Crypto Providers  ❯  Cryptoki/PKCS

• General instructions
  • Supported Linux distributions
  • Installation
  • Parameters
  • Error handling
  • Integration with signing tools
• OpenSSL
  • Setup
  • Invocation
• osslsigncode
  • Setup
  • Invocation
• OpenSC pkcs11-tool (Linux)
  • Setup
  • Invocation
• Java jarsigner
  • Setup
  • Invocation

General instructions

The SignPath Cryptoki library is used to enables code signing using tools that support the Cryptoki/PKCS #11 standard.

Cryptoki and PKCS #11

Cryptoki is the Cryptographic Token Interface defined by the PKCS #11 standard. It is used by cryotographic software to access encryption and signing keys that are not stored on disks.

Cryptoki/PKCS #11 is primarily used in the Open Source ecosystem, e.g. Linux tools and their ports to other platforms including Windows. Some tools support it indirectly through their own provider ecosystem, e.g. Java via SunPKCS11 and GPG via gnupg-pkcs11-scd.

This section provides general information about using the SignPath Cryptoki library with code signing tools. Subsequent sections provide instructions for specific tools.

Supported Linux distributions

OpenSSL 3.0.0 - 3.0.8 incompatibility

Distributions with an OpenSSL version between 3.0.0 and 3.0.8 (including) don’t support the the OpenSSL and osslsigncode scenarios. The reason is an OpenSSL bug which has been fixed in OpenSSL 3.0.9. The issue results in “http_exception occurred (error code= generic:168296454): Error in SSL handshake” errors.

You need to replace the system’s OpenSSL version with >= 3.0.9 or use an isolated OpenSSL installation.

Installation

Simply copy the library file from the Crypto Providers ZIP archive to a directory in your system’s file path.

• Windows: Windows\SignPath.Cryptoki.dll
• Linux: Linux/libSignPath.Cryptoki/$OpenSslVersion/libSignPath.Cryptoki.so

Check the output of openssl version on your target system to select the correct OpenSSL version.

Parameters

Signing tools with Cryptoki support usually provide PIN and key ID parameters. These are passed to the respective Cryptoki provider. For SignPath, provide the following values:

Name and synopsis for these parameters depend on the tool. For tools that support Cryptoki only indirectly, parameters may also be passed indirectly or using a specific syntax for an existing tool parameter (see below).

Keys are not specified directly

The Cryptoki API expects you to identify a key, but SignPath requires you to specify a Project and a Signing Policy. SignPath will select the key or certificate of the specified Signing Policy.

Error handling

The following table shows the PKCS #11 Cryptoki function return values for the different error situations when calling the SignPath REST API.

Integration with signing tools

For Cryptoki-based signing, tool setup can be complex. Unlike the KSP/CSP provider architecture of Windows, Cryptoki is not a system API. As a consequence, support for Cryptoki libraries varies significantly between tools:

• A tool might directly support Cryptoki (and will provide a parameter or configuration option to specify the Cryptoki library and key identifier)
• A tool might support different engines. If it doesn’t come with a Cryptoki engine, you need to get it from another source and install it. In this case you need to
  • specify the engine in the tool’s configuration or parameter list,
  • and specify the SignPath Cryptoki library in the engine’s configuration
• A tool might internally call another tool such as OpenSSL or GPG to create the signature

If your signing tool does not provide guidance for using Cryptoki libraries, you probably need a solid understanding of the specific tool chain to configure it. For better results, please also refer to signing flow.

OpenSSL

OpenSSL is a toolkit that provides a range of cryptographic operations, including signing.

Important

Only latest OpenSSL 1.1 and 3.x versions are supported. For Linux, see also the notes in supported Linux distributions.

Setup

OpenSSL cannot directly communicate with a Cryptoki library. Instead, the OpenSC pkcs11 OpenSSL engine can be used as adapter between OpenSSL and the SignPath Cryptoki/PKCS #11 library.

Windows: Download libp11-...-windows.zip from OpenSC libp11 Releases and copy-deploy pkcs11.dll (x64 version).

Linux: Install the OpenSC pkcs11 engine via your package manager (e.g. apt-get install libengine-pkcs11-openssl in Ubuntu).

