76 lines
2.7 KiB
Diff
76 lines
2.7 KiB
Diff
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From 44ed6a1724bac01cd1c1dd25defb62237df5f379 Mon Sep 17 00:00:00 2001
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From: Thomas Haller <thaller@redhat.com>
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Date: Fri, 21 May 2021 18:32:07 +0200
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Subject: [PATCH 1/1] teamd: better handle failures to chown(TEAMD_RUN_DIR)
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during teamd_drop_privileges()
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NetworkManager is exec-ing teamd while running without CAP_CHOWN.
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When teamd is configured to drop privileges, then it will call chown
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while still running as root user. But the command will fail because of
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lack of CAP_CHOWN.
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Note that chown() succeeds if the calling process has CAP_CHOWN or if
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the file already is owned by the calling user/group (whereas, changing
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the group will still work, if the user is a member of that group).
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The directory might have already been prepared with the right user/group.
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Let's handle that. If the first chown() as root succeeds, we are good.
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If it fails, we will retry after changing the user id. If the directory
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already has the right/compatible user, this command will succeeds too
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and teamd can proceed.
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See-also: https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/722
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Signed-off-by: Thomas Haller <thaller@redhat.com>
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---
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teamd/teamd.c | 18 +++++++++++++-----
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1 file changed, 13 insertions(+), 5 deletions(-)
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diff --git a/teamd/teamd.c b/teamd/teamd.c
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index b310140570c5..3ef3d6cf09f6 100644
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--- a/teamd/teamd.c
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+++ b/teamd/teamd.c
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@@ -1714,6 +1714,7 @@ static int teamd_drop_privileges()
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cap_t my_caps;
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struct passwd *pw = NULL;
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struct group *grpent = NULL;
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+ int chown_succeeded;
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if ((pw = getpwnam(TEAMD_USER)) == NULL) {
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fprintf(stderr, "Error reading user %s entry (%m)\n", TEAMD_USER);
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@@ -1734,11 +1735,12 @@ static int teamd_drop_privileges()
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goto error;
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}
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- if (chown(TEAMD_RUN_DIR, pw->pw_uid, pw->pw_gid) < 0) {
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- fprintf(stderr, "Unable to change ownership of %s to %s/%s (%m)\n",
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- TEAMD_RUN_DIR, TEAMD_USER, TEAMD_GROUP);
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- goto error;
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- }
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+ /* Try to change owner while still being root. We might not have
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+ * capabilities, so this might fail. At this point, we accept that,
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+ * because the directory might have been prepared with a suitable owner
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+ * already. But on failure, we will retry as the new user below.
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+ */
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+ chown_succeeded = (chown(TEAMD_RUN_DIR, pw->pw_uid, pw->pw_gid) == 0);
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if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0)
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goto error;
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@@ -1758,6 +1760,12 @@ static int teamd_drop_privileges()
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goto error;
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}
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+ if (!chown_succeeded && chown(TEAMD_RUN_DIR, pw->pw_uid, pw->pw_gid) < 0) {
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+ fprintf(stderr, "Unable to change ownership of %s to %s/%s (%m)\n",
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+ TEAMD_RUN_DIR, TEAMD_USER, TEAMD_GROUP);
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+ goto error;
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+ }
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+
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if ((my_caps = cap_init()) == NULL)
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goto error;
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if (cap_set_flag(my_caps, CAP_EFFECTIVE, ARRAY_SIZE(cv), cv, CAP_SET) < 0)
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--
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2.31.1
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