Otherwise, we have a time-of-check/time-of-use vulnerability:
rcs_preprevert previously looked at what changed in the commit we are
reverting, not at what would result from reverting it now. In
particular, if some files were renamed since the commit we are
reverting, a revert of changes that were within the designated
subdirectory and allowed by check_canchange() might now affect
files that are outside the designated subdirectory or disallowed
by check_canchange().
It is not sufficient to disable rename detection, since git older
than 2.8.0rc0 (in particular the version in Debian stable) silently
accepts and ignores the relevant options.
OVE-20161226-0002
CGI::FormBuilder->field has behaviour similar to the CGI.pm misfeature
we avoided in f4ec7b0. Force it into scalar context where it is used
in an argument list.
This prevents two (relatively minor) commit metadata forgery
vulnerabilities:
* In the comments plugin, an attacker who was able to post a comment
could give it a user-specified author and author-URL even if the wiki
configuration did not allow for that, by crafting multiple values
to other fields.
* In the editpage plugin, an attacker who was able to edit a page
could potentially forge commit authorship by crafting multiple values
for the rcsinfo field.
The remaining plugins changed in this commit appear to have been
protected by use of explicit scalar prototypes for the called functions,
but have been changed anyway to make them more obviously correct.
In particular, checkpassword() in passwordauth has a known prototype,
so an attacker cannot trick it into treating multiple values of the
name field as being the username, password and field to check for.
OVE-20161226-0001
Previously it was relying on running with an installed ikiwiki
and being able to copy in recentchanges.mdwn and wikiicons/ from the
underlay in /usr. The underlay in ./underlays/basewiki can't be used
(yet) because ikiwiki doesn't allow following symlinks, even from
underlays.
I'd like to make ikiwiki follow symlinks whose destinations can be
verified to be safe (for example making it willing to expose
/usr/share/javascript to the web, but not /etc/passwd), at least from
underlays, but this is security-sensitive so I'm not going to rush
into it.
Otherwise, if third-party plugins extend newenviron by more than
3 entries, we could overflow the array. It seems unlikely that any
third-party plugin manipulates newenviron in practice, so this
is mostly theoretical. Just in case, I have deliberately avoided
using "i" as the variable name, so that any third-party plugin
that was manipulating newenviron directly will now result in the
wrapper failing to compile.
I have not assumed that realloc(NULL, ...) works as an equivalent of
malloc(...), in case there are still operating systems where that
doesn't work.
SVG scaling by img directives has subtly changed; where before size=wxh
would preserve aspect ratio, this cannot be done when passing them through
and so specifying both a width and height can change the SVG's aspect
ratio.
(This patch looks significantly more complex than it was, because a large
block of code had to be indented.)
[smcv: drop trailing whitespace, fix some spelling]
Simon McVittie
Joey Hess
Amitai Schlair