sbkeysync: read & print signature databases

Add some initial code to parse the EFI signature databases.

Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>

2 files changed, 403 insertions, 1 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index da7a6b9..19a7766 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,5 +1,5 @@
 
-bin_PROGRAMS = sbsign sbverify sbattach sbvarsign sbsiglist
+bin_PROGRAMS = sbsign sbverify sbattach sbvarsign sbsiglist sbkeysync
 
 coff_headers = coff/external.h coff/pe.h
 AM_CFLAGS = -Wall -Wextra --std=gnu99
@@ -30,3 +30,8 @@ sbsiglist_SOURCES = sbsiglist.c $(common_SOURCES)
 sbsiglist_LDADD = $(common_LDADD) $(uuid_LIBS)
 sbsiglist_CPPFLAGS = $(EFI_CPPFLAGS)
 sbsiglist_CFLAGS = $(AM_CFLAGS) $(common_CFLAGS)
+
+sbkeysync_SOURCES = sbkeysync.c $(common_SOURCES)
+sbkeysync_LDADD = $(common_LDADD) $(uuid_LIBS)
+sbkeysync_CPPFLAGS = $(EFI_CPPFLAGS)
+sbkeysync_CFLAGS = $(AM_CFLAGS) $(common_CFLAGS)
diff --git a/src/sbkeysync.c b/src/sbkeysync.c
new file mode 100644
index 0000000..2e2595e
--- /dev/null
+++ b/src/sbkeysync.c
@@ -0,0 +1,397 @@
+/*
+ * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 3
+ * of the License, or (at your option) any later version.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+ * USA.
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the OpenSSL
+ * library under certain conditions as described in each individual source file,
+ * and distribute linked combinations including the two.
+ *
+ * You must obey the GNU General Public License in all respects for all
+ * of the code used other than OpenSSL. If you modify file(s) with this
+ * exception, you may extend this exception to your version of the
+ * file(s), but you are not obligated to do so. If you do not wish to do
+ * so, delete this exception statement from your version. If you delete
+ * this exception statement from all source files in the program, then
+ * also delete it here.
+ */
+#define _GNU_SOURCE
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/statfs.h>
+
+#include <getopt.h>
+
+#include <efi.h>
+
+#include <ccan/list/list.h>
+#include <ccan/array_size/array_size.h>
+#include <ccan/talloc/talloc.h>
+
+#include "fileio.h"
+#include "efivars.h"
+
+#define EFIVARS_MOUNTPOINT	"/sys/firmware/efi/vars"
+#define EFIVARS_FSTYPE		0x6165676C
+
+#define EFI_IMAGE_SECURITY_DATABASE_GUID \
+	{ 0xd719b2cb, 0x3d3a, 0x4596, \
+	{ 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f } }
+
+static const char *efivars_mountpoint = EFIVARS_MOUNTPOINT;
+static const char *toolname = "sbkeysync";
+
+enum sigdb_type {
+	SIGDB_KEK,
+	SIGDB_DB,
+	SIGDB_DBX,
+};
+
+struct efi_sigdb_desc {
+	enum sigdb_type	type;
+	const char	*name;
+	EFI_GUID	guid;
+};
+
+struct efi_sigdb_desc efi_sigdb_descs[] = {
+	{ SIGDB_KEK, "KEK", EFI_GLOBAL_VARIABLE },
+	{ SIGDB_DB,  "db",  EFI_IMAGE_SECURITY_DATABASE_GUID },
+	{ SIGDB_DBX, "dbx", EFI_IMAGE_SECURITY_DATABASE_GUID },
+};
+
+#if 0
+static const char *keystores[] = {
+	"/usr/share/secureboot/keys",
+	"/etc/secureboot/keys",
+};
+#endif
+
+typedef int (*key_id_func)(void *, EFI_SIGNATURE_DATA *, size_t,
+				uint8_t **, int *);
+
+struct cert_type {
+	EFI_GUID	guid;
+	key_id_func	get_id;
+};
+
