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SFTP chroot users are unable to upload to a subdirectory in home folder with supplementary group ownership after upgrading to latest version of openssh
Description of problem:
After upgrading to "openssh-6.6.1p1-31.el7.x86_64", sftp chroot users are unable to write/execute to a sub-directory in their home folder. The sub directory's ownership is different, though the sftp user is a part of the group, of the new ownership.
This was working fine in "openssh-6.6.1p1-25.el7_2.x86_64"
Version-Release number of selected component (if applicable): openssh-6.6.1p1-31.el7.x86_64
How reproducible:
Always
Steps to Reproduce:
1. Follow steps to create SFTP chroot users as per: https://access.redhat.com/solutions/20764
2. Create an additional group, add it as a supplementary group of the sftp user.
3. Within the home directory of the sftp user, create a sub-directory with the new group ownership.
4. SFTP in and attempt put, get and rm commands after moving into the sub directory
Additional info:
Reproducer details -
# getenforce
Permissive
sftp user: test-user
Supplementary group: oper
# id test-user
uid=1000(test-user) gid=1000(sftponly) groups=1000(sftponly),1002(oper)
# grep test-user /etc/passwd
test-user:x:1000:1000::/myhome:/bin/false
/etc/ssh/sshd_config:
...
Subsystem sftp internal-sftp
Match Group sftponly
ChrootDirectory /chroots/%u
AllowTcpForwarding no
ForceCommand internal-sftp
X11Forwarding no
# ll -R /chroots/
/chroots/:
total 0
drwxr-xr-x. 3 root root 19 Nov 25 12:27 test-user
/chroots/test-user:
total 0
drwxr-xr-x. 3 test-user sftponly 20 Nov 25 14:45 myhome
/chroots/test-user/myhome:
total 0
drwxrwxr-x. 2 root oper 32 Nov 25 15:10 testdir
Actual results:
sftp> pwd
Remote working directory: /myhome
sftp> put test.txt
Uploading test.txt to /myhome/test.txt
test.txt 100% 0 0.0KB/s 00:00
sftp> cd testdir/
sftp> put test.txt
Uploading test.txt to /myhome/testdir/test.txt
remote open("/myhome/testdir/test.txt"): Permission denied
sftp> get sub_list
Fetching /myhome/testdir/sub_list to sub_list
/myhome/testdir/sub_list 100% 166 36.9KB/s 00:00
sftp> rm sub_list
Removing /myhome/testdir/sub_list
Couldn't delete file: Permission denied
Expected results:
sftp> put mozilla.pdf
Uploading mozilla.pdf to /myhome/testdir/mozilla.pdf
mozilla.pdf
sftp> rm mozilla.pdf
Removing /myhome/testdir/mozilla.pdf
Other logs:
- Nothing in /var/lg/secure on tailing this when it happens, LogLevel is DEBUG3.
- strace of the sftp process on the server shows:
# strace -ttTvf -s 4096 -p 12675
Process 12675 attached
14:54:42.664495 select(2, [0], [], NULL, NULL) = 1 (in [0]) <9.040468>
14:54:51.732312 read(0, "\0\0\0-\3\0\0\0$\0\0\0\30/myhome/testdir/test.txt\0\0\0\32\0\0\0\4\0\0\1\264", 16384) = 49 <0.001814>
14:54:51.738676 open("/myhome/testdir/test.txt", O_WRONLY|O_CREAT|O_TRUNC, 0664) = -1 EACCES (Permission denied) <0.003286>
14:54:51.753734 select(2, [0], [1], NULL, NULL) = 1 (out [1]) <0.002482>
14:54:51.762840 write(1, "\0\0\0\"e\0\0\0$\0\0\0\3\0\0\0\21Permission denied\0\0\0\0", 38) = 38 <0.002549>
14:54:51.773565 select(2, [0], [], NULL, NULL