[nginx] Mp4: fixed reading 64-bit atoms.

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/fdc19a3289c1
branches:  stable-1.14
changeset: 7384:fdc19a3289c1
user:      Roman Arutyunyan <arut at nginx.com>
date:      Tue Nov 06 16:29:18 2018 +0300
description:
Mp4: fixed reading 64-bit atoms.

Previously there was no validation for the size of a 64-bit atom
in an mp4 file.  This could lead to a CPU hog when the size is 0,
or various other problems due to integer underflow when calculating
atom data size, including segmentation fault or worker process
memory disclosure.

diffstat:

 src/http/modules/ngx_http_mp4_module.c |  7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diffs (17 lines):

diff --git a/src/http/modules/ngx_http_mp4_module.c b/src/http/modules/ngx_http_mp4_module.c
--- a/src/http/modules/ngx_http_mp4_module.c
+++ b/src/http/modules/ngx_http_mp4_module.c
@@ -942,6 +942,13 @@ ngx_http_mp4_read_atom(ngx_http_mp4_file
                 atom_size = ngx_mp4_get_64value(atom_header + 8);
                 atom_header_size = sizeof(ngx_mp4_atom_header64_t);
 
+                if (atom_size < sizeof(ngx_mp4_atom_header64_t)) {
+                    ngx_log_error(NGX_LOG_ERR, mp4->file.log, 0,
+                                  "\"%s\" mp4 atom is too small:%uL",
+                                  mp4->file.name.data, atom_size);
+                    return NGX_ERROR;
+                }
+
             } else {
                 ngx_log_error(NGX_LOG_ERR, mp4->file.log, 0,
                               "\"%s\" mp4 atom is too small:%uL",