Bad permissions in /var/log/nginx after logs are rotated

[Juan Fco. Giordana]

Hello,

I'm using daemontools to run nginx [1] and I'm experiencing the 
following problem when I send the USR1 signal to rotate the logs with 
another script [2]:

The problem is that after sending the USR1 signal to nginx, the logs 
owner becomes 'nginx' instead of 'root', which is a potential security 
breach.

~ # ls -la /var/log/nginx
total 627
drwxr-xr-x  2 root root   1088 Feb 23 04:29 .
drwxr-xr-x 15 root root   1088 Feb 22 01:27 ..
-rw-r--r--  1 root root      0 Feb 23 04:25 access_log
-rw-r--r--  1 root root      0 Feb 23 04:25 error_log
-rw-r--r--  1 root root  19164 Feb 23 04:29 site1.com-access_log
-rw-r--r--  1 root root      0 Feb 23 04:25 site1.com-error_log
-rw-r--r--  1 root root      0 Feb 23 04:25 site1.com-ssl_access_log
-rw-r--r--  1 root root      0 Feb 23 04:25 site1.com-ssl_error_log

~ # nginx-rotate.sh [2]

~ # ls -la /var/log/nginx
total 11
drwxr-xr-x  3 root  root 1112 Feb 23 04:29 .
drwxr-xr-x 15 root  root 1088 Feb 22 01:27 ..
drwxr-xr-x  2 root  root 1088 Feb 23 04:29 old
-rw-r--r--  1 nginx root    0 Feb 23 04:29 access_log
-rw-r--r--  1 nginx root    0 Feb 23 04:29 error_log
-rw-r--r--  1 nginx root  123 Feb 23 04:29 site1.com-access_log
-rw-r--r--  1 nginx root    0 Feb 23 04:29 site1.com-error_log
-rw-r--r--  1 nginx root    0 Feb 23 04:29 site1.com-ssl_access_log
-rw-r--r--  1 nginx root    0 Feb 23 04:29 site1.com-ssl_error_log

If instead of this if I restart [3] the nginx process or send the HUP 
signal [4] then the log files permissions remains correct (owned by root).

I'm not sure if this is a bug or a known issue but I appreciate any 
clarifications.

Thanks.


[1] nginx daemontools startup script:
#! /bin/sh -

exec 2>&1
exec /srv/sbin/nginx -c /srv/etc/nginx/nginx.conf


[2] nginx log rotation script
#! /bin/sh -

cd /var/log/nginx
mkdir -p old
mv *_log old

kill -USR1 `cat /var/run/nginx.pid`

sudo -u user /home/user/awstats.sh
rm /var/log/nginx/old/*access_log

[3]
# Send TERM signal
svc -t /service/nginx

# OR stop and start
svc -d /service/nginx
# ... rotate logs
svc -u /service/nginx

[4]
svc -h /service/nginx