mdw@git.distorted.org.uk Git - userv-utils/blob - ipif/service-wrap

   1 #!/usr/bin/perl -w
   2 #
   3 # When invoked appropriately, it creates a point-to-point network
   4 # interface with specified parameters.  It arranges for packets sent out
   5 # via that interface by the kernel to appear on its own stdout in SLIP or
   6 # CSLIP encoding, and packets injected into its own stdin to be given to
   7 # the kernel as if received on that interface.  Optionally, additional
   8 # routes can be set up to arrange for traffic for other address ranges to
   9 # be routed through the new interface.
  10 #
  11 # This is the access control wrapper for the service program.
  12 # Arrangments should be made to invoke this as root from userv.
  13 #
  14 # Usage:
  15 #
  16 #   .../ipif1 <v1config> <real-service-program> -- <service-args>...
  17 #
  18 # Config file is a series of lines.
  19 #
  20 #   permit <keyword>....
  21 #
  22 #      if caller, local addr, all remote addrs and networks, and
  23 #      ifname, all match, permits the request (and stops reading
  24 #      the config)
  25 #
  26 #          group <groupname>|<gid>
  27 #              matches caller if they are in that group
  28 #          user <username>|<uid>
  29 #              matches caller if they are that user
  30 #          everyone
  31 #              always matches caller
  32 #
  33 #          hostnet <ipaddr>/<prefixlen>
  34 #              equivalent to   local <ipv4addr> remote <ipv4addr&prefix>
  35 #          local <ipaddr>
  36 #              matches local address when it is <ipv4addr>
  37 #          remote <ipnetnet>/<prefixlen>
  38 #              matches aplicable remote addrs (including p-t-p)
  39 #          addrs <ipaddr>|<ipnetnet>/<prefixlen>
  40 #              matches applicable local ore remote addrs
  41 #
  42 #          ifname <ifname>
  43 #              matches interface name if it is exactly <ifname>
  44 #              (<ifname> may contain %d, which is interpreted by
  45 #              the kernel)
  46 #              wildcards are not supported
  47 #              if a permit has no ifname at all, it is as if
  48 #              `ifname userv%d' was specified
  49 #
  50 #   include <other-config-file>
  51 #
  52 #   v0config <v0configfile>
  53 #
  54 #     If none of the `permit' lines match, will read <v0configfile>
  55 #     in old format.  Must come after all `permit' lines.
  56 #
  57 #   <config> --
  58
  59 use strict;
  60 use POSIX;
  61 use Carp;
  62 use NetAddr::IP::Lite qw(:nofqdn :lower);
  63
  64 our $default_ifname = 'userv%d';
  65
  66 sub badusage ($) {
  67     my ($m) = @_;
  68     die "bad usage: $m\n";
  69 }
  70
  71 sub oneaddr ($) {
  72     my ($ar) = @_;
  73     my $x = $$ar;
  74     $x // badusage "missing IP address";
  75     $x = new NetAddr::IP::Lite $x // badusage "bad IP address";
  76     $x->masklen == $x->bits or badusage "IP network where addr expected";
  77     die if $x->addr =~ m,/,;
  78     $$ar = $x;
  79 }
  80
  81 @ARGV == 5 or badusage "wrong number of arguments";
  82 our ($v1config, $realservice, $sep, $addrsarg, $rnets) = @ARGV;
  83
  84 $sep eq '--' or badusage "separator should be \`--'";
  85 my ($local_addr, $peer_addr, $mtu, $protocol, $ifname) =
  86     split /\,/, $addrsarg;
  87
  88 oneaddr \$local_addr;
  89 oneaddr \$peer_addr;
  90 $mtu = 1500 unless length $mtu;
  91 $mtu =~ m/^[1-9]\d{1,4}/ or badusage "bad mtu";
  92 $mtu += 0;
  93
  94 $protocol = 'slip' unless length $protocol;
