From 8c254edb9a55e99fa524f3faa969233ae60ae9f3 Mon Sep 17 00:00:00 2001 From: Stephen J Day Date: Wed, 18 Mar 2015 18:26:09 -0700 Subject: [PATCH] Correctly close pipe after error in tarsum verification This addresses a subtle deadlock where an error during a copy prevented pipe closure to propagate correctly. By closing down the read end of the pipe rather than the write end, the waiting writer is properly signaled. A nice side-effect of this change is that errors encountered by io.Copy are no propagated to the verifier's Write method. A test to ensure validation errors for unsupported digest types has been added, as well. Signed-off-by: Stephen J Day --- digest/digest.go | 2 +- digest/verifiers.go | 7 +++- digest/verifiers_test.go | 83 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 89 insertions(+), 3 deletions(-) diff --git a/digest/digest.go b/digest/digest.go index 6efec569..d640026c 100644 --- a/digest/digest.go +++ b/digest/digest.go @@ -58,7 +58,7 @@ var ( // ErrDigestInvalidFormat returned when digest format invalid. ErrDigestInvalidFormat = fmt.Errorf("invalid checksum digest format") - // ErrDigestUnsupported returned when the digest algorithm is unsupported by registry. + // ErrDigestUnsupported returned when the digest algorithm is unsupported. ErrDigestUnsupported = fmt.Errorf("unsupported digest algorithm") ) diff --git a/digest/verifiers.go b/digest/verifiers.go index 5180a588..11d9d7ae 100644 --- a/digest/verifiers.go +++ b/digest/verifiers.go @@ -56,8 +56,11 @@ func NewDigestVerifier(d Digest) (Verifier, error) { // TODO(sday): Ick! A goroutine per digest verification? We'll have to // get the tarsum library to export an io.Writer variant. go func() { - io.Copy(ioutil.Discard, ts) - pw.Close() + if _, err := io.Copy(ioutil.Discard, ts); err != nil { + pr.CloseWithError(err) + } else { + pr.Close() + } }() return &tarsumVerifier{ diff --git a/digest/verifiers_test.go b/digest/verifiers_test.go index 32599c94..408720b5 100644 --- a/digest/verifiers_test.go +++ b/digest/verifiers_test.go @@ -3,8 +3,10 @@ package digest import ( "bytes" "crypto/rand" + "encoding/base64" "io" "os" + "strings" "testing" "github.com/docker/distribution/testutil" @@ -67,6 +69,87 @@ func TestDigestVerifier(t *testing.T) { } } +// TestVerifierUnsupportedDigest ensures that unsupported digest validation is +// flowing through verifier creation. +func TestVerifierUnsupportedDigest(t *testing.T) { + unsupported := Digest("bean:0123456789abcdef") + + _, err := NewDigestVerifier(unsupported) + if err == nil { + t.Fatalf("expected error when creating verifier") + } + + if err != ErrDigestUnsupported { + t.Fatalf("incorrect error for unsupported digest: %v %p %p", err, ErrDigestUnsupported, err) + } +} + +// 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.