Sample: openssl-signpath.cnf

config_diagnostics = 1
openssl_conf = openssl_init

[openssl_init]
engines = engines_section

[engines_section]
pkcs11 = pkcs11_section

[pkcs11_section]
engine_id = pkcs11
dynamic_path = /path/to/libpkcs11.so
MODULE_PATH = /path/to/libSignPath.Cryptoki.so
default_algorithms = ALL
init = 0
PIN = CONFIG

Default installation paths of libp11

Note that Linux distributions have different default installation paths for libpkcs11.so:

Distribution	Default path
Debian/Ubuntu w/ OpenSSL 1.1	/usr/lib/x86_64-linux-gnu/engines-1.1/libpkcs11.so
Debian/Ubuntu w/ OpenSSL 3.x	/usr/lib/x86_64-linux-gnu/engines-3/libpkcs11.so
RedHat w/ OpenSSL 1.1	/usr/lib64/engines-1.1/libpkcs11.so
RedHat w/ OpenSSL 3.x	/usr/lib64/engines-3/libpkcs11.so

For Windows use .dll paths respectively (note the double backslashes):

dynamic_path = C:\\path\\to\\pkcs11.dll
MODULE_PATH = C:\\path\\to\\SignPath.Cryptoki.dll

Also set the following environment variable:

Invocation

OpenSSL provides a variety of commands that can be used for signing. In this section, a few of them are outlined.

Tip

For Linux, configuration, signing invocation and verification examples are provided in the Docker container samples via .\RunScenario.ps1 ... -Scenario OpenSSL. See Linux container samples.

Generally, all commands require the following parameters to work with the SignPath Cryptoki library:

openssl dgst

The dgst command calculates digests of files, but can also be used to create and verify signatures.

Sample: sign artifact.bin and write the signature to artifact.sig.

openssl dgst -engine pkcs11 -keyform engine -sign "pkcs11:id=$ProjectSlug/$SigningPolicySlug;type=private" -sha256 -out "artifact.sig" "artifact.bin"

Supported digests

The following digests are supported: sha256, sha384, sha512

openssl pkeyutl

The pkeyutl command performs low-level cryptographic operations, such as signing.

Note: provide binary hash digest

The command does hash the input data but will use the data directly as an input for the signature algorithm. To create the hash of a file, you can use the following snippet:

$ArtifactHash = Get-FileHash "artifact.bin" -Algorithm "SHA256" # SHA1, SHA256, SHA384 and SHA512 are supported
$ArtifactHashBytes = [byte[]] -split ($ArtifactHash.Hash -replace '..', '0x$& ')
[IO.File]::WriteAllBytes("artifact.hash.bin", $ArtifactHashBytes)

Sample: sign the hash code in artifact.hash.bin using PKCS1 padding, write the signature to artifact.sig

openssl pkeyutl -engine pkcs11 -keyform engine -inkey "pkcs11:id=$ProjectSlug/$SigningPolicySlug;type=private" -sign -in "artifact.hash.bin" -out "artifact.sig" -pkeyopt digest:sha256 -pkeyopt rsa_padding_mode:pkcs1

Sample: sign the hash code in artifact.hash.bin using PSS padding, write the signature to artifact.sig

openssl pkeyutl -engine pkcs11 -keyform engine -inkey "pkcs11:id=$ProjectSlug/$SigningPolicySlug;type=private" -sign -in "artifact.hash.bin" -out "artifact.sig" -pkeyopt digest:sha256 -pkeyopt rsa_padding_mode:pss -pkeyopt rsa_pss_saltlen:-1 -pkeyopt rsa_mgf1_md:sha256

openssl cms

The cms command can be used to create embedded S/MIME or detached PEM/DER signatures. It uses the Cryptographic Message Syntax format (CMS, formerly known as PKCS#7).

openssl cms requires the X.509 certificate corresponding to the SignPath Project and Signing Policy to be downloaded from SignPath and converted to PEM format. You can convert the certificate using OpenSSL via the following example.

openssl x509 -inform DER -in "certificate.cer" -outform PEM -out "certificate.pem"

Sample: sign the file artifact.bin using certificate.pem, write the detached signature to artifact.sig in PEM format

openssl cms -engine pkcs11 -signer "certificate.pem" -inkey "pkcs11:id=$ProjectSlug/$SigningPolicySlug;type=private" -keyform engine -sign -binary -in "artifact.bin" -noattr -out "artifact.sig" -outform PEM

Important

OpenSSL fails to verify signatures that were created using X.509 certificates with the Extended Key Usage Code Signing (1.3.6.1.5.5.7.3.3).

osslsigncode

osslsigncode is a tool that allows applying Windows Authenticode signatures on Linux systems using OpenSSL. Accordingly, it also requires an OpenSC pkcs11 OpenSSL engine installation. See the OpenSSL section for details.

