Skip to content

fix: add buffer-length check in ruler.c #1

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
orbisai0security wants to merge 2 commits into
base: main
Choose a base branch
from
Open

fix: add buffer-length check in ruler.c #1

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
236a240
fix: V-001 security vulnerability
orbisai0security May 30, 2026
15fa4f8
fix: add buffer-length check in ruler.c
orbisai0security May 30, 2026
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
18 changes: 10 additions & 8 deletions ruler/ruler.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,7 @@ strip_quotes(char *str)
if (str[0] != '"' || str[len + 1] != '"')
return str;

char *s = malloc((len + 1) * sizeof(char));
char *s = malloc(len + 1);
int i;

for (i = 1; i < strlen(str) - 1; i++) {
Expand Down Expand Up @@ -364,7 +364,7 @@ window_type_to_string(xcb_ewmh_get_atoms_reply_t *reply)
char *str;

if (reply != NULL) {
str = malloc((WINDOW_TYPE_STRING_LENGTH + 1) * sizeof(char));
str = malloc(WINDOW_TYPE_STRING_LENGTH + 1);
str[0] = '\0';
for (i = 0; i < reply->atoms_len; i++) {
xcb_atom_t a = reply->atoms[i];
Expand All @@ -387,10 +387,10 @@ window_type_to_string(xcb_ewmh_get_atoms_reply_t *reply)

if (atom_name != NULL) {
if (i == 0)
sprintf(str, "%s", atom_name);
snprintf(str, WINDOW_TYPE_STRING_LENGTH + 1, "%s", atom_name);
else {
size_t slen = strlen(str);
sprintf(str + slen, ",%s", atom_name);
snprintf(str + slen, WINDOW_TYPE_STRING_LENGTH + 1 - slen, ",%s", atom_name);
}
}

Expand Down Expand Up @@ -430,9 +430,10 @@ get_string_prop(xcb_window_t win, xcb_atom_t prop, int utf8)
DMSG("unable to get window property for 0x%08x\n", win);
} else {
len = xcb_get_property_value_length(r);
p = malloc((len + 1) * sizeof(char));
p = malloc(len + 1);
value = xcb_get_property_value(r);
strncpy(p, value, len);
memcpy(p, value, len);
p[len] = '\0';
p[len] = '\0';
}
free(r);
Expand Down Expand Up @@ -692,8 +693,9 @@ register_events(void)
void
set_environ(xcb_window_t win)
{
char *wid = malloc((2 + 8 + 1) * sizeof(char));
sprintf(wid, "0x%08x", win);
char *wid = malloc(2 + 8 + 1);

snprintf(wid, 2 + 8 + 1, "0x%08x", win);
setenv(ENV_VARIABLE, wid, 1);
}

Expand Down
210 changes: 210 additions & 0 deletions tests/test_invariant_ruler.c
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,210 @@
#include <check.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stdint.h>

/*
* We simulate the vulnerable pattern from ruler.c:
* sprintf(str, "%s", atom_name);
* sprintf(str + slen, ",%s", atom_name);
*
* The invariant: buffer reads/writes must never exceed the declared buffer size.
* We implement a safe version and verify that the safe version handles
* oversized inputs correctly (truncation or rejection), and that the
* buffer boundary is never exceeded.
*/

#define SAFE_BUFFER_SIZE 256

/*
* Safe formatting function that mimics what ruler.c should do.
* Returns 0 on success, -1 if input would overflow.
*/
static int safe_format_atom(char *buf, size_t buf_size, const char *atom_name) {
if (!buf || !atom_name || buf_size == 0) return -1;

size_t name_len = strlen(atom_name);
if (name_len >= buf_size) {
/* Would overflow - reject */
return -1;
}

int ret = snprintf(buf, buf_size, "%s", atom_name);
if (ret < 0 || (size_t)ret >= buf_size) {
buf[0] = '\0';
return -1;
}
return 0;
}

static int safe_append_atom(char *buf, size_t buf_size, const char *atom_name) {
if (!buf || !atom_name || buf_size == 0) return -1;

size_t current_len = strlen(buf);
size_t name_len = strlen(atom_name);

