# HG changeset patch
# User Roman Arutyunyan <arut@nginx.com>
# Date 1503426179 -10800
# Node ID c7d4017c8876af6d8570e400320537d7d39e9578
# Parent  acc2cddc7b451046d45aeed62ab7f2661fd2808c
Secure link: fixed stack buffer overflow.

When secure link checksum has length of 23 or 24 bytes, decoded base64 value
could occupy 17 or 18 bytes which is more than 16 bytes previously allocated
for it on stack.  The buffer overflow does not have any security implications
since only one local variable was corrupted and this variable was not used in
this case.

The fix is to increase buffer size up to 18 bytes.  Useless buffer size
initialization is removed as well.

diff --git a/src/http/modules/ngx_http_secure_link_module.c b/src/http/modules/ngx_http_secure_link_module.c
--- a/src/http/modules/ngx_http_secure_link_module.c
+++ b/src/http/modules/ngx_http_secure_link_module.c
@@ -107,7 +107,7 @@ ngx_http_secure_link_variable(ngx_http_r
     ngx_md5_t                     md5;
     ngx_http_secure_link_ctx_t   *ctx;
     ngx_http_secure_link_conf_t  *conf;
-    u_char                        hash_buf[16], md5_buf[16];
+    u_char                        hash_buf[18], md5_buf[16];
 
     conf = ngx_http_get_module_loc_conf(r, ngx_http_secure_link_module);
 
@@ -154,7 +154,6 @@ ngx_http_secure_link_variable(ngx_http_r
         goto not_found;
     }
 
-    hash.len = 16;
     hash.data = hash_buf;
 
     if (ngx_decode_base64url(&hash, &val) != NGX_OK) {