eml: enforce a maximum header length

[public-inbox.git] / lib / PublicInbox / Eml.pm

diff --git a/lib/PublicInbox/Eml.pm b/lib/PublicInbox/Eml.pm
index 4508bd84c6b1b3457fa7b9247331b94694eabc51..2ccbb6597de406680376ad9a02a419ee53d1015b 100644 (file)
--- a/lib/PublicInbox/Eml.pm
+++ b/lib/PublicInbox/Eml.pm
@@ -41,6 +41,7 @@ $PublicInbox::EmlContentFoo::STRICT_PARAMS = 0;
 our $MAXPARTS = 1000; # same as SpamAssassin
 our $MAXDEPTH = 20; # seems enough, Perl sucks, here
 our $MAXBOUNDLEN = 2048; # same as postfix
+our $header_size_limit = 102400; # same as postfix
 
 my %MIME_ENC = (qp => \&enc_qp, base64 => \&encode_base64);
 my %MIME_DEC = (qp => \&dec_qp, base64 => \&decode_base64);
@@ -68,19 +69,47 @@ sub re_memo ($) {
                                        /ismx
 }
 
+sub hdr_truncate ($) {
+       my $len = length($_[0]);
+       substr($_[0], $header_size_limit, $len) = '';
+       my $end = rindex($_[0], "\n");
+       if ($end >= 0) {
+               ++$end;
+               substr($_[0], $end, $len) = '';
+               warn "header of $len bytes truncated to $end bytes\n";
+       } else {
+               $_[0] = '';
+               warn <<EOF
+header of $len bytes without `\\n' within $header_size_limit ignored
+EOF
+       }
+}
+
 # compatible with our uses of Email::MIME
 sub new {
        my $ref = ref($_[1]) ? $_[1] : \(my $cpy = $_[1]);
-       if ($$ref =~ /(?:\r?\n(\r?\n))/gs) { # likely
-               # This can modify $$ref in-place and to avoid memcpy/memmove
-               # on a potentially large $$ref.  It does need to make a
-               # copy for $hdr, though.  Idea stolen from Email::Simple
-               my $hdr = substr($$ref, 0, pos($$ref), ''); # sv_chop on $$ref
+       # substr() can modify the first arg in-place and to avoid
+       # memcpy/memmove on a potentially large scalar.  It does need
+       # to make a copy for $hdr, though.  Idea stolen from Email::Simple.
+
+       # We also prefer index() on common LFLF emails since it's faster
+       # and re scan can bump RSS by length($$ref) on big strings
+       if (index($$ref, "\r\n") < 0 && (my $pos = index($$ref, "\n\n")) >= 0) {
+               # likely on *nix
+               my $hdr = substr($$ref, 0, $pos + 2, ''); # sv_chop on $$ref
+               chop($hdr); # lower SvCUR
+               hdr_truncate($hdr) if length($hdr) > $header_size_limit;
+               bless { hdr => \$hdr, crlf => "\n", bdy => $ref }, __PACKAGE__;
+       } elsif ($$ref =~ /\r?\n(\r?\n)/s) {
+               my $hdr = substr($$ref, 0, $+[0], ''); # sv_chop on $$ref
                substr($hdr, -(length($1))) = ''; # lower SvCUR
+               hdr_truncate($hdr) if length($hdr) > $header_size_limit;
                bless { hdr => \$hdr, crlf => $1, bdy => $ref }, __PACKAGE__;
        } elsif ($$ref =~ /^[a-z0-9-]+[ \t]*:/ims && $$ref =~ /(\r?\n)\z/s) {
                # body is optional :P
-               bless { hdr => \($$ref), crlf => $1 }, __PACKAGE__;
+               my $hdr = substr($$ref, 0, $header_size_limit + 1);
+               hdr_truncate($hdr) if length($hdr) > $header_size_limit;
+               bless { hdr => \$hdr, crlf => $1 }, __PACKAGE__;
        } else { # nothing useful
                my $hdr = $$ref = '';
                bless { hdr => \$hdr, crlf => "\n" }, __PACKAGE__;
@@ -90,8 +119,8 @@ sub new {
 sub new_sub {
        my (undef, $ref) = @_;
        # special case for messages like <85k5su9k59.fsf_-_@lola.goethe.zz>
-       $$ref =~ /\A(?:(\r?\n))/gs or goto &new;
-       my $hdr = substr($$ref, 0, pos($$ref), ''); # sv_chop on $$ref
+       $$ref =~ /\A(\r?\n)/s or goto &new;
+       my $hdr = substr($$ref, 0, $+[0], ''); # sv_chop on $$ref
        bless { hdr => \$hdr, crlf => $1, bdy => $ref }, __PACKAGE__;
 }
 
@@ -132,8 +161,8 @@ sub mp_descend ($$) {
        # *sigh* just the regexp match alone seems to bump RSS by
        # length($$bdy) on a ~30M string:
        my $epilogue_missing;
-       if ($$bdy =~ /((?:\r?\n)?^--$bnd--[ \t]*\r?$)/gsm) {
-               substr($$bdy, pos($$bdy) - length($1)) = '';
+       if ($$bdy =~ /(?:\r?\n)?^--$bnd--[ \t]*\r?$/sm) {
+               substr($$bdy, $-[0]) = '';
        } else {
                $epilogue_missing = 1;
        }