Kees Cook <keesc...@chromium.org> wrote:
> Which means this loop will walk past the end of the memory (loop is
> bounded by n_sections, so secs[loop] can go past datalen). While
> data_addr and raw_data_size will stay bounded, the read of sec->name
> can be out of bounds.
Assuming n_sections is checked, sec->name can't be out of bounds because it's
a char array, not a pointer.
> (Also, do you want a "break" in there after the first .keylist is found, or
> is this intentionally "use last key list"?)
Actually, no I don't. The loop also checks the limits on each section - which
I need to do since I have to individually digest the sections later.
Attached is a patch I'm applying to pefile_parse_binary() to be more rigorous
about the checking of values in the PE binary.
David
---
diff --git a/crypto/asymmetric_keys/pefile_parser.c
b/crypto/asymmetric_keys/pefile_parser.c
index efae278..fb80cf0 100644
--- a/crypto/asymmetric_keys/pefile_parser.c
+++ b/crypto/asymmetric_keys/pefile_parser.c
@@ -42,8 +42,8 @@ static int pefile_parse_binary(struct key_preparsed_payload
*prep,
#define chkaddr(base, x, s) \
do { \
- if ((x) < base || (s) >= datalen || (x) > datalen - (s))
\
- return -ERANGE; \
+ if ((x) < base || (s) >= datalen || (x) > datalen - (s)) \
+ return -ELIBBAD; \
} while(0)
chkaddr(0, 0, sizeof(*mz));
@@ -88,7 +88,13 @@ static int pefile_parse_binary(struct key_preparsed_payload
*prep,
pr_devel("checksum @ %x\n", ctx->image_checksum_offset);
pr_devel("header size = %x\n", ctx->header_size);
- chkaddr(0, cursor, sizeof(*ddir));
+ if (cursor >= ctx->header_size || ctx->header_size >= datalen)
+ return -ELIBBAD;
+
+ if (ctx->n_data_dirents > (ctx->header_size - cursor) / sizeof(*dde) ||
+ ctx->n_data_dirents < sizeof(*ddir) / sizeof(*dde))
+ return -ELIBBAD;
+
ddir = prep->data + cursor;
cursor += sizeof(*dde) * ctx->n_data_dirents;
@@ -101,7 +107,7 @@ static int pefile_parse_binary(struct key_preparsed_payload
*prep,
return -EKEYREJECTED;
}
- chkaddr(cursor, ddir->certs.virtual_address, ddir->certs.size);
+ chkaddr(ctx->header_size, ddir->certs.virtual_address,
ddir->certs.size);
ctx->sig_offset = ddir->certs.virtual_address;
ctx->sig_len = ddir->certs.size;
pr_devel("cert = %x @%x [%*ph]\n",
@@ -112,7 +118,8 @@ static int pefile_parse_binary(struct key_preparsed_payload
*prep,
* section containing the list of keys.
*/
ctx->n_sections = pe->sections;
- chkaddr(0, cursor, sizeof(*sec) * ctx->n_sections);
+ if (ctx->n_sections > (ctx->header_size - cursor) / sizeof(*sec))
+ return -ELIBBAD;
ctx->secs = secs = prep->data + cursor;
cursor += sizeof(*sec) * ctx->n_sections;
--
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