Correcly handle comments appended to nameserver declarations (#14658)

normanmaurer · bryce-anderson · web-flow · commit 1bd459ac11ff · 2025-01-13T21:24:00.000+01:00
Motivation: We need to ensure we correctly filter out appended comments in resolv.conf Modifications: - Skip comments - Add unit test Result: Fixes #14514 --------- Co-authored-by: Bryce Anderson <bl_anderson@apple.com>
diff --git a/resolver-dns/src/main/java/io/netty/resolver/dns/ResolvConf.java b/resolver-dns/src/main/java/io/netty/resolver/dns/ResolvConf.java
@@ -80,7 +80,15 @@ private ResolvConf(BufferedReader reader) throws IOException {
             }
 
             if (ln.startsWith("nameserver")) {
-                ln = ln.substring("nameserver".length()).trim();
+                ln = ln.substring("nameserver".length());
+                int cIndex = ln.indexOf('#');
+                if (cIndex != -1) {
+                    ln = ln.substring(0, cIndex);
+                }
+                ln = ln.trim();
+                if (ln.isEmpty()) {
+                    continue;
+                }
                 nameservers.add(new InetSocketAddress(ln, 53));
             }
         }
diff --git a/resolver-dns/src/test/java/io/netty/resolver/dns/ResolvConfTest.java b/resolver-dns/src/test/java/io/netty/resolver/dns/ResolvConfTest.java
@@ -48,13 +48,13 @@ public void readSystem() {
     @MethodSource
     public void scenarios(String resolvConf, List<String> nameservers) throws Exception {
         assertIterableEquals(
-                ResolvConf.fromReader(new BufferedReader(new StringReader(resolvConf))).getNameservers(),
                 nameservers.stream().map(new Function<String, InetSocketAddress>() {
                     @Override
                     public InetSocketAddress apply(String n) {
                         return new InetSocketAddress(n, 53);
                     }
-                }).collect(Collectors.toList()));
+                }).collect(Collectors.toList()),
+                ResolvConf.fromReader(new BufferedReader(new StringReader(resolvConf))).getNameservers());
     }
 
     static List<Arguments> scenarios() {
@@ -74,6 +74,11 @@ static List<Arguments> scenarios() {
                                 + "nameserver 1.2.3.4\n"
                                 + "nameserver 127.1.2.3",
                         Arrays.asList("1.2.3.4", "127.1.2.3")),
+                arguments(
+                        "# some comment\n"
+                                + "nameserver 1.2.3.4 # comment\n"
+                                + "nameserver 127.1.2.3",
+                        Arrays.asList("1.2.3.4", "127.1.2.3")),
                 arguments(
                         "# some comment\n" + "nameserver 0:0:0:0:0:0:0:1\n" + "nameserver 127.0.0.1",
                         Arrays.asList("0:0:0:0:0:0:0:1", "127.0.0.1")),

Original file line number	Diff line number	Diff line change
`@@ -80,7 +80,15 @@ private ResolvConf(BufferedReader reader) throws IOException {`
`80`	`80`	`}`
`81`	`81`
`82`	`82`	`if (ln.startsWith("nameserver")) {`
`83`		`- ln = ln.substring("nameserver".length()).trim();`
	`83`	`+ ln = ln.substring("nameserver".length());`
	`84`	`+ int cIndex = ln.indexOf('#');`
	`85`	`+ if (cIndex != -1) {`
	`86`	`+ ln = ln.substring(0, cIndex);`
	`87`	`+ }`
	`88`	`+ ln = ln.trim();`
	`89`	`+ if (ln.isEmpty()) {`
	`90`	`+ continue;`
	`91`	`+ }`
`84`	`92`	`nameservers.add(new InetSocketAddress(ln, 53));`
`85`	`93`	`}`
`86`	`94`	`}`