[PATCH RFC u-boot-mvebu 44/59] tools: kwbimage: Fix invalid secure boot header signature

Pali Rohár
2023-02-21T20:36:15Z

Secure boot header signature is calculated from the image header with
zeroed header checksum. Calculation is done in add_secure_header_v1()
function. So after calling this function no header member except
main_hdr->checksum can be modified. Commit 2b0980c24027 ("tools: kwbimage:
Fill the real header size into the main header") broke this requirement as
final header size started to be filled into main_hdr->headersz_* members
after the add_secure_header_v1() call.

Fix this issue by following steps:
- Split header size and image data offset into two variables (headersz and
*dataoff).
- Change image_headersz_v0() and add_binary_header_v1() functions to return
real (unaligned) header size instead of image data offset.
- On every place use correct variable (headersz or *dataoff)

After these steps variable headersz is correctly filled into the
main_hdr->headersz_* members and so overwriting them in the end of the
image_create_v1() function is not needed anymore. Remove those overwriting
which effectively reverts changes in problematic commit without affecting
value in main_hdr->headersz_* members and makes secure boot header
signature valid again.

Fixes: 2b0980c24027 ("tools: kwbimage: Fill the real header size into the main header")
Signed-off-by: Pali Rohár <pali@kernel.org>
---
tools/kwbimage.c | 41 ++++++++++++++---------------------------
1 file changed, 14 insertions(+), 27 deletions(-)

diff --git a/tools/kwbimage.c b/tools/kwbimage.c
index a8a59c154b9c..da539541742d 100644
--- a/tools/kwbimage.c
+++ b/tools/kwbimage.c
@@ -959,7 +959,7 @@ static size_t image_headersz_v0(int *hasext)
*hasext = 1;
}

- return image_headersz_align(headersz, image_get_bootfrom());
+ return headersz;
}

static void *image_create_v0(size_t *dataoff, struct image_tool_params *params,
@@ -972,10 +972,11 @@ static void *image_create_v0(size_t *dataoff, struct image_tool_params *params,
int has_ext = 0;

/*
- * Calculate the size of the header and the size of the
+ * Calculate the size of the header and the offset of the
* payload
*/
headersz = image_headersz_v0(&has_ext);
+ *dataoff = image_headersz_align(headersz, image_get_bootfrom());

image = malloc(headersz);
if (!image) {
@@ -990,7 +991,7 @@ static void *image_create_v0(size_t *dataoff, struct image_tool_params *params,
/* Fill in the main header */
main_hdr->blocksize =
cpu_to_le32(payloadsz);
- main_hdr->srcaddr = cpu_to_le32(headersz);
+ main_hdr->srcaddr = cpu_to_le32(*dataoff);
main_hdr->ext = has_ext;
main_hdr->version = 0;
main_hdr->destaddr = cpu_to_le32(params->addr);
@@ -1013,10 +1014,9 @@ static void *image_create_v0(size_t *dataoff, struct image_tool_params *params,
/*
* For SATA srcaddr is specified in number of sectors.
* This expects the sector size to be 512 bytes.
- * Header size is already aligned.
*/
if (main_hdr->blockid == IBR_HDR_SATA_ID)
- main_hdr->srcaddr = cpu_to_le32(headersz / 512);
+ main_hdr->srcaddr = cpu_to_le32(le32_to_cpu(main_hdr->srcaddr) / 512);

/* For PCIe srcaddr is not used and must be set to 0xFFFFFFFF. */
if (main_hdr->blockid == IBR_HDR_PEX_ID)
@@ -1050,7 +1050,6 @@ static void *image_create_v0(size_t *dataoff, struct image_tool_params *params,
main_hdr->checksum = image_checksum8(image,
sizeof(struct main_hdr_v0));

- *dataoff = headersz;
return image;
}

@@ -1064,10 +1063,6 @@ static size_t image_headersz_v1(int *hasext)
int cfgi;
int ret;

- /*
- * Calculate the size of the header and the size of the
- * payload
- */
headersz = sizeof(struct main_hdr_v1);

if (image_get_csk_index() >= 0) {
@@ -1163,7 +1158,7 @@ static size_t image_headersz_v1(int *hasext)
if (count > 0)
headersz += sizeof(struct register_set_hdr_v1) + 8 * count + 4;

