[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
This bug was fixed in the package openssh - 1:7.2p2-4ubuntu2.10
---
openssh (1:7.2p2-4ubuntu2.10) xenial; urgency=medium
* Fix deadlock when AuthorizedKeysCommand produces a large output.
(LP: #1877454)
- d/p/authkeyscommand-deadlock-01.patch: Make sure to call fclose(2)
and assign NULL to the file handler used to read
"Authorized{Keys,Principal}Command" directives.
- d/p/authkeyscommand-deadlock-02.patch: Consume entire output
generated by the command pointed by
"Authorized{Keys,Principal}Command" in order to avoid sending a
SIGPIPE to the process.
openssh (1:7.2p2-4ubuntu2.9) xenial; urgency=medium
* Apply upstream patch to stop using 2020 as a future date in regress
tests. LP: #1859013
-- Sergio Durigan Junior Wed, 13 May
2020 10:12:28 -0400
** Changed in: openssh (Ubuntu Xenial)
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/1877454
Title:
openssh-server hangs with AuthorizedKeysCommand
Status in openssh package in Ubuntu:
Fix Released
Status in openssh source package in Xenial:
Fix Released
Bug description:
[Impact]
On a default Xenial install, when sshd is configured to obtain the
list of allowed keys using AuthorizedKeysCommand (or the list of
allowed certificate principals using AuthorizedPrincipalsCommand), and
if the command pointed by Authorized{Keys,Principals}Command generates
a lot of output, sshd will hang while reading this same output. In a
nutshell, the problem happens when the subprocess generates enough
data to fill the pipe's buffer; in this scenario, sshd will wait(2) on
the subprocess, which will be blocked trying to write the rest of the
output.
[Test Case]
In order to reproduce the bug, one can:
$ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
$ lxc shell openssh-server-bug1877454
# ssh-keygen
(no need to choose a passphrase for the key, just hit ENTER on all prompts)
# cat > authkeyscommand.sh << __EOF__
#!/bin/bash
cat /root/.ssh/id_rsa.pub
echo
head -c 1M < /dev/urandom
__EOF__
# chmod +x authkeyscommand.sh
# cat >> /etc/ssh/sshd_config << __EOF__
AuthorizedKeysCommand /root/authkeyscommand.sh
AuthorizedKeysCommandUser root
__EOF__
# systemctl reload sshd.service
# ssh root@127.0.0.1
You will notice that ssh will stay there waiting for sshd's reply,
which won't come. The expected result would be for ssh to succeed.
[Regression Potential]
Since the affected code deals with executing a subprocess, reading its
output through a pipe, and then relying on wait(2) to determine
whether the subprocess exited correctly; and considering that this
code is written in C without the help of features like RAII and with
the use of goto statements, we are not able to disconsider the chances
of making a mistake and forgetting to free a resource or to properly
read/write from/to pipes, for example. This is, after all, the reason
the bug happened in the first place.
Having said that, openssh contains extensive tests and the code is
well organized and relatively easy to follow. Upon close inspection,
there doesn't seem to be an evident problem with the backported fixes.
As usual when dealing with a somewhat older distribution, there is
always the possibility of encountering problems because we will be
recompiling openssh using the most recent versions of its build
dependencies.
[Original Description]
Please consider applying this change to openssh-server distributed in Xenial
(16.04).
Without it, sshd can sporadically hang when making use of the
`AuthorizedKeysCommand` option.
https://github.com/openssh/openssh-
portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions
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Re: [Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
On Thursday, June 25 2020, Łukasz Zemczak wrote:
> Thank you for the verification Sergio! Could you please note down which
> package version has been used for verification and what kind of
> verification has been performed?
Hi Łukasz,
The package version I tested is 1:7.2p2-4ubuntu2.10. I performed the
steps listed in the "Test Case" section of the SRU above. Everything
worked as expected:
$ ssh root@127.0.0.1
Warning: Permanently added '127.0.0.1' (ECDSA) to the list of known hosts.
Welcome to Ubuntu 16.04.6 LTS (GNU/Linux 5.4.0-31-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support:https://ubuntu.com/advantage
The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.
