Add HTTP/3 Host header support for ModSecurity

src/ngx_http_modsecurity_access.c

@@ -198,6 +198,11 @@ ngx_http_modsecurity_access_handler(ngx_http_request_t *r)
             case NGX_HTTP_VERSION_20 :
                 http_version = "2.0";
                 break;
+#endif
+#if defined(nginx_version) && nginx_version >= 1025000
+            case NGX_HTTP_VERSION_30 :
+                http_version = "3.0";
+                break;
 #endif
             default :
                 http_version = ngx_str_to_char(r->http_protocol, r->pool);
@@ -233,9 +238,26 @@ ngx_http_modsecurity_access_handler(ngx_http_request_t *r)
         }
 
         /**
-         * Since incoming request headers are already in place, lets send it to ModSecurity
+         * HTTP/3 uses :authority pseudo-header instead of Host header and nginx
+         * parses it into r->headers_in.server (see ngx_http_v3_request.c#L982)
+         * but doesn't add it to the headers list, so ModSecurity never sees it.
          *
+         * Per RFC 9114 §4.3.1, when an HTTP/3 request is normalized to HTTP/1.1,
+         * a `Host` header must be generated from the `:authority` pseudo-header
+         * if `Host` is absent. This code does not check for a pre-existing `Host`
+         * header because, if present, it will be overwritten by the subsequent
+         * call to `msc_add_n_request_header()`.
          */
+        if (strcmp(http_version, "3.0") == 0 && r->headers_in.server.len > 0) {
+            dd("adding Host header from :authority: %.*s",
+               (int)r->headers_in.server.len, r->headers_in.server.data);
+
+            msc_add_n_request_header(ctx->modsec_transaction,
+                (const unsigned char *)"Host", 4,
+                (const unsigned char *)r->headers_in.server.data,
+                r->headers_in.server.len);
+        }
+
         ngx_list_part_t *part = &r->headers_in.headers.part;
         ngx_table_elt_t *data = part->elts;
         ngx_uint_t i = 0;

tests/modsecurity-h3.t

@@ -0,0 +1,143 @@
+#!/usr/bin/perl
+
+# Tests for ModSecurity module (HTTP/3).
+# Tests that Host header from :authority pseudo-header is passed to ModSecurity.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx;
+use Test::Nginx::HTTP3;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+my $t = Test::Nginx->new()->has(qw/http http_v3/)
+	->has_daemon('openssl');
+
+$t->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    ssl_certificate_key localhost.key;
+    ssl_certificate localhost.crt;
+
+    server {
+        listen       127.0.0.1:%%PORT_8980_UDP%% quic;
+        server_name  localhost;
+
+        location / {
+            modsecurity on;
+            modsecurity_rules '
+                SecRuleEngine On
+                SecRule ARGS "@streq whee" "id:10,phase:2"
+            ';
+            return 200 "OK";
+        }
+
+        location /check-host {
+            modsecurity on;
+            modsecurity_rules '
+                SecRuleEngine On
+                SecRule &REQUEST_HEADERS:Host "@gt 0" "id:999,phase:1,log,pass,msg:Host header FOUND with value %{REQUEST_HEADERS.Host}"
+                SecRule &REQUEST_HEADERS:Host "@eq 0" "id:920280,phase:1,deny,status:449,msg:Missing Host Header"
+            ';
+            return 200 "Host header present";
+        }
+
+        location /inspect-host {
+            modsecurity on;
+            modsecurity_rules '
+                SecRuleEngine On
+                SecRule REQUEST_HEADERS:Host "@streq localhost" "id:100,phase:1,pass,setvar:tx.host_matched=1"
+                SecRule TX:host_matched "!@eq 1" "id:101,phase:1,deny,status:400,msg:Host header mismatch"
+            ';
+            return 200 "Host matched";
+        }
+
+    }
+}
+EOF
+
+$t->write_file('openssl.conf', <<EOF);
+[ req ]
+default_bits = 2048
+encrypt_key = no
+distinguished_name = req_distinguished_name
+[ req_distinguished_name ]
+EOF
+
+my $d = $t->testdir();
+
+foreach my $name ('localhost') {
+	system('openssl req -x509 -new '
+		. "-config $d/openssl.conf -subj /CN=$name/ "
+		. "-out $d/$name.crt -keyout $d/$name.key "
+		. ">>$d/openssl.out 2>&1") == 0
+		or die "Can't create certificate for $name: $!\n";
+}
+
+$t->run();
+$t->plan(3);
+
+###############################################################################
+
+my ($s, $sid, $frames, $frame);
+
+$s = Test::Nginx::HTTP3->new();
+$sid = $s->new_stream({
+    headers => [
+        { name => ':method', value => 'GET', mode => 0 },
+        { name => ':scheme', value => 'http', mode => 0 },
+        { name => ':path', value => '/', mode => 0 },
+        { name => ':authority', value => 'localhost', mode => 4 },
+    ]
+});
+$frames = $s->read(all => [{ sid => $sid, fin => 1 }]);
+($frame) = grep { $_->{type} eq "HEADERS" } @$frames;
+is($frame->{headers}->{':status'}, 200, 'basic HTTP/3 request');
+
+$s = Test::Nginx::HTTP3->new();
+$sid = $s->new_stream({
+    headers => [
+        { name => ':method', value => 'GET', mode => 0 },
+        { name => ':scheme', value => 'http', mode => 0 },
+        { name => ':path', value => '/check-host', mode => 4 },
+        { name => ':authority', value => 'localhost', mode => 4 },
+    ]
+});
+$frames = $s->read(all => [{ sid => $sid, fin => 1 }]);
+($frame) = grep { $_->{type} eq "HEADERS" } @$frames;
+is($frame->{headers}->{':status'}, 200, 'Host header from :authority visible to ModSecurity');
+
+$s = Test::Nginx::HTTP3->new();
+$sid = $s->new_stream({
+    headers => [
+        { name => ':method', value => 'GET', mode => 0 },
+        { name => ':scheme', value => 'http', mode => 0 },
+        { name => ':path', value => '/inspect-host', mode => 4 },
+        { name => ':authority', value => 'localhost', mode => 4 },
+    ]
+});
+$frames = $s->read(all => [{ sid => $sid, fin => 1 }]);
+($frame) = grep { $_->{type} eq "HEADERS" } @$frames;
+is($frame->{headers}->{':status'}, 200, 'Host header value matches :authority');
+
+###############################################################################