  95 $protocol =~ m/\W/ and badusage "bad protocol";
  96
  97 $ifname = $default_ifname unless length $ifname;
  98
  99 our @rnets = ($rnets eq '-' ? () : split /\,/, $rnets);
 100 @rnets = map { new NetAddr::IP::Lite $_ } @rnets;
 101
 102
 103 sub execreal ($) {
 104     my ($use_v0config) = @_;
 105     exec $realservice, $use_v0config, '--',
 106         (join ',', $local_addr->addr, $peer_addr->addr,
 107                    $mtu, $protocol, $ifname),
 108         @rnets ? (join ",", map { "$_" } @rnets) : "-"
 109         or die "exec $realservice: $!\n";
 110 }
 111
 112 our $v0config;
 113
 114 our $cfgpath;
 115
 116 sub badcfg ($) {
 117     my ($m) = @_;
 118     die "bad configuration: $cfgpath:$.: $m\n";
 119 }
 120
 121 our %need_allow;
 122 # $need_allow{CLASS}[]
 123 # $need_allow{CLASS}[]{Desc}   # For error messages
 124 # $need_allow{CLASS}[]{Allow}  # Starts out nonexistent
 125 # $need_allow{CLASS}[]{IpAddr} # CLASS eq Local or Remote only
 126
 127 sub allowent ($@) {
 128     my ($desc, @xtra) = @_;
 129     return { Desc => $desc, @xtra };
 130 }
 131 sub allowent_addr ($$) {
 132     my ($what, $addr) = @_;
 133     return allowent "$what $addr", IpAddr => $addr;
 134 }
 135 sub need_allow_item ($$) {
 136     my ($cl, $ne) = @_;
 137     push @{ $need_allow{$cl} }, $ne
 138 }
 139 sub need_allow_singleton ($$) {
 140     my ($cl, $ne) = @_;
 141     $need_allow{$cl} ||= [ $ne ];
 142 }
 143
 144 sub maybe_allow__entry ($$) {
 145     my ($ne, $yes) = @_;
 146     $ne->{Allowed} ||= $yes;
 147 }
 148 sub maybe_allow_singleton ($$) {
 149     my ($cl, $yes) = @_;
 150     my $ents = $need_allow{$cl};
 151     die $cl unless @$ents==1;
 152     maybe_allow__entry $ents->[0], $yes;
 153 }
 154 sub default_allow_singleton ($$) {
 155     # does nothing if maybe_allow_singleton was called for this $cl;
 156     # otherwise allows the singleton iff $yes
 157     my ($cl, $yes) = @_;
 158     my $ents = $need_allow{$cl};
 159     die $cl unless @$ents==1;
 160     $ents->[0]{Allowed} //= $yes;
 161 }
 162 sub maybe_allow_caller_env ($$$) {
 163     my ($spec, @envvars) = @_;
 164     foreach my $envvar (@envvars) {
 165         my $val = $ENV{$envvar} // die $envvar;
 166         my @vals = split / /, $val;
 167         #use Data::Dumper; print Dumper($spec,$envvar,\@vals);
 168         maybe_allow_singleton 'Caller', !!grep { $_ eq $spec } @vals;
 169     }
 170 }
 171 sub maybe_allow_addrs ($$) {
 172     my ($cl, $permitrange) = @_;
 173     foreach my $ne (@{ $need_allow{$cl} }) {
 174         confess unless defined $ne->{IpAddr};
 175         maybe_allow__entry $ne, $permitrange->contains($ne->{IpAddr});
 176     }
 177 }
 178
 179 sub readconfig ($) {
 180     local ($cfgpath) = @_;
 181     my $cfgfh = new IO::File $cfgpath, "<";
 182     if (!$cfgfh) {
 183         die "$0: $cfgpath: $!\n" unless $!==ENOENT;
 184         return;
 185     }
 186     while (<$cfgfh>) {
 187         s/^\s+//;
 188         s/\s+$/\n/;
 189         next if m/^\#/;
 190         next unless m/\S/;
 191         if (s{^permit\s+}{}) {
 192             badcfg "v0config before permit" if defined $v0config;
 193             %need_allow = ();
 194             need_allow_singleton 'Caller', allowent 'caller';
 195             need_allow_singleton 'Local',
 196                 allowent_addr "local interface", $local_addr;
 197             need_allow_singleton 'Ifname', allowent 'interface name';
 198             need_allow_item 'Remote',