$
Thanks!
--
Sergio
GPG key ID: E92F D0B3 6B14 F1F4 D8E0 EB2F 106D A1C8 C3CB BF14
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https://bugs.launchpad.net/bugs/1877454
Title:
openssh-server hangs with AuthorizedKeysCommand
Status in openssh package in Ubuntu:
Fix Released
Status in openssh source package in Xenial:
Fix Committed
Bug description:
[Impact]
On a default Xenial install, when sshd is configured to obtain the
list of allowed keys using AuthorizedKeysCommand (or the list of
allowed certificate principals using AuthorizedPrincipalsCommand), and
if the command pointed by Authorized{Keys,Principals}Command generates
a lot of output, sshd will hang while reading this same output. In a
nutshell, the problem happens when the subprocess generates enough
data to fill the pipe's buffer; in this scenario, sshd will wait(2) on
the subprocess, which will be blocked trying to write the rest of the
output.
[Test Case]
In order to reproduce the bug, one can:
$ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
$ lxc shell openssh-server-bug1877454
# ssh-keygen
(no need to choose a passphrase for the key, just hit ENTER on all prompts)
# cat > authkeyscommand.sh << __EOF__
#!/bin/bash
cat /root/.ssh/id_rsa.pub
echo
head -c 1M < /dev/urandom
__EOF__
# chmod +x authkeyscommand.sh
# cat >> /etc/ssh/sshd_config << __EOF__
AuthorizedKeysCommand /root/authkeyscommand.sh
AuthorizedKeysCommandUser root
__EOF__
# systemctl reload sshd.service
# ssh root@127.0.0.1
You will notice that ssh will stay there waiting for sshd's reply,
which won't come. The expected result would be for ssh to succeed.
[Regression Potential]
Since the affected code deals with executing a subprocess, reading its
output through a pipe, and then relying on wait(2) to determine
whether the subprocess exited correctly; and considering that this
code is written in C without the help of features like RAII and with
the use of goto statements, we are not able to disconsider the chances
of making a mistake and forgetting to free a resource or to properly
read/write from/to pipes, for example. This is, after all, the reason
the bug happened in the first place.
Having said that, openssh contains extensive tests and the code is
well organized and relatively easy to follow. Upon close inspection,
there doesn't seem to be an evident problem with the backported fixes.
As usual when dealing with a somewhat older distribution, there is
always the possibility of encountering problems because we will be
recompiling openssh using the most recent versions of its build
dependencies.
[Original Description]
Please consider applying this change to openssh-server distributed in Xenial
(16.04).
Without it, sshd can sporadically hang when making use of the
`AuthorizedKeysCommand` option.
https://github.com/openssh/openssh-
portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions
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[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
Thank you for the verification Sergio! Could you please note down which
package version has been used for verification and what kind of
verification has been performed?
--
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to openssh in Ubuntu.
https://bugs.launchpad.net/bugs/1877454
Title:
openssh-server hangs with AuthorizedKeysCommand
Status in openssh package in Ubuntu:
Fix Released
Status in openssh source package in Xenial:
Fix Committed
Bug description:
[Impact]
On a default Xenial install, when sshd is configured to obtain the
list of allowed keys using AuthorizedKeysCommand (or the list of
allowed certificate principals using AuthorizedPrincipalsCommand), and
if the command pointed by Authorized{Keys,Principals}Command generates
a lot of output, sshd will hang while reading this same output. In a
nutshell, the problem happens when the subprocess generates enough
data to fill the pipe's buffer; in this scenario, sshd will wait(2) on
the subprocess, which will be blocked trying to write the rest of the
output.
[Test Case]
In order to reproduce the bug, one can:
$ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
$ lxc shell openssh-server-bug1877454
# ssh-keygen
(no need to choose a passphrase for the key, just hit ENTER on all prompts)
# cat > authkeyscommand.sh << __EOF__
#!/bin/bash
cat /root/.ssh/id_rsa.pub
echo
head -c 1M < /dev/urandom
__EOF__
# chmod +x authkeyscommand.sh
# cat >> /etc/ssh/sshd_config << __EOF__
AuthorizedKeysCommand /root/authkeyscommand.sh
AuthorizedKeysCommandUser root
__EOF__
# systemctl reload sshd.service
# ssh root@127.0.0.1
You will notice that ssh will stay there waiting for sshd's reply,
which won't come. The expected result would be for ssh to succeed.
