsm/libsofthsm2.so \
    --pkcs11-token-label ghostunnel-server \
    --pkcs11-pin 1234 \
    --listen localhost:8443 \
    --target localhost:8080 \
    --cacert test-keys/cacert.pem \
    --allow-cn client

The --pkcs11-module, --pkcs11-token-label and --pkcs11-pin flags can be used to select the private key to be used the PKCS11 module. It's also possible to use environment variables to set PKCS11 options instead of flags (via PKCS11_MODULE, PKCS11_TOKEN_LABEL and PKCS11_PIN), useful if you don't want to show the PIN on the command line.

Note that --cert needs to point to the certificate chain that corresponds to the private key in the PKCS#11 module, with the leaf certificate being the first certificate in the chain. Ghostunnel doesn't have the ability to read the certificate chain directly from the module at this point in time.

If you need to inspect the state of a PKCS11 module/token, we recommend the pkcs11-tool utility from OpenSC. For example, it can be used to list slots or read certificate(s) from a module:

# List slots on a module
pkcs11-tool --module $MODULE -L

# Show certificates (if any) available
pkcs11-tool --module $MODULE -O -y cert

# Read certificate chain given a label
pkcs11-tool --module $MODULE --label $LABEL --read-object -y cert