+struct key {
+	EFI_GUID		type;
+	int			id_len;
+	uint8_t			*id;
+
+	size_t			len;
+	uint8_t			*data;
+
+	struct list_node	list;
+};
+
+struct key_database {
+	const char		*name;
+	struct list_head	keys;
+};
+
+struct sync_context {
+	struct key_database	*kek;
+	struct key_database	*db;
+	struct key_database	*dbx;
+};
+
+#define GUID_STRLEN (8 + 1 + 4 + 1 + 4 + 1 + 4 + 1 + 12 + 1)
+static void guid_to_str(const EFI_GUID *guid, char *str)
+{
+	snprintf(str, GUID_STRLEN,
+		"%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
+			guid->Data1, guid->Data2, guid->Data3,
+			guid->Data4[0], guid->Data4[1],
+			guid->Data4[2], guid->Data4[3],
+			guid->Data4[4], guid->Data4[5],
+			guid->Data4[6], guid->Data4[7]);
+}
+
+static int sha256_key_id(void *ctx, EFI_SIGNATURE_DATA *sigdata,
+		size_t sigdata_datalen, uint8_t **buf, int *len)
+{
+	const unsigned int sha256_id_size = 256 / 8;
+	uint8_t *id;
+
+	if (sigdata_datalen != sha256_id_size)
+		return -1;
+
+	id = talloc_array(ctx, uint8_t, sha256_id_size);
+	memcpy(sigdata->SignatureData, buf, sha256_id_size);
+
+	*buf = id;
+	*len = sha256_id_size;
+
+	return 0;
+}
+
+struct cert_type cert_types[] = {
+	{ EFI_CERT_SHA256_GUID, sha256_key_id },
+};
+
+static int guidcmp(const EFI_GUID *a, const EFI_GUID *b)
+{
+	return memcmp(a, b, sizeof(EFI_GUID));
+}
+
+static int key_id(void *ctx, const EFI_GUID *type, EFI_SIGNATURE_DATA *sigdata,
+		size_t sigdata_datalen, uint8_t **buf, int *len)
+{
+	char guid_str[GUID_STRLEN];
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(cert_types); i++) {
+		if (guidcmp(&cert_types[i].guid, type))
+			continue;
+
+		return cert_types[i].get_id(ctx, sigdata, sigdata_datalen,
+				buf, len);
+	}
+
+	guid_to_str(type, guid_str);
+	printf("warning: unknown signature type found:\n  %s\n",
+			guid_str);
+	return -1;
+
+}
+
+struct efi_sigdb_desc *efi_sigdb_desc_lookup(enum sigdb_type type)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(efi_sigdb_descs); i++)
+		if (efi_sigdb_descs[i].type == type)
+			return &efi_sigdb_descs[i];
+
+	abort();
+}
+
+typedef int (*sigdata_fn)(EFI_SIGNATURE_DATA *, int, const EFI_GUID *, void *);
+
+static int sigdb_iterate(void *db_data, size_t len,
+		sigdata_fn fn, void *arg)
+{
+	EFI_SIGNATURE_LIST *siglist;
+	EFI_SIGNATURE_DATA *sigdata;
+	unsigned int i, j;
+	int rc = 0;
+
+	if (len == 0)
+		return 0;
+
+	if (len < sizeof(*siglist))
+		return -1;
+
+	for (i = 0, siglist = db_data + i;
+			i + sizeof(*siglist) <= len &&
+			i + siglist->SignatureListSize > i &&
+			i + siglist->SignatureListSize <= len && !rc;
+			siglist = db_data + i,
+			i += siglist->SignatureListSize) {
+
+		/* ensure that the header & sig sizes are sensible */
+		if (siglist->SignatureHeaderSize > siglist->SignatureListSize)
+			continue;
+
+		if (siglist->SignatureSize > siglist->SignatureListSize)
+			continue;
+
+		if (siglist->SignatureSize < sizeof(*sigdata))
+			continue;
+
+		/* iterate through the (constant-sized) signature data blocks */
+		for (j = sizeof(*siglist) + siglist->SignatureHeaderSize;
+				j < siglist->SignatureListSize && !rc;
+				j += siglist->SignatureSize)
+		{
+			sigdata = (void *)(siglist) + j;
+
+			rc = fn(sigdata, siglist->SignatureSize,
