Advanced PHP/Linux/SSH question

[basvanmeurs]

I've booted up an instance of a bitnami LAMP stack on the AWS cloud and found myself with the following problem.

I can easily ssh to other instances using public/private keys. The following works:

bitnami@ip-10-48-126-61:/opt/bitnami/apps/drupal/htdocs$ ssh -v bitnami@176.34.248.84 "ls"
OpenSSH_5.3p1 Debian-3ubuntu7, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 176.34.248.84 [176.34.248.84] port 22.
debug1: Connection established.
debug1: identity file /home/bitnami/.ssh/identity type -1
debug1: identity file /home/bitnami/.ssh/id_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/bitnami/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3p1 Debian-3ubuntu6
debug1: match: OpenSSH_5.3p1 Debian-3ubuntu6 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu7
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '176.34.248.84' is known and matches the RSA host key.
debug1: Found key in /home/bitnami/.ssh/known_hosts:1
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /home/bitnami/.ssh/identity
debug1: Offering public key: /home/bitnami/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 277
debug1: read PEM private key done: type RSA
debug1: Authentication succeeded (publickey).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
debug1: Sending command: ls
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype eow@openssh.com reply 0
test
debug1: channel 0: free: client-session, nchannels 1
Transferred: sent 2272, received 2280 bytes, in 0.3 seconds
Bytes per second: sent 7207.8, received 7233.2
debug1: Exit status 0

But then I tried exactly the same via php:
<?php

echo system('ssh -v bitnami@176.34.248.84 "ls"');
?>

It gave me the following:

bitnami@ip-10-48-126-61:/opt/bitnami/apps/drupal/htdocs$ php test.php
OpenSSH_5.3p1 Debian-3ubuntu7, OpenSSL 0.9.8r 8 Feb 2011
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 176.34.248.84 [176.34.248.84] port 22.
debug1: Connection established.
debug1: identity file /home/bitnami/.ssh/identity type -1
debug1: identity file /home/bitnami/.ssh/id_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/bitnami/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3p1 Debian-3ubuntu6
debug1: match: OpenSSH_5.3p1 Debian-3ubuntu6 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu7
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: skipped DNS lookup for numerical hostname
Segmentation fault

I think that the segmentation fault is a bug in ssh, not in php.

Notice how the version of ssh differs (0.9.8k vs 0.9.8r). I am puzzled how this is possible. I tried several things such as the 'which' command, printing out all environment variables and much more, but I really don't understand why the version of ssh would be different when starting it from the php parser.

Then, I tried rsync. It worked on the command line but failed from PHP again with the message:
rsync: connection unexpectedly closed (0 bytes received so far) [Receiver]
rsync error: error in rsync protocol data stream (code 12) at io.c(601) [Receiver=3.0.7]

In non-Bitnami stacks it works just fine, even on AWS.

Can someone give me a suggestion on where to look next?

[ahundiak]

You could try using the full path to ssh
echo system('/usr/bin/ssh -v bitnami@176.34.248.84 "ls"');