Skip to content

Fix 3 security problems found by fuzzer #23

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
everestsummer wants to merge 6 commits into
base: master
Choose a base branch
from
Open

Fix 3 security problems found by fuzzer #23

Changes from all commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
777d74f
Fix: Security: Uninitialized variables may cause SIGSEGV
everestsummer Aug 20, 2022
f29dc41
Fix: Security: 'key' maybe a value bigger than table->nentries, causi…
everestsummer Aug 20, 2022
9705582
Fix: Security: entry.prefix may be a bigger value than table->nentrie…
everestsummer Aug 20, 2022
bdfad6b
Fix: Security: Infinite loop in discard_sub_blocks
everestsummer Aug 20, 2022
271d1d2
Fix: Security: Infinite loop in read_ext
everestsummer Aug 20, 2022
b17f410
Fix: Security: Prevent i from being overflowed to negative value (and…
everestsummer Aug 20, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
24 changes: 17 additions & 7 deletions gifdec.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ gd_open_gif(const char *fname)
uint8_t sigver[3];
uint16_t width, height, depth;
uint8_t fdsz, bgidx, aspect;
int i;
size_t i;
uint8_t *bgcolor;
int gct_sz;
gd_GIF *gif;
Expand Down Expand Up @@ -121,11 +121,17 @@ gd_open_gif(const char *fname)
static void
discard_sub_blocks(gd_GIF *gif)
{
uint8_t first_try = 1;
uint8_t seek_pos;
uint8_t size;

do {
read(gif->fd, &size, 1);
if (!first_try && size == seek_pos) //To prevent infinite loop

@Voidless7125 Voidless7125 May 22, 2024

Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is Uninitialized when used.

break;
lseek(gif->fd, size, SEEK_CUR);
seek_pos = size;
first_try = 0;
} while (size);
}

Expand Down Expand Up @@ -218,7 +224,9 @@ read_ext(gd_GIF *gif)
{
uint8_t label;

read(gif->fd, &label, 1);
if(read(gif->fd, &label, 1) < 1)
return;

switch (label) {
case 0x01:
read_plain_text_ext(gif);
Expand Down Expand Up @@ -333,12 +341,12 @@ static int
read_image_data(gd_GIF *gif, int interlace)
{
uint8_t sub_len, shift, byte;
int init_key_size, key_size, table_is_full;
int frm_off, frm_size, str_len, i, p, x, y;
int init_key_size, key_size, table_is_full = 0;
int frm_off, frm_size, str_len = 0, i, p, x, y;
uint16_t key, clear, stop;
int ret;
Table *table;
Entry entry;
Entry entry = { 0 };
off_t start, end;

read(gif->fd, &byte, 1);
Expand Down Expand Up @@ -379,6 +387,7 @@ read_image_data(gd_GIF *gif, int interlace)
key = get_key(gif, key_size, &sub_len, &shift, &byte);
if (key == clear) continue;
if (key == stop || key == 0x1000) break;
if (key >= table->nentries) break;
if (ret == 1) key_size++;
entry = table->entries[key];
str_len = entry.length;
Expand All @@ -389,7 +398,7 @@ read_image_data(gd_GIF *gif, int interlace)
if (interlace)
y = interlaced_line_index((int) gif->fh, y);
gif->frame[(gif->fy + y) * gif->width + gif->fx + x] = entry.suffix;
if (entry.prefix == 0xFFF)
if (entry.prefix == 0xFFF || entry.prefix >= table->nentries)
break;
else
entry = table->entries[entry.prefix];
Expand Down Expand Up @@ -495,7 +504,8 @@ gd_get_frame(gd_GIF *gif)
if (sep == '!')
read_ext(gif);
else return -1;
read(gif->fd, &sep, 1);
if(read(gif->fd, &sep, 1) < 1)
return -1;
}
if (read_image(gif) == -1)
return -1;
Expand Down