[Regression Potential]
Since the affected code deals with executing a subprocess, reading its
output through a pipe, and then relying on wait(2) to determine
whether the subprocess exited correctly; and considering that this
code is written in C without the help of features like RAII and with
the use of goto statements, we are not able to disconsider the chances
of making a mistake and forgetting to free a resource or to properly
read/write from/to pipes, for example. This is, after all, the reason
the bug happened in the first place.
Having said that, openssh contains extensive tests and the code is
well organized and relatively easy to follow. Upon close inspection,
there doesn't seem to be an evident problem with the backported fixes.
As usual when dealing with a somewhat older distribution, there is
always the possibility of encountering problems because we will be
recompiling openssh using the most recent versions of its build
dependencies.
[Original Description]
Please consider applying this change to openssh-server distributed in Xenial
(16.04).
Without it, sshd can sporadically hang when making use of the
`AuthorizedKeysCommand` option.
https://github.com/openssh/openssh-
portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions
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[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
Just double checked that the fix works and tagged as verification-done-
xenial.
** Tags removed: verification-needed verification-needed-xenial
** Tags added: verification-done-xenial
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You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to openssh in Ubuntu.
https://bugs.launchpad.net/bugs/1877454
Title:
openssh-server hangs with AuthorizedKeysCommand
Status in openssh package in Ubuntu:
Fix Released
Status in openssh source package in Xenial:
Fix Committed
Bug description:
[Impact]
On a default Xenial install, when sshd is configured to obtain the
list of allowed keys using AuthorizedKeysCommand (or the list of
allowed certificate principals using AuthorizedPrincipalsCommand), and
if the command pointed by Authorized{Keys,Principals}Command generates
a lot of output, sshd will hang while reading this same output. In a
nutshell, the problem happens when the subprocess generates enough
data to fill the pipe's buffer; in this scenario, sshd will wait(2) on
the subprocess, which will be blocked trying to write the rest of the
output.
[Test Case]
In order to reproduce the bug, one can:
$ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
$ lxc shell openssh-server-bug1877454
# ssh-keygen
(no need to choose a passphrase for the key, just hit ENTER on all prompts)
# cat > authkeyscommand.sh << __EOF__
#!/bin/bash
cat /root/.ssh/id_rsa.pub
echo
head -c 1M < /dev/urandom
__EOF__
# chmod +x authkeyscommand.sh
# cat >> /etc/ssh/sshd_config << __EOF__
AuthorizedKeysCommand /root/authkeyscommand.sh
AuthorizedKeysCommandUser root
__EOF__
# systemctl reload sshd.service
# ssh root@127.0.0.1
You will notice that ssh will stay there waiting for sshd's reply,
which won't come. The expected result would be for ssh to succeed.
[Regression Potential]
Since the affected code deals with executing a subprocess, reading its
output through a pipe, and then relying on wait(2) to determine
whether the subprocess exited correctly; and considering that this
code is written in C without the help of features like RAII and with
the use of goto statements, we are not able to disconsider the chances
of making a mistake and forgetting to free a resource or to properly
read/write from/to pipes, for example. This is, after all, the reason
the bug happened in the first place.
Having said that, openssh contains extensive tests and the code is
well organized and relatively easy to follow. Upon close inspection,
there doesn't seem to be an evident problem with the backported fixes.
As usual when dealing with a somewhat older distribution, there is
always the possibility of encountering problems because we will be
recompiling openssh using the most recent versions of its build
dependencies.
[Original Description]
Please consider applying this change to openssh-server distributed in Xenial
(16.04).
Without it, sshd can sporadically hang when making use of the
`AuthorizedKeysCommand` option.
https://github.com/openssh/openssh-
portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions
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[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
Hello Jeremy, or anyone else affected,
Accepted openssh into xenial-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/openssh/1:7.2p2-4ubuntu2.10 in a
few hours, and then in the -proposed repository.
