From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Tue, 10 Mar 2026 20:09:42 +0000 (+0200)
Subject: lib: punycode_decode() - Fix parsing empty string [after delimiter]
X-Git-Tag: 2.4.3~100
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=faee72d64d5a014361b8ecbfffefd9761766029d;p=thirdparty%2Fdovecot%2Fcore.git

lib: punycode_decode() - Fix parsing empty string [after delimiter]

This caused an assert crash when --enable-experimental-mail-utf8 was
used and invalid punycode domain was being parsed.

Based on code by rootvector2 (Dexter.k)
---

diff --git a/src/lib/punycode.c b/src/lib/punycode.c
index 1c8853a8b6..c9e03a5f8d 100644
--- a/src/lib/punycode.c
+++ b/src/lib/punycode.c
@@ -90,6 +90,8 @@ int punycode_decode(const char *input, size_t len, string_t *output)
 		ptr = delim + 1;
 	else
 		ptr = input;
+	if (ptr == end)
+		return -1;
 
 	i_assert(ptr < end);
 	while (ptr < end) {
diff --git a/src/lib/test-punycode.c b/src/lib/test-punycode.c
index 485a5cfa42..f6ed829de2 100644
--- a/src/lib/test-punycode.c
+++ b/src/lib/test-punycode.c
@@ -25,6 +25,8 @@ static void test_punycode_decode(void)
 		  .ret = 0 },
 		/* broken */
 		{ .in = "zz-zzzz", .out = "", .ret = -1 },
+		{ .in = "zz-", .out = "", .ret = -1 },
+		{ .in = "", .out = "", .ret = -1 },
 	};
 
 	unsigned int i;