internal/format/packfile: Panic on implausible hash sizes

2 files changed, 12 insertions, 12 deletions

diff --git a/internal/format/packfile/entry_header.go b/internal/format/packfile/entry_header.go
index 1428600b..e5f2d62d 100644
--- a/internal/format/packfile/entry_header.go
+++ b/internal/format/packfile/entry_header.go
@@ -13,12 +13,6 @@ import (
 // or declares a size that overflows uint64.
 var ErrMalformedEntryHeader = errors.New("internal/format/packfile: malformed entry header")
 
-// ErrInvalidHashSize reports that
-// a supplied hash size is not a plausible object ID size.
-// This indicates a caller bug,
-// not malformed pack data.
-var ErrInvalidHashSize = errors.New("internal/format/packfile: invalid hash size")
-
 // MaxTypeSizeLen is the maximum encoded length
 // of the type/size prefix of an entry header.
 // Every uint64 size is encodable within this bound,
@@ -73,7 +67,8 @@ type EntryHeader struct {
 // from the beginning of data.
 //
 // hashSize must be the object ID size
-// of the pack's object format.
+// of the pack's object format;
+// ParseEntryHeader panics on implausible hash sizes.
 //
 // data need not contain the whole entry;
 // [MaxEntryHeaderLen] bytes always suffice.
@@ -83,7 +78,7 @@ func ParseEntryHeader(data []byte, hashSize int) (EntryHeader, error) {
 	var zero EntryHeader
 
 	if hashSize <= 0 || hashSize > id.MaxObjectIDSize {
-		return zero, fmt.Errorf("%w: %d", ErrInvalidHashSize, hashSize)
+		panic("internal/format/packfile: invalid hash size")
 	}
 
 	if len(data) == 0 {
diff --git a/internal/format/packfile/entry_header_test.go b/internal/format/packfile/entry_header_test.go
index 807c544e..79dc2740 100644
--- a/internal/format/packfile/entry_header_test.go
+++ b/internal/format/packfile/entry_header_test.go
@@ -130,10 +130,15 @@ func TestParseEntryHeaderBadHashSize(t *testing.T) {
 	t.Parallel()
 
 	for _, hashSize := range []int{-1, 0, id.MaxObjectIDSize + 1} {
-		_, err := packfile.ParseEntryHeader([]byte{0x95, 0x05}, hashSize)
-		if err == nil {
-			t.Fatalf("ParseEntryHeader hash size %d: expected error", hashSize)
-		}
+		func() {
+			defer func() {
+				if recover() == nil {
+					t.Fatalf("ParseEntryHeader hash size %d: expected panic", hashSize)
+				}
+			}()
+
+			_, _ = packfile.ParseEntryHeader([]byte{0x95, 0x05}, hashSize)
+		}()
 	}
 }