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Resolves #1070 Signed-off-by: Luiz Carvalho <lucarval@redhat.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,36 @@ | ||
| package blobby | ||
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| import future.keywords.contains | ||
| import future.keywords.if | ||
| import future.keywords.in | ||
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| # METADATA | ||
| # custom: | ||
| # short_name: spam | ||
| deny contains result if { | ||
| content := ec.oci.blob(uri) | ||
| content != "spam" | ||
| result := { | ||
| "code": "blobby.spam_success", | ||
| "msg": sprintf("Unexpected content %q for blob at %q", [content, uri]) | ||
| } | ||
| } | ||
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| # METADATA | ||
| # custom: | ||
| # short_name: fetchable | ||
| deny contains result if { | ||
| not ec.oci.blob(uri) | ||
| result := { | ||
| "code": "blobby.fetchable", | ||
| "msg": sprintf("Cannot fetch blob at %q", [uri]) | ||
| } | ||
| } | ||
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| uri := value { | ||
| # Assume the blob is on the same repo as the image | ||
| repo := split(input.image.ref, "@")[0] | ||
| # The digest of the word "spam" | ||
| digest := "sha256:4e388ab32b10dc8dbc7e28144f552830adc74787c1e2c0824032078a79f227fb" | ||
| value := sprintf("%s@%s", [repo, digest]) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,120 @@ | ||
| // Copyright The Enterprise Contract Contributors | ||
| // | ||
| // 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. | ||
| // | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
|
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| // IMPORTANT: The rego functions in this file never return an error. Instead, they return no value | ||
| // when an error is encountered. If they did return an error, opa would exit abruptly and it would | ||
| // not produce a report of which policy rules succeeded/failed. | ||
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| package evaluator | ||
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| import ( | ||
| "bytes" | ||
| "crypto/sha256" | ||
| "fmt" | ||
| "io" | ||
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| "github.com/google/go-containerregistry/pkg/authn" | ||
| "github.com/google/go-containerregistry/pkg/name" | ||
| "github.com/google/go-containerregistry/pkg/v1/remote" | ||
| "github.com/open-policy-agent/opa/ast" | ||
| "github.com/open-policy-agent/opa/rego" | ||
| "github.com/open-policy-agent/opa/types" | ||
| log "github.com/sirupsen/logrus" | ||
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| "github.com/enterprise-contract/ec-cli/internal/fetchers/oci" | ||
| ) | ||
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| const ociBlobName = "ec.oci.blob" | ||
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| func registerOCIBlob() { | ||
| decl := rego.Function{ | ||
| Name: ociBlobName, | ||
| Decl: types.NewFunction( | ||
| types.Args( | ||
| types.Named("ref", types.S).Description("OCI blob reference"), | ||
| ), | ||
| types.Named("blob", types.S).Description("the OCI blob"), | ||
| ), | ||
| Memoize: true, | ||
| Nondeterministic: true, | ||
| } | ||
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| rego.RegisterBuiltin1(&decl, ociBlob) | ||
| } | ||
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| const maxBytes = 10 * 1024 * 1024 // 10 MB | ||
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| func ociBlob(bctx rego.BuiltinContext, a *ast.Term) (*ast.Term, error) { | ||
| uri, ok := a.Value.(ast.String) | ||
| if !ok { | ||
| return nil, nil | ||
| } | ||
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| ref, err := name.NewDigest(string(uri)) | ||
| if err != nil { | ||
| log.Errorf("%s new digest: %s", ociBlobName, err) | ||
| return nil, nil | ||
| } | ||
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| opts := []remote.Option{ | ||
| remote.WithTransport(remote.DefaultTransport), | ||
| remote.WithContext(bctx.Context), | ||
| remote.WithAuthFromKeychain(authn.DefaultKeychain), | ||
| } | ||
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| rawLayer, err := oci.NewClient(bctx.Context).Layer(ref, opts...) | ||
| if err != nil { | ||
| log.Errorf("%s fetch layer: %s", ociBlobName, err) | ||
| return nil, nil | ||
| } | ||
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| layer, err := rawLayer.Uncompressed() | ||
| if err != nil { | ||
| log.Errorf("%s layer uncompressed: %s", ociBlobName, err) | ||
| return nil, nil | ||
| } | ||
| defer layer.Close() | ||
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| // TODO: Other algorithms are technically supported, e.g. sha512. However, support for those is | ||
| // not complete in the go-containerregistry library, e.g. name.NewDigest throws an error if | ||
| // sha256 is not used. This is good for now, but may need revisiting later. | ||
| hasher := sha256.New() | ||
| // Setup some safeguards. First, use LimitReader to avoid an unbounded amount of data from being | ||
| // read. Second, use TeeReader so we can compute the digest of the content read. | ||
| reader := io.TeeReader(io.LimitReader(layer, maxBytes), hasher) | ||
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| var blob bytes.Buffer | ||
| if _, err := io.Copy(&blob, reader); err != nil { | ||
| log.Errorf("%s copy buffer: %s", ociBlobName, err) | ||
| return nil, nil | ||
| } | ||
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| sum := fmt.Sprintf("sha256:%x", hasher.Sum(nil)) | ||
| // io.LimitReader truncates the layer if it exceeds its limits. This ensures unexpected behavior | ||
| // by not returning partial data. | ||
| if sum != ref.DigestStr() { | ||
| log.Errorf( | ||
| "%s computed digest, %q, not as expected, %q. Content may have been truncated at %d bytes", | ||
| ociBlobName, sum, ref.DigestStr(), maxBytes) | ||
| return nil, nil | ||
| } | ||
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| return ast.StringTerm(blob.String()), nil | ||
| } | ||
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| func init() { | ||
| registerOCIBlob() | ||
| } | ||
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