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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Sebastian Krahmer <krahmer@suse.com>
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Date: Tue, 28 Nov 2017 17:24:38 +0800
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Subject: [PATCH] AUDIT-0: http boot tracker bug
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Fixing a memory leak in case of error, and a integer overflow, leading to a
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heap overflow due to overly large chunk sizes.
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We need to check against some maximum value, otherwise values like 0xffffffff
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will eventually lead in the allocation functions to small sized buffers, since
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the len is rounded up to the next reasonable alignment. The following memcpy
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will then smash the heap, leading to RCE.
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This is no big issue for pure http boot, since its going to execute an
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untrusted kernel anyway, but it will break trusted boot scenarios, where only
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signed code is allowed to be executed.
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Signed-off-by: Michael Chang <mchang@suse.com>
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---
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grub-core/net/efi/net.c | 4 +++-
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grub-core/net/http.c | 5 ++++-
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2 files changed, 7 insertions(+), 2 deletions(-)
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diff --git a/grub-core/net/efi/net.c b/grub-core/net/efi/net.c
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index 86bce6535d..4bb308026c 100644
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--- a/grub-core/net/efi/net.c
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+++ b/grub-core/net/efi/net.c
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@@ -645,8 +645,10 @@ grub_efihttp_chunk_read (grub_file_t file, char *buf,
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rd = efi_net_interface (read, file, chunk, sz);
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- if (rd <= 0)
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+ if (rd <= 0) {
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+ grub_free (chunk);
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return rd;
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+ }
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if (buf)
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{
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diff --git a/grub-core/net/http.c b/grub-core/net/http.c
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index 12a2632ea5..b52b558d63 100644
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--- a/grub-core/net/http.c
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+++ b/grub-core/net/http.c
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@@ -31,7 +31,8 @@ GRUB_MOD_LICENSE ("GPLv3+");
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enum
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{
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- HTTP_PORT = 80
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+ HTTP_PORT = 80,
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+ HTTP_MAX_CHUNK_SIZE = 0x80000000
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};
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@@ -78,6 +79,8 @@ parse_line (grub_file_t file, http_data_t data, char *ptr, grub_size_t len)
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if (data->in_chunk_len == 2)
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{
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data->chunk_rem = grub_strtoul (ptr, 0, 16);
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+ if (data->chunk_rem > HTTP_MAX_CHUNK_SIZE)
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+ return GRUB_ERR_NET_PACKET_TOO_BIG;
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grub_errno = GRUB_ERR_NONE;
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if (data->chunk_rem == 0)
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{
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