Please help us by testing this new package. See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed. Your feedback will aid us getting this
update out to other Ubuntu users.
If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
xenial to verification-done-xenial. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-xenial. In either case, without details of your testing we will
not be able to proceed.
Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in
advance for helping!
N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.
** Changed in: openssh (Ubuntu Xenial)
Status: Confirmed => Fix Committed
** Tags added: verification-needed verification-needed-xenial
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https://bugs.launchpad.net/bugs/1877454
Title:
openssh-server hangs with AuthorizedKeysCommand
Status in openssh package in Ubuntu:
Fix Released
Status in openssh source package in Xenial:
Fix Committed
Bug description:
[Impact]
On a default Xenial install, when sshd is configured to obtain the
list of allowed keys using AuthorizedKeysCommand (or the list of
allowed certificate principals using AuthorizedPrincipalsCommand), and
if the command pointed by Authorized{Keys,Principals}Command generates
a lot of output, sshd will hang while reading this same output. In a
nutshell, the problem happens when the subprocess generates enough
data to fill the pipe's buffer; in this scenario, sshd will wait(2) on
the subprocess, which will be blocked trying to write the rest of the
output.
[Test Case]
In order to reproduce the bug, one can:
$ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
$ lxc shell openssh-server-bug1877454
# ssh-keygen
(no need to choose a passphrase for the key, just hit ENTER on all prompts)
# cat > authkeyscommand.sh << __EOF__
#!/bin/bash
cat /root/.ssh/id_rsa.pub
echo
head -c 1M < /dev/urandom
__EOF__
# chmod +x authkeyscommand.sh
# cat >> /etc/ssh/sshd_config << __EOF__
AuthorizedKeysCommand /root/authkeyscommand.sh
AuthorizedKeysCommandUser root
__EOF__
# systemctl reload sshd.service
# ssh root@127.0.0.1
You will notice that ssh will stay there waiting for sshd's reply,
which won't come. The expected result would be for ssh to succeed.
[Regression Potential]
Since the affected code deals with executing a subprocess, reading its
output through a pipe, and then relying on wait(2) to determine
whether the subprocess exited correctly; and considering that this
code is written in C without the help of features like RAII and with
the use of goto statements, we are not able to disconsider the chances
of making a mistake and forgetting to free a resource or to properly
read/write from/to pipes, for example. This is, after all, the reason
the bug happened in the first place.
Having said that, openssh contains extensive tests and the code is
well organized and relatively easy to follow. Upon close inspection,
there doesn't seem to be an evident problem with the backported fixes.
As usual when dealing with a somewhat older distribution, there is
always the possibility of encountering problems because we will be
recompiling openssh using the most recent versions of its build
dependencies.
[Original Description]
Please consider applying this change to openssh-server distributed in Xenial
(16.04).
Without it, sshd can sporadically hang when making use of the
`AuthorizedKeysCommand` option.
https://github.com/openssh/openssh-
portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions
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[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
** Description changed:
[Impact]
On a default Xenial install, when sshd is configured to obtain the list
of allowed keys using AuthorizedKeysCommand (or the list of allowed
certificate principals using AuthorizedPrincipalsCommand), and if the
command pointed by Authorized{Keys,Principals}Command generates a lot of
output, sshd will hang while reading this same output. In a nutshell,
the problem happens when the subprocess generates enough data to fill
the pipe's buffer; in this scenario, sshd will wait(2) on the
subprocess, which will be blocked trying to write the rest of the
output.
[Test Case]
In order to reproduce the bug, one can:
$ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
$ lxc shell openssh-server-bug1877454
# ssh-keygen
(no need to choose a passphrase for the key, just hit ENTER on all prompts)
# cat > authkeyscommand.sh << __EOF__
#!/bin/bash
cat /root/.ssh/id_rsa.pub
echo
head -c 1M < /dev/urandom
__EOF__
+ # chmod +x authkeyscommand.sh
# cat >> /etc/ssh/sshd_config << __EOF__
AuthorizedKeysCommand /root/authkeyscommand.sh
AuthorizedKeysCommandUser root
__EOF__
# systemctl reload sshd.service
# ssh root@127.0.0.1
You will notice that ssh will stay there waiting for sshd's reply, which
won't come. The expected result would be for ssh to succeed.
