diff --git a/lib/util/samba_util.h b/lib/util/samba_util.h
index 4e279b72df1..ca185909997 100644
--- a/lib/util/samba_util.h
+++ b/lib/util/samba_util.h
@@ -325,6 +325,20 @@ _PUBLIC_ bool conv_str_u64(const char * str, uint64_t * val);
  */
 _PUBLIC_ int memcmp_const_time(const void *s1, const void *s2, size_t n);
 
+/**
+ * @brief Build up a string buffer, handle allocation failure
+ *
+ * @param[in] ps Pointer to the talloc'ed string to be extended
+ * @param[in] fmt The format string
+ * @param[in] ... The parameters used to fill fmt.
+ *
+ * This does nothing if *ps is NULL and sets *ps to NULL if the
+ * intermediate reallocation fails. Useful when building up a string
+ * step by step, no intermediate NULL checks are required.
+ */
+
+_PUBLIC_ void talloc_asprintf_addbuf(char **ps, const char *fmt, ...) PRINTF_ATTRIBUTE(2,3);
+
 /**
 Do a case-insensitive, whitespace-ignoring string compare.
 **/
diff --git a/lib/util/util_str.c b/lib/util/util_str.c
index da1989f80f2..b5ba3fb716b 100644
--- a/lib/util/util_str.c
+++ b/lib/util/util_str.c
@@ -316,3 +316,26 @@ _PUBLIC_ int memcmp_const_time(const void *s1, const void *s2, size_t n)
 
 	return sum != 0;
 }
+
+_PUBLIC_ void talloc_asprintf_addbuf(char **ps, const char *fmt, ...)
+{
+	va_list ap;
+	char *s = *ps;
+	char *t = NULL;
+
+	if (s == NULL) {
+		return;
+	}
+
+	va_start(ap, fmt);
+	t = talloc_vasprintf_append_buffer(s, fmt, ap);
+	va_end(ap);
+
+	if (t == NULL) {
+		/* signal failure to the next caller */
+		TALLOC_FREE(s);
+		*ps = NULL;
+	} else {
+		*ps = t;
+	}
+}