libinterimap: factor out hostname/IP parsing.

Also, document that enclosing 'host' value in square brackets forces its
interpretation as an IP literal (hence skips name resolution).

4 files changed, 51 insertions, 21 deletions

diff --git a/Changelog b/Changelog
index 7a04963..71e11f7 100644
--- a/Changelog
+++ b/Changelog
@@ -4,6 +4,9 @@ interimap (0.5.4) upstream;
  + test suite: always generate new certificates on `make test`.  Hence
    running `make test` now requires OpenSSL 1.1.1 or later.
  + test suite: sign all test certificates with the same root CA.
+ + libinterimap: factor out hostname/IP parsing.
+ + document that enclosing 'host' value in square brackets forces its
+   interpretation as an IP literal (hence skips name resolution).
  - documentation: replace example.org with example.net for consistency.
 
  -- Guilhem Moulin <guilhem@fripost.org>  Thu, 10 Dec 2020 14:22:05 +0100
diff --git a/doc/interimap.1.md b/doc/interimap.1.md
index 2c9ddc6..ab35275 100644
--- a/doc/interimap.1.md
+++ b/doc/interimap.1.md
@@ -317,7 +317,9 @@ Valid options are:
 
 *host*
 
-:   Server hostname, for `type=imap` and `type=imaps`.
+:   Server hostname or IP address, for `type=imap` and `type=imaps`.
+    The value can optionally be enclosed in square brackets to force its
+    interpretation as an IP literal (hence skip name resolution).
     (Default: `localhost`.)
 
 *port*
diff --git a/doc/pullimap.1.md b/doc/pullimap.1.md
index 42ea282..57790a6 100644
--- a/doc/pullimap.1.md
+++ b/doc/pullimap.1.md
@@ -139,7 +139,9 @@ Valid options are:
 
 *host*
 
-:   Server hostname, for `type=imap` and `type=imaps`.
+:   Server hostname or IP address, for `type=imap` and `type=imaps`.
+    The value can optionally be enclosed in square brackets to force its
+    interpretation as an IP literal (hence skip name resolution).
     (Default: `localhost`.)
 
 *port*
diff --git a/lib/Net/IMAP/InterIMAP.pm b/lib/Net/IMAP/InterIMAP.pm
index 849dc0f..e3a539d 100644
--- a/lib/Net/IMAP/InterIMAP.pm
+++ b/lib/Net/IMAP/InterIMAP.pm
@@ -1446,23 +1446,39 @@ my $RE_IPv6 = do {
       | (?: (?: $h16 : ){0,6} $h16 )? ::
       /x };
 
+# Parse an IPv4 or IPv6.  In list context, return a pair (IP, family),
+# otherwise only the IP.  If the argument is not an IP (for instance if
+# it's a hostname), then return (undef, undef) resp. undef.  The input
+# can optionaly be enclosed in square brackets which forces its
+# interpretation as an IP literal: an error is raised if it is not the
+# case.
+my $RE_IPv4_anchored = qr/\A($RE_IPv4)\z/;
+my $RE_IPv6_anchored = qr/\A($RE_IPv6)\z/;
+sub _parse_hostip($) {
+    my $v = shift // return;
+    my $literal = $v =~ s/\A\[(.*)\]\z/$1/ ? 1 : 0;
+    my ($ip, $af) = $v =~ $RE_IPv4_anchored ? ($1, AF_INET)
+                  : $v =~ $RE_IPv6_anchored ? ($1, AF_INET6)
+                  : (undef, undef);
+    die "Invalid IP literal: $v\n" if $literal and !defined($ip);
+    return wantarray ? ($ip, $af) : $ip;
+}
 
 # Opens a TCP socket to the given $host and $port.
 sub _tcp_connect($$$) {
     my ($self, $host, $port) = @_;
 
     my %hints = (socktype => SOCK_STREAM, protocol => IPPROTO_TCP);
-    if ($host =~ qr/\A$RE_IPv4\z/) {
-        $hints{family} = AF_INET;
-        $hints{flags} |= AI_NUMERICHOST;
-    } elsif ($host =~ qr/\A\[($RE_IPv6)\]\z/) {
-        $host = $1;
-        $hints{family} = AF_INET6;
+    my ($host2, $family) = _parse_hostip($host);
+    if (defined $family) {
+        $hints{family} = $family;
         $hints{flags} |= AI_NUMERICHOST;
+    } else {
+        $host2 = $host;
     }
 