[Regression Potential]
Since the affected code deals with executing a subprocess, reading its
output through a pipe, and then relying on wait(2) to determine whether
the subprocess exited correctly; and considering that this code is
written in C without the help of features like RAII and with the use of
goto statements, we are not able to disconsider the chances of making a
mistake and forgetting to free a resource or to properly read/write
from/to pipes, for example. This is, after all, the reason the bug
happened in the first place.
Having said that, openssh contains extensive tests and the code is well
organized and relatively easy to follow. Upon close inspection, there
doesn't seem to be an evident problem with the backported fixes.
As usual when dealing with a somewhat older distribution, there is
always the possibility of encountering problems because we will be
recompiling openssh using the most recent versions of its build
dependencies.
[Original Description]
Please consider applying this change to openssh-server distributed in Xenial
(16.04).
Without it, sshd can sporadically hang when making use of the
`AuthorizedKeysCommand` option.
https://github.com/openssh/openssh-
portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2
--
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https://bugs.launchpad.net/bugs/1877454
Title:
openssh-server hangs with AuthorizedKeysCommand
Status in openssh package in Ubuntu:
Fix Released
Status in openssh source package in Xenial:
Confirmed
Bug description:
[Impact]
On a default Xenial install, when sshd is configured to obtain the
list of allowed keys using AuthorizedKeysCommand (or the list of
allowed certificate principals using AuthorizedPrincipalsCommand), and
if the command pointed by Authorized{Keys,Principals}Command generates
a lot of output, sshd will hang while reading this same output. In a
nutshell, the problem happens when the subprocess generates enough
data to fill the pipe's buffer; in this scenario, sshd will wait(2) on
the subprocess, which will be blocked trying to write the rest of the
output.
[Test Case]
In order to reproduce the bug, one can:
$ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
$ lxc shell openssh-server-bug1877454
# ssh-keygen
(no need to choose a passphrase for the key, just hit ENTER on all prompts)
# cat > authkeyscommand.sh << __EOF__
#!/bin/bash
cat /root/.ssh/id_rsa.pub
echo
head -c 1M < /dev/urandom
__EOF__
# chmod +x authkeyscommand.sh
# cat >> /etc/ssh/sshd_config << __EOF__
AuthorizedKeysCommand /root/authkeyscommand.sh
AuthorizedKeysCommandUser root
__EOF__
# systemctl reload sshd.service
# ssh root@127.0.0.1
You will notice that ssh will stay there waiting for sshd's reply,
which won't come. The expected result would be for ssh to succeed.
[Regression Potential]
Since the affected code deals with executing a subprocess, reading its
output through a pipe, and then relying on wait(2) to determine
whether the subprocess exited correctly; and considering that this
code is written in C without the help of features like RAII and with
the use of goto statements, we are not able to disconsider the chances
of making a mistake and forgetting to free a resource or to properly
read/write from/to pipes, for example. This is, after all, the reason
the bug happened in the first place.
Having said that, openssh contains
[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
** Description changed:
+ [Impact]
+
+ On a default Xenial install, when sshd is configured to obtain the list
+ of allowed keys using AuthorizedKeysCommand (or the list of allowed
+ certificate principals using AuthorizedPrincipalsCommand), and if the
+ command pointed by Authorized{Keys,Principals}Command generates a lot of
+ output, sshd will hang while reading this same output. In a nutshell,
+ the problem happens when the subprocess generates enough data to fill
+ the pipe's buffer; in this scenario, sshd will wait(2) on the
+ subprocess, which will be blocked trying to write the rest of the
+ output.
