From: Aki Tuomi <aki.tuomi@open-xchange.com>
Date: Tue, 23 Sep 2025 09:58:07 +0000 (+0300)
Subject: lib-var-expand: regex - Support older back references
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2ad89fd4c7fcbd8830588f1ca1abffae973f983a;p=thirdparty%2Fdovecot%2Fcore.git

lib-var-expand: regex - Support older back references
---

diff --git a/src/lib-var-expand/expansion-filter.c b/src/lib-var-expand/expansion-filter.c
index 4bff618d97..a72bd1e132 100644
--- a/src/lib-var-expand/expansion-filter.c
+++ b/src/lib-var-expand/expansion-filter.c
@@ -750,6 +750,32 @@ static int fn_ldap_dn(const struct var_expand_statement *stmt,
 	return 0;
 }
 
+static const char *fix_replacement_pattern(const char *pattern)
+{
+	const char *p1, *p0 = pattern;
+	string_t *dest = t_str_new(strlen(pattern));
+
+	while ((p1 = strchr(p0, '\\')) != NULL) {
+		str_append_data(dest, p0, p1 - p0);
+		if (i_isdigit(p1[1])) {
+			str_append_c(dest, '$');
+			str_append_c(dest, p1[1]);
+			p1 += 2;
+		} else if (p1[1] == '\\') {
+			str_append_c(dest, '\\');
+			p1 += 2;
+		} else {
+			str_append_c(dest, *p1);
+			p1++;
+		}
+		p0 = p1;
+	}
+
+	str_append(dest, p0);
+
+	return str_c(dest);
+}
+
 static int fn_regexp(const struct var_expand_statement *stmt,
 		     struct var_expand_state *state, const char **error_r)
 {
@@ -798,6 +824,11 @@ static int fn_regexp(const struct var_expand_statement *stmt,
 	const char *input ATTR_UNUSED = str_c(state->transfer);
 	string_t *dest = t_str_new(strlen(rep));
 
+	if (strchr(rep, '\\') != NULL) {
+		/* fix replacement pattern */
+		rep = fix_replacement_pattern(rep);
+	}
+
 	int ret = dregex_replace(pat, input, rep, dest, 0, error_r);
 
 	if (ret > 0)
diff --git a/src/lib-var-expand/test-var-expand.c b/src/lib-var-expand/test-var-expand.c
index 6ee360c637..2e7ba232a7 100644
--- a/src/lib-var-expand/test-var-expand.c
+++ b/src/lib-var-expand/test-var-expand.c
@@ -199,6 +199,9 @@ static void test_var_expand_builtin_filters(void) {
 #ifdef HAVE_LIBPCRE
 		/* regexp */
 		{ .in = "%{literal('hello world') | regexp('(.*) (.*)', '$2 $1')}", .out = "world hello" },
+		{ .in = "%{literal('hello world') | regexp('(.*) (.*)', '\\\\2 \\\\1')}", .out = "world hello" },
+		{ .in = "%{literal('hello world') | regexp('(.*) (.*)', '\\\\\\\\2 \\\\\\\\1')}", .out = "\\2 \\1" },
+		{ .in = "%{literal('hello world') | regexp('(.*) (.*)', '\\\\\\\\\\\\2 \\\\\\\\\\\\1')}", .out = "\\world \\hello" },
 #endif
 		/* index */
 		{ .in = "%{user | index('@',0)}", .out = "user", .ret = 0 },