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Description of problem:
sftp -m doesn't work as advertised.
Reference- https://access.redhat.com/solutions/32851
Version-Release number of selected component (if applicable):
openssh-server-5.3p1-118.1.el6_8.x86_64
How reproducible:
Always.
Steps to Reproduce:
As root: su -
01. yum install openssh openssh-server openssh-clients
02. useradd testuser
# grep testuser /etc/passwd
testuser:x:502:502::/home/testuser:/bin/bash
03. passwd testuser
04. vim /etc/ssh/sshd_config
modify the file as shown in *figure 1*
05. service sshd restart
06. # mkdir -p /www/server/docs ; chown testuser /www/server/docs ; chgrp testuser /www/server/docs
compare permissions to *figure 2*
07. su - testuser
$ pwd
/home/testuser
08. mkdir test ; cd test
$ pwd
/home/testuser/test
09. touch 1 2 3
$ ls
1 2 3
10. setenforce 0
disable selinux to simplify the permissions test
11. $ sftp localhost
Connecting to localhost...
testuser@localhost's password:
12. sftp> cd docs
13. sftp> put 1
14. sftp> mkdir a
15. sftp> exit
16. # pwd
/www/server/docs
17. # ls -la
total 12
drwxr-xr-x. 3 testuser testuser 4096 Jun 1 12:19 .
drwxr-xr-x. 3 root root 4096 Jun 1 11:57 ..
-rw-rw-r--. 1 testuser testuser 0 Jun 1 12:18 1 <<<
drwxrwxrwx. 2 testuser testuser 4096 Jun 1 12:19 b <<<
18. $ umask
0002
The umask for files and directories have not been
changed from the RHEL 6 default
figure 1:
# cat /etc/ssh/sshd_config
Protocol 2
SyslogFacility AUTHPRIV
PasswordAuthentication yes
ChallengeResponseAuthentication no
GSSAPIAuthentication yes
GSSAPICleanupCredentials yes
UsePAM yes
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL
X11Forwarding yes
Subsystem sftp internal-sftp
Match user testuser
ChrootDirectory /www/server
AllowTCPForwarding no
X11Forwarding no
ForceCommand internal-sftp -m 664
figure 2:
# ls -la /www/server/
total 12
drwxr-xr-x. 3 root root 4096 Jun 1 11:57 .
drwxr-xr-x. 3 root root 4096 Jun 1 11:57 ..
drwxr-xr-x. 3 testuser testuser 4096 Jun 1 12:12 docs
Actual results:
File (1) got the right permissions (664), but the directory (b) has elevated write permissions (777).
Expected results:
664 permissions
Additional info:
Oddly, if you continue to create subsiquent directories, they will have the correct permissions.
sftp> mkdir c
sftp> mkdir d
...
drwxr-xr-x. 2 testuser testuser 4096 Jun 1 12:28 c
drwxr-xr-x. 2 testuser testuser 4096 Jun 1 12:29 d
Manual page describes the option as
-m force_file_perms
Sets explicit file permissions to be applied to newly-created files [...]
It affects only files. Created directories are not affected by this option, because directory permissions are of different nature.
The directory creation is affected only by the umask (-u) settings and permission inheritance in filesystem. Maybe the note
Option -u is ineffective if -m is set.
is a bit misleading, since it still applies on the directories.
Can you verify with customer that the settings
ForceCommand internal-sftp -m 664 -u 113
will solve the issue in this case?
Response from Customer:
No, it doesn't ( you should be able to try it yourself too):
Config file:
[..]
Match user deployhq
AllowTCPForwarding no
X11Forwarding no
# next one gave me 644 for files, drwxrwsr-x for dir
#ForceCommand internal-sftp -u 002
# next one gave me 664 for file; 777 for dir
#ForceCommand internal-sftp -m 664
# Trying what Redhat says:
ForceCommand internal-sftp -m 664 -u 113
----------------
# ls -l
total 8
-rw-rw-r--. 1 deployhq cms 499 Jun 7 15:12 a
drwxrwsrwx. 2 deployhq cms 4096 Jun 7 15:12 b
Please advise.
Created attachment 1166246[details]
patch restoring old umask settings
Ouch. That is embarrassing.
If you would create the directory first and the file later, it would get the expected permissions. But you did the file first and then the umask is overwritten (for file creation) and not restored afterward, which is certainly a bug. It probably slipped through both me and our testing.
The attached patch should solve the issue. I attached also the scratch build with this patch applied:
https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=11160702
Can you verify that it works for you too (or possibly with a customer?).
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHSA-2017-0641.html