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.h
+++ b/src/core/ngx_string.h
@@ -60,6 +60,8 @@ void ngx_strlow(u_char *dst, u_char *src
 #define ngx_strstr(s1, s2)  strstr((const char *) s1, (const char *) s2)
 #define ngx_strlen(s)       strlen((const char *) s)
 
+size_t ngx_strnlen(u_char *p, size_t n);
+
 #define ngx_strchr(s1, c)   strchr((const char *) s1, (int) c)
 
 static ngx_inline u_char *