Vulnerability Discussion

Centralized cryptographic policies simplify applying secure ciphers across an operating system and the applications that run on that operating system. Use of weak or untested encryption algorithms undermines the purposes of utilizing encryption to protect data.

Satisfies: SRG-OS-000396-GPOS-00176, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174, SRG-OS-000424-GPOS-00188, SRG-OS-000073-GPOS-00041, SRG-OS-000120-GPOS-00061

Check

Verify Amazon Linux 2023 custom crypto policies are loaded correctly with the following command:

$ ls -l /etc/crypto-policies/back-ends/
lrwxrwxrwx. 1 root root 40 Mar 7 19:22 bind.config -> /usr/share/crypto-policies/FIPS/bind.txt
lrwxrwxrwx. 1 root root 42 Mar 7 19:22 gnutls.config -> /usr/share/crypto-policies/FIPS/gnutls.txt
lrwxrwxrwx. 1 root root 40 Mar 7 19:22 java.config -> /usr/share/crypto-policies/FIPS/java.txt
lrwxrwxrwx. 1 root root 46 Mar 7 19:22 javasystem.config -> /usr/share/crypto-policies/FIPS/javasystem.txt
lrwxrwxrwx. 1 root root 40 Mar 7 19:22 krb5.config -> /usr/share/crypto-policies/FIPS/krb5.txt
lrwxrwxrwx. 1 root root 45 Mar 7 19:22 libreswan.config -> /usr/share/crypto-policies/FIPS/libreswan.txt
lrwxrwxrwx. 1 root root 42 Mar 7 19:22 libssh.config -> /usr/share/crypto-policies/FIPS/libssh.txt
-rw-r--r--. 1 root root 398 Mar 7 19:22 nss.config
lrwxrwxrwx. 1 root root 43 Mar 7 19:22 openssh.config -> /usr/share/crypto-policies/FIPS/openssh.txt
lrwxrwxrwx. 1 root root 49 Mar 7 19:22 opensshserver.config -> /usr/share/crypto-policies/FIPS/opensshserver.txt
lrwxrwxrwx. 1 root root 43 Mar 7 19:22 openssl.config -> /usr/share/crypto-policies/FIPS/openssl.txt
lrwxrwxrwx. 1 root root 48 Mar 7 19:22 openssl_fips.config -> /usr/share/crypto-policies/FIPS/openssl_fips.txt
lrwxrwxrwx. 1 root root 46 Mar 7 19:22 opensslcnf.config -> /usr/share/crypto-policies/FIPS/opensslcnf.txt

If the paths do not point to the respective files under /usr/share/crypto-policies/FIPS path, this is a finding.
Note: nss.config must not be hyperlinked.

Fix

Configure Amazon Linux 2023 to correctly implement the systemwide cryptographic policies by reinstalling the crypto-policies package contents.

Reinstall crypto-policies with the following command:

$ sudo dnf -y reinstall crypto-policies

Set the crypto-policy to FIPS with the following command:

$ sudo update-crypto-policies --set FIPS
Setting system policy to FIPS

Note: Systemwide crypto policies are applied on application startup. It is recommended to restart the system for the change of policies to fully take place.