pacparser

Used by: pactester, python pacparser, old findproxyforurl.net backend.

Helper library

The checker runs this engine's own PAC helper library, copied verbatim at v1.5.3 (LGPL-3.0-or-later). Upstream source.

Version ranges and quirks

Later ranges list only what changes compared with the range before.

pacparser ≤ 1.4 (<=1.4.6)

SpiderMonkey 1.7 engine: ES3 syntax only.

pacparser 1.5.0 (1.5.0)

First QuickJS release: modern JavaScript syntax.

pacparser ≥ 1.5.1 (>=1.5.1)

QuickJS-ng; adds alert() and console.log().

Function availability

Rules with notes for pacparser

• PAC-C001Hostname pattern applied to url instead of host

  shExpMatch(url, "example.com") does not match http://example.com/x; the same pattern on host does. lab, verified 2026-05-20

• PAC-C018Upper-case letters in a hostname pattern

  Passes host as given; dnsDomainIs(host, ".example.com") does not match "Example.com". lab, verified 2026-05-20

• PAC-E012Proxy port out of range or not numeric

  Returns the malformed string unchanged; no validation. lab, verified 2026-05-20

• PAC-K001ES2015+ syntax (let, const, arrow functions, template literals)

  Depends on the bundled SpiderMonkey version; older builds reject ES2015 syntax. expert, unverified

• PAC-K002alert() used in the PAC

  Message is passed to the host application's alert handler (pactester prints it). expert, unverified

• PAC-K003IPv6 extension functions (isInNetEx, dnsResolveEx, myIpAddressEx)

  Ex functions are not implemented. expert, unverified

• PAC-K009Case-sensitive host comparisons without lower-casing host

  Passes host as given to pactester; case-sensitive comparison. lab, verified 2026-05-20

• PAC-K013Routing decided by myIpAddress()

  Resolves the local hostname via getaddrinfo; a fixed value can be injected for tests. expert, unverified

• PAC-X001No unconditional return at the end of FindProxyForURL

  Returns undefined to the caller (pactester prints "undefined"). lab, verified 2026-05-20

• PAC-X002Trailing * in a host pattern matches attacker-controlled suffixes

  "example.com*" matches example.com.evil.test lab, verified 2026-05-20

• PAC-X003dnsDomainIs pattern without a leading dot matches look-alike domains

  dnsDomainIs(host, "example.com") is true for a look-alike ending in "example.com", for example.com itself and for www.example.com. lab, verified 2026-05-20

• PAC-X004Leading * without a dot matches look-alike domains

  "*example.com" matches a look-alike domain ending in "example.com"; "*.example.com" does not. lab, verified 2026-05-20

• PAC-X006IP range matched as a text prefix

  "127.*" matches the hostname 127.foo.evil.test; "127example.test" does not (the dot is required). lab, verified 2026-05-20

• PAC-X012Wildcard inside a domain label

  A pattern of the form "name*.tld" matches look-alike names with extra characters before the TLD. lab, verified 2026-05-20

• PAC-X013PROXY entry without a port

  Returns the unported string unchanged; no validation. lab, verified 2026-05-20