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NISTIR 7966
Security of Interactive and Automated Access Management Using Secure Shell (SSH) Tatu Ylonen Paul Turner Karen Scarfone Murugiah Souppaya
This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.IR.7966
NISTIR 7966
Security of Interactive and Automated Access Management Using Secure Shell (SSH) Tatu Ylonen SSH Communications Security Helsinki, Finland Paul Turner Venafi Salt Lake City, UT Karen Scarfone Scarfone Cybersecurity Clifton, VA Murugiah Souppaya Computer Security Division Information Technology Laboratory This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.IR.7966 October 2015
U.S. Department of Commerce Penny Pritzker, Secretary National Institute of Standards and Technology Willie May, Under Secretary of Commerce for Standards and Technology and Director
NISTIR 7966
SECURITY OF INTERACTIVE AND AUTOMATED ACCESS MANAGEMENT USING SECURE SHELL (SSH)
National Institute of Standards and Technology Internal Report 7966 50 pages (October 2015)
This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.IR.7966
Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by NIST, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. There may be references in this publication to other publications currently under development by NIST in accordance with its assigned statutory responsibilities. The information in this publication, including concepts and methodologies, may be used by Federal agencies even before the completion of such companion publications. Thus, until each publication is completed, current requirements, guidelines, and procedures, where they exist, remain operative. For planning and transition purposes, Federal agencies may wish to closely follow the development of these new publications by NIST. Organizations are encouraged to review all draft publications during public comment periods and provide feedback to NIST. All NIST Computer Security Division publications, other than the ones noted above, are available at http://csrc.nist.gov/publications.
Comments on this publication may be submitted to: National Institute of Standards and Technology Attn: Computer Security Division, Information Technology Laboratory 100 Bureau Drive (Mail Stop 8930) Gaithersburg, MD 20899-8930
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NISTIR 7966
SECURITY OF INTERACTIVE AND AUTOMATED ACCESS MANAGEMENT USING SECURE SHELL (SSH)
Reports on Computer Systems Technology The Information Technology Laboratory (ITL) at the National Institute of Standards and Technology (NIST) promotes the U.S. economy and public welfare by providing technical leadership for the Nation’s measurement and standards infrastructure. ITL develops tests, test methods, reference from=" restriction in an authorized keys file.
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NISTIR 7966
SECURITY OF INTERACTIVE AND AUTOMATED ACCESS MANAGEMENT USING SECURE SHELL (SSH)
SSH Client
The software implementation that enables a user or an automated process to remotely access an SSH server. An SSH client is responsible for reliably performing all of the operations necessary to ensure a secure connection, including generating identity keys, prompting users to verify host keys, authenticating and establishing encrypted connections with SSH servers, prompting users for credentials, performing public key authentication, etc.
SSH Key
A term that is generally used to refer to an identity and authorized keys. The term may also be occasionally used to refer to host or server private keys.
SSH Server
A software implementation that enables SSH access to a system from SSH clients. SSH server may be included with an operating system or appliance or may be add-on software. An SSH server is typically a complex set of software modules responsible for a broad number of tasks, including enforcing configured SSH settings, authenticating users, limiting access to certain users and groups, ensuring secure connections, interfacing with other systems (e.g., PAM and Kerberos), performing file transfers, etc.
Trust Relationship
The access relationship that is granted by an authorized key in an account on one system (server) and a corresponding identity key in an account on another system (client). Once deployed, these two keys establish a persistent trust relationship between the two accounts/systems that enables ongoing access.
User Key
A key that is used for granting access to a user account via the SSH protocol (as opposed to a host key, which does not grant access to anything but serves to authenticate a host). Both authorized keys and identity keys are user keys. A user key is the equivalent of an access token.
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NISTIR 7966
SECURITY OF INTERACTIVE AND AUTOMATED ACCESS MANAGEMENT USING SECURE SHELL (SSH)
Appendix F—References References for the publication are listed below.
[ID-SSH]
Ylonen, T., Kent, G., and Souppaya, M., “Managing SSH Keys for Automated Access – Current Recommended Practice”, Internet-Draft, April 2013.
[RFC4251]
Ylonen, T. and Lonvick, C., “The Secure Shell (SSH) Protocol Architecture”, RFC 4251, January 2006.
[RFC4252]
Ylonen, T. and Lonvick, C., “The Secure Shell (SSH) Authentication Protocol”, RFC 4252, January 2006.
[RFC4253]
Ylonen, T. and Lonvick, C., “The Secure Shell (SSH) Transport Layer Protocol”, RFC 4253, January 2006.
[RFC4254]
Ylonen, T. and Lonvick, C., “The Secure Shell (SSH) Connection Protocol”, RFC 4254, January 2006.
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