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Add writeable group flag to log file

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Resolves: rhbz#2024166
This commit is contained in:
Petr Menšík 2022-01-16 12:18:48 +01:00
parent 6ad2d1af9f
commit b77271d4fc
2 changed files with 69 additions and 1 deletions
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62
dnsmasq-2.87-root-log-writeable.patch Normal file
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@ -0,0 +1,62 @@
From 1f8f78a49b8fd6b2862a3882053b1c6e6e111e5c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20Men=C5=A1=C3=ADk?= <pemensik@redhat.com>
Date: Mon, 10 Jan 2022 12:34:42 +0100
Subject: [PATCH] Add root group writeable flag to log file
Some systems strips even root process capability of writing to different
users file. That include systemd under Fedora. When
log-facility=/var/log/dnsmasq.log is used, log file with mode 0640
is created. But restart then fails, because such log file can be used
only when created new. Existing file cannot be opened by root when
starting, causing fatal error. Avoid that by adding root group writeable flag.
Ensure group is always root when granting write access. If it is
anything else, administrator has to configure correct rights.
---
src/log.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/src/log.c b/src/log.c
index 1ec3447..bcd6e52 100644
--- a/src/log.c
+++ b/src/log.c
@@ -100,10 +100,23 @@ int log_start(struct passwd *ent_pw, int errfd)
/* If we're running as root and going to change uid later,
change the ownership here so that the file is always owned by
the dnsmasq user. Then logrotate can just copy the owner.
- Failure of the chown call is OK, (for instance when started as non-root) */
- if (log_to_file && !log_stderr && ent_pw && ent_pw->pw_uid != 0 &&
- fchown(log_fd, ent_pw->pw_uid, -1) != 0)
- ret = errno;
+ Failure of the chown call is OK, (for instance when started as non-root).
+
+ If we've created a file with group-id root, we also make
+ the file group-writable. This gives processes in the root group
+ write access to the file and avoids the problem that on some systems,
+ once the file is owned by the dnsmasq user, it can't be written
+ whilst dnsmasq is running as root during startup.
+ */
+ if (log_to_file && !log_stderr && ent_pw && ent_pw->pw_uid != 0)
+ {
+ struct stat ls;
+ if (getgid() == 0 && fstat(log_fd, &ls) == 0 && ls.st_gid == 0 &&
+ (ls.st_mode & S_IWGRP) == 0)
+ (void)fchmod(log_fd, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP);
+ if (fchown(log_fd, ent_pw->pw_uid, -1) != 0)
+ ret = errno;
+ }
return ret;
}
@@ -118,7 +131,7 @@ int log_reopen(char *log_file)
/* NOTE: umask is set to 022 by the time this gets called */
if (log_file)
- log_fd = open(log_file, O_WRONLY|O_CREAT|O_APPEND, S_IRUSR|S_IWUSR|S_IRGRP);
+ log_fd = open(log_file, O_WRONLY|O_CREAT|O_APPEND, S_IRUSR|S_IWUSR|S_IRGRP);
else
{
#if defined(HAVE_SOLARIS_NETWORK) || defined(__ANDROID__)
--
2.31.1

8
dnsmasq.spec
View File

@ -20,7 +20,7 @@
Name: dnsmasq
Version: 2.86
Release: 3%{?extraversion:.%{extraversion}}%{?dist}
Release: 4%{?extraversion:.%{extraversion}}%{?dist}
Summary: A lightweight DHCP/caching DNS server
License: GPLv2 or GPLv3
@ -64,6 +64,9 @@ Patch25: dnsmasq-2.86-domain-match-local.patch
Patch26: dnsmasq-2.86-build_server_array.patch
# https://bugzilla.redhat.com/show_bug.cgi?id=2014019
Patch28: dnsmasq-2.87-tcp-strcasecmp.patch
# https://bugzilla.redhat.com/show_bug.cgi?id=2024166
# http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=1f8f78a49b8fd6b2862a3882053b1c6e6e111e5c
Patch29: dnsmasq-2.87-root-log-writeable.patch
@ -207,6 +210,9 @@ install -Dpm 644 %{SOURCE2} %{buildroot}%{_sysusersdir}/%{name}.conf
%{_mandir}/man1/dhcp_*
%changelog
* Sun Jan 16 2022 Petr Menšík <pemensik@redhat.com> - 2.86-4
- Add writeable group flag to log file (#2024166)
* Thu Oct 14 2021 Petr Menšík <pemensik@redhat.com> - 2.86-3
- Rebuild server_array on any server change (#2009975)
- Compare case-insensitive also TCP queries (#2014019)