+
+ [Test Case]
+
+ In order to reproduce the bug, one can:
+
+ $ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
+ $ lxc shell openssh-server-bug1877454
+ # ssh-keygen
+ (no need to choose a passphrase for the key, just hit ENTER on all prompts)
+ # cat > authkeyscommand.sh << __EOF__
+ #!/bin/bash
+
+ cat /root/.ssh/id_rsa.pub
+ echo
+ head -c 1M < /dev/urandom
+ __EOF__
+ # cat >> /etc/ssh/sshd_config << __EOF__
+ AuthorizedKeysCommand /root/authkeyscommand.sh
+ AuthorizedKeysCommandUser root
+ __EOF__
+ # systemctl reload sshd.service
+ # ssh root@127.0.0.1
+
+ You will notice that ssh will stay there waiting for sshd's reply, which
+ won't come. The expected result would be for ssh to succeed.
+
+ [Regression Potential]
+
+ Since the affected code deals with executing a subprocess, reading its
+ output through a pipe, and then relying on wait(2) to determine whether
+ the subprocess exited correctly; and considering that this code is
+ written in C without the help of features like RAII and with the use of
+ goto statements, we are not able to disconsider the chances of making a
+ mistake and forgetting to free a resource or to properly read/write
+ from/to pipes, for example. This is, after all, the reason the bug
+ happened in the first place.
+
+ Having said that, openssh contains extensive tests and the code is well
+ organized and relatively easy to follow. Upon close inspection, there
+ doesn't seem to be an evident problem with the backported fixes.
+
+ As usual when dealing with a somewhat older distribution, there is
+ always the possibility of encountering problems because we will be
+ recompiling openssh using the most recent versions of its build
+ dependencies.
+
+ [Original Description]
+
Please consider applying this change to openssh-server distributed in Xenial
(16.04).
Without it, sshd can sporadically hang when making use of the
`AuthorizedKeysCommand` option.
https://github.com/openssh/openssh-
portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2
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https://bugs.launchpad.net/bugs/1877454
Title:
openssh-server hangs with AuthorizedKeysCommand
Status in openssh package in Ubuntu:
Fix Released
Status in openssh source package in Xenial:
Confirmed
Bug description:
[Impact]
On a default Xenial install, when sshd is configured to obtain the
list of allowed keys using AuthorizedKeysCommand (or the list of
allowed certificate principals using AuthorizedPrincipalsCommand), and
if the command pointed by Authorized{Keys,Principals}Command generates
a lot of output, sshd will hang while reading this same output. In a
nutshell, the problem happens when the subprocess generates enough
data to fill the pipe's buffer; in this scenario, sshd will wait(2) on
the subprocess, which will be blocked trying to write the rest of the
output.
[Test Case]
In order to reproduce the bug, one can:
$ lxc launch ubuntu-daily:xenial openssh-server-bug1877454
$ lxc shell openssh-server-bug1877454
# ssh-keygen
(no need to choose a passphrase for the key, just hit ENTER on all prompts)
# cat > authkeyscommand.sh << __EOF__
#!/bin/bash
cat /root/.ssh/id_rsa.pub
echo
head -c 1M < /dev/urandom
__EOF__
# cat >> /etc/ssh/sshd_config << __EOF__
AuthorizedKeysCommand /root/authkeyscommand.sh
AuthorizedKeysCommandUser root
__EOF__
# systemctl reload sshd.service
# ssh root@127.0.0.1
You will notice that ssh will stay there waiting for sshd's reply,
which won't come. The expected result would be for ssh to succeed.
[Regression Potential]
Since the affected code deals with executing a subprocess, reading its
output through a pipe, and then relying on wait(2) to determine
whether the subprocess exited correctly; and considering that this
code is written in C without the help of features like RAII and with
the use of goto statements, we are not able to disconsider the chances
of making a mistake and forgetting to free a resource or to properly
read/write from/to pipes, for example. This is, after all, the reason
the bug happened in the first place.