+					&siglist->SignatureType, arg);
+
+		}
+
+	}
+
+	return rc;
+}
+
+static int sigdb_add_key(EFI_SIGNATURE_DATA *sigdata, int len,
+		const EFI_GUID *type, void *arg)
+{
+	struct key_database *kdb = arg;
+	struct key *key;
+	int rc;
+
+	key = talloc(kdb, struct key);
+
+	rc = key_id(kdb, type, sigdata, len - sizeof(sigdata), &key->id,
+			&key->id_len);
+
+	if (rc)
+		talloc_free(key);
+	else
+		list_add(&kdb->keys, &key->list);
+
+	return 0;
+}
+
+
+static int read_efivars_key_database(struct sync_context *ctx,
+		enum sigdb_type type, struct key_database *kdb)
+{
+	struct efi_sigdb_desc *desc;
+	char guid_str[GUID_STRLEN];
+	char *filename;
+	uint8_t *buf;
+	size_t len;
+
+	desc = efi_sigdb_desc_lookup(type);
+
+	guid_to_str(&desc->guid, guid_str);
+
+	filename = talloc_asprintf(ctx, "%s/%s-%s", efivars_mountpoint,
+					desc->name, guid_str);
+
+	if (fileio_read_file_noerror(ctx, filename, &buf, &len))
+		return -1;
+
+	/* efivars files start with a 32-bit attribute block */
+	buf += sizeof(uint32_t);
+	len -= sizeof(uint32_t);
+
+	sigdb_iterate(buf, len, sigdb_add_key, kdb);
+
+	return 0;
+}
+
+static void print_key_database(struct key_database *kdb)
+{
+	struct key *key;
+
+	printf("kdb %s\n", kdb->name);
+
+	list_for_each(&kdb->keys, key, list)
+		printf("  id: %p, %d bytes\n", key->id,  key->id_len);
+}
+
+static int read_key_databases(struct sync_context *ctx)
+{
+	struct efi_sigdb_desc *desc;
+	unsigned int i;
+	int rc;
+	struct {
+		enum sigdb_type type;
+		struct key_database **kdb;
+	} databases[] = {
+		{ SIGDB_KEK, &ctx->kek },
+		{ SIGDB_DB,  &ctx->db },
+		{ SIGDB_DBX, &ctx->dbx },
+	};
+
+	for (i = 0; i < ARRAY_SIZE(databases); i++) {
+		struct key_database *kdb;
+
+		desc = efi_sigdb_desc_lookup(databases[i].type);
+
+		kdb = talloc(ctx, struct key_database);
+		kdb->name = desc->name;
+		list_head_init(&kdb->keys);
+
+		rc = read_efivars_key_database(ctx, databases[i].type, kdb);
+
+		if (!rc)
+			print_key_database(kdb);
+
+		*databases[i].kdb = kdb;
+	}
+
+	return 0;
+}
+
+static int check_efivars_mount(void)
+{
+	struct statfs statbuf;
+	int rc;
+
+	rc = statfs(efivars_mountpoint, &statbuf);
+	if (rc)
+		return -1;
+
+	if (statbuf.f_type != EFIVARS_FSTYPE)
+		return -1;
+
+	return 0;
+}
+
+static struct option options[] = {
+	{ "help", no_argument, NULL, 'h' },
+	{ "version", no_argument, NULL, 'V' },
+	{ NULL, 0, NULL, 0 },
+};
+
+static void usage(void)
+{
+	printf("Usage: %s [options]\n"
+		"Update EFI key databases from the filesystem\n",
+		toolname);
+}
+
+static void version(void)
+{
+	printf("%s %s\n", toolname, VERSION);
+}
+
+int main(int argc, char **argv)
+{
+	struct sync_context *ctx;
+
+	for (;;) {
+		int idx, c;
+		c = getopt_long(argc, argv, "a:d:rhV", options, &idx);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'V':
+			version();
+			return EXIT_SUCCESS;
+		case 'h':
+			usage();
+			return EXIT_SUCCESS;
+		}
+	}
+
+	if (argc != optind) {
+		usage();
+		return EXIT_FAILURE;
+	}
+
+	if (check_efivars_mount()) {
+		fprintf(stderr, "Can't access efivars filesystem, aborting\n");
+		return EXIT_FAILURE;
+	}
+
+	ctx = talloc(NULL, struct sync_context);
+
+	read_key_databases(ctx);
+
+	return EXIT_SUCCESS;
+}