path: root/IkiWiki/Wrapper.pm

#!/usr/bin/perl

package IkiWiki;

use warnings;
use strict;
use File::Spec;
use Data::Dumper;
use IkiWiki;

sub gen_wrapper () {
    $config{srcdir}=File::Spec->rel2abs($config{srcdir});
    $config{destdir}=File::Spec->rel2abs($config{destdir});
    my $this=File::Spec->rel2abs($0);
    if (! -x $this) {
        error(sprintf(gettext("%s doesn't seem to be executable"), $this));
    }

    if ($config{setup}) {
        error(gettext("cannot create a wrapper that uses a setup file"));
    }
    my $wrapper=possibly_foolish_untaint($config{wrapper});
    if (! defined $wrapper || ! length $wrapper) {
        error(gettext("wrapper filename not specified"));
    }
    delete $config{wrapper};
    
    my @envsave;
    push @envsave, qw{REMOTE_ADDR QUERY_STRING REQUEST_METHOD REQUEST_URI
                   CONTENT_TYPE CONTENT_LENGTH GATEWAY_INTERFACE
               HTTP_COOKIE REMOTE_USER HTTPS REDIRECT_STATUS
               REDIRECT_URL} if $config{cgi};
    my $envsave="";
    foreach my $var (@envsave) {
        $envsave.=<<"EOF";
    if ((s=getenv("$var")))
        addenv("$var", s);
EOF
    }
    
    my @wrapper_hooks;
    run_hooks(genwrapper => sub { push @wrapper_hooks, shift->() });

    my $check_commit_hook="";
    my $pre_exec="";
    if ($config{post_commit}) {
        # Optimise checking !commit_hook_enabled() , 
        # so that ikiwiki does not have to be started if the
        # hook is disabled.
        #
        # Note that perl's flock may be implemented using fcntl
        # or lockf on some systems. If so, and if there is no
        # interop between the locking systems, the true C flock will
        # always succeed, and this optimisation won't work.
        # The perl code will later correctly check the lock,
        # so the right thing will still happen, though without
        # the benefit of this optimisation.
        $check_commit_hook=<<"EOF";
    {
        int fd=open("$config{wikistatedir}/commitlock", O_CREAT | O_RDWR, 0666);
        if (fd != -1) {
            if (flock(fd, LOCK_SH | LOCK_NB) != 0)
                exit(0);
            close(fd);
        }
    }
EOF
    }
    elsif ($config{cgi}) {
        # Avoid more than one ikiwiki cgi running at a time by
        # taking a cgi lock. Since ikiwiki uses several MB of
        # memory, a pile up of processes could cause thrashing
        # otherwise. The fd of the lock is stored in
        # IKIWIKI_CGILOCK_FD so unlockwiki can close it.
        $pre_exec=<<"EOF";
    {
        int fd=open("$config{wikistatedir}/cgilock", O_CREAT | O_RDWR, 0666);
        if (fd != -1 && flock(fd, LOCK_EX) == 0) {
            char *fd_s;
            asprintf(&fd_s, "%i", fd);
            setenv("IKIWIKI_CGILOCK_FD", fd_s, 1);
        }
    }
EOF
    }

    $Data::Dumper::Indent=0; # no newlines
    my $configstring=Data::Dumper->Dump([\%config], ['*config']);
    $configstring=~s/\\/\\\\/g;
    $configstring=~s/"/\\"/g;
    $configstring=~s/\n/\\n/g;
    
    writefile(basename("$wrapper.c"), dirname($wrapper), <<"EOF");
/* A wrapper for ikiwiki, can be safely made suid. */
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>

extern char **environ;
char *newenviron[$#envsave+6];
int i=0;

addenv(char *var, char *val) {
    char *s=malloc(strlen(var)+1+strlen(val)+1);
    if (!s)
        perror("malloc");
    sprintf(s, "%s=%s", var, val);
    newenviron[i++]=s;
}

int main (int argc, char **argv) {
    char *s;

$check_commit_hook
@wrapper_hooks
$envsave
    newenviron[i++]="HOME=$ENV{HOME}";
    newenviron[i++]="WRAPPED_OPTIONS=$configstring";
    newenviron[i]=NULL;
    environ=newenviron;

    if (setregid(getegid(), -1) != 0 &&
        setregid(getegid(), -1) != 0) {
        perror("failed to drop real gid");
        exit(1);
    }
    if (setreuid(geteuid(), -1) != 0 &&
        setreuid(geteuid(), -1) != 0) {
        perror("failed to drop real uid");
        exit(1);
    }

$pre_exec
    execl("$this", "$this", NULL);
    perror("exec $this");
    exit(1);
}
EOF

    my $cc=exists $ENV{CC} ? possibly_foolish_untaint($ENV{CC}) : 'cc';
    if (system($cc, "$wrapper.c", "-o", "$wrapper.new") != 0) {
        #translators: The parameter is a C filename.
        error(sprintf(gettext("failed to compile %s"), "$wrapper.c"));
    }
    unlink("$wrapper.c");
    if (defined $config{wrappergroup}) {
        my $gid=(getgrnam($config{wrappergroup}))[2];
        if (! defined $gid) {
            error(sprintf("bad wrappergroup"));
        }
        if (! chown(-1, $gid, "$wrapper.new")) {
            error("chown $wrapper.new: $!");
        }
    }
    if (defined $config{wrappermode} &&
        ! chmod(oct($config{wrappermode}), "$wrapper.new")) {
        error("chmod $wrapper.new: $!");
    }
    if (! rename("$wrapper.new", $wrapper)) {
        error("rename $wrapper.new $wrapper: $!");
    }
    #translators: The parameter is a filename.
    printf(gettext("successfully generated %s"), $wrapper);
    print "\n";
}

1