fix(build): honor provenance/sbom false in per-service bake attest

When a service set `build.provenance: false` (or `sbom: false`), the
bake attest entry was silently omitted (the field is `omitempty`),
so BuildKit applied its defaults and attached a provenance attestation
anyway. The attestation changes the manifest-list digest on every build,
which caused containers to be needlessly recreated on `up --build`.

Emit `"type=<t>,disabled=true"` instead, which BuildKit's
`Attest.UnmarshalText` parses as `Disabled:true` and forwards to
BuildKit as an explicit disable signal.

Extract `appendAttest` to avoid duplicating the three-branch switch
for both provenance and sbom.

Fixes #14111

Signed-off-by: Guillaume Lours <[email protected]>

pkg/compose/build_bake.go

@@ -599,25 +599,21 @@ func toBakeSecrets(project *types.Project, secrets []types.ServiceSecretConfig)
 
 func toBakeAttest(buildConfig types.BuildConfig) []string {
 	var attests []string
+	attests = appendAttest(attests, "provenance", buildConfig.Provenance)
+	attests = appendAttest(attests, "sbom", buildConfig.SBOM)
+	return attests
+}
 
-	// Handle per-service provenance configuration (only from build config, not global options)
-	if buildConfig.Provenance != "" {
-		if buildConfig.Provenance == "true" {
-			attests = append(attests, "type=provenance")
-		} else if buildConfig.Provenance != "false" {
-			attests = append(attests, fmt.Sprintf("type=provenance,%s", buildConfig.Provenance))
-		}
+func appendAttest(attests []string, attestType, value string) []string {
+	switch value {
+	case "":
+	case "true":
+		attests = append(attests, "type="+attestType)
+	case "false":
+		attests = append(attests, "type="+attestType+",disabled=true")
+	default:
+		attests = append(attests, fmt.Sprintf("type=%s,%s", attestType, value))
 	}
-
-	// Handle per-service SBOM configuration (only from build config, not global options)
-	if buildConfig.SBOM != "" {
-		if buildConfig.SBOM == "true" {
-			attests = append(attests, "type=sbom")
-		} else if buildConfig.SBOM != "false" {
-			attests = append(attests, fmt.Sprintf("type=sbom,%s", buildConfig.SBOM))
-		}
-	}
-
 	return attests
 }
 

pkg/compose/build_bake_test.go

@@ -51,6 +51,55 @@ func TestBakeTargetNames(t *testing.T) {
 	})
 }
 
+func TestToBakeAttest(t *testing.T) {
+	tests := []struct {
+		name     string
+		config   types.BuildConfig
+		expected []string
+	}{
+		{
+			name:     "empty — no attest entries",
+			config:   types.BuildConfig{},
+			expected: nil,
+		},
+		{
+			name:     "provenance true",
+			config:   types.BuildConfig{Provenance: "true"},
+			expected: []string{"type=provenance"},
+		},
+		{
+			name:     "provenance false — must disable, not omit",
+			config:   types.BuildConfig{Provenance: "false"},
+			expected: []string{"type=provenance,disabled=true"},
+		},
+		{
+			name:     "provenance mode=max",
+			config:   types.BuildConfig{Provenance: "mode=max"},
+			expected: []string{"type=provenance,mode=max"},
+		},
+		{
+			name:     "sbom true",
+			config:   types.BuildConfig{SBOM: "true"},
+			expected: []string{"type=sbom"},
+		},
+		{
+			name:     "sbom false — must disable, not omit",
+			config:   types.BuildConfig{SBOM: "false"},
+			expected: []string{"type=sbom,disabled=true"},
+		},
+		{
+			name:     "provenance false + sbom false",
+			config:   types.BuildConfig{Provenance: "false", SBOM: "false"},
+			expected: []string{"type=provenance,disabled=true", "type=sbom,disabled=true"},
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.DeepEqual(t, toBakeAttest(tc.config), tc.expected)
+		})
+	}
+}
+
 // makeConsole must hand the genuine *os.File over when the stream wraps one:
 // on Windows, containerd/console rejects anything but the exact
 // os.Stdin/Stdout/Stderr values, so a wrapper would disable the TTY progress