Fixed handling of non-null-terminated unix sockets. At least FreeBSD, macOS, NetBSD, and OpenBSD can return unix sockets with non-null-terminated sun_path. Additionally, the address may become non-null-terminated if it does not fit into the buffer provided and was truncated (may happen on macOS, NetBSD, and Solaris, which allow unix socket addresess larger than struct sockaddr_un). As such, ngx_sock_ntop() might overread the sockaddr provided, as it used "%s" format and thus assumed null-terminated string. To fix this, the ngx_strnlen() function was introduced, and it is now used to calculate correct length of sun_path.

--- a/src/core/ngx_string.c
+++ b/src/core/ngx_string.c
@@ -29,6 +29,22 @@ ngx_strlow(u_char *dst, u_char *src, siz
 }
 
 
+size_t
+ngx_strnlen(u_char *p, size_t n)
+{
+    size_t  i;
+
+    for (i = 0; i < n; i++) {
+
+        if (p[i] == '\0') {
+            return i;
+        }
+    }
+
+    return n;
+}
+
+
 u_char *
 ngx_cpystrn(u_char *dst, u_char *src, size_t n)
 {