Add a .sbat section to EFI binaries

The Secure Boot Advanced Targeting (SBAT) [0] is a Generation Number Based
Revocation mechanism that is meant to replace the DBX revocation file list.

Binaries must contain a .sbat data section that has a set entries, each of
them consisting of UTF-8 strings as comma separated values. Allow to embed
this information into the fwupd EFI binary at build time.

The SBAT metadata must contain at least two entries. One that defines the
SBAT version used and another one that defines the component generation.

This patch adds a sbat.csv that contains these two entries and downstream
users can override if additional entries are needed due changes that make
them diverge from upstream code and potentially add other vulnerabilities.

The same SBAT metadata is added to the fallback and MOK manager binaries
because these are built from the same shim source. These need to have SBAT
metadata as well to be booted if a .sbat section is mandatory.

[0]: https://github.com/rhboot/shim/blob/sbat/SBAT.md

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

9 files changed, 47 insertions, 9 deletions

diff --git a/Make.defaults b/Make.defaults
index 811db718..10e1ad52 100644
--- a/Make.defaults
+++ b/Make.defaults
@@ -22,6 +22,7 @@ DEBUGSOURCE	?= $(prefix)/src/debug/
 OSLABEL		?= $(EFIDIR)
 DEFAULT_LOADER	?= \\\\grub$(ARCH_SUFFIX).efi
 DASHJ		?= -j$(shell echo $$(($$(grep -c "^model name" /proc/cpuinfo) + 1)))
+SBATPATH	?= data/sbat.csv
 
 ARCH		?= $(shell $(CC) -dumpmachine | cut -f1 -d- | sed s,i[3456789]86,ia32,)
 OBJCOPY_GTE224	= $(shell expr `$(OBJCOPY) --version |grep ^"GNU objcopy" | sed 's/^.*\((.*)\|version\) //g' | cut -f1-2 -d.` \>= 2.24)
diff --git a/Makefile b/Makefile
index a17fa2be..63867f92 100644
--- a/Makefile
+++ b/Makefile
@@ -33,12 +33,12 @@ CFLAGS += -DENABLE_SHIM_CERT
 else
 TARGETS += $(MMNAME) $(FBNAME)
 endif
-OBJS	= shim.o mok.o netboot.o cert.o replacements.o tpm.o version.o errlog.o
+OBJS	= shim.o mok.o netboot.o cert.o replacements.o tpm.o version.o errlog.o sbat.o
 KEYS	= shim_cert.h ocsp.* ca.* shim.crt shim.csr shim.p12 shim.pem shim.key shim.cer
 ORIG_SOURCES	= shim.c mok.c netboot.c replacements.c tpm.c errlog.c shim.h version.h $(wildcard include/*.h)
-MOK_OBJS = MokManager.o PasswordCrypt.o crypt_blowfish.o errlog.o
+MOK_OBJS = MokManager.o PasswordCrypt.o crypt_blowfish.o errlog.o sbat.o
 ORIG_MOK_SOURCES = MokManager.c PasswordCrypt.c crypt_blowfish.c shim.h $(wildcard include/*.h)
-FALLBACK_OBJS = fallback.o tpm.o errlog.o
+FALLBACK_OBJS = fallback.o tpm.o errlog.o sbat.o
 ORIG_FALLBACK_SRCS = fallback.c
 
 ifneq ($(origin ENABLE_HTTPBOOT), undefined)
@@ -84,6 +84,10 @@ shim.o: $(wildcard $(TOPDIR)/*.h)
 cert.o : $(TOPDIR)/cert.S
 	$(CC) $(CFLAGS) -c -o $@ $<
 
+sbat.o : $(TOPDIR)/sbat.c
+	$(CC) $(CFLAGS) -c -o $@ $<
+	$(OBJCOPY) --add-section .sbat=$(SBATPATH) $@
+
 $(SHIMNAME) : $(SHIMSONAME)
 $(MMNAME) : $(MMSONAME)
 $(FBNAME) : $(FBSONAME)
@@ -192,8 +196,8 @@ endif
 	$(OBJCOPY) -D -j .text -j .sdata -j .data -j .data.ident \
 		-j .dynamic -j .dynsym -j .rel* \
 		-j .rela* -j .reloc -j .eh_frame \
-		-j .vendor_cert \
-		$(FORMAT) $^ $@
+		-j .vendor_cert -j .sbat \
+		$(FORMAT) $< $@
 	# I am tired of wasting my time fighting binutils timestamp code.
 	dd conv=notrunc bs=1 count=4 seek=$(TIMESTAMP_LOCATION) if=/dev/zero of=$@
 
