FreeBSD-SA-05:14.bzip2 "bzip2 denial of service and permission race vulnerabilities"

t ! security

The FreeBSD Project よりセキュリティ勧告が出ました。要点を以下にまとめます。

  • 未稿

セキュリティ勧告は ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:14.bzip2.asc にあります。
以下は上記のセキュリティ勧告の一部とその訳文です。ただし品質は保証致しません。

I. 背景 - Background

bzip2 is a block-sorting file compression utility.

II. 問題の詳細 - Problem Description

Two problems have been discovered relating to the extraction of bzip2-compressed files. First, a carefully constructed invalid bzip2 archive can cause bzip2 to enter an infinite loop. Second, when creating a new file, bzip2 closes the file before setting its permissions.

III. 影響範囲 - Impact

The first problem can cause bzip2 to extract a bzip2 archive to an infinitely large file. If bzip2 is used in automated processing of untrusted files this could be exploited by an attacker to create an denial-of-service situation by exhausting disk space or by consuming all available cpu time.
The second problem can allow a local attacker to change the permissions of local files owned by the user executing bzip2 providing that they have write access to the directory in which the file is being extracted.

IV. 回避方法 - Workaround

Do not uncompress bzip2 archives from untrusted sources and do not uncompress files in directories where untrusted users have write access.

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