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systemd/SOURCES/0644-creds-util-check-for-C...

58 lines
2.3 KiB

From b052e96d1b8fb75ec2ae1e6da889de67fbbade7a Mon Sep 17 00:00:00 2001
From: Alberto Planas <aplanas@suse.com>
Date: Fri, 13 Jan 2023 15:31:39 +0100
Subject: [PATCH] creds-util: check for CAP_DAC_READ_SEARCH
In make_credential_host_secret, the credential.secret file is generated
first as a temporary anonymous file that is later instantiated with
linkat(2). This system call requires CAP_DAC_READ_SEARCH capability
when the flag AT_EMPTY_PATH is used.
This patch check if the capability is effective, and if not uses the
alternative codepath for creating named temporary files.
Non-root users can now create per-user credentials with:
export SYSTEMD_CREDENTIAL_SECRET=$HOME/.config/systemd/credential.secret
systemd-creds setup
Signed-off-by: Alberto Planas <aplanas@suse.com>
(cherry picked from commit 1615578f2792fdeecaf65606861bd3db9eb949c3)
Related: RHEL-16182
---
src/shared/creds-util.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/src/shared/creds-util.c b/src/shared/creds-util.c
index 27548a0eec..20b3b83369 100644
--- a/src/shared/creds-util.c
+++ b/src/shared/creds-util.c
@@ -9,6 +9,7 @@
#include "sd-id128.h"
#include "blockdev-util.h"
+#include "capability-util.h"
#include "chattr-util.h"
#include "creds-util.h"
#include "def.h"
@@ -172,10 +173,15 @@ static int make_credential_host_secret(
assert(dfd >= 0);
assert(fn);
- fd = openat(dfd, ".", O_CLOEXEC|O_WRONLY|O_TMPFILE, 0400);
+ /* For non-root users creating a temporary file using the openat(2) over "." will fail later, in the
+ * linkat(2) step at the end. The reason is that linkat(2) requires the CAP_DAC_READ_SEARCH
+ * capability when it uses the AT_EMPTY_PATH flag. */
+ if (have_effective_cap(CAP_DAC_READ_SEARCH) > 0) {
+ fd = openat(dfd, ".", O_CLOEXEC|O_WRONLY|O_TMPFILE, 0400);
+ if (fd < 0)
+ log_debug_errno(errno, "Failed to create temporary credential file with O_TMPFILE, proceeding without: %m");
+ }
if (fd < 0) {
- log_debug_errno(errno, "Failed to create temporary credential file with O_TMPFILE, proceeding without: %m");
-
if (asprintf(&t, "credential.secret.%016" PRIx64, random_u64()) < 0)
return -ENOMEM;