Bug#985997: exim4: possible formatting bug: exim4 creates file with %s in file name

[Vincas Dargis]

Package: exim4
Version: 4.92-8+deb10u5
Severity: minor

Dear Maintainer,

After installing Debian 10.9, I've noticed this denial (due to my own
"WIP" AppArmor profile applied):
```
type=AVC msg=audit(1616860912.170:123): apparmor="DENIED"
operation="mknod" profile="exim4" name="/var/spool/exim4/%s.X0JzJon"
pid=3530 comm="exim4" requested_mask="c" denied_mask="c" fsuid=106
ouid=106
```

I've noticed that file has `%s` in it's file name. It seems like a
formatting bug.

After allowing this write (and also writing
`/var/spool/exim4/gnutls-params-2048` later), exim4 seems to work
normally.

%s.X0JzJon generated file has "-----BEGIN DH PARAMETERS-----" in it's
%first line.


-- Package-specific info:
Exim version 4.92 #3 built 18-Mar-2021 08:10:15
Copyright (c) University of Cambridge, 1995 - 2018
(c) The Exim Maintainers and contributors in ACKNOWLEDGMENTS file, 2007 - 2018
Berkeley DB: Berkeley DB 5.3.28: (September  9, 2013)
Support for: crypteq iconv() IPv6 PAM Perl Expand_dlfunc GnuTLS move_frozen_messages Content_Scanning DANE DKIM DNSSEC Event OCSP PRDR PROXY SOCKS TCP_Fast_Open
Lookups (built-in): lsearch wildlsearch nwildlsearch iplsearch cdb dbm dbmjz dbmnz dnsdb dsearch ldap ldapdn ldapm mysql nis nis0 passwd pgsql sqlite
Authenticators: cram_md5 cyrus_sasl dovecot plaintext spa tls
Routers: accept dnslookup ipliteral iplookup manualroute queryprogram redirect
Transports: appendfile/maildir/mailstore/mbx autoreply lmtp pipe smtp
Malware: f-protd f-prot6d drweb fsecure sophie clamd avast sock cmdline
Fixed never_users: 0
Configure owner: 0:0
Size of off_t: 8
Configuration file search path is /etc/exim4/exim4.conf:/var/lib/exim4/config.autogenerated
Configuration file is /var/lib/exim4/config.autogenerated

-- System Information:
Debian Release: 10.9
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: armhf (armv7l)

Kernel: Linux 4.19.0-16-armmp-lpae (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages exim4 depends on:
ii  debconf [debconf-2.0]  1.5.71
ii  exim4-base             4.92-8+deb10u5
ii  exim4-daemon-heavy     4.92-8+deb10u5

exim4 recommends no packages.

exim4 suggests no packages.

-- debconf information excluded