 199                 allowent_addr "peer point-to-point addr", $peer_addr;
 200             foreach (@rnets) {
 201                 need_allow_item 'Remote',
 202                     allowent_addr "remote network", $_;
 203             }
 204             #use Data::Dumper; print Dumper(\%need_allow);
 205             while (m{\S}) {
 206                 if (s{^user\s+(\S+)\s+}{}) {
 207                     maybe_allow_caller_env $1, 'USERV_USER', 'USERV_UID';
 208                 } elsif (s{^group\s+(\S+)\s+}{}) {
 209                     maybe_allow_caller_env $1, 'USERV_GROUP', 'USERV_GID';
 210                 } elsif (s{^everyone\s+}{}) {
 211                     maybe_allow_singleton 'Caller', 1;
 212                 } elsif (s{^hostnet\s+(\S+/\d+)\s+}{}) {
 213                     my $hn = new NetAddr::IP::Lite $1 or
 214                         badcfg "invalid ip address in hostnet";
 215                     my $host = new NetAddr::IP::Lite $hn->addr or die;
 216                     my $net = $hn->network() or die;
 217                     maybe_allow_addrs 'Local', $host;
 218                     maybe_allow_addrs 'Remote', $net;
 219                 } elsif (s{^(local|remote|addrs)\s+(\S+)\ s+}{}) {
 220                     my $h = $1;
 221                     my $s = new NetAddr::IP::Lite $2 or
 222                         badcfg "invalid ip address or mask in $h";
 223                     maybe_allow_addrs 'Local', $s if $h =~ m/addrs|local/;
 224                     maybe_allow_addrs 'Remote', $s if $h =~ m/addrs|remote/;
 225                 } elsif (s{^ifname\s+(\S+)\s+}{}) {
 226                     my ($spec) = $1;
 227                     maybe_allow_singleton 'Ifname', $ifname eq $spec;
 228                 } elsif (m{^\S+}) {
 229                     badcfg "unknown keyword in permit \`$1'";
 230                 } else {
 231                     die;
 232                 }
 233             }
 234             default_allow_singleton 'Ifname', $ifname eq $default_ifname;
 235             my @wrong;
 236             foreach my $clval (values %need_allow) {
 237                 foreach my $ne (@$clval) {
 238                     next if $ne->{Allowed};
 239                     push @wrong, $ne->{Desc};
 240                 }
 241             }
 242             if (!@wrong) {
 243                 # yay!
 244                 if ($protocol eq 'debug') {
 245                     print "config $cfgpath:$.: matches\n";
 246                     exit 0;
 247                 }
 248                 execreal '*';
 249             }
 250             if ($protocol eq 'debug') {
 251                 #use Data::Dumper; print Dumper(\%need_allow);
 252                 print "config $cfgpath:$.: mismatch: $_\n"
 253                     foreach @wrong;
 254             }
 255         } elsif (m{^v0config\s+(\S+)$}) {
 256             badcfg "repeated v0config" if defined $v0config;
 257             $v0config = $1;
 258         } elsif (m{^include\s+(\S+)$}) {
 259             readconfig $1;
 260         } else {
 261             badcfg "unknown config directive or bad syntax";
 262         }
 263     }
 264     $cfgfh->error and die $!;
 265     close $cfgfh;
 266
 267     if (defined $v0config) {
 268         $v0config =~ s{^}{./} unless $v0config =~ m{^/};
 269         print "trying v0 config $v0config...\n" if $protocol eq 'debug';
 270         execreal $v0config;
 271     }
 272     die "permission denied\n";
 273 }
 274
 275 readconfig $v1config;