Goal: Relaxed usernames/groupnames checking patch.

Status wrt upstream: Debian specific. Not to be used upstream

Details:
 Allows any non-empty user/grounames that don't contain ':' and '\n'
 characters and don't start with '-'. This patch is more restrictive
 than original Karl's version. closes: #264879
 Also closes: #377844
 
 Comments from Karl Ramm (shadow 1:4.0.3-9, 20 Aug 2003 02:06:50 -0400):
 
 I can't come up with a good justification as to why characters other
 than ':'s and '\0's should be disallowed in group and usernames (other
 than '-' as the leading character).  Thus, the maintenance tools don't
 anymore.  closes: #79682, #166798, #171179

--- a/libmisc/chkname.c
+++ b/libmisc/chkname.c
@@ -48,6 +48,7 @@
 
 static bool is_valid_name (const char *name)
 {
+#if 0
 	/*
 	 * User/group names must match [a-z_][a-z0-9_-]*[$]
 	 */
@@ -66,6 +67,20 @@
 			return false;
 		}
 	}
+#endif
+	/*
+     * POSIX indicate that usernames are composed of characters from the
+     * portable filename character set [A-Za-z0-9._-], and that the hyphen
+     * should not be used as the first character of a portable user name.
+     *
+	 * Allow more relaxed user/group names in Debian -- ^[^-:\s][^:\s]*$
+	 */
+	if (!*name || isspace(*name))
+		return 0;
+	do
+		if (*name == ':' || isspace(*name))
+			return 0;
+	while (*++name);
 
 	return true;
 }
--- a/man/useradd.8.xml
+++ b/man/useradd.8.xml
@@ -607,12 +607,19 @@
     </para>
 
     <para>
-      Usernames must start with a lower case letter or an underscore,
+      It is usually recommended to only use usernames that begin with a lower case letter or an underscore,
       followed by lower case letters, digits, underscores, or dashes.
       They can end with a dollar sign.
       In regular expression terms: [a-z_][a-z0-9_-]*[$]?
     </para>
     <para>
+      On Debian, the only constraints are that usernames must neither start
+      with a dash ('-') nor contain a colon (':') or a whitespace (space: ' ',
+      end of line: '\n', tabulation: '\t', etc.). Note that using a slash
+      ('/') may break the default algorithm for the definition of the
+      user's home directory.
+    </para>
+    <para>
       Usernames may only be up to 32 characters long.
     </para>
   </refsect1>
--- a/man/groupadd.8.xml
+++ b/man/groupadd.8.xml
@@ -223,12 +223,17 @@
    <refsect1 id='caveats'>
      <title>CAVEATS</title>
      <para>
-       Groupnames must start with a lower case letter or an underscore,
+       It is usually recommended to only use groupnames that begin with a lower case letter or an underscore,
        followed by lower case letters, digits, underscores, or dashes.
        They can end with a dollar sign.
        In regular expression terms: [a-z_][a-z0-9_-]*[$]?
      </para>
      <para>
+       On Debian, the only constraints are that groupnames must neither start
+       with a dash ('-') nor contain a colon (':') or a whitespace (space:' ',
+       end of line: '\n', tabulation: '\t', etc.).
+     </para>
+     <para>
        Groupnames may only be up to &GROUP_NAME_MAX_LENGTH; characters long.
      </para>
      <para>