-    my ($err, @res) = getaddrinfo($host, $port, \%hints);
-    $self->fail("Can't getaddrinfo: $err") if $err ne '';
+    my ($err, @res) = getaddrinfo($host2, $port, \%hints);
+    $self->fail("getaddrinfo($host2): $err") if $err ne '';
 
     SOCKETS:
     foreach my $ai (@res) {
@@ -1520,7 +1536,7 @@ sub _proxify($$$$) {
     $port = getservbyname($port, 'tcp') // $self->fail("Can't getservbyname $port")
         unless $port =~ /\A[0-9]+\z/;
 
-    $proxy =~ /\A([A-Za-z0-9]+):\/\/(\P{Control}*\@)?($RE_IPv4|\[$RE_IPv6\]|[^:]+)(:[A-Za-z0-9]+)?\z/
+    $proxy =~ /\A([A-Za-z0-9]+):\/\/(\P{Control}*\@)?([^:]+|\[[^\]]+\])(:[A-Za-z0-9]+)?\z/
         or $self->fail("Invalid proxy URI $proxy");
     my ($proto, $userpass, $proxyhost, $proxyport) = ($1, $2, $3, $4);
     $userpass =~ s/\@\z// if defined $userpass;
@@ -1553,23 +1569,30 @@ sub _proxify($$$$) {
             $self->fail('SOCKSv5', 'No acceptable authentication methods');
         }
 
-        if ($host !~ /\A(?:$RE_IPv4|\[$RE_IPv6\])\z/ and !$resolv) {
+        my ($hostip, $fam) = _parse_hostip($host);
+        unless (defined($fam) or $resolv) {
             # resove the hostname $host locally
             my ($err, @res) = getaddrinfo($host, undef, {socktype => SOCK_RAW});
-            $self->fail("Can't getaddrinfo: $err") if $err ne '';
-            ($host) = first { defined $_ } map {
+            $self->fail("getaddrinfo($host): $err") if $err ne '';
+            my ($addr) = first { defined($_) } map {
                 my ($err, $ipaddr) = getnameinfo($_->{addr}, NI_NUMERICHOST, NIx_NOSERV);
-                $err eq '' ? $ipaddr : undef
+                $err eq '' ? [$ipaddr,$_->{family}] : undef
             } @res;
-            $self->fail("Can't getnameinfo") unless defined $host;
+            $self->fail("Can't getnameinfo") unless defined $addr;
+            ($hostip, $fam) = @$addr;
         }
 
         # send a CONNECT command (CMD 0x01)
-        my ($typ, $addr) =
-            $host =~ /\A$RE_IPv4\z/                                      ? (0x01, Socket::inet_pton(AF_INET, $host))
-          : ($host =~ /\A\[($RE_IPv6)\]\z/ or $host =~ /\A($RE_IPv6)\z/) ? (0x04, Socket::inet_pton(AF_INET6, $1))
-          :                                                                (0x03, pack('C',length($host)).$host);
-        $self->_xwrite($socket, pack('C4', $v, 0x01, 0x00, $typ).$addr.pack('n', $port));
+        my ($typ, $addr);
+        if (defined $fam) {
+            $typ = $fam == AF_INET ? 0x01 : $fam == AF_INET6 ? 0x04 : $self->panic();
+            $addr = Socket::inet_pton($fam, $hostip);
+        } else {
+            # let the SOCKS server do the resolution
+            $typ = 0x03;
+            $addr = pack('C',length($host)) . $host;
+        }
+        $self->_xwrite($socket, pack('C4', $v, 0x01, 0x00, $typ) . $addr . pack('n', $port));
 
         ($v2, my $r, my $rsv, $typ) = unpack('C4', $self->_xread($socket, 4));
         $self->fail('SOCKSv5', 'Invalid protocol') unless $v == $v2 and $rsv == 0x00;