From b5c3492f31a98f5ef0f9bec2c0665ad0b71ad5cb Mon Sep 17 00:00:00 2001 From: Sebastian Krahmer Date: Tue, 28 Nov 2017 17:24:38 +0800 Subject: [PATCH] AUDIT-0: http boot tracker bug Fixing a memory leak in case of error, and a integer overflow, leading to a heap overflow due to overly large chunk sizes. We need to check against some maximum value, otherwise values like 0xffffffff will eventually lead in the allocation functions to small sized buffers, since the len is rounded up to the next reasonable alignment. The following memcpy will then smash the heap, leading to RCE. This is no big issue for pure http boot, since its going to execute an untrusted kernel anyway, but it will break trusted boot scenarios, where only signed code is allowed to be executed. Signed-off-by: Michael Chang --- grub-core/net/efi/net.c | 4 +++- grub-core/net/http.c | 5 ++++- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/grub-core/net/efi/net.c b/grub-core/net/efi/net.c index 0bac343b4..5bc604ff0 100644 --- a/grub-core/net/efi/net.c +++ b/grub-core/net/efi/net.c @@ -645,8 +645,10 @@ grub_efihttp_chunk_read (grub_file_t file, char *buf, rd = efi_net_interface (read, file, chunk, sz); - if (rd <= 0) + if (rd <= 0) { + grub_free (chunk); return rd; + } if (buf) { diff --git a/grub-core/net/http.c b/grub-core/net/http.c index f182d7b87..5004ecfee 100644 --- a/grub-core/net/http.c +++ b/grub-core/net/http.c @@ -31,7 +31,8 @@ GRUB_MOD_LICENSE ("GPLv3+"); enum { - HTTP_PORT = 80 + HTTP_PORT = 80, + HTTP_MAX_CHUNK_SIZE = 0x80000000 }; @@ -78,6 +79,8 @@ parse_line (grub_file_t file, http_data_t data, char *ptr, grub_size_t len) if (data->in_chunk_len == 2) { data->chunk_rem = grub_strtoul (ptr, 0, 16); + if (data->chunk_rem > HTTP_MAX_CHUNK_SIZE) + return GRUB_ERR_NET_PACKET_TOO_BIG; grub_errno = GRUB_ERR_NONE; if (data->chunk_rem == 0) { -- 2.12.0