firmware-utils: tplink-safeloader: refactor meta-partition generation

TP-Link safeloader firmware images contain a number of (small)
partitions with information about the device. These consist of:
* The data length as a 32-bit integer
* A 32-bit zero padding
* The partition data, with its length set in the first field

The OpenWrt factory image partitions that follow this structure are
soft-version, support-list, and extra-para. Refactor the code to put all
common logic into one allocation call, and let the rest of the data be
filled in by the original functions.

Due to the extra-para changes, this patch results in factory images that
change by 2 bytes (not counting the checksum) for three devices:
* ARCHER-A7-V5
* ARCHER-C7-V4
* ARCHER-C7-V5

These were the devices where the extra-para blob didn't match the common
format. The hardcoded data also didn't correspond to TP-Link's (recent)
upgrade images, which actually matches the meta-partition format.

A padding byte is also added to the extra-para partition for EAP245-V3.

Signed-off-by: Sander Vanheule <sander@svanheule.net>

2 files changed, 91 insertions, 84 deletions

diff --git a/tools/firmware-utils/Makefile b/tools/firmware-utils/Makefile
index 81c62d977a..9c9a0ba40f 100644
--- a/tools/firmware-utils/Makefile
+++ b/tools/firmware-utils/Makefile
@@ -7,7 +7,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME := firmware-utils
-PKG_RELEASE := 5
+PKG_RELEASE := 6
 
 include $(INCLUDE_DIR)/host-build.mk
 include $(INCLUDE_DIR)/kernel.mk
diff --git a/tools/firmware-utils/src/tplink-safeloader.c b/tools/firmware-utils/src/tplink-safeloader.c
index cb3cf69948..41b3b8aff9 100644
--- a/tools/firmware-utils/src/tplink-safeloader.c
+++ b/tools/firmware-utils/src/tplink-safeloader.c
@@ -83,10 +83,13 @@ struct device_info {
 	const char *last_sysupgrade_partition;
 };
 
+struct __attribute__((__packed__)) meta_header {
+	uint32_t length;
+	uint32_t zero;
+};
+
 /** The content of the soft-version structure */
 struct __attribute__((__packed__)) soft_version {
-	uint32_t data_len;
-	uint32_t zero;
 	uint8_t pad1;
 	uint8_t version_major;
 	uint8_t version_minor;
@@ -96,6 +99,7 @@ struct __attribute__((__packed__)) soft_version {
 	uint8_t month;
 	uint8_t day;
 	uint32_t rev;
+	uint32_t compat_level;
 };
 
 
@@ -2299,6 +2303,35 @@ static inline void put32(uint8_t *buf, uint32_t val) {
 	buf[3] = val;
 }
 
+/** Allocate a padded meta partition with a correctly initialised header
+ * If the `data` pointer is NULL, then the required space is only allocated,
+ * otherwise `data_len` bytes will be copied from `data` into the partition
+ * entry. */
+static struct image_partition_entry init_meta_partition_entry(
+	const char *name, const void *data, uint32_t data_len,
+	uint8_t pad_value)
+{
+	uint32_t total_len = sizeof(struct meta_header) + data_len + 1;
+	struct image_partition_entry entry = {
+		.name = name,
+		.size = total_len,
+		.data = malloc(total_len)
+	};
+	if (!entry.data)
+		error(1, errno, "failed to allocate meta partition entry");
+
+	struct meta_header *header = (struct meta_header *)entry.data;
+	header->length = htonl(data_len);
+	header->zero = 0;
+
+	if (data)
+		memcpy(entry.data+sizeof(*header), data, data_len);
+
+	entry.data[total_len - 1] = pad_value;
+
+	return entry;
+}
+
 /** Allocates a new image partition */
 static struct image_partition_entry alloc_image_partition(const char *name, size_t len) {
 	struct image_partition_entry entry = {name, len, malloc(len)};
@@ -2364,14 +2397,16 @@ static inline uint8_t bcd(uint8_t v) {
 
