mkeficapsule: Add support for generating empty capsules

The Dependable Boot specification[1] describes the structure of the
firmware accept and revert capsules. These are empty capsules which
are used for signalling the acceptance or rejection of the updated
firmware by the OS. Add support for generating these empty capsules.

[1] - https://git.codelinaro.org/linaro/dependable-boot/mbfw/uploads/6f7ddfe3be24e18d4319e108a758d02e/mbfw.pdf

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@linaro.org>

doc/mkeficapsule.1

@@ -8,7 +8,7 @@ mkeficapsule \- Generate EFI capsule file for U-Boot
 
 .SH SYNOPSIS
 .B mkeficapsule
-.RI [ options "] " image-blob " " capsule-file
+.RI [ options ] " " [ image-blob ] " " capsule-file
 
 .SH "DESCRIPTION"
 .B mkeficapsule
@@ -23,8 +23,13 @@ Optionally, a capsule file can be signed with a given private key.
 In this case, the update will be authenticated by verifying the signature
 before applying.
 
+Additionally, an empty capsule file can be generated for acceptance or
+rejection of firmware images by a governing component like an Operating
+System. The empty capsules do not require an image-blob input file.
+
+
 .B mkeficapsule
-takes any type of image files, including:
+takes any type of image files when generating non empty capsules, including:
 .TP
 .I raw image
 format is a single binary blob of any type of firmware.
@@ -36,18 +41,16 @@ multiple binary blobs in a single capsule file.
 This type of image file can be generated by
 .BR mkimage .
 
-.PP
-If you want to use other types than above two, you should explicitly
-specify a guid for the FMP driver.
-
 .SH "OPTIONS"
+
 .TP
 .BI "-g\fR,\fB --guid " guid-string
 Specify guid for image blob type. The format is:
     xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
 
 The first three elements are in little endian, while the rest
-is in big endian.
+is in big endian. The option must be specified for all non empty and
+image acceptance capsules
 
 .TP
 .BI "-i\fR,\fB --index " index
@@ -57,6 +60,18 @@ Specify an image index
 .BI "-I\fR,\fB --instance " instance
 Specify a hardware instance
 
+.PP
+For generation of firmware accept empty capsule
+.BR --guid
+is mandatory
+.TP
+.BI "-A\fR,\fB --fw-accept "
+Generate a firmware acceptance empty capsule
+
+.TP
+.BI "-R\fR,\fB --fw-revert "
+Generate a firmware revert empty capsule
+
 .TP
 .BR -h ", " --help
 Print a help message

tools/eficapsule.h

@@ -41,6 +41,14 @@ typedef struct {
 	EFI_GUID(0x4aafd29d, 0x68df, 0x49ee, 0x8a, 0xa9, \
 		 0x34, 0x7d, 0x37, 0x56, 0x65, 0xa7)
 
+#define FW_ACCEPT_OS_GUID \
+	EFI_GUID(0x0c996046, 0xbcc0, 0x4d04, 0x85, 0xec, \
+		 0xe1, 0xfc, 0xed, 0xf1, 0xc6, 0xf8)
+
+#define FW_REVERT_OS_GUID \
+	EFI_GUID(0xacd58b4b, 0xc0e8, 0x475f, 0x99, 0xb5, \
+		 0x6b, 0x3f, 0x7e, 0x07, 0xaa, 0xf0)
+
 /* flags */
 #define CAPSULE_FLAGS_PERSIST_ACROSS_RESET      0x00010000
 

tools/mkeficapsule.c

@@ -29,7 +29,13 @@ static const char *tool_name = "mkeficapsule";
 efi_guid_t efi_guid_fm_capsule = EFI_FIRMWARE_MANAGEMENT_CAPSULE_ID_GUID;
 efi_guid_t efi_guid_cert_type_pkcs7 = EFI_CERT_TYPE_PKCS7_GUID;
 
-static const char *opts_short = "g:i:I:v:p:c:m:dh";
+static const char *opts_short = "g:i:I:v:p:c:m:dhAR";
+
+enum {
+	CAPSULE_NORMAL_BLOB = 0,
+	CAPSULE_ACCEPT,
+	CAPSULE_REVERT,
+} capsule_type;
 
 static struct option options[] = {
 	{"guid", required_argument, NULL, 'g'},
@@ -39,6 +45,8 @@ static struct option options[] = {
 	{"certificate", required_argument, NULL, 'c'},
 	{"monotonic-count", required_argument, NULL, 'm'},
 	{"dump-sig", no_argument, NULL, 'd'},
+	{"fw-accept", no_argument, NULL, 'A'},
+	{"fw-revert", no_argument, NULL, 'R'},
 	{"help", no_argument, NULL, 'h'},
 	{NULL, 0, NULL, 0},
 };
@@ -55,6 +63,8 @@ static void print_usage(void)
 		"\t-c, --certificate <cert file>     signer's certificate file\n"
 		"\t-m, --monotonic-count <count>     monotonic count\n"
 		"\t-d, --dump_sig              dump signature (*.p7)\n"
+		"\t-A, --fw-accept  firmware accept capsule, requires GUID, no image blob\n"
+		"\t-R, --fw-revert  firmware revert capsule, takes no GUID, no image blob\n"
 		"\t-h, --help                  print a help message\n",
 		tool_name);
 }
@@ -564,6 +574,49 @@ void convert_uuid_to_guid(unsigned char *buf)
 	buf[7] = c;
 }
 
