Move identifiers to pkg/identifiers

Signed-off-by: Derek McGowan <derek@mcg.dev>

pkg/identifiers/validate.go

@@ -0,0 +1,73 @@
+/*
+   Copyright The containerd Authors.
+
+   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.
+*/
+
+// Package identifiers provides common validation for identifiers and keys
+// across containerd.
+//
+// Identifiers in containerd must be a alphanumeric, allowing limited
+// underscores, dashes and dots.
+//
+// While the character set may be expanded in the future, identifiers
+// are guaranteed to be safely used as filesystem path components.
+package identifiers
+
+import (
+	"fmt"
+	"regexp"
+
+	"github.com/containerd/containerd/v2/pkg/errdefs"
+)
+
+const (
+	maxLength  = 76
+	alphanum   = `[A-Za-z0-9]+`
+	separators = `[._-]`
+)
+
+var (
+	// identifierRe defines the pattern for valid identifiers.
+	identifierRe = regexp.MustCompile(reAnchor(alphanum + reGroup(separators+reGroup(alphanum)) + "*"))
+)
+
+// Validate returns nil if the string s is a valid identifier.
+//
+// identifiers are similar to the domain name rules according to RFC 1035, section 2.3.1. However
+// rules in this package are relaxed to allow numerals to follow period (".") and mixed case is
+// allowed.
+//
+// In general identifiers that pass this validation should be safe for use as filesystem path components.
+func Validate(s string) error {
+	if len(s) == 0 {
+		return fmt.Errorf("identifier must not be empty: %w", errdefs.ErrInvalidArgument)
+	}
+
+	if len(s) > maxLength {
+		return fmt.Errorf("identifier %q greater than maximum length (%d characters): %w", s, maxLength, errdefs.ErrInvalidArgument)
+	}
+
+	if !identifierRe.MatchString(s) {
+		return fmt.Errorf("identifier %q must match %v: %w", s, identifierRe, errdefs.ErrInvalidArgument)
+	}
+	return nil
+}
+
+func reGroup(s string) string {
+	return `(?:` + s + `)`
+}
+
+func reAnchor(s string) string {
+	return `^` + s + `$`
+}

pkg/identifiers/validate_test.go

@@ -0,0 +1,73 @@
+/*
+   Copyright The containerd Authors.
+
+   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.
+*/
+
+package identifiers
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/containerd/containerd/v2/pkg/errdefs"
+)
+
+func TestValidIdentifiers(t *testing.T) {
+	for _, input := range []string{
+		"default",
+		"Default",
+		t.Name(),
+		"default-default",
+		"containerd.io",
+		"foo.boo",
+		"swarmkit.docker.io",
+		"0912341234",
+		"task.0.0123456789",
+		"container.system-75-f19a.00",
+		"underscores_are_allowed",
+		strings.Repeat("a", maxLength),
+	} {
+		t.Run(input, func(t *testing.T) {
+			if err := Validate(input); err != nil {
+				t.Fatalf("unexpected error: %v != nil", err)
+			}
+		})
+	}
+}
+
+func TestInvalidIdentifiers(t *testing.T) {
+	for _, input := range []string{
+		"",
+		".foo..foo",
+		"foo/foo",
+		"foo/..",
+		"foo..foo",
+		"foo.-boo",
+		"-foo.boo",
+		"foo.boo-",
+		"but__only_tasteful_underscores",
+		"zn--e9.org", // or something like it!
+		"default--default",
+		strings.Repeat("a", maxLength+1),
+	} {
+
+		t.Run(input, func(t *testing.T) {
+			if err := Validate(input); err == nil {
+				t.Fatal("expected invalid error")
+			} else if !errdefs.IsInvalidArgument(err) {
+				t.Fatal("error should be an invalid identifier error")
+			}
+		})
+	}
+}