Introduction

This is a library that provides SSH and SFTP functionality from within Python, using "libssh". Although libssh2 was considered, it appears that its SFTP functionality is slower (1).

This solution exists as an alternative to Paramiko. I love Paramiko, but as "libssh" is very complete and actively-maintained, it has a greater breadth of functionality, such as support for elliptic-curve encryption (recently added). It is also written in C.

This project is in active development. It -is- Python3 compatible.

(1) http://daniel.haxx.se/blog/2010/12/05/re-evaluating-the-criticism/

Status

Remote execution is currently broken in libssh 0.6.0, but our library is no longer compatible with 0.5.5 (key-related changes involved new/changed functions in libssh).

Dependencies

• libssh 0.6.0rc1

Installing

Just expand, and make sure PYTHONPATH includes the directory.

NOTE: Though this project is on PyPI, it's -highly- recommended to use "easy_install" to get it, rather than "pip". The latter has the tendency to not get the latest version.

Logging

To allow for standard logging to go out to the console, import "pysecure.log_config".

To enable "debug" logging, set the environment variable "DEBUG" to "1".

To enable debug verbosity from the "libssh" library, pass the "verbosity" argument into the connect_* functions with a value of True.

Common Setup Code for Examples

To make the examples more concise, some code has been removed, so as to not be repeated in every case.

A complete, working example using some included convenience functions would look like the following:

from pysecure.easy import connect_ssh, connect_sftp, get_key_auth_cb

user = 'dustin'
host = 'localhost'
key_filepath = '/home/dustin/.ssh/id_dsa'

auth_cb = get_key_auth_cb(key_filepath)

# For simple SSH functionality.

with connect_ssh(user, host, auth_cb) as ssh:
    # Main logic, here.
    pass

# Or, for SFTP-enabled SSH functionality.

with connect_sftp(user, host, auth_cb) as (ssh, sftp):
    # Main logic, here.
    pass

SFTP Examples

File resources are file-like objects that are similar to standard file objects. Calls will have traditional methods, as identified here:

http://docs.python.org/2/library/stdtypes.html#file-objects

List a directory:

from pysecure.adapters.sftpa import SftpFile

print("Name                         Size Perms    Owner\tGroup\n")
for attributes in sftp.listdir('.'):
    print("%-40s %10d %.8o %s(%d)\t%s(%d)" % 
          (attributes.name[0:40], attributes.size, 
           attributes.permissions, attributes.owner, 
           attributes.uid, attributes.group,
           attributes.gid))

Recurse a directory:

def dir_cb(path, entry):
    full_path = ('%s/%s' % (path, entry.name))
    print("DIR: %s" % (full_path))

def listing_cb(path, list_):
    print("[%s]: (%d) files" % (path, len(list_)))

sftp.recurse('Pictures', dir_cb, listing_cb)

Read through text-file, one line at a time:

with SftpFile(sftp, 'text_file.txt') as sf:
    i = 0
    for data in sf:
        stdout.write("> " + data)

        if i >= 30:
            break

        i += 1

To read a complete file (binary friendly). It could also be read one chunk at a time:

with SftpFile(sftp, 'binary_file.dat') as sf:
    buffer_ = sf.read()

    print("Read (%d) bytes." % (len(buffer_)))

Mirroring:

from pysecure.sftp_mirror import SftpMirror

mirror = SftpMirror(sftp)

# Mirror from server to local.
mirror.mirror(mirror.mirror_to_local_no_recursion, 
              "Pictures", 
              "/tmp/Pictures")

# Mirror from local to server.
mirror.mirror(mirror.mirror_to_remote_no_recursion, 
              "/home/dustin/Pictures", 
              "/tmp/RemotePictures")

Mirroring will ignore special (device) files. It also won't specially handle hard-links.

Port-Forwarding Examples

Local Forwarding:

from pysecure.adapters.channela import SshChannel

host_source = 'localhost'
port_local = 1111
host_remote = 'localhost'
port_remote = 80

data = "GET / HTTP/1.1\nHost: localhost\n\n"

with SshChannel(ssh) as sc:
    # The following command activates forwarding, but does not bind any
    # ports. Although a "port_local" parameter is expected, this is 
    # allegedly for little more than logging. Binding is left as a concern
    # for the implementing developer.
    sc.open_forward(host_remote, port_remote, host_source, port_local)

    sc.write(data)

    received = sc.read(1024)
    print("Received:\n\n%s" % (received))

Reverse Forwarding:

# This functionality starts with an SshSession. Therefore, an import of
# SshChannel isn't necessary.

server_address = None
server_port = 8080
accept_timeout_ms = 60000

port = ssh.forward_listen(server_address, server_port)
with ssh.forward_accept(accept_timeout_ms) as sc:
    while 1:
        data = sc.read(2048)
        if data == '':
            continue

        # Do something with the data.
        response = "Received."

        sc.write(response)

Remote Execution

Remote Command (efficient for single command):

This functionality can be used to execute one command at a time:

```python
for line from ssh.execute('lsb_release -a'):
    print(line)

data = ssh.execute('whoami')
print(data)
```

Output:

```
Distributor ID: Ubuntu
Description:    Ubuntu 13.04
Release:    13.04
Codename:   raring

dustin
```

Remote Shell (efficient for many commands):

Example:

```python
rsp = RemoteShellProcessor(ssh)

def shell_context_cb(sc, welcome):
    output = rsp.do_command('cat /proc/uptime')
    print(output)

    output = rsp.do_command('whoami')
    print(output)

rsp.shell(shell_context_cb)
```

Output:

```
$ PYTHONPATH=. test/example.py 
631852.37 651773.95
dustin
```

EasySsh

We always recommend the use of the connect_ssh and connect_sftp calls mentioned above, as they are meant to be used with a context-manager ("with") block, and will automatically be cleaned-up properly. However, this strategy makes it impossible to keep a connection open while passing control back to the caller of the function, and therefoe requires that a new, subsequent connection is opened for the next operation.

Whereas the above strategy relies on the use of a callback when the SSH or SFTP session(s) are ready, we also provide the EasySsh class to make it easy to open a connection and close that connection at two separate times.

For example:

from pysecure.easy import EasySsh, get_key_auth_cb

auth_cb = get_key_auth_cb(key_filepath)
easy = EasySsh(user, host, auth_cb)

easy.open_ssh()
easy.open_sftp()

# easy.ssh and, if opened, easy.sftp are now ready.

# Do your logic, here. For example, list directory entries.
entries = easy.sftp.listdir('.')

easy.close_sftp()   # We do this just to be explicit. This will 
                    # automatically be done at SSH close.
easy.close_ssh()