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//
// Copyright 2022 The Sigstore Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package policy
import (
"context"
"fmt"
"cuelang.org/go/cue/cuecontext"
)
// EvaluatePolicyAgainstJson is used to run a policy engine against JSON bytes.
// These bytes can be for example Attestations, or ClusterImagePolicy result
// types.
// name - which attestation are we evaluating
// policyType - cue|rego
// policyBody - String representing either cue or rego language
// jsonBytes - Bytes to evaluate against the policyBody in the given language
func EvaluatePolicyAgainstJSON(ctx context.Context, name, policyType string, policyBody string, jsonBytes []byte) (warnings error, errors error) {
switch policyType {
case "cue":
cueValidationErr := evaluateCue(ctx, jsonBytes, policyBody)
if cueValidationErr != nil {
return nil, &EvaluationFailure{
fmt.Errorf("failed evaluating cue policy for %s: %w", name, cueValidationErr),
}
}
default:
return nil, fmt.Errorf("sorry Type %s is not supported yet", policyType)
}
return nil, nil
}
// evaluateCue evaluates a cue policy `evaluator` against `attestation`
func evaluateCue(_ context.Context, attestation []byte, evaluator string) error {
cueCtx := cuecontext.New()
cueEvaluator := cueCtx.CompileString(evaluator)
if cueEvaluator.Err() != nil {
return fmt.Errorf("failed to compile the cue policy with error: %w", cueEvaluator.Err())
}
cueAtt := cueCtx.CompileBytes(attestation)
if cueAtt.Err() != nil {
return fmt.Errorf("failed to compile the attestation data with error: %w", cueAtt.Err())
}
result := cueEvaluator.Unify(cueAtt)
if err := result.Validate(); err != nil {
return fmt.Errorf("failed to evaluate the policy with error: %w", err)
}
return nil
}
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