git: Add package that handles sha256 hashes

SHA256 hashes are 64 hexadecimal characters, compared to the 40 chars
for SHA1. This change adds validators for this longer object format.

2 files changed, 142 insertions, 0 deletions

diff --git a/internal/git/sha256/id.go b/internal/git/sha256/id.go
new file mode 100644
index 000000000..42a4a7c5f
--- /dev/null
+++ b/internal/git/sha256/id.go
@@ -0,0 +1,36 @@
+package sha256
+
+import (
+	"fmt"
+	"regexp"
+
+	"gitlab.com/gitlab-org/gitaly/v15/internal/git"
+)
+
+const (
+	// EmptyTreeOID is the Git tree object sha256 hash that corresponds to an empty tree (directory)
+	EmptyTreeOID = git.ObjectID("6ef19b41225c5369f1c104d45d8d85efa9b057b53b14b4b9b939dd74decc5321")
+)
+
+var objectIDRegex = regexp.MustCompile(`\A[0-9a-f]{64}\z`)
+
+// NewObjectIDFromHex constructs a new ObjectID from the given hex
+// representation of the object ID. Returns ErrInvalidObjectID if the given
+// OID is not valid.
+func NewObjectIDFromHex(hex string) (git.ObjectID, error) {
+	if err := ValidateObjectID(hex); err != nil {
+		return "", err
+	}
+	return git.ObjectID(hex), nil
+}
+
+// ValidateObjectID checks if id is a syntactically correct object ID. Abbreviated
+// object IDs are not deemed to be valid. Returns an ErrInvalidObjectID if the
+// id is not valid.
+func ValidateObjectID(id string) error {
+	if objectIDRegex.MatchString(id) {
+		return nil
+	}
+
+	return fmt.Errorf("%w: %q", git.ErrInvalidObjectID, id)
+}
diff --git a/internal/git/sha256/id_test.go b/internal/git/sha256/id_test.go
new file mode 100644
index 000000000..1be75e98f
--- /dev/null
+++ b/internal/git/sha256/id_test.go
@@ -0,0 +1,106 @@
+package sha256
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestValidateObjectID(t *testing.T) {
+	for _, tc := range []struct {
+		desc  string
+		oid   string
+		valid bool
+	}{
+		{
+			desc:  "valid object ID",
+			oid:   "cff96308c1b0c36602ca031013b563074edddb203efa61c4f01be1bd2482d92e",
+			valid: true,
+		},
+		{
+			desc:  "object ID with non-hex characters fails",
+			oid:   "xff96308c1b0c36602ca031013b563074edddb203efa61c4f01be1bd2482d92e",
+			valid: false,
+		},
+		{
+			desc:  "object ID with upper-case letters fails",
+			oid:   "CFF96308C1B0C36602CA031013B563074EDDDB203EFA61C4F01BE1BD2482D92E",
+			valid: false,
+		},
+		{
+			desc:  "too short object ID fails",
+			oid:   "cff96308c1b0c36602ca031013b563074edddb203efa61c4f01be1bd2482d92",
+			valid: false,
+		},
+		{
+			desc:  "too long object ID fails",
+			oid:   "cff96308c1b0c36602ca031013b563074edddb203efa61c4f01be1bd2482d92eb",
+			valid: false,
+		},
+		{
+			desc:  "empty string fails",
+			oid:   "",
+			valid: false,
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			err := ValidateObjectID(tc.oid)
+			if tc.valid {
+				require.NoError(t, err)
+			} else {
+				require.Error(t, err)
+				require.EqualError(t, err, fmt.Sprintf("invalid object ID: %q", tc.oid))
+			}
+		})
+	}
+}
+
+func TestNewObjectIDFromHex(t *testing.T) {
+	for _, tc := range []struct {
+		desc  string
+		oid   string
+		valid bool
+	}{
+		{
+			desc:  "valid object ID",
+			oid:   "cff96308c1b0c36602ca031013b563074edddb203efa61c4f01be1bd2482d92e",
+			valid: true,
+		},
+		{
+			desc:  "object ID with non-hex characters fails",
+			oid:   "xff96308c1b0c36602ca031013b563074edddb203efa61c4f01be1bd2482d92e",
+			valid: false,
+		},
+		{
+			desc:  "object ID with upper-case letters fails",
+			oid:   "CFF96308C1B0C36602CA031013B563074EDDDB203EFA61C4F01BE1BD2482D92E",
+			valid: false,
+		},
+		{
+			desc:  "too short object ID fails",
+			oid:   "cff96308c1b0c36602ca031013b563074edddb203efa61c4f01be1bd2482d92",
+			valid: false,
+		},
+		{
+			desc:  "too long object ID fails",
+			oid:   "cff96308c1b0c36602ca031013b563074edddb203efa61c4f01be1bd2482d92eb",
+			valid: false,
+		},
+		{
+			desc:  "empty string fails",
+			oid:   "",
+			valid: false,
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			oid, err := NewObjectIDFromHex(tc.oid)
+			if tc.valid {
+				require.NoError(t, err)
+				require.Equal(t, tc.oid, oid.String())
+			} else {
+				require.Error(t, err)
+			}
+		})
+	}
+}