Version: 1.0
2021-05-13
National Information Assurance Partnership
| Version | Date | Comment |
|---|---|---|
| 1.0 | 2021-05-13 | Converted SSH EP to a Functional Package and incorporated CCUF CWG input. |
Secure Shell (SSH) is a protocol for secure remote login and other secure network services over an untrusted network. SSH software can act as a client, server, or both.
This Functional Package for Secure Shell provides a collection of Secure Shell (SSH) protocol related SFRs and Evaluation Activities (EAs) covering audit, authentication, cryptographic algorithms, and protocol negotiation. The intent of this package is to provide PP, cPP, and PP-Module authors with a readily consumable collection of SFRs and EAs to be integrated into their documents.
Assurance | Grounds for confidence that a TOE meets the SFRs [CC]. |
Base Protection Profile (Base-PP) | Protection Profile used as a basis to build a PP-Configuration. |
Collaborative Protection Profile (cPP) | A Protection Profile developed by international technical communities and approved by multiple schemes |
Common Criteria (CC) | Common Criteria for Information Technology Security Evaluation (International Standard ISO/IEC 15408). |
Common Criteria Testing Laboratory | Within the context of the Common Criteria Evaluation and Validation Scheme (CCEVS), an IT security evaluation facility, accredited by the National Voluntary Laboratory Accreditation Program (NVLAP) and approved by the NIAP Validation Body to conduct Common Criteria-based evaluations. |
Common Evaluation Methodology (CEM) | Common Evaluation Methodology for Information Technology Security Evaluation. |
Distributed TOE | A TOE composed of multiple components operating as a logical whole. |
Extended Package (EP) | A deprecated document form for collecting SFRs that implement a particular protocol, technology, or functionality. See Functional Packages. |
Functional Package (FP) | A document that collects SFRs for a particular protocol, technology, or functionality. |
Operational Environment (OE) | Hardware and software that are outside the TOE boundary that support the TOE functionality and security policy. |
Protection Profile (PP) | An implementation-independent set of security requirements for a category of products. |
Protection Profile Configuration (PP-Configuration) | A comprehensive set of security requirements for a product type that consists of at least one Base-PP and at least one PP-Module. |
Protection Profile Module (PP-Module) | An implementation-independent statement of security needs for a TOE type complementary to one or more Base Protection Profiles. |
Security Assurance Requirement (SAR) | A requirement to assure the security of the TOE. |
Security Functional Requirement (SFR) | A requirement for security enforcement by the TOE. |
Security Target (ST) | A set of implementation-dependent security requirements for a specific product. |
Target of Evaluation (TOE) | The product under evaluation. |
| The security functionality of the product under evaluation. | |
| A description of how a TOE satisfies the SFRs in an ST. |
Connection | The SSH transport layer between a client and a server. Within a connection there can be multiple sessions. |
Rekey | Where the connection renegotiates the shared secret and each session subsequently derives a new encryption key. |
Secure Shell (SSH) | Cryptographic network protocol for initiating text-based shell sessions on remote systems. |
Session | A discrete stream of data within a connection. |
The Target of Evaluation (TOE) in this Functional Package (FP) is a product which acts as an SSH client, SSH server, or both. This FP describes the extended security functionality of SSH in terms of [CC].
The contents of this Functional Package must be appropriately incoporated into a PP, cPP, or PP-Module. When this package is so incorporated, the ST must include selection-based requirements in accordance with the selections or assignments indicated in the incorporating document.
The PP, cPP, or PP-Module that instantiates this Package must typically include the following components in order to satisfy dependencies of this Package. It is the responsibility of the PP, cPP, or PP-Module author who incorporates this FP to ensure that dependence on these components is satisfied, either by the TOE or by assumptions about its Operational Environment.
An ST must identify the applicable version of the PP, cPP, or PP-Module and this Functional Package in its conformance claims.
| Component | Explanation |
|---|---|
| FCS_CKM.1 | To support key generation for SSH, the incoporating document must
include FCS_CKM.1 and specify the corresponding algorithm(s). |
| FCS_CKM.2 | To support key establishment for SSH, the incoporating document must
include FCS_CKM.2 and specify the corresponding algorithm(s). |
| FCS_COP.1 |
To support the cryptography needed for SSH communications, the incoporating document must include FCS_COP.1
(iterating as needed) to specify AES with corresponding key sizes and modes, digital signature generation and
verification function (at least one of RSA or ECDSA), a cryptographic hash function, and a keyed-hash message
authentication function. In particular, the incoporating document must support AES-CTR as defined in NIST SP 800-38A
with key sizes of both 128 and 256 bits.
|
| FCS_RBG_EXT.1 | To support random bit generation needed for SSH key generation,
the incorporating document must include a requirement that specifies the TOE's ability to invoke or provide
random bit generation services, commonly identified as FCS_RBG_EXT.1. |
| FIA_X509_EXT.1 | To support establishment of SSH communications using a public key algorithm that includes X.509,
the incorporating document must include FIA_X509_EXT.1. Note however that support for X.509 is selectable
and not mandatory. |
| FIA_X509_EXT.2 | To support establishment of SSH communications using a public key algorithm that includes X.509,
the incoporating document must include FIA_X509_EXT.2. Note however that support for X.509 is selectable
and not mandatory. |
| FPT_STM.1 | To support establishment of SSH communications using a public key algorithm that includes X.509,
the incorporating document must include FPT_STM.1 or some other requirement that ensures reliable system time.
