The branch main has been updated by olce:
URL:
https://cgit.FreeBSD.org/src/commit/?id=e395e354823b690ba19ecc8e3688bacec6f67ad3
commit e395e354823b690ba19ecc8e3688bacec6f67ad3
Author: Olivier Certner <o...@freebsd.org>
AuthorDate: 2024-07-29 14:24:08 +0000
Commit: Olivier Certner <o...@freebsd.org>
CommitDate: 2024-12-16 14:42:40 +0000
mdo(1): Use setcred() to change credentials
As this is the only system call that MAC/do currently supports, and the
only one that really can be for transitions involving simultaneous
changes of user and group IDs.
Reviewed by: bapt
Approved by: markj (mentor)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D47621
---
usr.bin/mdo/mdo.c | 42 +++++++++++++++++++++++++++++++++++-------
1 file changed, 35 insertions(+), 7 deletions(-)
diff --git a/usr.bin/mdo/mdo.c b/usr.bin/mdo/mdo.c
index 22e2838daa08..8435fc17f26f 100644
--- a/usr.bin/mdo/mdo.c
+++ b/usr.bin/mdo/mdo.c
@@ -5,6 +5,7 @@
*/
#include <sys/limits.h>
+#include <sys/ucred.h>
#include <err.h>
#include <paths.h>
@@ -27,6 +28,8 @@ main(int argc, char **argv)
{
struct passwd *pw;
const char *username = "root";
+ struct setcred wcred = SETCRED_INITIALIZER;
+ u_int setcred_flags = 0;
bool uidonly = false;
int ch;
@@ -50,20 +53,45 @@ main(int argc, char **argv)
const char *errp = NULL;
uid_t uid = strtonum(username, 0, UID_MAX, &errp);
if (errp != NULL)
- err(EXIT_FAILURE, "%s", errp);
+ err(EXIT_FAILURE, "invalid user ID '%s'",
+ username);
pw = getpwuid(uid);
}
if (pw == NULL)
err(EXIT_FAILURE, "invalid username '%s'", username);
}
+
+ wcred.sc_uid = wcred.sc_ruid = wcred.sc_svuid = pw->pw_uid;
+ setcred_flags |= SETCREDF_UID | SETCREDF_RUID | SETCREDF_SVUID;
+
if (!uidonly) {
- if (initgroups(pw->pw_name, pw->pw_gid) == -1)
- err(EXIT_FAILURE, "failed to call initgroups");
- if (setgid(pw->pw_gid) == -1)
- err(EXIT_FAILURE, "failed to call setgid");
+ /*
+ * If there are too many groups specified for some UID, setting
+ * the groups will fail. We preserve this condition by
+ * allocating one more group slot than allowed, as
+ * getgrouplist() itself is just some getter function and thus
+ * doesn't (and shouldn't) check the limit, and to allow
+ * setcred() to actually check for overflow.
+ */
+ const long ngroups_alloc = sysconf(_SC_NGROUPS_MAX) + 2;
+ gid_t *const groups = malloc(sizeof(*groups) * ngroups_alloc);
+ int ngroups = ngroups_alloc;
+
+ if (groups == NULL)
+ err(EXIT_FAILURE, "cannot allocate memory for groups");
+
+ getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups);
+
+ wcred.sc_gid = wcred.sc_rgid = wcred.sc_svgid = pw->pw_gid;
+ wcred.sc_supp_groups = groups + 1;
+ wcred.sc_supp_groups_nb = ngroups - 1;
+ setcred_flags |= SETCREDF_GID | SETCREDF_RGID | SETCREDF_SVGID |
+ SETCREDF_SUPP_GROUPS;
}
- if (setuid(pw->pw_uid) == -1)
- err(EXIT_FAILURE, "failed to call setuid");
+
+ if (setcred(setcred_flags, &wcred, sizeof(wcred)) != 0)
+ err(EXIT_FAILURE, "calling setcred() failed");
+
if (*argv == NULL) {
const char *sh = getenv("SHELL");
if (sh == NULL)
