Hi,
checksum-fix.diff fixes a checksum calculation bug in the lar utility,
where it would checksum less bytes then desired.
lar-check-sum.diff implements checksum checking in the runtime lar code.
I implemented the check inside the filename check, thus it wont be
executed on unneeded entries. As my assumption was that I cant modify
the memory, the code is skipping bytes between 20-24 of the header
(checksum field) to generate a correct sum.
This is bad, as the numbers shall be updated at every lar structure
change. This is good, as we are not writing to memory.
--
Alex
Signed-off-by: Alex Beregszaszi <[EMAIL PROTECTED]>
Index: util/lar/stream.c
===================================================================
--- util/lar/stream.c (revision 494)
+++ util/lar/stream.c (working copy)
@@ -815,7 +825,7 @@
csum = 0;
for (walk = (u32 *) (lar->map + offset);
- walk < (u32 *) (lar->map + complen + hlen);
+ walk < (u32 *) (lar->map + offset + complen + hlen);
walk++) {
csum += ntohl(*walk);
}
Signed-off-by: Alex Beregszaszi <[EMAIL PROTECTED]>
Index: lib/lar.c
===================================================================
--- lib/lar.c (revision 494)
+++ lib/lar.c (working copy)
@@ -99,9 +99,21 @@
fullname = walk + sizeof(struct lar_header);
printk(BIOS_SPEW, "LAR: search for %s\n", fullname);
- // FIXME: check checksum
if (strcmp(fullname, filename) == 0) {
+ u32 csum = 0, *p = (u32 *)walk;
+
+ /* validate checksum */
+ for (; p < (u32 *)(walk+ntohl(header->len)+ntohl(header->offset)); p++)
+ /* skip the checksum field itself */
+ if (((char*)p-walk) < 20 || ((char*)p - walk) > 24)
+ csum += ntohl(*p);
+ if (csum != ntohl(header->checksum)) {
+ printk(BIOS_SPEW, "LAR: checksum failed on %s, skipping (%x != %x)\n",
+ fullname, csum, ntohl(header->checksum));
+ return 1;
+ }
+
printk(BIOS_SPEW, "LAR: CHECK %s @ %p\n", fullname, header);
result->start = walk + ntohl(header->offset);
result->len = ntohl(header->len);
--
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