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From f03f09c2a07eae7f3a4646e33a406ae2689afb9e Mon Sep 17 00:00:00 2001
From: Hitendra Prajapati <hprajapati@mvista.com>
Date: Mon, 1 Aug 2022 10:59:41 +0530
Subject: [PATCH] CVE-2022-28734
Upstream-Status: Backport [https://git.savannah.gnu.org/gitweb/?p=grub.git;a=commit;h=b26b4c08e7119281ff30d0fb4a6169bd2afa8fe4]
CVE: CVE-2022-28734
Signed-off-by: Hitendra Prajapati <hprajapati@mvista.com>
net/http: Fix OOB write for split http headers
GRUB has special code for handling an http header that is split
across two packets.
The code tracks the end of line by looking for a "\n" byte. The
code for split headers has always advanced the pointer just past the
end of the line, whereas the code that handles unsplit headers does
not advance the pointer. This extra advance causes the length to be
one greater, which breaks an assumption in parse_line(), leading to
it writing a NUL byte one byte past the end of the buffer where we
reconstruct the line from the two packets.
It's conceivable that an attacker controlled set of packets could
cause this to zero out the first byte of the "next" pointer of the
grub_mm_region structure following the current_line buffer.
Do not advance the pointer in the split header case.
Fixes: CVE-2022-28734
---
grub-core/net/http.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/grub-core/net/http.c b/grub-core/net/http.c
index 5aa4ad3..a220d21 100644
--- a/grub-core/net/http.c
+++ b/grub-core/net/http.c
@@ -68,7 +68,15 @@ parse_line (grub_file_t file, http_data_t data, char *ptr, grub_size_t len)
char *end = ptr + len;
while (end > ptr && *(end - 1) == '\r')
end--;
+
+ /* LF without CR. */
+ if (end == ptr + len)
+ {
+ data->errmsg = grub_strdup (_("invalid HTTP header - LF without CR"));
+ return GRUB_ERR_NONE;
+ }
*end = 0;
+
/* Trailing CRLF. */
if (data->in_chunk_len == 1)
{
@@ -190,9 +198,7 @@ http_receive (grub_net_tcp_socket_t sock __attribute__ ((unused)),
int have_line = 1;
char *t;
ptr = grub_memchr (nb->data, '\n', nb->tail - nb->data);
- if (ptr)
- ptr++;
- else
+ if (ptr == NULL)
{
have_line = 0;
ptr = (char *) nb->tail;
--
2.25.1
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