CVE-2020-1722: prevent use of too long passwords #4525
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ACK was added because this fix was pre-approved during several offline review sessions. |
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NIST SP 800-63-3B sets a recommendation to have password length upper bound limited in A.2: https://pages.nist.gov/800-63-3/sp800-63b.html#appA Users should be encouraged to make their passwords as lengthy as they want, within reason. Since the size of a hashed password is independent of its length, there is no reason not to permit the use of lengthy passwords (or pass phrases) if the user wishes. Extremely long passwords (perhaps megabytes in length) could conceivably require excessive processing time to hash, so it is reasonable to have some limit. FreeIPA already applied 256 characters limit for non-random passwords set through ipa-getkeytab tool. The limit was not, however, enforced in other places. MIT Kerberos limits the length of the password to 1024 characters in its tools. However, these tools (kpasswd and 'cpw' command of kadmin) do not differentiate between a password larger than 1024 and a password of 1024 characters. As a result, longer passwords are silently cut off. To prevent silent cut off for user passwords, use limit of 1000 characters. Thus, this patch enforces common limit of 1000 characters everywhere: - LDAP-based password changes - LDAP password change control - LDAP ADD and MOD operations on clear-text userPassword - Keytab setting with ipa-getkeytab - Kerberos password setting and changing Fixes: https://pagure.io/freeipa/issue/8268 Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com> Signed-off-by: Rob Crittenden <rcritten@redhat.com> Reviewed-by: Simo Sorce <ssorce@redhat.com>
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Forgot to update the test after the error message was changed to include 'clear-text password is too long'. |
no, we don't need them because they are doing LDAP MODIFY operations and those tested already. The test suite covers all actual ways of modifying passwords from the LDAP server and KDC server perspectives. |
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master:
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This was referenced Apr 14, 2020
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NIST SP 800-63-3B sets a recommendation to have password length upper bound limited in A.2:
https://pages.nist.gov/800-63-3/sp800-63b.html#appA
FreeIPA already applied 256 characters limit for non-random passwords
set through ipa-getkeytab tool. The limit was not, however, enforced in
other places.
MIT Kerberos limits the length of the password to 1024 characters in its
tools. However, these tools (kpasswd and 'cpw' command of kadmin) do not
differentiate between a password larger than 1024 and a password of 1024
characters. As a result, longer passwords are silently cut off.
To prevent silent cut off for user passwords, use limit of 1000
characters.
Thus, this patch enforces common limit of 1000 characters everywhere:
Signed-off-by: Alexander Bokovoy abokovoy@redhat.com
Signed-off-by: Rob Crittenden rcritten@redhat.com
Reviewed-by: Simo Sorce ssorce@redhat.com