Important

Only osslsigncode 2.x or higher is supported. Also see the notes in supported Linux distributions regarding the supported OpenSSL versions.

Setup

osslsigncode requires the X.509 certificate corresponding to the SignPath Project and Signing Policy to be downloaded from SignPath and converted to PEM format. You can convert the certificate using OpenSSL via the following example.

openssl x509 -inform DER -in "certificate.cer" -outform PEM -out "certificate.pem"

Invocation

osslsigncode sign `
   -pkcs11module $LibSignPathCryptokiPath `
   -key "pkcs11:id=$ProjectSlug/$SigningPolicySlug;type=private;pin-value=CONFIG" `
   -certs "certificate.pem" `
   -in "sample.exe" -out "sample.signed.exe"

Tip

This invocation example is also provided in the Docker container samples via .\RunScenario.ps1 ... -Scenario osslsigncode. See Linux container samples.

OpenSC pkcs11-tool (Linux)

The OpenSC pkcs11-tool utility can be used to troubleshoot PKCS #11 modules (e.g. listing all available objects or supported algorithms) but also can be used to read certificates/public keys and to perform signing operations.

Setup

pkcs11-tool before version 0.23

Set Cryptoki.DoNotFailOnReadWriteSessions to true in the SignPath Crypto Provider configuration.

Background: pkcs11-tool used to open the Cryptoki session in a read/write mode (see GitHub issue #2182) and therefore fails with PKCS11 function C_OpenSession failed: rv = CKR_TOKEN_WRITE_PROTECTED. This flag enables compatibility with these earlier versions.

Invocation

Tip

The following invocation examples are also provided in the Docker container samples via .\RunScenario.ps1 ... -Scenario Pkcs11Tool. See Linux container samples.

Common parameters

pkcs11-tool --module $LibSignPathCryptokiPath --pin CONFIG ...

Listing of the available PKCS #11 objects

The following command lists available objects, which corresponds to the list of signing policies for which the authenticated user has Submitter permissions.

pkcs11-tool --module $LibSignPathCryptokiPath --pin CONFIG --list-objects

Signing operation

The following sample call shows an RSA signing operation using PSS padding and SHA-256.

pkcs11-tool --module $LibSignPathCryptokiPath --pin CONFIG `
   --sign --mechanism "RSA-PKCS-PSS" --hash-algorithm "SHA256" --label "$ProjectSlug/$SigningPolicySlug" `
   --input-file "artifact.hash.bin" --output-file "artifact.sig"

Java jarsigner

The jarsigner command signs and verifies Java archives (e.g. JAR, WAR, EAR). It is included with the Java Development Kit (JDK).

Setup

1. Configure the SunPKCS11 Provider
   • OpenJDK: the provider is configured automatically
   • Oracle JDK: see Oracle PKCS #11 Reference Guide
2. Register the SignPath Cryptoki library for the SunPKCS11 Provider

Sample pkcs11.config

name=SignPath.Cryptoki
library=<path>\SignPath.Cryptoki.dll
slot=1

Invocation

Tip

For Linux, configuration and invocation examples are provided in the Docker container samples via .\RunScenario.ps1 ... -Scenario JarSigner. See Linux container samples.

Synopsis for jarsigner when using the SignPath Cryptoki library:

jarsigner <parameters> <jar-files> <keystore-alias>

Sample: sign myapp.jar

jarsigner -keystore NONE -storetype PKCS11 -providerClass "sun.security.pkcs11.SunPKCS11" -providerArg pkcs11.config -sigalg "SHA256withRSA" -storepass "CONFIG" myapp.jar "$ProjectSlug/$SigningPolicySlug" 

Warning: Produce correct timestamps

When using jarsigner (or any other signing tool) directly, you are responsible for correct time stamping. See Timestamps