 
 /** Generates the soft-version partition */
-static struct image_partition_entry make_soft_version(struct device_info *info, uint32_t rev) {
-	size_t part_len = sizeof(struct soft_version);
-	if (info->soft_ver_compat_level > 0)
-		part_len += sizeof(uint32_t);
-
-	struct image_partition_entry entry =
-	    alloc_image_partition("soft-version", part_len+1);
-	struct soft_version *s = (struct soft_version *)entry.data;
+static struct image_partition_entry make_soft_version(
+	const struct device_info *info, uint32_t rev)
+{
+	/** If an info string is provided, use this instead of
+	 * the structured data, and include the null-termination */
+	if (info->soft_ver) {
+		uint32_t len = strlen(info->soft_ver) + 1;
+		return init_meta_partition_entry("soft-version",
+			info->soft_ver, len, 0);
+	}
 
 	time_t t;
 
@@ -2382,58 +2417,43 @@ static struct image_partition_entry make_soft_version(struct device_info *info,
 
 	struct tm *tm = gmtime(&t);
 
-	/* Partition contents size, minus 8 byte header and trailing byte */
-	s->data_len = htonl(entry.size-9);
-	s->zero = 0;
-	s->pad1 = 0xff;
-
-	s->version_major = 0;
-	s->version_minor = 0;
-	s->version_patch = 0;
-
-	s->year_hi = bcd((1900+tm->tm_year)/100);
-	s->year_lo = bcd(tm->tm_year%100);
-	s->month = bcd(tm->tm_mon+1);
-	s->day = bcd(tm->tm_mday);
-	s->rev = htonl(rev);
+	struct soft_version s = {
+		.pad1 = 0xff,
 
-	if (info->soft_ver_compat_level > 0)
-		*(uint32_t *)(entry.data + sizeof(struct soft_version)) =
-		    htonl(info->soft_ver_compat_level);
+		.version_major = 0,
+		.version_minor = 0,
+		.version_patch = 0,
 
-	entry.data[entry.size-1] = 0xff;
+		.year_hi = bcd((1900+tm->tm_year)/100),
+		.year_lo = bcd(tm->tm_year%100),
+		.month = bcd(tm->tm_mon+1),
+		.day = bcd(tm->tm_mday),
 
-	return entry;
-}
+		.compat_level = htonl(info->soft_ver_compat_level)
+	};
 
-static struct image_partition_entry make_soft_version_from_string(const char *soft_ver) {
-	/** String length _including_ the terminating zero byte */
-	uint32_t ver_len = strlen(soft_ver) + 1;
-	/** Partition contains 64 bit header, the version string, and one additional null byte */
-	size_t partition_len = 2*sizeof(uint32_t) + ver_len + 1;
-	struct image_partition_entry entry = alloc_image_partition("soft-version", partition_len);
-
-	uint32_t *len = (uint32_t *)entry.data;
-	len[0] = htonl(ver_len);
-	len[1] = 0;
-	memcpy(&len[2], soft_ver, ver_len);
-
-	entry.data[partition_len - 1] = 0;
-
-	return entry;
+	if (info->soft_ver_compat_level == 0)
+		return init_meta_partition_entry("soft-version", &s,
+			(uint8_t *)(&s.compat_level) - (uint8_t *)(&s), 0xff);
+	else
+		return init_meta_partition_entry("soft-version", &s,
+			sizeof(s), 0xff);
 }
 
 /** Generates the support-list partition */
-static struct image_partition_entry make_support_list(struct device_info *info) {
-	size_t len = strlen(info->support_list);
-	struct image_partition_entry entry = alloc_image_partition("support-list", len + 9);
-
-	put32(entry.data, len);
-	memset(entry.data+4, 0, 4);
-	memcpy(entry.data+8, info->support_list, len);
-	entry.data[len+8] = info->support_trail;
+static struct image_partition_entry make_support_list(
+	const struct device_info *info)
+{
+	uint32_t len = strlen(info->support_list);
+	return init_meta_partition_entry("support-list", info->support_list,
+		len, info->support_trail);
+}
 
