efi: add tests for grubImageHandle.Prefix

efi/grub.go

@@ -56,9 +56,12 @@ type grubModule struct {
 	*io.SectionReader
 }
 
+// grubImageHandle corresponds to a grub image.
 type grubImageHandle interface {
 	peImageHandle
 
+	// Prefix returns the path that grub uses to load its configuration
+	// from the ESP.
 	Prefix() (string, error)
 }
 

efi/grub_test.go

@@ -0,0 +1,66 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2023 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package efi_test
+
+import (
+	. "gopkg.in/check.v1"
+
+	. "github.com/snapcore/secboot/efi"
+)
+
+type grubSuite struct{}
+
+var _ = Suite(&grubSuite{})
+
+func (s *grubSuite) TestGrubImageHandlePrefix1(c *C) {
+	image, err := OpenPeImage(NewFileImage("testdata/amd64/mockgrub.efi"))
+	c.Assert(err, IsNil)
+	defer image.Close()
+
+	grubImage := NewGrubImageHandle(image)
+
+	prefix, err := grubImage.Prefix()
+	c.Check(err, IsNil)
+	c.Check(prefix, Equals, "/EFI/ubuntu")
+}
+
+func (s *grubSuite) TestGrubImageHandlePrefix2(c *C) {
+	image, err := OpenPeImage(NewFileImage("testdata/amd64/mockgrub_debian.efi"))
+	c.Assert(err, IsNil)
+	defer image.Close()
+
+	grubImage := NewGrubImageHandle(image)
+
+	prefix, err := grubImage.Prefix()
+	c.Check(err, IsNil)
+	c.Check(prefix, Equals, "/EFI/debian")
+}
+
+func (s *grubSuite) TestGrubImageHandlePrefixNone(c *C) {
+	image, err := OpenPeImage(NewFileImage("testdata/amd64/mockgrub_no_prefix.efi"))
+	c.Assert(err, IsNil)
+	defer image.Close()
+
+	grubImage := NewGrubImageHandle(image)
+
+	prefix, err := grubImage.Prefix()
+	c.Check(err, IsNil)
+	c.Check(prefix, Equals, "")
+}

efi/pe_test.go

@@ -127,7 +127,7 @@ func (s *peSuite) TestPeImageHandleSbatComponents1(c *C) {
 
 func (s *peSuite) TestPeImageHandleSbatComponents2(c *C) {
 	s.testPeImageHandleSbatComponents(
-		c, "testdata/amd64/mockgrub1.efi.signed.shim.1",
+		c, "testdata/amd64/mockgrub.efi",
 		[]SbatComponent{
 			{Name: "grub", Generation: 1, VendorName: "Free Software Foundation", VendorPackageName: "grub", VendorVersion: "2.06", VendorUrl: "https://www.gnu.org/software/grub/"},
 			{Name: "grub.acme", Generation: 1, VendorName: "Acme Corporation", VendorPackageName: "grub", VendorVersion: "1", VendorUrl: "https://acme.invalid/grub"},
@@ -158,7 +158,7 @@ func (s *peSuite) TestPeImageHandleImageDigest1(c *C) {
 }
 
 func (s *peSuite) TestPeImageHandleImageDigest2(c *C) {
-	s.testPeImageHandleImageDigest(c, "testdata/amd64/mockgrub1.efi.signed.shim.1", crypto.SHA256)
+	s.testPeImageHandleImageDigest(c, "testdata/amd64/mockgrub.efi", crypto.SHA256)
 }
 
 func (s *peSuite) TestPeImageHandleImageDigestSHA1(c *C) {

efi/testdata/src/grub/Makefile

@@ -13,14 +13,17 @@ NAME		?= mock
 SBAT_CSV	?= $(TOPDIR)/sbat.csv
 
 CPPFLAGS += -DNAME=\"$(NAME)\"
+ifneq ($(origin GRUB_PREFIX), undefined)
+	CPPFLAGS += -DGRUB_PREFIX=\"$(GRUB_PREFIX)\"
+endif
 
 sbat_data.o: $(SBAT_CSV)
 	$(CC) $(CFLAGS) -x c -c -o $@ /dev/null
 	objcopy --add-section .sbat=$< \
 		--set-section-flags .sbat=contents,alloc,load,readonly,data \
 		$@
 
-OBJS    = main_$(ARCH).o data.o
+OBJS    = main_$(ARCH).o data.o mods.o
 ifneq ($(origin WITH_SBAT), undefined)
 	OBJS += sbat_data.o
 endif
@@ -32,4 +35,4 @@ $(NAME).so: $(OBJS)
 	$(LD) $(LDFLAGS) $(OBJS) -o $@
 
 %.efi: %.so
-	$(OBJCOPY) -j .text -j .data -j .reloc -j .sbat --target=efi-app-$(ARCH) $^ $@
+	$(OBJCOPY) -j .text -j .data -j .reloc -j .sbat -jmods --target=efi-app-$(ARCH) $^ $@

efi/testdata/src/grub/mods.S

@@ -0,0 +1,17 @@
+	.section mods, "a", %progbits
+	.balignl 8, 0
+.Lgrub_module_info:
+	.4byte 0x676d696d
+	.balignl 8, 0
+	.8byte .Lgrub_modules_start - .Lgrub_module_info
+	.8byte .Lgrub_modules_end - .Lgrub_module_info
+.Lgrub_modules_start:
+#ifdef GRUB_PREFIX
+.Lgrub_prefix_start:
+	.4byte 3
+	.4byte .Lgrub_prefix_end - .Lgrub_prefix_start
+	.ascii GRUB_PREFIX
+	.byte 0
+.Lgrub_prefix_end:
+#endif
+.Lgrub_modules_end:

tools/make-efi-testdata/apps.go

@@ -108,13 +108,29 @@ func newMockAppData(srcDir, vendorCertDir string, certs map[string][]byte) []moc
 			signCerts: [][]byte{certs["TestUefiSigning1.1.1"]},
 			filename:  "mockshim_no_sbat.efi.signed.1.1.1",
 		},
+		{
+			path: filepath.Join(srcDir, "grub"),
+			name: "mockgrub",
+			makeExtraArgs: []string{
+				"GRUB_PREFIX=/EFI/ubuntu",
+				"WITH_SBAT=1",
+			},
+			filename: "mockgrub.efi",
+		},
+		{
+			path: filepath.Join(srcDir, "grub"),
+			name: "mockgrub_debian",
+			makeExtraArgs: []string{
+				"GRUB_PREFIX=/EFI/debian",
+				"WITH_SBAT=1",
+			},
+			filename: "mockgrub_debian.efi",
+		},
 		{
 			path:          filepath.Join(srcDir, "grub"),
-			name:          "mockgrub1",
+			name:          "mockgrub_no_prefix",
 			makeExtraArgs: []string{"WITH_SBAT=1"},
-			signKeys:      []string{filepath.Join(srcDir, "keys", "TestShimVendorSigning.1.key")},
-			signCerts:     [][]byte{certs["TestShimVendorSigning.1"]},
-			filename:      "mockgrub1.efi.signed.shim.1",
+			filename:      "mockgrub_no_prefix.efi",
 		},
 		{
 			path:     filepath.Join(srcDir, "kernel"),