- return image_headersz_align(headersz, image_get_bootfrom());
+ return headersz;
}

static int add_binary_header_v1(uint8_t **cur, uint8_t **next_ext,
@@ -1390,7 +1385,6 @@ static void *image_create_v1(size_t *dataoff, struct image_tool_params *params,
{
struct image_cfg_element *e;
struct main_hdr_v1 *main_hdr;
- struct opt_hdr_v1 *ohdr;
struct register_set_hdr_v1 *register_set_hdr;
struct secure_hdr_v1 *secure_hdr = NULL;
size_t headersz;
@@ -1401,12 +1395,13 @@ static void *image_create_v1(size_t *dataoff, struct image_tool_params *params,
uint8_t delay;

/*
- * Calculate the size of the header and the size of the
+ * Calculate the size of the header and the offset of the
* payload
*/
headersz = image_headersz_v1(&hasext);
if (headersz == 0)
return NULL;
+ *dataoff = image_headersz_align(headersz, image_get_bootfrom());

image = malloc(headersz);
if (!image) {
@@ -1428,7 +1423,7 @@ static void *image_create_v1(size_t *dataoff, struct image_tool_params *params,
main_hdr->headersz_msb = (headersz & 0xFFFF0000) >> 16;
main_hdr->destaddr = cpu_to_le32(params->addr);
main_hdr->execaddr = cpu_to_le32(params->ep);
- main_hdr->srcaddr = cpu_to_le32(headersz);
+ main_hdr->srcaddr = cpu_to_le32(*dataoff);
main_hdr->ext = hasext;
main_hdr->version = 1;
main_hdr->blockid = image_get_bootfrom();
@@ -1458,10 +1453,9 @@ static void *image_create_v1(size_t *dataoff, struct image_tool_params *params,
/*
* For SATA srcaddr is specified in number of sectors.
* This expects the sector size to be 512 bytes.
- * Header size is already aligned.
*/
if (main_hdr->blockid == IBR_HDR_SATA_ID)
- main_hdr->srcaddr = cpu_to_le32(headersz / 512);
+ main_hdr->srcaddr = cpu_to_le32(le32_to_cpu(main_hdr->srcaddr) / 512);

/* For PCIe srcaddr is not used and must be set to 0xFFFFFFFF. */
if (main_hdr->blockid == IBR_HDR_PEX_ID)
@@ -1528,19 +1522,10 @@ static void *image_create_v1(size_t *dataoff, struct image_tool_params *params,
&datai, delay);
}

- if (secure_hdr && add_secure_header_v1(params, ptr + headersz, payloadsz,
+ if (secure_hdr && add_secure_header_v1(params, ptr + *dataoff, payloadsz,
image, headersz, secure_hdr))
return NULL;

- *dataoff = headersz;
-
- /* Fill the real header size without padding into the main header */
- headersz = sizeof(*main_hdr);
- for_each_opt_hdr_v1 (ohdr, main_hdr)
- headersz += opt_hdr_v1_size(ohdr);
- main_hdr->headersz_lsb = cpu_to_le16(headersz & 0xFFFF);
- main_hdr->headersz_msb = (headersz & 0xFFFF0000) >> 16;
-
/* Calculate and set the header checksum */
main_hdr->checksum = image_checksum8(main_hdr, headersz);

@@ -1889,7 +1874,7 @@ static void kwbimage_set_header(void *ptr, struct stat *sbuf, int ifd,
memcpy((uint8_t *)ptr + dataoff + datasz, &checksum, sizeof(uint32_t));

/* Finally copy the header into the image area */
- memcpy(ptr, image, dataoff);
+ memcpy(ptr, image, kwbheader_size(image));

free(image);
}
@@ -2109,6 +2094,8 @@ static int kwbimage_generate(struct image_tool_params *params,
exit(EXIT_FAILURE);
}

+ alloc_len = image_headersz_align(alloc_len, image_get_bootfrom());
+
free(image_cfg);

hdr = malloc(alloc_len);
--
2.20.1