tpl/crypto: Add crypto.Hash

Add a generic crypto.Hash template function returning the hex-encoded
checksum of a string using one of md5, sha1, sha256 (default), sha384 or
sha512. The supported algorithms match those used for the SRI hash in
.Data.Integrity on fingerprinted resources, so an SRI hash can be built
by composing with encoding.HexDecode and encoding.Base64Encode.

Fixes #15072

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tpl/crypto/crypto.go

@@ -68,6 +68,62 @@ func (ns *Namespace) SHA256(v any) (string, error) {
 	return hex.EncodeToString(hash[:]), nil
 }
 
+// Hash returns the hex-encoded checksum of v using the given algorithm; one of
+// md5, sha1, sha256 (the default), sha384 or sha512.
+//
+// The supported algorithms match those used for the Subresource Integrity (SRI)
+// hash in .Data.Integrity on fingerprinted resources, so an SRI hash can be
+// constructed by combining this with encoding.HexDecode and encoding.Base64Encode.
+func (ns *Namespace) Hash(args ...any) (string, error) {
+	var algo, v any
+	switch len(args) {
+	case 1:
+		algo, v = "sha256", args[0]
+	case 2:
+		algo, v = args[0], args[1]
+	default:
+		return "", fmt.Errorf("crypto.Hash: expected 1 or 2 arguments, got %d", len(args))
+	}
+
+	conv, err := cast.ToStringE(v)
+	if err != nil {
+		return "", err
+	}
+
+	algoS, err := cast.ToStringE(algo)
+	if err != nil {
+		return "", err
+	}
+
+	h, err := newHash(algoS)
+	if err != nil {
+		return "", err
+	}
+
+	if _, err := h.Write([]byte(conv)); err != nil {
+		return "", err
+	}
+
+	return hex.EncodeToString(h.Sum(nil)), nil
+}
+
+func newHash(algo string) (hash.Hash, error) {
+	switch algo {
+	case "md5":
+		return md5.New(), nil
+	case "sha1":
+		return sha1.New(), nil
+	case "sha256":
+		return sha256.New(), nil
+	case "sha384":
+		return sha512.New384(), nil
+	case "sha512":
+		return sha512.New(), nil
+	default:
+		return nil, fmt.Errorf("crypto.Hash: %q is not a supported hash algorithm", algo)
+	}
+}
+
 // HMAC returns a cryptographic hash that uses a key to sign a message.
 func (ns *Namespace) HMAC(h any, k any, m any, e ...any) (string, error) {
 	ha, err := cast.ToStringE(h)

tpl/crypto/crypto_integration_test.go

@@ -0,0 +1,46 @@
+// Copyright 2026 The Hugo Authors. All rights reserved.
+//
+// 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 crypto_test
+
+import (
+	"testing"
+
+	"github.com/gohugoio/hugo/hugolib"
+)
+
+// crypto.Hash combined with encoding.HexDecode and encoding.Base64Encode should
+// reproduce the SRI hash in .Data.Integrity on a fingerprinted resource.
+// See issue 15072.
+func TestHashIntegrity(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+-- layouts/home.html --
+{{ $content := "hello world" }}
+{{ range $algo := slice "sha256" "sha384" "sha512" }}
+{{ $integrity := $content | resources.FromString "data.txt" | fingerprint $algo }}
+{{ $composed := printf "%s-%s" $algo ($content | crypto.Hash $algo | encoding.HexDecode | encoding.Base64Encode) }}
+{{ $algo }}: {{ eq $integrity.Data.Integrity $composed }}
+{{ end }}
+`
+
+	b := hugolib.Test(t, files)
+
+	b.AssertFileContent("public/index.html",
+		"sha256: true",
+		"sha384: true",
+		"sha512: true",
+	)
+}

tpl/crypto/crypto_test.go

@@ -101,6 +101,42 @@ func TestSHA256(t *testing.T) {
 	}
 }
 
+func TestHash(t *testing.T) {
+	t.Parallel()
+	c := qt.New(t)
+	ns := New()
+
+	const in = "Hello world, gophers!"
+
+	for i, test := range []struct {
+		args   []any
+		expect any
+	}{
+		// Default algo is sha256, matching ns.SHA256.
+		{[]any{in}, "6ec43b78da9669f50e4e422575c54bf87536954ccd58280219c393f2ce352b46"},
+		{[]any{"md5", in}, "b3029f756f98f79e7f1b7f1d1f0dd53b"},
+		{[]any{"sha1", in}, "c8b5b0e33d408246e30f53e32b8f7627a7a649d4"},
+		{[]any{"sha256", in}, "6ec43b78da9669f50e4e422575c54bf87536954ccd58280219c393f2ce352b46"},
+		{[]any{"sha384", in}, "e914b060e06f1115fd98b494257d652403305b585c29a54636e7262b5e44adfc61f195f03d4192d89a006b28192fdd25"},
+		{[]any{"sha512", in}, "e2b74589547d8954a47321e19e2987ffce366317e3843be7da7eae3090a0eacb46393b52978933afa65c8bc365c329e55950b6106119a382a3b4f4cd5886ddcf"},
+		{[]any{"unsupported", in}, false},
+		{[]any{}, false},
+		{[]any{"sha256", in, "extra"}, false},
+	} {
+		errMsg := qt.Commentf("[%d] %v", i, test.args)
+
+		result, err := ns.Hash(test.args...)
+
+		if b, ok := test.expect.(bool); ok && !b {
+			c.Assert(err, qt.Not(qt.IsNil), errMsg)
+			continue
+		}
+
+		c.Assert(err, qt.IsNil, errMsg)
+		c.Assert(result, qt.Equals, test.expect, errMsg)
+	}
+}
+
 func TestHMAC(t *testing.T) {
 	t.Parallel()
 	c := qt.New(t)

tpl/crypto/init.go

@@ -1,4 +1,4 @@
-// Copyright 2017 The Hugo Authors. All rights reserved.
+// Copyright 2026 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -60,6 +60,16 @@ func init() {
 			},
 		)
 
+		ns.AddMethodMapping(ctx.Hash,
+			nil,
+			[][2]string{
+				{`{{ crypto.Hash "sha256" "Hello world, gophers!" }}`, `6ec43b78da9669f50e4e422575c54bf87536954ccd58280219c393f2ce352b46`},
+				{`{{ "Hello world" | crypto.Hash "sha256" }}`, `64ec88ca00b268e5ba1a35678a1b5316d212f4f366b2477232534a8aeca37f3c`},
+				{`{{ "Hello world" | crypto.Hash }}`, `64ec88ca00b268e5ba1a35678a1b5316d212f4f366b2477232534a8aeca37f3c`},
+				{`{{ "Hello world" | crypto.Hash "sha512" }}`, `b7f783baed8297f0db917462184ff4f08e69c2d5e5f79a942600f9725f58ce1f29c18139bf80b06c0fff2bdd34738452ecf40c488c22a7e3d80cdf6f9c1c0d47`},
+			},
+		)
+
 		return ns
 	}