Note however that support for time-based rekey thresholds is selectable and not mandatory. |
The auditable events specified in this Package are included in a Security Target if the incorporating PP, cPP, or PP-Module supports audit event reporting through FAU_GEN.1 and all other criteria in the incorporating PP or PP-Module are met.
| Requirement | Auditable Events | Additional Audit Record Contents |
|---|---|---|
| FCS_SSH_EXT.1 | [selection: Failure to establish SSH connection, None]. | Reason for failure. [selection: Non-TOE endpoint of attempted connection (IP Address) , None]. |
| FCS_SSH_EXT.1 | [selection: Establishment of SSH connection, None]. | [selection: Non-TOE endpoint of connection (IP Address)
, None]. |
| FCS_SSH_EXT.1 | [selection: Termination of SSH connection session, None]. | [selection: Non-TOE endpoint of connection (IP Address)
, None]. |
| FCS_SSH_EXT.1 | [selection: Dropping of packet(s) outside defined size limits, None]. | [selection: Packet size
, None]. |
The ST author selects which of the additional RFCs to which conformance is being claimed. An SSH product can implement additional RFCs, but only those listed in the selection can be claimed as conformant under CC. The RFC selections for this requirement must be consistent with selections in later elements of this Functional Package (e.g., cryptographic algorithms permitted).
For the purposes of this package (and subsequent integration into cPPs) only the claimed algorithms listed in the package must be enabled for use.
RFC 4253 indicates that certain cryptographic algorithms are "REQUIRED." This means that from the Internet Engineering Task Force's (IETF's) perspective the implementation must include support, not that the algorithms must be enabled for use. For the purposes of this SFR's evaluation activity and this Functional Package overall, it is not necessary to ensure that algorithms listed as "REQUIRED" by the RFC but not listed in later elements of this Functional Package are actually implemented.
RFC 4344 must be selected if aes128-ctr or aes256-ctr is selected in FCS_SSH_EXT.1.4.
RFC 4356 must be selected if "keyboard-interactive" is selected in FCS_SSH_EXT.1.2.
RFC 5647 must be selected when AEAD_AES_128_GCM, AEAD_AES_256_GCM, aes128-gcm@openssh.com, or aes256-gcm@openssh.com is selected as an encryption algorithm in FCS_SSH_EXT.1.4 and when AEAD_AES_128_GCM or AEAD_AES_256_GCM is selecyed as MAC algorithm in FCS_SSH_EXT.1.5.
RFC 5656 must be selected when ecdsa-sha2-nistp256, ecdsa-sha2-nistp384, ecdsa-sha2-nistp521 is selected as a public key algorithm in FCS_SSH_EXT.1.2, or when ecdh-sha2-nistp256, ecdh-sha2-nistp384, or ecdh-sha2-nistp521 is selected as a key exchange algorithm in FCS_SSH_EXT.1.6, or when "RFC 5656" is selected in FCS_SSH_EXT.1.7.
RFC 6187 must be selected when x509v3-ecdsa-sha2-nistp256, x509v3-ecdsa-sha2-nistp384, x509v3-ecdsa-sha2-nistp521, or x509v3-rsa2048-sha256 is selected as a public key algorithm in FCS_SSH_EXT.1.2.
RFC 6668 must be selected when hmac-sha2-256 or hmac-sha2-512 is selected as a MAC algorithm in FCS_SSH_EXT.1.5.
RFC 8268 must be selected when diffie-hellman-group14-sha256, diffie-hellman-group15-sha512, diffie-hellman-group16-sha512, diffie-hellman-group17-sha512, or diffie-hellman-group18-sha512 is selected as a key exchange algorithm in FCS_SSH_EXT.1.6.
RFC 8332 must be selected when rsa-sha2-256 or rsa-sha2-512 is selected as a public key algorithm in FCS_SSH_EXT.1.2.
RFC 8709 must be selected when ssh-ed25519 or ssh-ed448 is selected as a public key algorithm in FCS_SSH_EXT.1.2.
RFC 8731 must be selected when curve25519-sha256 or curve448-sha512 is selected as a key exchange algorithm in FCS_SSH_EXT.1.6.
If "client" is selected, then the ST must include FCS_SSHC_EXT.1.
If "server" is selected, then the ST must include FCS_SSHS_EXT.1.
This Package does not define any Strictly Optional requirements.
This Package does not define any Objective requirements.
This Package does not define any Implementation-Based requirements.
As indicated in the introduction to this Package, the baseline requirements (those that must be performed by the TOE or its underlying platform) are contained in the body of this Package. There are additional requirements based on selections in the body of the Package: if certain selections are made, then additional requirements below must be included.
The auditable events in the table below are included in a Security Target if both the associated requirement is included and the incorporating PP or PP-Module supports audit event reporting through FAU_GEN.1 and any other criteria in the incorporating PP or PP-Module are met.
| Requirement | Auditable Events | Additional Audit Record Contents |
|---|---|---|
| FCS_SSHC_EXT.1 | No events specified. | N/A |
| FCS_SSHS_EXT.1 | No events specified. | N/A |
| Acronym | Meaning |
|---|---|
| Base-PP | Base Protection Profile |
| CC | Common Criteria |
| CEM | Common Evaluation Methodology |
| EP | Extended Package |
| FP | Functional Package |
| OE | Operational Environment |
| PP | Protection Profile |
| PP-Configuration | Protection Profile Configuration |
| PP-Module | Protection Profile Module |
| SAR | Security Assurance Requirement |
| SFR | Security Functional Requirement |
| SSH | Secure Shell |
| ST | Security Target |
| TOE | Target of Evaluation |
| TSF | TOE Security Functionality |
| TSFI | TSF Interface |
| TSS | TOE Summary Specification |
| cPP | Collaborative Protection Profile |