login.defs: warn about weak choices

According to crypt(5), MD5 and DES should not be used for new
hashes. Also the default number of SHA rounds chosen by libc is orders
of magnitude too low for modern hardware. Let's warn the users about
weak choices.

Signed-off-by: Topi Miettinen <toiwoton@gmail.com>

diff --git a/etc/login.defs b/etc/login.defs
index a2f8cd5006485a80c907d2212f03470141176bce..a0c3b0d1fd921211541fe56af8dd98d06c314a49 100644 (file)
--- a/etc/login.defs
+++ b/etc/login.defs
@@ -327,6 +327,7 @@ CHFN_RESTRICT               rwh
 # If set to SHA512, SHA512-based algorithm will be used for encrypting password
 # If set to BCRYPT, BCRYPT-based algorithm will be used for encrypting password
 # If set to DES, DES-based algorithm will be used for encrypting password (default)
+# MD5 and DES should not be used for new hashes, see crypt(5) for recommendations.
 # Overrides the MD5_CRYPT_ENAB option
 #
 # Note: If you use PAM, it is recommended to use a value consistent with
@@ -342,7 +343,8 @@ CHFN_RESTRICT               rwh
 # However, more CPU resources will be needed to authenticate users if
 # this value is increased.
 #
-# If not specified, the libc will choose the default number of rounds (5000).
+# If not specified, the libc will choose the default number of rounds (5000),
+# which is orders of magnitude too low for modern hardware.
 # The values must be within the 1000-999999999 range.
 # If only one of the MIN or MAX values is set, then this value will be used.
 # If MIN > MAX, the highest value will be used.

diff --git a/man/login.defs.d/ENCRYPT_METHOD.xml b/man/login.defs.d/ENCRYPT_METHOD.xml
index 325d02516bbc19ec7bf9b84582525642f36b803c..af9d7f122427e6212554797a163ad96ef152e97e 100644 (file)
--- a/man/login.defs.d/ENCRYPT_METHOD.xml
+++ b/man/login.defs.d/ENCRYPT_METHOD.xml
@@ -39,6 +39,9 @@
       <replaceable>MD5</replaceable><phrase condition="sha_crypt">,
       <replaceable>SHA256</replaceable>,
       <replaceable>SHA512</replaceable></phrase>.
+      MD5 and DES should not be used for new hashes, see
+      <refentrytitle>crypt</refentrytitle><manvolnum>5</manvolnum>
+      for recommendations.
     </para>
     <para>
       Note: this parameter overrides the <option>MD5_CRYPT_ENAB</option>

diff --git a/man/login.defs.d/SHA_CRYPT_MIN_ROUNDS.xml b/man/login.defs.d/SHA_CRYPT_MIN_ROUNDS.xml
index 0755e69055ad0eeec3e9459779d85eebab5b57ba..7f0f9648f05e5d0308d236f0b19d46818eb76d34 100644 (file)
--- a/man/login.defs.d/SHA_CRYPT_MIN_ROUNDS.xml
+++ b/man/login.defs.d/SHA_CRYPT_MIN_ROUNDS.xml
@@ -44,7 +44,7 @@
     </para>
     <para>
       If not specified, the libc will choose the default number of rounds
-      (5000).
+      (5000), which is orders of magnitude too low for modern hardware.
     </para>
     <para>
       The values must be inside the 1000-999,999,999 range.