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TD0332:  Support for RSA SHA2 host keys

Publication Date
2018.06.08

Protection Profiles
PP_SSH_EP_v1.0

Other References
FCS_SSHC_EXT.1.4, FCS_SSHS_EXT.1.4

Issue Description

Rsa-sha2-512 and rsa-sha2-256 were standardized in March 2018 as RFC 8332, but are not included in the SSH EP.

Resolution

 

This TD supersedes TD0313.

FCS_SSHC_EXT.1.4 is modified as follows:

FCS_SSHC_EXT.1.4   The SSH client shall ensure that the SSH transport implementation uses [selection: ssh-rsa, rsa-sha2-256, rsa-sha2-512, ecdsa-sha2-nistp256] and [selection: ecdsa-sha2-nistp384, x509v3-ecdsa-sha2-nistp256, x509v3-ecdsa-sha2-nistp384, no other public key algorithms] as its public key algorithm(s) and rejects all other public key algorithms.

The application note is updated as follows:

Application Note: Implementations that select only ssh-rsa will not achieve the 112-bit security strength in the digital signature generation for SSH authentication as is recommended in NIST SP 800-131A. Future versions of this document may remove ssh-rsa as a selection. If x509v3-ecdsa-sha2-nistp256 or x509v3-ecdsa-sha2-nistp384 are selected, then the list of trusted certification authorities must be selected in FCS_SSHC_EXT.1.8.  RFC 8332 specifies the use of rsa-sha2-256 or rsa-sha2-512 in SSH. The SFRs for cryptographic key generation and certificate validation are inherited from the base PP.

FCS_SSHS_EXT.1.4 is modified as follows:

FCS_SSHS_EXT.1.4  The SSH server shall ensure that the SSH transport implementation uses [selection: ssh-rsa, rsa-sha2-256, rsa-sha2-512, ecdsa-sha2-nistp256] and [selection: ecdsa-sha2-nistp384, x509v3-ecdsa-sha2-nistp256, x509v3-ecdsa-sha2-nistp384, no other public key algorithms] as its public key algorithm(s) and rejects all other public key algorithms.

The application note is updated as follows:

Application Note: Implementations that select only ssh-rsa will not achieve the 112-bit security strength in the digital signature generation for SSH authentication as is recommended in NIST SP 800-131A. Future versions of this profile may remove ssh-rsa as a selection. RFC 8332 specifies the use of rsa-sha2-256 or rsa-sha2-512 in SSH.  The SFRs for cryptographic key generation and certificate validation are inherited from the base PP.

There are no changes to the Assurance Activities.

Justification

See issue description.

 
 
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