This is the online reference for developing with the libssh library. It documents the libssh C API and the C++ wrapper.
Linking
We created a small howto how to link libssh against your application, read The Linking HowTo.
Tutorial
You should start by reading The Tutorial, then reading the documentation of the interesting functions as you go.
Features
The libssh library provides:
- Full C library functions for manipulating a client-side SSH connection
- SSH2 and SSH1 protocol compliant
- Fully configurable sessions
- Server support
- SSH agent authentication support
- Support for AES-128, AES-192, AES-256, Blowfish, 3DES in CBC mode, and AES in CTR mode
- Supports OpenSSL and GCrypt
- Use multiple SSH connections in a same process, at same time
- Use multiple channels in the same connection
- Thread safety when using different sessions at same time
- POSIX-like SFTP (Secure File Transfer) implementation with openssh extension support
- SCP implementation
- Large file system support (files bigger than 4GB)
- RSA and DSS server public key supported
- Compression support (with zlib)
- Public key (RSA and DSS), password and keyboard-interactive authentication
- Full poll()/WSAPoll() support and a poll-emulation for Win32.
- Runs and tested under x86_64, x86, ARM, Sparc32, PPC under Linux, BSD, MacOSX, Solaris and Windows
Copyright Policy
The developers of libssh have a policy of asking for contributions to be made under the personal copyright of the contributor, instead of a corporate copyright.
There are some reasons for the establishment of this policy:
- Individual copyrights make copyright registration in the US a simpler process.
- If libssh is copyrighted by individuals rather than corporations, decisions regarding enforcement and protection of copyright will, more likely, be made in the interests of the project, and not in the interests of any corporation’s shareholders.
- If we ever need to relicense a portion of the code contacting individuals for permission to do so is much easier than contacting a company.
Internet standard
Secure Shell (SSH)
The following RFC documents described SSH-2 protcol as an Internet standard.
- RFC 4250, The Secure Shell (SSH) Protocol Assigned Numbers
- RFC 4251, The Secure Shell (SSH) Protocol Architecture
- RFC 4252, The Secure Shell (SSH) Authentication Protocol
- RFC 4253, The Secure Shell (SSH) Transport Layer Protocol
- RFC 4254, The Secure Shell (SSH) Connection Protocol
- RFC 4255, Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints
- RFC 4256, Generic Message Exchange Authentication for the Secure Shell Protocol (SSH)
- RFC 4335, The Secure Shell (SSH) Session Channel Break Extension
- RFC 4344, The Secure Shell (SSH) Transport Layer Encryption Modes
- RFC 4345, Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol
It was later modified and expanded by the following RFCs.
- RFC 4419, Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol
- RFC 4432, RSA Key Exchange for the Secure Shell (SSH) Transport Layer Protocol
- RFC 4462, Generic Security Service Application Program Interface (GSS-API) Authentication and Key Exchange for the Secure Shell (SSH) Protocol
- RFC 4716, The Secure Shell (SSH) Public Key File Format
- RFC 5656, Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer
Interesting cryptography documents:
- PKCS #11, PKCS #11 reference documents, describing interface with smartcards.
Secure Shell File Transfer Protocol (SFTP)
The protocol is not an Internet standard but it is still widely implemented. OpenSSH and most other implementation implement Version 3 of the protocol. We do the same in libssh.
Secure Shell Extensions
The OpenSSH project has defined some extensions to the protocol. We support some of them like the statvfs calls in SFTP or the ssh-agent.
