Date: Thu, 28 Feb 2019 18:08:00 +0000 From: Simon McVittie <smcv@...ian.org> To: oss-security@...ts.openwall.com Subject: ikiwiki: CVE-2019-9187: Server-side request forgery Reference: https://ikiwiki.info/security/#cve-2019-9187 Affected versions: >= 1.13 Fixed versions: >= 3.20190228 Fixed versions (3.20170111.x branch): >= 3.20170111.1 ikiwiki is a static site generator with some dynamic features, used for wikis, blogs and other websites. The ikiwiki maintainers discovered that the aggregate plugin (a blog aggregator) did not try to use the LWPx::ParanoidAgent Perl module, unlike other parts of ikiwiki that request URIs. On sites where the aggregate plugin is enabled, authorized wiki editors could tell ikiwiki to fetch potentially undesired URIs even if LWPx::ParanoidAgent was installed: * local files via file: URIs * other URI schemes that might be misused by attackers, such as gopher: * hosts that resolve to loopback IP addresses (127.x.x.x) * hosts that resolve to RFC 1918 IP addresses (192.168.x.x etc.) This could be used by an attacker to publish information that should not have been accessible, cause denial of service by requesting "tarpit" URIs that are slow to respond, or cause undesired side-effects if local web servers implement "unsafe" GET requests (https://tools.ietf.org/html/rfc7231#section-4.2.1). (CVE-2019-9187) Additionally, if the LWPx::ParanoidAgent module was not installed, the blogspam, openid and pinger plugins would fall back to the ordinary LWP module, which is susceptible to similar attacks. This is unlikely to be a practical problem for the blogspam plugin because the URL it requests is under the control of the wiki administrator, but the openid plugin can request URLs controlled by unauthenticated remote users, and the pinger plugin can request URLs controlled by authorized wiki editors. This is addressed in ikiwiki 3.20190228 as follows, with the same fixes backported to Debian 9 in version 3.20170111.1: * URI schemes other than http: and https: are not accepted, preventing access to file:, gopher:, etc. * If a proxy is configured in the ikiwiki setup file, it is used for all outgoing http: and https: requests. In this case the proxy is responsible for blocking any requests that are undesired, including loopback or RFC 1918 addresses. * If a proxy is not configured, and LWPx::ParanoidAgent is installed, it will be used. This prevents loopback and RFC 1918 IP addresses, and sets a timeout to avoid denial of service via "tarpit" URIs. * Otherwise, the ordinary LWP user-agent will be used. This allows requests to loopback and RFC 1918 IP addresses, and has less robust timeout behaviour. We are not treating this as a vulnerability: if this behaviour is not acceptable for your site, please make sure to install LWPx::ParanoidAgent or disable the affected plugins. If your distribution includes an older version of ikiwiki, please either update to a current version or backport the following commits: * e7b0d4a "useragent: Raise an exception if the LWP module can't be loaded" * 67543ce "useragent: Don't allow non-HTTP protocols to be used" * d283e4c "useragent: Automatically choose whether to use LWPx::ParanoidAgent" * 9a275b2 "doc: Document security issues involving LWP::UserAgent" (optional) Regards, smcv
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