Witness prevents tampering of build materials and verifies the integrity of the build process from source to target. It works by wrapping commands executed in a continuous integration process. Its attestation system is pluggable and offers support out of the box for most major CI and infrastructure providers. Verification of Witness metadata and a secure PKI distribution system will mitigate against many software supply chain attack vectors and can be used as a framework for automated governance.
Witness is an implementation of the in-toto spec including ITE-5, ITE-6, ITE-7 with an embedded rego policy engine.
- Does NOT require elevated privileges.
- Can run in a containerized or non-containerized environment
- Records secure hashes of materials, artifacts, and events occurring during the CI process
- Integrations with cloud identity services
- Keyless signing with SPIFFE/SPIRE
- Support for uploading attestation evidence to rekor server (sigstore)
- Build policy enforcement with Open Policy Agent.
- Alpha support for tracing and process tampering prevention
- Verifies file integrity between CI steps, and across air gap.
- Experimental Windows and ARM Support
- Run - Runs the provided command and records attestations about the execution.
- Sign - Signs the provided file with the provided key.
- Verify - Verifies a witness policy.
- Witness Attestors
curl -LO https://github.com/testifysec/witness/releases/download/${VERSION}/witness_${VERSION}_${ARCH}.tar.gz
tar -xzf witness_${VERSION}_${ARCH}.tar.gz
Witness supports keyless signing with SPIRE!
openssl genpkey -algorithm ed25519 -outform PEM -out testkey.pem
openssl pkey -in testkey.pem -pubout > testpub.pem
- This file generally resides in your source code repository along with the public keys generated above.
.witness yaml
is the default location for the configuration filewitness help
will show all configuration options- command-line arguments overrides configuration file values.
## .witness.yaml
run:
key: testkey.pem
trace: false
verify:
attestations:
- "test-att.json"
policy: policy-signed.json
publickey: testpub.pem
- The
-a {attestor}
flag allows you to define which attestors run- ex.
-a maven -a was -a gitlab
would be used for a maven build running on a GitLab runner on GCP.- Defining step names is important, these will be used in the policy.
- This should happen as a part of a CI step
witness run --step build -o test-att.json -- go build -o=testapp .
- This data can be stored and retrieved from rekor!
- This is the data that is evaluated against the Rego policy
cat test-att.json | jq -r .payload | base64 -d | jq
- Make sure to replace the keys in this file with the ones from the step above (sed command below).
- Rego policies should be base64 encoded
- Steps are bound to keys. Policy can be written to check the certificate data. For example, we can require a step is signed by a key with a specific
CN
attribute.- Witness will require all attestations to succeed
- Witness will evaluate the rego policy against the JSON object in the corresponding attestor
## policy.json
{
"expires": "2023-12-17T23:57:40-05:00",
"steps": {
"build": {
"name": "build",
"attestations": [
{
"type": "https://witness.testifysec.com/attestations/material/v0.1",
"regopolicies": []
},
{
"type": "https://witness.testifysec.com/attestations/command-run/v0.1",
"regopolicies": []
},
{
"type": "https://witness.testifysec.com/attestations/product/v0.1",
"regopolicies": []
}
],
"functionaries": [
{
"publickeyid": "{{PUBLIC_KEY_ID}}"
}
]
}
},
"publickeys": {
"{{PUBLIC_KEY_ID}}": {
"keyid": "{{PUBLIC_KEY_ID}}",
"key": "{{B64_PUBLIC_KEY}}"
}
}
}
id=`sha256sum testpub.pem | awk '{print $1}'` && sed -i "s/{{PUBLIC_KEY_ID}}/$id/g" policy.json
pubb64=`cat testpub.pem | base64 -w 0` && sed -i "s/{{B64_PUBLIC_KEY}}/$pubb64/g" policy.json
Keep this key safe, its owner will control the policy gates.
witness sign -f policy.json --key testkey.pem --outfile policy-signed.json
This process works across air-gap as long as you have the signed policy file, correct binary, and public key or certificate authority corresponding to the private key that signed the policy.
