vol_id: add --offset option

[elogind.git] / extras / volume_id / vol_id.c

diff --git a/extras/volume_id/vol_id.c b/extras/volume_id/vol_id.c
index e17e7abb0c7eaa6bac3633e70136af2a3c33f543..04e85abb7f8bd02bd69a59ad09a0d112de0bfe5d 100644 (file)
--- a/extras/volume_id/vol_id.c
+++ b/extras/volume_id/vol_id.c
@@ -134,6 +134,7 @@ int main(int argc, char *argv[])
                { "export", 0, NULL, 'x' },
                { "skip-raid", 0, NULL, 's' },
                { "probe-all", 0, NULL, 'a' },
+               { "offset", 1, NULL, 'o' },
                { "help", 0, NULL, 'h' },
                {}
        };
@@ -153,8 +154,8 @@ int main(int argc, char *argv[])
        uint64_t size;
        int skip_raid = 0;
        int probe_all = 0;
+       uint64_t offset = 0;
        const char *node;
-       struct passwd *pw;
        int fd;
        const char *label, *uuid, *type, *type_version, *usage;
        int retval;
@@ -168,7 +169,7 @@ int main(int argc, char *argv[])
        while (1) {
                int option;
 
-               option = getopt_long(argc, argv, "lLutxsah", options, NULL);
+               option = getopt_long(argc, argv, "lLutxsaoh", options, NULL);
                if (option == -1)
                        break;
 
@@ -194,6 +195,9 @@ int main(int argc, char *argv[])
                case 'a':
                        probe_all = 1;
                        break;
+               case 'o':
+                       offset = strtoull(optarg, NULL, 0);
+                       break;
                case 'h':
                        printf("Usage: vol_id [options] <device>\n"
                            " --export        export key/value pairs\n"
@@ -203,6 +207,7 @@ int main(int argc, char *argv[])
                            " --uuid          filesystem uuid\n"
                            " --skip-raid     don't probe for raid\n"
                            " --probe-all     find possibly conflicting signatures\n"
+                           " --offset        skip given number of bytes of input\n"
                            " --help\n\n");
                        goto exit;
                default:
@@ -237,28 +242,27 @@ int main(int argc, char *argv[])
        dbg("BLKGETSIZE64=%llu", (unsigned long long)size);
 
        /* try to drop all privileges before reading disk content */
-       pw = getpwnam ("nobody");
-       if (pw != NULL && pw->pw_uid > 0 && pw->pw_gid > 0) {
-               dbg("dropping privileges to %u:%u",
-                   (unsigned int)pw->pw_uid, (unsigned int)pw->pw_gid);
-               if (setgroups(0, NULL) != 0 ||
-                   setgid(pw->pw_gid) != 0 ||
-                   setuid(pw->pw_uid) != 0) {
-                       fprintf(stderr, "error dropping privileges: %s\n", strerror(errno));
-                       rc = 3;
-                       goto exit;
+       if (getuid() == 0) {
+               struct passwd *pw;
+
+               pw = getpwnam("nobody");
+               if (pw != NULL && pw->pw_uid > 0 && pw->pw_gid > 0) {
+                       if (setgroups(0, NULL) != 0 ||
+                           setgid(pw->pw_gid) != 0 ||
+                           setuid(pw->pw_uid) != 0)
+                               info("unable to drop privileges: %s\n", strerror(errno));
                }
        }
 
        if (probe_all) {
-               volume_id_all_probers(all_probers, vid, 0, size, NULL);
+               volume_id_all_probers(all_probers, vid, offset, size, NULL);
                goto exit;
        }
 
        if (skip_raid)
-               retval = volume_id_probe_filesystem(vid, 0, size);
+               retval = volume_id_probe_filesystem(vid, offset, size);
        else
-               retval = volume_id_probe_all(vid, 0, size);
+               retval = volume_id_probe_all(vid, offset, size);
        if (retval != 0) {
                fprintf(stderr, "%s: unknown volume type\n", node);
                rc = 4;