Bug 2192395
| Summary: | sftp fails without -d (debugmode) | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | customercare |
| Component: | openssh | Assignee: | Dmitry Belyavskiy <dbelyavs> |
| Status: | NEW --- | QA Contact: | Fedora Extras Quality Assurance <extras-qa> |
| Severity: | high | Docs Contact: | |
| Priority: | medium | ||
| Version: | 37 | CC: | crypto-team, dbelyavs, dwalsh, jjelen, lkundrak, mattias.ellert, tm |
| Target Milestone: | --- | Keywords: | Triaged |
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | Type: | Bug | |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
Could you please check it against upstream? I don't recall any sftp patches that could cause such behavior. whats the best build source? https://www.openssh.com/portable.html - the last one (9.3p1) from any mirrors. Server# /usr/src/openssh/openssh/sshd -V -D -p 30 OpenSSH_9.3, OpenSSL 3.0.8 7 Feb 2023 Server# /usr/src/openssh/openssh/sshd -D -p 30 Client# sftp -P 30 user@thatserver Connected to thatserver. sftp> ls -la /proc/ dr-xr-xr-x 3 root root 4096 Apr 25 19:53 . drwxr-xr-x 18 root root 4096 Apr 25 14:31 .. drwxr-xr-x 3 root root 4096 Apr 19 15:03 self sftp> exit So the unpatched native openssh-server version works like a charm on a Fedora 37. My Buildline looks like this: ./configure --with-md5-passwords --with-pam --with-selinux --sysconfdir=/etc/ssh and for my stuff, it seems to work. So... do you finally upgrade to 9.3 or do I need to create a replacement rpm for my Fedora Cluster? :D |
Description of problem: The server in question has a chroot env with a fake /proc to deny attackers, who gained control, to proceed further and check processid's etc. etc. /opt/root/proc/ └── self └── fd ├── 0 -> /dev/pts/0 ├── 1 -> /dev/pts/0 ├── 2 -> /dev/pts/0 └── 3 ├── 0 -> /dev/null └── 9 -> /dev/null 4 directories, 5 files sshd puts anyone except root in this chroot. A none-root user with ssh as client can log into the system and start bash -> op success A none-root user with sftp as client can not log into the system -> op fail At this point we started sshd manually to use strace to dig into it. As long as sshd is not started with at least one "-d" option, sftp keeps failing. As soon as we start sshd with "-d" option, which means debug level 1, sftp can flawlessly log in and use the server inside the chroot as it should be -> op success Conclusion: something besides the obvious log_print() changes inside openssh-server changes to make sftp work. I can not verify IF this is a Fedora only bug due to the many downstream patches or a common bug in all releases. Version-Release number of selected component (if applicable): Name : openssh-server Version : 8.8p1 Release : 10.fc37 Architecture: x86_64 Install Date: Mo 01 Mai 2023 17:54:23 CEST How reproducible: - create a chroot with minimal system and bash - mkdir /chroot/proc mkdir -p /chroot/proc/self/fd/3 ln -s /dev/pts/0 /chroot/proc/self/fd/0 ln -s /dev/pts/0 /chroot/proc/self/fd/1 ln -s /dev/pts/0 /chroot/proc/self/fd/2 ln -s /dev/null /chroot/proc/self/fd/3/0 ln -s /dev/null /chroot/proc/self/fd/3/9 - mount dev to /chroot/dev change your /etc/ssh/sshd_config and add: ChrootDirectory /opt/root/ Match user root ChrootDirectory none now stop sshd and run it manually i.e. on another port: $(which sshd) -D -p 22 $(which sshd) -D -d -p 22 and try sftp to log into your none-root account ( you may need to copy /etc/passwd etc. into the chroot env ) it will fail. O== Wanted solution working sftp without enabling debug mode and without a /proc filesystem (if you have a better idea than the described above, i'm all ear)