@@ -208,11 +212,11 @@ ifneq ($(OBJCOPY_GTE224),1)
 endif
 	$(OBJCOPY) -D -j .text -j .sdata -j .data \
 		-j .dynamic -j .dynsym -j .rel* \
-		-j .rela* -j .reloc -j .eh_frame \
+		-j .rela* -j .reloc -j .eh_frame -j .sbat \
 		-j .debug_info -j .debug_abbrev -j .debug_aranges \
 		-j .debug_line -j .debug_str -j .debug_ranges \
 		-j .note.gnu.build-id \
-		$^ $@
+		$< $@
 
 ifneq ($(origin ENABLE_SBSIGN),undefined)
 %.efi.signed: %.efi shim.key shim.crt
diff --git a/data/sbat.csv b/data/sbat.csv
new file mode 100755
index 00000000..08a24590
--- /dev/null
+++ b/data/sbat.csv
@@ -0,0 +1,2 @@
+sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
+shim,0,UEFI shim,shim,0,https://github.com/rhboot/shim
diff --git a/elf_aarch64_efi.lds b/elf_aarch64_efi.lds
index 96f15d56..48ba8ba2 100644
--- a/elf_aarch64_efi.lds
+++ b/elf_aarch64_efi.lds
@@ -58,7 +58,12 @@ SECTIONS
     *(.vendor_cert)
   }
   . = ALIGN(4096);
-
+  .sbat :
+  {
+    _sbat = .;
+    *(.sbat)
+    _esbat = .;
+  }
   . = ALIGN(4096);
   .rela :
   {
diff --git a/elf_arm_efi.lds b/elf_arm_efi.lds
index b12424ed..7d699483 100644
--- a/elf_arm_efi.lds
+++ b/elf_arm_efi.lds
@@ -56,7 +56,12 @@ SECTIONS
     *(.vendor_cert)
   }
   . = ALIGN(4096);
-
+  .sbat :
+  {
+    _sbat = .;
+    *(.sbat)
+    _esbat = .;
+  }
   . = ALIGN(4096);
   .rel :
   {
diff --git a/elf_ia32_efi.lds b/elf_ia32_efi.lds
index deec2eca..043a3583 100644
--- a/elf_ia32_efi.lds
+++ b/elf_ia32_efi.lds
@@ -54,6 +54,13 @@ SECTIONS
    *(.vendor_cert)
   }
   . = ALIGN(4096);
+  .sbat :
+  {
+    _sbat = .;
+    *(.sbat)
+    _esbat = .;
+  }
+  . = ALIGN(4096);
   .dynamic  : { *(.dynamic) }
   . = ALIGN(4096);
   .rel :
diff --git a/elf_ia64_efi.lds b/elf_ia64_efi.lds
index e7d85e2b..ce2e34cb 100644
--- a/elf_ia64_efi.lds
+++ b/elf_ia64_efi.lds
@@ -56,6 +56,13 @@ SECTIONS
    *(.vendor_cert)
   }
   . = ALIGN(4096);
+  .sbat :
+  {
+    _sbat = .;
+    *(.sbat)
+    _esbat = .;
+  }
+  . = ALIGN(4096);
   .dynamic  : { *(.dynamic) }
   . = ALIGN(4096);
   .rela :
diff --git a/elf_x86_64_efi.lds b/elf_x86_64_efi.lds
index 1f561b25..3e1f1385 100644
--- a/elf_x86_64_efi.lds
+++ b/elf_x86_64_efi.lds
@@ -59,6 +59,13 @@ SECTIONS
    *(.vendor_cert)
   }
   . = ALIGN(4096);
+  .sbat :
+  {
+    _sbat = .;
+    *(.sbat)
+    _esbat = .;
+  }
+  . = ALIGN(4096);
   .dynamic  : { *(.dynamic) }
   . = ALIGN(4096);
   .rela :
diff --git a/sbat.c b/sbat.c
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/sbat.c