/* Check: current_len + 1 (comma) + name_len + 1 (null) <= buf_size */
if (current_len + 1 + name_len + 1 > buf_size) {
return -1;
}

int ret = snprintf(buf + current_len, buf_size - current_len, ",%s", atom_name);
if (ret < 0 || (size_t)ret >= buf_size - current_len) {
buf[current_len] = '\0';
return -1;
}
return 0;
}

/*
* Canary-protected buffer structure to detect overflows.
*/
#define CANARY_VALUE 0xDEADBEEF
#define CANARY_SIZE 8

typedef struct {
uint32_t pre_canary[CANARY_SIZE];
char buffer[SAFE_BUFFER_SIZE];
uint32_t post_canary[CANARY_SIZE];
} protected_buffer_t;

static void init_protected_buffer(protected_buffer_t *pb) {
for (int i = 0; i < CANARY_SIZE; i++) {
pb->pre_canary[i] = CANARY_VALUE;
pb->post_canary[i] = CANARY_VALUE;
}
memset(pb->buffer, 0, SAFE_BUFFER_SIZE);
}

static int check_canaries(const protected_buffer_t *pb) {
for (int i = 0; i < CANARY_SIZE; i++) {
if (pb->pre_canary[i] != CANARY_VALUE) return 0;
if (pb->post_canary[i] != CANARY_VALUE) return 0;
}
return 1;
}

START_TEST(test_buffer_reads_never_exceed_declared_length)
{
/* Invariant: Buffer reads/writes must never exceed SAFE_BUFFER_SIZE bytes.
* Any atom name that would cause an overflow must be rejected or truncated,
* and canary values surrounding the buffer must remain intact.
*/
const char *payloads[] = {
/* Normal inputs */
"ATOM_NAME",
"_NET_WM_STATE",
"",
/* Boundary inputs */
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA", /* 64 bytes */
/* 2x buffer size (512 bytes) */
"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB"
"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB"
"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB"
"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB"
"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB"
"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB"
"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB"
"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB",
/* 10x buffer size (2560 bytes) */
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC"
"CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC",
/* Exactly buffer size - 1 (255 bytes) */
"DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD"
"DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD"
"DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD"
"DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD",
/* Exactly buffer size (256 bytes) - should be rejected */
"EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE"
"EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE"
"EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE"
"EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE",
/* Attack payloads with special characters */
"%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
"%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n%n",
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
"%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
/* Null-like and whitespace */
" ",
"\t\n\r",
/* Single char */
"A",
};
int num_payloads = sizeof(payloads) / sizeof(payloads[0]);

for (int i = 0; i < num_payloads; i++) {
protected_buffer_t pb;
init_protected_buffer(&pb);

const char *atom_name = payloads[i];
int result = safe_format_atom(pb.buffer, SAFE_BUFFER_SIZE, atom_name);

/* Canaries must be intact regardless of input */
ck_assert_msg(check_canaries(&pb),
"Canary corruption detected after safe_format_atom with payload index %d", i);

/* Buffer must be null-terminated within bounds */
int null_found = 0;
for (size_t j = 0; j < SAFE_BUFFER_SIZE; j++) {
if (pb.buffer[j] == '\0') {
null_found = 1;
break;
}
}
ck_assert_msg(null_found,
"Buffer not null-terminated within bounds for payload index %d", i);

/* If format succeeded, the result length must be within buffer */
if (result == 0) {
size_t written_len = strlen(pb.buffer);
ck_assert_msg(written_len < SAFE_BUFFER_SIZE,
"Written length %zu exceeds buffer size %d for payload index %d",
written_len, SAFE_BUFFER_SIZE, i);
}

/* Test append operation: fill buffer partially then try to append */
init_protected_buffer(&pb);
/* First, write a short known-good atom */
safe_format_atom(pb.buffer, SAFE_BUFFER