witness verify
will return anon-zero
exit and reason in the case of failure. Success will be silent with a0
exit status for policies that require multiple steps, multiple attestations are required.
witness verify -f testapp -a test-att.json -p policy-signed.json -k testpub.pem
Witness attestors are pieces of code that assert facts about a system and store those facts in a versioned schema. Each attestor has a Name
, Type
, and RunType
. The Type
is a versioned string corresponding to the JSON schema of the attestation. For example, the AWS attestor is defined as follows:
Name = "aws"
Type = "https://witness.testifysec.com/attestation/aws/v0.1"
RunType = attestation.PreRunType
The attestation types are used when we evaluate policy against these attestations.
Attestations are only as secure as the data that feeds them. Where possible cryptographic material should be validated, evidence of validation should be included in the attestation for out-of-band validation.
Examples of cryptographic validation is found in the GCP, AWS, and GitLab attestors.
-
PreRun:
PreRun
attestors run before thematerial
attestor andcommandRun
attestors. These attestors generally collect information about the environment. -
Material Attestor: The
material
attestor is an internal attestor and runs immediately after -
CommandRun Attestor: The CommandRun attestor is an internal attestor. It has experimental tracing support that can be enabled with the
--trace
flag -
Product Attestor: The Product attestor collects the products produced by the
commandRun
attestor and calculates the secure hash, and makes the file descriptor available to thepostRun
attestors.
- AWS - Attestor for AWS Instance Metadata
- GCP - Attestor for GCP Instance Idenity Service
- GitLab - Attestor for GitLab Pipelines
- Git - Attestor for Git Repository
- Maven Attestor for Maven Projects
- Environment - Attestor for environment variables (be careful with this - there is no way to mask values yet)
- JWT - Attestor for JWT Tokens
- CommandRun - Records traces and metadata about the actual process being run
- Material - Records secure hashes of files in current working directory
- Product - Records secure hashes of files produced by commandrun attestor (only detects new files)
PostRun attestors collect have access to the files discovered by the product attestor. The purpose of PostRun attestors is to select metadata from the products. For example, in the OCI attestor the attestor examines the tar file and extracts OCI container meta-data.
- OCI - Attestor for tar'd OCI images
An attestationCollection
is a collection of attestations that are cryptographically bound together. Because the attestations are bound together, we can trust that they all happened as part of the same attesation life cycle. Witness policy defines which attestations are required.
Attestors define subjects that act as lookup indexes. The attestationCollection can be looked up by any of the subjects defined by the attestors.
A witness policy is a signed document that encodes the requirements for an artifact to be validated. A witness policy includes public keys for trusted functionaries, which attestations must be found, and rego policy to evaluate against the attestation meta-data.
I witness policy allowers administrators trace the compliance status of an artifact at any point during it's lifecycle.
Using SPIRE for Keyless Signing
Witness can consume ephemeral keys from a SPIRE node agent. Configure witness with the flag --spiffe-socket
to enable keyless signing.
During the verification process witness will use the Rekor integrated time to make a determination on certificate validity. The SPIRE certificate only needs to remain valid long enough for the attestation to be integrated into the Rekor log.
- Using Witness To Prevent SolarWinds Type Attacks
- Using Witness To Find Artifacts With Hidden Vulnerable Log4j Dependencies
- Blog - What is a supply chain attestation, and why do I need it?
- Talk - Securing the Software Supply Chain with the in-toto & SPIRE projects
- Talk - Securing the Software Supply Chain with SBOM and Attestation
- Attestors for all major platforms
- CaC Card Attestor
- GovCloud Attestor
- OIDC Attestor
- FIDO Attestor
- Vault Key Provider
- Cloud KMS Support
- Kubernetes Admission Controller
- SIEM Collection Agent
- Cosign Signature Validation
- Notary v2 Signature Validation
- Zarf Integration
- IronBank Attestor
TestifySec Provides support for witness and other CI security tools. Contact Us