efi: Disable secure boot if shim is in insecure mode

A user can manually tell the shim boot loader to disable validation of
images it loads.  When a user does this, it creates a UEFI variable called
MokSBState that does not have the runtime attribute set.  Given that the
user explicitly disabled validation, we can honor that and not enable
secure boot mode if that variable is set.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Gbp-Pq: Topic features/all/securelevel
Gbp-Pq: Name efi-disable-secure-boot-if-shim-is-in-insecure-mode.patch

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 2f80a7cae373fc13d296da9aaa76094fea5857f4..d0abbf674bec19994c4b8a2122d1834164780ca8 100644 (file)
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -747,8 +747,9 @@ void setup_graphics(struct boot_params *boot_params)
 
 static int get_secure_boot(void)
 {
-       u8 sb, setup;
+       u8 sb, setup, moksbstate;
        unsigned long datasize = sizeof(sb);
+       u32 attr;
        efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
        efi_status_t status;
 
@@ -772,6 +773,23 @@ static int get_secure_boot(void)
        if (setup == 1)
                return 0;
 
+       /* See if a user has put shim into insecure_mode.  If so, and the variable
+        * doesn't have the runtime attribute set, we might as well honor that.
+        */
+       var_guid = EFI_SHIM_LOCK_GUID;
+       status = efi_early->call((unsigned long)sys_table->runtime->get_variable,
+                               L"MokSBState", &var_guid, &attr, &datasize,
+                               &moksbstate);
+
+       /* If it fails, we don't care why.  Default to secure */
+       if (status != EFI_SUCCESS)
+               return 1;
+
+       if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS)) {
+               if (moksbstate == 1)
+                       return 0;
+       }
+
        return 1;
 }
 

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 0148a3046b4864733200d76a3a45ff26e38c1523..7c299443c71dc75f8ef5150e4efd37dbe8db3465 100644 (file)
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -628,6 +628,9 @@ typedef struct {
 #define EFI_1_10_SYSTEM_TABLE_REVISION  ((1 << 16) | (10))
 #define EFI_1_02_SYSTEM_TABLE_REVISION  ((1 << 16) | (02))
 
+#define EFI_SHIM_LOCK_GUID \
+    EFI_GUID(  0x605dab50, 0xe046, 0x4300, 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23 )
+
 typedef struct {
        efi_table_hdr_t hdr;
        u64 fw_vendor;  /* physical addr of CHAR16 vendor string */