Mail Content-Type fallback to US_ASCII fails

[tlhackque]

In cron.c, line 104 we have:

setlocale(LC_COLLATE, "C"); /* Except for collation, since load_database() uses a-z */
       /* Except that "US-ASCII" is preferred to "ANSI_x3.4-1968" in MIME,
        * even though "ANSI_x3.4-1968" is the official charset name. */
       if ( ( cs = nl_langinfo( CODESET ) ) != 0L && 
               strcmp(cs, "ANSI_x3.4-1968") != 0 )
           strncpy( cron_default_mail_charset, cs, MAX_ENVSTR );
       else
           strcpy( cron_default_mail_charset, "US-ASCII" );

But nl_langinfo() can return ANSI_X3.4-1968. Note the upper-case 'X'. This results in cron_default_mail_charset acquiring that value instead of the intended US-ASCII.

It's not clear whether any environment returns the lower-case 'x', but the simplest fix is to replace strcmp with the case-insensitive strcasecmp(3). (strings.h or string.h)

You can demonstrate this with the following Perl on-liner (Perl exposes the same APIs):

$  perl -MPOSIX -MI18N::Langinfo=langinfo,CODESET -e'setlocale(LC_ALL,"fr_FRX");print langinfo(CODESET),"\n";'
ANSI_X3.4-1968
$

In my case, on Linux 5.17.12-100.fc34.x86_64, Perl v5.32.1; fr_FRX is not a defined locale.

[tlhackque]

Wrong, repo, sorry. See vixie/cron#10