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Bug#698669: Access to escape functions with ControlPersist



Package: openssh-client
Version: 1:6.0p1-3
Severity: normal

Setting ControlPersist seems to cause the initial SSH session to
become a client of the master session, which is launched in the
background. This works beautifully, except that now it seems
impossible to gain access to some of the functionality previously
accessible with the escape char, specifically getting a command line
with ~C, which could be used to manage port forwardings. Also, the
current (client) session cannot be suspended (~^Z), although it is
possible to request rekeying.

I cannot deduce a logic here. Surely, port forwardings are managed
in the master session and it might be impossible to let that be
controlled from client sessions, but rekeying is also a master
operation, and clients can do that. Also, suspending the current
session is/can/should be a client operation, yet it does not seem
possible to do that.

The following shows the escape functions accessible in master
sessions. Those prefixed with X are inaccessible in client sessions.

arnold:~% ~?                                                                                                                                                                                                                                                                                                           #126,65
Supported escape sequences:
  ~.  - terminate connection (and any multiplexed sessions)
  ~B  - send a BREAK to the remote system
X ~C  - open a command line
  ~R  - Request rekey (SSH protocol 2 only)
X ~^Z - suspend ssh
  ~#  - list forwarded connections
X ~&  - background ssh (when waiting for connections to terminate)
  ~?  - this message
  ~~  - send the escape character by typing it twice
(Note that escapes are only recognized immediately after newline.)

-- System Information:
Debian Release: 7.0
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 3.7-trunk-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_NZ, LC_CTYPE=en_NZ.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages openssh-client depends on:
ii  adduser                3.113+nmu3
ii  debconf [debconf-2.0]  1.5.49
ii  dpkg                   1.16.9
ii  libc6                  2.13-38
ii  libedit2               2.11-20080614-5
ii  libgssapi-krb5-2       1.10.1+dfsg-3
ii  libselinux1            2.1.9-5
ii  libssl1.0.0            1.0.1c-4
ii  passwd                 1:4.1.5.1-1
ii  zlib1g                 1:1.2.7.dfsg-13

Versions of packages openssh-client recommends:
ii  openssh-blacklist        0.4.1+nmu1
ii  openssh-blacklist-extra  0.4.1+nmu1
ii  xauth                    1:1.0.7-1

Versions of packages openssh-client suggests:
ii  keychain                         2.7.1-1
pn  libpam-ssh                       <none>
ii  monkeysphere                     0.35-2
ii  ssh-askpass-gnome [ssh-askpass]  1:6.0p1-3

-- Configuration Files:
/etc/ssh/ssh_config changed [not included]

-- no debconf information


-- 
 .''`.   martin f. krafft <madduck@d.o>      Related projects:
: :'  :  proud Debian developer               http://debiansystem.info
`. `'`   http://people.debian.org/~madduck    http://vcs-pkg.org
  `-  Debian - when you have better things to do than fixing systems

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