liblxc: Add username and uid lookup/check.

Add the ability to lookup usernames and check uids. Bails out early if the given
uid/name does not exist and avoids using atoi() (which is bad because we can't
tell if it parsed an int or a pumpkin).

Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>

diff --git a/src/lxc/lxc_unshare.c b/src/lxc/lxc_unshare.c
index fb5ec62dabe4d683e36aead5baaad4e645564e61..5e9de2a98417ed4df2556d49e44db3895992f1c2 100644 (file)
--- a/src/lxc/lxc_unshare.c
+++ b/src/lxc/lxc_unshare.c
@@ -30,6 +30,7 @@
 #include <errno.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <pwd.h>
 
 #include "lxc_namespace.h"
 
@@ -48,12 +49,37 @@ void usage(char *cmd)
        _exit(1);
 }
 
+static uid_t lookup_user(const char *optarg)
+{
+       char name[sysconf(_SC_LOGIN_NAME_MAX)];
+       uid_t uid = -1;
+
+       if (!optarg || (optarg[0] == '\0'))
+               return uid;
+       if (sscanf(optarg, "%u", &uid) < 1) {
+               struct passwd pwent; /* not a uid -- perhaps a username */
+               struct passwd *pent;
+
+               if (sscanf(optarg, "%s", name) < 1)
+                       return uid;
+               if (getpwnam_r(name, &pwent, NULL, 0, &pent) || !pent)
+                       return uid;
+               uid = pent->pw_uid;
+       } else {
+               if (getpwuid_r(uid, NULL, NULL, 0, NULL)) {
+                       uid = -1;
+                       return uid;
+               }
+       }
+       return uid;
+}
+
 int main(int argc, char *argv[])
 {
        int opt, nbargs = 0, status = 1, hastofork = 0;
        char **args;
        long flags = 0;
-       uid_t uid = 0;
+       uid_t uid = -1; /* valid only if (flags & CLONE_NEWUSER) */
        pid_t pid;
 
        while ((opt = getopt(argc, argv, "fmphiu:n")) != -1) {
@@ -71,8 +97,10 @@ int main(int argc, char *argv[])
                        flags |= CLONE_NEWIPC;
                        break;
                case 'u':
+                       uid = lookup_user(optarg);
+                       if (uid == -1)
+                               break;
                        flags |= CLONE_NEWUSER;
-                       uid = atoi(optarg);
                        break;
                case 'n':
                        flags |= CLONE_NEWNET;