d4f93c3c5e
When log-facility is used to create a new file, make that file also
writeable by root. Systemd strips the ability to write into this file
even when started by root. Allow root explicitly.
Resolves: rhbz#2207798
(cherry picked from commit cafac891ea)
65 lines
2.6 KiB
Diff
65 lines
2.6 KiB
Diff
From e342e4d5c3093d8dd9e2d622e46d36f67bfb4925 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Petr=20Men=C5=A1=C3=ADk?= <pemensik@redhat.com>
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Date: Mon, 10 Jan 2022 12:34:42 +0100
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Subject: [PATCH] Add root group writeable flag to log file
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Some systems strips even root process capability of writing to different
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users file. That include systemd under Fedora. When
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log-facility=/var/log/dnsmasq.log is used, log file with mode 0640
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is created. But restart then fails, because such log file can be used
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only when created new. Existing file cannot be opened by root when
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starting, causing fatal error. Avoid that by adding root group writeable flag.
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Ensure group is always root when granting write access. If it is
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anything else, administrator has to configure correct rights.
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(cherry picked from commit 1f8f78a49b8fd6b2862a3882053b1c6e6e111e5c)
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---
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src/log.c | 23 ++++++++++++++++++-----
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1 file changed, 18 insertions(+), 5 deletions(-)
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diff --git a/src/log.c b/src/log.c
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index 1ec3447..bcd6e52 100644
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--- a/src/log.c
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+++ b/src/log.c
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@@ -100,10 +100,23 @@ int log_start(struct passwd *ent_pw, int errfd)
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/* If we're running as root and going to change uid later,
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change the ownership here so that the file is always owned by
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the dnsmasq user. Then logrotate can just copy the owner.
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- Failure of the chown call is OK, (for instance when started as non-root) */
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- if (log_to_file && !log_stderr && ent_pw && ent_pw->pw_uid != 0 &&
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- fchown(log_fd, ent_pw->pw_uid, -1) != 0)
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- ret = errno;
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+ Failure of the chown call is OK, (for instance when started as non-root).
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+
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+ If we've created a file with group-id root, we also make
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+ the file group-writable. This gives processes in the root group
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+ write access to the file and avoids the problem that on some systems,
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+ once the file is owned by the dnsmasq user, it can't be written
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+ whilst dnsmasq is running as root during startup.
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+ */
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+ if (log_to_file && !log_stderr && ent_pw && ent_pw->pw_uid != 0)
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+ {
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+ struct stat ls;
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+ if (getgid() == 0 && fstat(log_fd, &ls) == 0 && ls.st_gid == 0 &&
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+ (ls.st_mode & S_IWGRP) == 0)
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+ (void)fchmod(log_fd, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP);
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+ if (fchown(log_fd, ent_pw->pw_uid, -1) != 0)
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+ ret = errno;
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+ }
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return ret;
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}
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@@ -118,7 +131,7 @@ int log_reopen(char *log_file)
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/* NOTE: umask is set to 022 by the time this gets called */
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if (log_file)
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- log_fd = open(log_file, O_WRONLY|O_CREAT|O_APPEND, S_IRUSR|S_IWUSR|S_IRGRP);
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+ log_fd = open(log_file, O_WRONLY|O_CREAT|O_APPEND, S_IRUSR|S_IWUSR|S_IRGRP);
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else
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{
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#if defined(HAVE_SOLARIS_NETWORK) || defined(__ANDROID__)
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--
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2.40.1
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