Remove tarsum support for digest package

tarsum is not actually used by the registry. Remove support for it.

Convert numerous uses in unit tests to SHA256.

Update docs to remove mentions of tarsums (which were often inaccurate).

Remove tarsum dependency.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

digest/verifiers_test.go

@@ -3,13 +3,8 @@ package digest
 import (
 	"bytes"
 	"crypto/rand"
-	"encoding/base64"
 	"io"
-	"os"
-	"strings"
 	"testing"
-
-	"github.com/docker/distribution/testutil"
 )
 
 func TestDigestVerifier(t *testing.T) {
@@ -27,43 +22,6 @@ func TestDigestVerifier(t *testing.T) {
 	if !verifier.Verified() {
 		t.Fatalf("bytes not verified")
 	}
-
-	tf, tarSum, err := testutil.CreateRandomTarFile()
-	if err != nil {
-		t.Fatalf("error creating tarfile: %v", err)
-	}
-
-	digest, err = FromTarArchive(tf)
-	if err != nil {
-		t.Fatalf("error digesting tarsum: %v", err)
-	}
-
-	if digest.String() != tarSum {
-		t.Fatalf("unexpected digest: %q != %q", digest.String(), tarSum)
-	}
-
-	expectedSize, _ := tf.Seek(0, os.SEEK_END) // Get tar file size
-	tf.Seek(0, os.SEEK_SET)                    // seek back
-
-	// This is the most relevant example for the registry application. It's
-	// effectively a read through pipeline, where the final sink is the digest
-	// verifier.
-	verifier, err = NewDigestVerifier(digest)
-	if err != nil {
-		t.Fatalf("unexpected error getting digest verifier: %s", err)
-	}
-
-	lengthVerifier := NewLengthVerifier(expectedSize)
-	rd := io.TeeReader(tf, lengthVerifier)
-	io.Copy(verifier, rd)
-
-	if !lengthVerifier.Verified() {
-		t.Fatalf("verifier detected incorrect length")
-	}
-
-	if !verifier.Verified() {
-		t.Fatalf("bytes not verified")
-	}
 }
 
 // TestVerifierUnsupportedDigest ensures that unsupported digest validation is
@@ -81,79 +39,11 @@ func TestVerifierUnsupportedDigest(t *testing.T) {
 	}
 }
 
-// TestJunkNoDeadlock ensures that junk input into a digest verifier properly
-// returns errors from the tarsum library. Specifically, we pass in a file
-// with a "bad header" and should see the error from the io.Copy to verifier.
-// This has been seen with gzipped tarfiles, mishandled by the tarsum package,
-// but also on junk input, such as html.
-func TestJunkNoDeadlock(t *testing.T) {
-	expected := Digest("tarsum.dev+sha256:62e15750aae345f6303469a94892e66365cc5e3abdf8d7cb8b329f8fb912e473")
-	junk := bytes.Repeat([]byte{'a'}, 1024)
-
-	verifier, err := NewDigestVerifier(expected)
-	if err != nil {
-		t.Fatalf("unexpected error creating verifier: %v", err)
-	}
-
-	rd := bytes.NewReader(junk)
-	if _, err := io.Copy(verifier, rd); err == nil {
-		t.Fatalf("unexpected error verifying input data: %v", err)
-	}
-}
-
-// TestBadTarNoDeadlock runs a tar with a "bad" tar header through digest
-// verifier, ensuring that the verifier returns an error properly.
-func TestBadTarNoDeadlock(t *testing.T) {
-	// TODO(stevvooe): This test is exposing a bug in tarsum where if we pass
-	// a gzipped tar file into tarsum, the library returns an error. This
-	// should actually work. When the tarsum package is fixed, this test will
-	// fail and we can remove this test or invert it.
-
-	// This tarfile was causing deadlocks in verifiers due mishandled copy error.
-	// This is a gzipped tar, which we typically don't see but should handle.
-	//
-	// From https://registry-1.docker.io/v2/library/ubuntu/blobs/tarsum.dev+sha256:62e15750aae345f6303469a94892e66365cc5e3abdf8d7cb8b329f8fb912e473
-	const badTar = `
-H4sIAAAJbogA/0otSdZnoDEwMDAxMDc1BdJggE6D2YZGJobGBmbGRsZAdYYGBkZGDAqmtHYYCJQW
-lyQWAZ1CqTnonhsiAAAAAP//AsV/YkEJTdMAGfFvZmA2Gv/0AAAAAAD//4LFf3F+aVFyarFeTmZx
-CbXtAOVnMxMTXPFvbGpmjhb/xobmwPinSyCO8PgHAAAA///EVU9v2z4MvedTEMihl9a5/26/YTkU
-yNKiTTDsKMt0rE0WDYmK628/ym7+bFmH2DksQACbIB/5+J7kObwiQsXc/LdYVGibLObRccw01Qv5
-19EZ7hbbZudVgWtiDFCSh4paYII4xOVxNgeHLXrYow+GXAAqgSuEQhzlTR5ZgtlsVmB+aKe8rswe
-zzsOjwtoPGoTEGplHHhMCJqxSNUPwesbEGbzOXxR34VCHndQmjfhUKhEq/FURI0FqJKFR5q9NE5Z
-qbaoBGoglAB+5TSK0sOh3c3UPkRKE25dEg8dDzzIWmqN2wG3BNY4qRL1VFFAoJJb5SXHU90n34nk
-SUS8S0AeGwqGyXdZel1nn7KLGhPO0kDeluvN48ty9Q2269ft8/PTy2b5GfKuh9/2LBIWo6oz+N8G
-uodmWLETg0mW4lMP4XYYCL4+rlawftpIO40SA+W6Yci9wRZE1MNOjmyGdhBQRy9OHpqOdOGh/wT7
-nZdOkHZ650uIK+WrVZdkgErJfnNEJysLnI5FSAj4xuiCQNpOIoNWmhyLByVHxEpLf3dkr+k9KMsV
-xV0FhiVB21hgD3V5XwSqRdOmsUYr7oNtZXTVzyTHc2/kqokBy2ihRMVRTN+78goP5Ur/aMhz+KOJ
-3h2UsK43kdwDo0Q9jfD7ie2RRur7MdpIrx1Z3X4j/Q1qCswN9r/EGCvXiUy0fI4xeSknnH/92T/+
-fgIAAP//GkWjYBSMXAAIAAD//2zZtzAAEgAA`
-	expected := Digest("tarsum.dev+sha256:62e15750aae345f6303469a94892e66365cc5e3abdf8d7cb8b329f8fb912e473")
-
-	verifier, err := NewDigestVerifier(expected)
-	if err != nil {
-		t.Fatalf("unexpected error creating verifier: %v", err)
-	}
-
-	rd := base64.NewDecoder(base64.StdEncoding, strings.NewReader(badTar))
-
-	if _, err := io.Copy(verifier, rd); err == nil {
-		t.Fatalf("unexpected error verifying input data: %v", err)
-	}
-
-	if verifier.Verified() {
-		// For now, we expect an error, since tarsum library cannot handle
-		// compressed tars (!!!).
-		t.Fatalf("no error received after invalid tar")
-	}
-}
-
 // TODO(stevvooe): Add benchmarks to measure bytes/second throughput for
-// DigestVerifier. We should be tarsum/gzip limited for common cases but we
-// want to verify this.
+// DigestVerifier.
 //
-// The relevant benchmarks for comparison can be run with the following
+// The relevant benchmark for comparison can be run with the following
 // commands:
 //
 // 	go test -bench . crypto/sha1
-// 	go test -bench . github.com/docker/docker/pkg/tarsum
 //