-	return entry;
+/** Partition with extra-para data */
+static struct image_partition_entry make_extra_para(
+	const struct device_info *info, const uint8_t *extra_para, size_t len)
+{
+	return init_meta_partition_entry("extra-para", extra_para, len, 0x00);
 }
 
 /** Creates a new image partition with an arbitrary name from a file */
@@ -2473,16 +2493,6 @@ static struct image_partition_entry read_file(const char *part_name, const char
 	return entry;
 }
 
-/** Creates a new image partition from arbitrary data */
-static struct image_partition_entry put_data(const char *part_name, const char *datain, size_t len) {
-
-	struct image_partition_entry entry = alloc_image_partition(part_name, len);
-
-	memcpy(entry.data, datain, len);
-
-	return entry;
-}
-
 /**
    Copies a list of image partitions into an image buffer and generates the image partition table while doing so
 
@@ -2710,36 +2720,33 @@ static void build_image(const char *output,
 	}
 
 	parts[0] = make_partition_table(info->partitions);
-	if (info->soft_ver)
-		parts[1] = make_soft_version_from_string(info->soft_ver);
-	else
-		parts[1] = make_soft_version(info, rev);
-
+	parts[1] = make_soft_version(info, rev);
 	parts[2] = make_support_list(info);
 	parts[3] = read_file("os-image", kernel_image, false, NULL);
 	parts[4] = read_file("file-system", rootfs_image, add_jffs2_eof, file_system_partition);
 
 	/* Some devices need the extra-para partition to accept the firmware */
-	if (strcasecmp(info->id, "ARCHER-C2-V3") == 0 ||
+	if (strcasecmp(info->id, "ARCHER-A7-V5") == 0 ||
+	    strcasecmp(info->id, "ARCHER-C2-V3") == 0 ||
+	    strcasecmp(info->id, "ARCHER-C7-V4") == 0 ||
+	    strcasecmp(info->id, "ARCHER-C7-V5") == 0 ||
 	    strcasecmp(info->id, "ARCHER-C25-V1") == 0 ||
 	    strcasecmp(info->id, "ARCHER-C59-V2") == 0 ||
 	    strcasecmp(info->id, "ARCHER-C60-V2") == 0 ||
 	    strcasecmp(info->id, "ARCHER-C60-V3") == 0 ||
 	    strcasecmp(info->id, "TLWR1043NV5") == 0) {
-		const char mdat[11] = {0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00};
-		parts[5] = put_data("extra-para", mdat, 11);
-	} else if (strcasecmp(info->id, "ARCHER-A7-V5") == 0 || strcasecmp(info->id, "ARCHER-C7-V4") == 0 || strcasecmp(info->id, "ARCHER-C7-V5") == 0) {
-		const char mdat[11] = {0x01, 0x00, 0x00, 0x02, 0x00, 0x00, 0xca, 0x00, 0x01, 0x00, 0x00};
-		parts[5] = put_data("extra-para", mdat, 11);
+		const uint8_t extra_para[2] = {0x01, 0x00};
+		parts[5] = make_extra_para(info, extra_para,
+			sizeof(extra_para));
 	} else if (strcasecmp(info->id, "ARCHER-C6-V2") == 0) {
-		const char mdat[11] = {0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00};
-		parts[5] = put_data("extra-para", mdat, 11);
-	} else if (strcasecmp(info->id, "ARCHER-C6-V2-US") == 0) {
-		const char mdat[11] = {0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x00};
-		parts[5] = put_data("extra-para", mdat, 11);
-	} else if (strcasecmp(info->id, "EAP245-V3") == 0) {
-		const char mdat[10] = {0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01};
-		parts[5] = put_data("extra-para", mdat, 10);
+		const uint8_t extra_para[2] = {0x00, 0x01};
+		parts[5] = make_extra_para(info, extra_para,
+			sizeof(extra_para));
+	} else if (strcasecmp(info->id, "ARCHER-C6-V2-US") == 0 ||
+		   strcasecmp(info->id, "EAP245-V3") == 0) {
+		const uint8_t extra_para[2] = {0x01, 0x01};
+		parts[5] = make_extra_para(info, extra_para,
+			sizeof(extra_para));
 	}
 
 	size_t len;