[coreboot-gerrit] Patch set updated for coreboot: ifwitool: Calculate checksum for subpart_dir

[Furquan Shaikh]

Furquan Shaikh ([e-mail]) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/15200

-gerrit

commit b73438d2b4f6ca7dd59f33741486b469c79a8652
Author: Furquan Shaikh 
Date:   Wed Jun 15 08:01:10 2016 -0700

ifwitool: Calculate checksum for subpart_dir

Checksum is calculated by using 2s complement method. 8-bit sum of the
    entire subpart directory from first byte of header to last byte of last
    partition directory entry.

BUG=chrome-os-partner:53508

Change-Id: I991d79dfdb5331ab732bf0d71cf8223d63426fa8
    Signed-off-by: Furquan Shaikh 
---
 util/cbfstool/ifwitool.c | 56 ++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 50 insertions(+), 6 deletions(-)

diff --git a/util/cbfstool/ifwitool.c b/util/cbfstool/ifwitool.c
index a1365bd..30b6f75 100644
--- a/util/cbfstool/ifwitool.c
+++ b/util/cbfstool/ifwitool.c
@@ -101,8 +101,8 @@ struct subpart_dir_header {
    /* Length of directory header in bytes. */
    uint8_t header_length;
    /*
-	 * TODO(furquan): Add checksum calculation once more details are
-	 * available.
+	 * 2s complement of 8-bit sum from first byte of header to last byte of
+	 * last directory entry.
     */
    uint8_t checksum;
    /* ASCII short name of sub-partition. */
@@ -750,7 +750,27 @@ static void parse_sbpdt(void *data, size_t size)
    		  "S-BPDT");
 }

-static void validate_subpart_dir(struct subpart_dir *s, const char *name)
+static uint8_t calc_checksum(struct subpart_dir *s)
+{
+	size_t size = subpart_dir_size(&s->h);
+	uint8_t *data = (uint8_t *)s;
+	uint8_t checksum = 0;
+	size_t i;
+
+	uint8_t old_checksum = s->h.checksum;
+	s->h.checksum = 0;
+
+	for (i = 0; i < size; i++)
+		checksum += data[i];
+
+	s->h.checksum = old_checksum;
+
+	/* 2s complement */
+	return -checksum;
+}
+
+static void validate_subpart_dir(struct subpart_dir *s, const char *name,
+				 bool checksum_check)
 {
    if ((s->h.marker != SUBPART_DIR_MARKER) ||
        (s->h.header_version != SUBPART_DIR_HEADER_VERSION_SUPPORTED) ||
@@ -759,6 +779,27 @@ static void validate_subpart_dir(struct subpart_dir *s, const char *name)
    	ERROR("Invalid subpart_dir for %s.\n", name);
    	exit(-1);
    }
+
+	if (checksum_check == false)
+		return;
+
+	uint8_t checksum = calc_checksum(s);
+
+	if (checksum != s->h.checksum)
+		ERROR("Invalid checksum for %s (Expected=0x%x, Actual=0x%x).\n",
+		      name, checksum, s->h.checksum);
+}
+
+static void validate_subpart_dir_without_checksum(struct subpart_dir *s,
+						  const char *name)
+{
+	validate_subpart_dir(s, name, 0);
+}
+
+static void validate_subpart_dir_with_checksum(struct subpart_dir *s,
+					       const char *name)
+{
+	validate_subpart_dir(s, name, 1);
 }

static void parse_subpart_dir(struct buffer *subpart_dir_buf,
@@ -784,7 +825,7 @@ static void parse_subpart_dir(struct buffer *subpart_dir_buf,
    memcpy(hdr.name, data + offset, sizeof(hdr.name));
    offset += sizeof(hdr.name);

-	validate_subpart_dir((struct subpart_dir *)&hdr, name);
+	validate_subpart_dir_without_checksum((struct subpart_dir *)&hdr, name);

assert(size > subpart_dir_size(&hdr));
    alloc_buffer(subpart_dir_buf, subpart_dir_size(&hdr), "Subpart Dir");
@@ -805,6 +846,8 @@ static void parse_subpart_dir(struct buffer *subpart_dir_buf,
    			     &e[i].rsvd);
    }

+	validate_subpart_dir_with_checksum(subpart_dir, name);
+
    print_subpart_dir(subpart_dir);
 }

@@ -1353,7 +1396,7 @@ static void create_subpart(struct buffer *dst, struct buffer *info[],
    	       buffer_size(info[i]));
    }

-	h->checksum = 0;
+	h->checksum = calc_checksum(buffer_get(&subpart_dir_buff));

struct subpart_dir *dir = buffer_get(&subpart_dir_buff);

@@ -1717,7 +1760,8 @@ static enum ifwi_ret ifwi_dir_replace(int type)
    	s->e[i].offset += offset;
    }

-	s->h.checksum = 0;
+	/* Re-calculate checksum. */
+	s->h.checksum = calc_checksum(s);

/* Convert members to litte-endian. */
    subpart_dir_fixup_write_buffer(&subpart_dir_buf);