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authorStefano Brivio <sbrivio@redhat.com>2023-05-21 14:47:07 +0200
committerStefano Brivio <sbrivio@redhat.com>2023-05-23 16:13:18 +0200
commitb0881aae6d91845821b2732f3fc8890e3d9ec4d2 (patch)
treef509bda5008a4f1737725eaa6d37295e8da0d937
parent25f1d1a84f459fe197508b07fc7cdb858d7468ee (diff)
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util, conf: Add and use ns_is_init() helper
We'll need this in isolate_initial(). While at it, don't rely on BUFSIZ: the earlier issue we had with musl reminded me it's not a magic "everything will fit" value. Size the read buffer to what we actually need from uid_map, and check for the final newline too, because uid_map is organised in lines. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
-rw-r--r--conf.c16
-rw-r--r--util.c25
-rw-r--r--util.h2
3 files changed, 28 insertions, 15 deletions
diff --git a/conf.c b/conf.c
index 447b000..984c3ce 100644
--- a/conf.c
+++ b/conf.c
@@ -1096,10 +1096,6 @@ static int conf_runas(char *opt, unsigned int *uid, unsigned int *gid)
*/
static void conf_ugid(char *runas, uid_t *uid, gid_t *gid)
{
- const char root_uid_map[] = " 0 0 4294967295";
- char buf[BUFSIZ];
- int fd;
-
/* If user has specified --runas, that takes precedence... */
if (runas) {
if (conf_runas(runas, uid, gid))
@@ -1116,18 +1112,8 @@ static void conf_ugid(char *runas, uid_t *uid, gid_t *gid)
return;
/* ...or at least not root in the init namespace... */
- if ((fd = open("/proc/self/uid_map", O_RDONLY | O_CLOEXEC)) < 0) {
- die("Can't determine if we're in init namespace: %s",
- strerror(errno));
- }
-
- if (read(fd, buf, BUFSIZ) != sizeof(root_uid_map) ||
- strncmp(buf, root_uid_map, sizeof(root_uid_map) - 1)) {
- close(fd);
+ if (!ns_is_init())
return;
- }
-
- close(fd);
/* ...otherwise use nobody:nobody */
warn("Don't run as root. Changing to nobody...");
diff --git a/util.c b/util.c
index c3e3471..1d00404 100644
--- a/util.c
+++ b/util.c
@@ -391,6 +391,31 @@ int ns_enter(const struct ctx *c)
}
/**
+ * ns_is_init() - Is the caller running in the "init" user namespace?
+ *
+ * Return: true if caller is in init, false otherwise, won't return on failure
+ */
+bool ns_is_init(void)
+{
+ const char root_uid_map[] = " 0 0 4294967295\n";
+ char buf[sizeof(root_uid_map)] = { 0 };
+ bool ret = true;
+ int fd;
+
+ if ((fd = open("/proc/self/uid_map", O_RDONLY | O_CLOEXEC)) < 0) {
+ die("Can't determine if we're in init namespace: %s",
+ strerror(errno));
+ }
+
+ if (read(fd, buf, sizeof(root_uid_map)) != sizeof(root_uid_map) - 1 ||
+ strncmp(buf, root_uid_map, sizeof(root_uid_map)))
+ ret = false;
+
+ close(fd);
+ return ret;
+}
+
+/**
* pid_file() - Write PID to file, if requested to do so, and close it
* @fd: Open PID file descriptor, closed on exit, -1 to skip writing it
* @pid: PID value to write
diff --git a/util.h b/util.h
index ba3e3da..26892aa 100644
--- a/util.h
+++ b/util.h
@@ -8,6 +8,7 @@
#include <stdlib.h>
#include <stdarg.h>
+#include <stdbool.h>
#include "log.h"
@@ -216,6 +217,7 @@ char *line_read(char *buf, size_t len, int fd);
void procfs_scan_listen(struct ctx *c, uint8_t proto, int ip_version, int ns,
uint8_t *map, uint8_t *exclude);
int ns_enter(const struct ctx *c);
+bool ns_is_init(void);
void write_pidfile(int fd, pid_t pid);
int __daemon(int pidfile_fd, int devnull_fd);
int fls(unsigned long x);