+static int create_empty_capsule(char *path, efi_guid_t *guid, bool fw_accept)
+{
+	struct efi_capsule_header header = { 0 };
+	FILE *f = NULL;
+	int ret = -1;
+	efi_guid_t fw_accept_guid = FW_ACCEPT_OS_GUID;
+	efi_guid_t fw_revert_guid = FW_REVERT_OS_GUID;
+	efi_guid_t capsule_guid;
+
+	f = fopen(path, "w");
+	if (!f) {
+		fprintf(stderr, "cannot open %s\n", path);
+		goto err;
+	}
+
+	capsule_guid = fw_accept ? fw_accept_guid : fw_revert_guid;
+
+	memcpy(&header.capsule_guid, &capsule_guid, sizeof(efi_guid_t));
+	header.header_size = sizeof(header);
+	header.flags = 0;
+
+	header.capsule_image_size = fw_accept ?
+		sizeof(header) + sizeof(efi_guid_t) : sizeof(header);
+
+	if (write_capsule_file(f, &header, sizeof(header),
+			       "Capsule header"))
+		goto err;
+
+	if (fw_accept) {
+		if (write_capsule_file(f, guid, sizeof(*guid),
+				       "FW Accept Capsule Payload"))
+			goto err;
+	}
+
+	ret = 0;
+
+err:
+	if (f)
+		fclose(f);
+
+	return ret;
+}
+
 /**
  * main - main entry function of mkeficapsule
  * @argc:	Number of arguments
@@ -592,6 +645,7 @@ int main(int argc, char **argv)
 	privkey_file = NULL;
 	cert_file = NULL;
 	dump_sig = 0;
+	capsule_type = CAPSULE_NORMAL_BLOB;
 	for (;;) {
 		c = getopt_long(argc, argv, opts_short, options, &idx);
 		if (c == -1)
@@ -639,22 +693,50 @@ int main(int argc, char **argv)
 		case 'd':
 			dump_sig = 1;
 			break;
-		case 'h':
+		case 'A':
+			if (capsule_type) {
+				fprintf(stderr,
+					"Select either of Accept or Revert capsule generation\n");
+				exit(1);
+			}
+			capsule_type = CAPSULE_ACCEPT;
+			break;
+		case 'R':
+			if (capsule_type) {
+				fprintf(stderr,
+					"Select either of Accept or Revert capsule generation\n");
+				exit(1);
+			}
+			capsule_type = CAPSULE_REVERT;
+			break;
+		default:
 			print_usage();
 			exit(EXIT_SUCCESS);
 		}
 	}
 
 	/* check necessary parameters */
-	if ((argc != optind + 2) || !guid ||
+	if ((capsule_type == CAPSULE_NORMAL_BLOB &&
+	    ((argc != optind + 2) || !guid ||
 	     ((privkey_file && !cert_file) ||
-	     (!privkey_file && cert_file))) {
+	      (!privkey_file && cert_file)))) ||
+	    (capsule_type != CAPSULE_NORMAL_BLOB &&
+	    ((argc != optind + 1) ||
+	     ((capsule_type == CAPSULE_ACCEPT) && !guid) ||
+	     ((capsule_type == CAPSULE_REVERT) && guid)))) {
 		print_usage();
 		exit(EXIT_FAILURE);
 	}
 
-	if (create_fwbin(argv[argc - 1], argv[argc - 2], guid, index, instance,
+	if (capsule_type != CAPSULE_NORMAL_BLOB) {
-			 mcount, privkey_file, cert_file) < 0) {
+		if (create_empty_capsule(argv[argc - 1], guid,
+					 capsule_type == CAPSULE_ACCEPT) < 0) {
+			fprintf(stderr, "Creating empty capsule failed\n");
+			exit(EXIT_FAILURE);
+		}
+	} else 	if (create_fwbin(argv[argc - 1], argv[argc - 2], guid,
+				 index, instance, mcount, privkey_file,
+				 cert_file) < 0) {
 		fprintf(stderr, "Creating firmware capsule failed\n");
 		exit(EXIT_FAILURE);
 	}