Having said that, openssh contains extensive tests and the code is
well organized and relatively easy
[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
** Merge proposal linked: https://code.launchpad.net/~sergiodj/ubuntu/+source/openssh/+git/openssh/+merge/383879 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1877454 Title: openssh-server hangs with AuthorizedKeysCommand Status in openssh package in Ubuntu: Fix Released Status in openssh source package in Xenial: Confirmed Bug description: Please consider applying this change to openssh-server distributed in Xenial (16.04). Without it, sshd can sporadically hang when making use of the `AuthorizedKeysCommand` option. https://github.com/openssh/openssh- portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
** Changed in: openssh (Ubuntu Xenial) Assignee: (unassigned) => Sergio Durigan Junior (sergiodj) -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1877454 Title: openssh-server hangs with AuthorizedKeysCommand Status in openssh package in Ubuntu: Fix Released Status in openssh source package in Xenial: Confirmed Bug description: Please consider applying this change to openssh-server distributed in Xenial (16.04). Without it, sshd can sporadically hang when making use of the `AuthorizedKeysCommand` option. https://github.com/openssh/openssh- portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
Another link discussing it: https://secure.phabricator.com/T11827 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1877454 Title: openssh-server hangs with AuthorizedKeysCommand Status in openssh package in Ubuntu: Fix Released Status in openssh source package in Xenial: Confirmed Bug description: Please consider applying this change to openssh-server distributed in Xenial (16.04). Without it, sshd can sporadically hang when making use of the `AuthorizedKeysCommand` option. https://github.com/openssh/openssh- portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
Also see: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=905226 ** Bug watch added: Debian Bug tracker #905226 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=905226 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1877454 Title: openssh-server hangs with AuthorizedKeysCommand Status in openssh package in Ubuntu: Fix Released Status in openssh source package in Xenial: Confirmed Bug description: Please consider applying this change to openssh-server distributed in Xenial (16.04). Without it, sshd can sporadically hang when making use of the `AuthorizedKeysCommand` option. https://github.com/openssh/openssh- portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
Thanks for the report Jeremy, The fix is in V_7_5_P1 and by that >=Bionic is fixed - I agree to you this only has to target Xenial. ** Tags added: bitesize server-next ** Also affects: openssh (Ubuntu Xenial) Importance: Undecided Status: New ** Changed in: openssh (Ubuntu Xenial) Status: New => Confirmed ** Changed in: openssh (Ubuntu Xenial) Importance: Undecided => Medium ** Changed in: openssh (Ubuntu) Status: New => Fix Released -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1877454 Title: openssh-server hangs with AuthorizedKeysCommand Status in openssh package in Ubuntu: Fix Released Status in openssh source package in Xenial: Confirmed Bug description: Please consider applying this change to openssh-server distributed in Xenial (16.04). Without it, sshd can sporadically hang when making use of the `AuthorizedKeysCommand` option. https://github.com/openssh/openssh- portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
Also see: https://bugzilla.mindrot.org/show_bug.cgi?id=2655 ** Bug watch added: OpenSSH Portable Bugzilla #2655 https://bugzilla.mindrot.org/show_bug.cgi?id=2655 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1877454 Title: openssh-server hangs with AuthorizedKeysCommand Status in openssh package in Ubuntu: New Bug description: Please consider applying this change to openssh-server distributed in Xenial (16.04). Without it, sshd can sporadically hang when making use of the `AuthorizedKeysCommand` option. https://github.com/openssh/openssh- portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
[Touch-packages] [Bug 1877454] Re: openssh-server hangs with AuthorizedKeysCommand
Additional discussion of this issue: https://bugzilla.redhat.com/show_bug.cgi?id=1496467 https://bugzilla.mindrot.org/show_bug.cgi?id=2496 https://discourse.phabricator-community.org/t/newly-added-ssh-keys-not- working/992 ** Bug watch added: Red Hat Bugzilla #1496467 https://bugzilla.redhat.com/show_bug.cgi?id=1496467 ** Bug watch added: OpenSSH Portable Bugzilla #2496 https://bugzilla.mindrot.org/show_bug.cgi?id=2496 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to openssh in Ubuntu. https://bugs.launchpad.net/bugs/1877454 Title: openssh-server hangs with AuthorizedKeysCommand Status in openssh package in Ubuntu: New Bug description: Please consider applying this change to openssh-server distributed in Xenial (16.04). Without it, sshd can sporadically hang when making use of the `AuthorizedKeysCommand` option. https://github.com/openssh/openssh- portable/commit/ddd3d34e5c7979ca6f4a3a98a7d219a4ed3d98c2 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1877454/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
