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Refactor policy related code, add support for vuln verify (#1747)
* Refactor policy related code, add support for vuln verify Signed-off-by: Ville Aikas <vaikas@chainguard.dev> * Thanks @hectorj2f for catching a bad upstream rebase. Signed-off-by: Ville Aikas <vaikas@chainguard.dev> * Fix typo. Signed-off-by: Ville Aikas <vaikas@chainguard.dev>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,130 @@ | ||
| // | ||
| // 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" | ||
| "encoding/base64" | ||
| "encoding/json" | ||
| "fmt" | ||
|
|
||
| "github.com/in-toto/in-toto-golang/in_toto" | ||
| "github.com/pkg/errors" | ||
| "github.com/sigstore/cosign/pkg/oci" | ||
|
|
||
| "github.com/sigstore/cosign/cmd/cosign/cli/options" | ||
| "github.com/sigstore/cosign/pkg/cosign/attestation" | ||
| ) | ||
|
|
||
| // AttestationToPayloadJSON takes in a verified Attestation (oci.Signature) and | ||
| // marshals it into a JSON depending on the payload that's then consumable | ||
| // by policy engine like cue, rego, etc. | ||
| // | ||
| // Anything fed here must have been validated with either | ||
| // `VerifyLocalImageAttestations` or `VerifyImageAttestations` | ||
| // | ||
| // If there's no error, and payload is empty means the predicateType did not | ||
| // match the attestation. | ||
| func AttestationToPayloadJSON(ctx context.Context, predicateType string, verifiedAttestation oci.Signature) ([]byte, error) { | ||
| // Check the predicate up front, no point in wasting time if it's invalid. | ||
| predicateURI, ok := options.PredicateTypeMap[predicateType] | ||
| if !ok { | ||
| return nil, fmt.Errorf("invalid predicate type: %s", predicateType) | ||
| } | ||
|
|
||
| var payloadData map[string]interface{} | ||
|
|
||
| p, err := verifiedAttestation.Payload() | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "getting payload") | ||
| } | ||
|
|
||
| err = json.Unmarshal(p, &payloadData) | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "unmarshaling payload data") | ||
| } | ||
|
|
||
| var decodedPayload []byte | ||
| if val, ok := payloadData["payload"]; ok { | ||
| decodedPayload, err = base64.StdEncoding.DecodeString(val.(string)) | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "decoding payload") | ||
| } | ||
| } else { | ||
| return nil, fmt.Errorf("could not find payload in payload data") | ||
| } | ||
|
|
||
| // Only apply the policy against the requested predicate type | ||
| var statement in_toto.Statement | ||
| if err := json.Unmarshal(decodedPayload, &statement); err != nil { | ||
| return nil, fmt.Errorf("unmarshal in-toto statement: %w", err) | ||
| } | ||
| if statement.PredicateType != predicateURI { | ||
| // This is not the predicate we're looking for, so skip it. | ||
| return nil, nil | ||
| } | ||
|
|
||
| // NB: In many (all?) of these cases, we could just return the | ||
| // 'json.Marshal', but we check for errors here to decorate them | ||
| // with more meaningful error message. | ||
| var payload []byte | ||
| switch predicateType { | ||
| case options.PredicateCustom: | ||
| payload, err = json.Marshal(statement) | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "generating CosignStatement") | ||
| } | ||
| case options.PredicateLink: | ||
| var linkStatement in_toto.LinkStatement | ||
| if err := json.Unmarshal(decodedPayload, &linkStatement); err != nil { | ||
| return nil, errors.Wrap(err, "unmarshaling LinkStatement") | ||
| } | ||
| payload, err = json.Marshal(linkStatement) | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "marshaling LinkStatement") | ||
| } | ||
| case options.PredicateSLSA: | ||
| var slsaProvenanceStatement in_toto.ProvenanceStatement | ||
| if err := json.Unmarshal(decodedPayload, &slsaProvenanceStatement); err != nil { | ||
| return nil, errors.Wrap(err, "unmarshaling ProvenanceStatement") | ||
| } | ||
| payload, err = json.Marshal(slsaProvenanceStatement) | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "marshaling ProvenanceStatement") | ||
| } | ||
| case options.PredicateSPDX: | ||
| var spdxStatement in_toto.SPDXStatement | ||
| if err := json.Unmarshal(decodedPayload, &spdxStatement); err != nil { | ||
| return nil, errors.Wrap(err, "unmarshaling SPDXStatement") | ||
| } | ||
| payload, err = json.Marshal(spdxStatement) | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "marshaling SPDXStatement") | ||
| } | ||
| case options.PredicateVuln: | ||
| var vulnStatement attestation.CosignVulnStatement | ||
| if err := json.Unmarshal(decodedPayload, &vulnStatement); err != nil { | ||
| return nil, errors.Wrap(err, "unmarshaling CosignVulnStatement") | ||
| } | ||
| payload, err = json.Marshal(vulnStatement) | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "marshaling CosignVulnStatement") | ||
| } | ||
| default: | ||
| return nil, fmt.Errorf("unsupported predicate type: %s", predicateType) | ||
| } | ||
| return payload, nil | ||
| } |
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