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authorLennart Poettering <lennart@poettering.net>2011-07-25 19:31:07 +0200
committerLennart Poettering <lennart@poettering.net>2011-07-25 19:32:43 +0200
commit8d41a963d66e54807e8b0fa69700107e39cf485a (patch)
tree7c0663207c517f67f313cc8a80a7f2e1605bd7a3 /src
parentfb922d4f822b32e9a046c7052b97f2ed3152e76e (diff)
machine-id: be nice and generate compliant v4 UUIDs
Newly generated machine IDs now qualify as randomized v4 UUIds. This is trivial to do and hopefully increases adoption of the ID for various purposes.
Diffstat (limited to 'src')
-rw-r--r--src/machine-id-setup.c38
1 files changed, 30 insertions, 8 deletions
diff --git a/src/machine-id-setup.c b/src/machine-id-setup.c
index 98e288e1b5..be51d0dec7 100644
--- a/src/machine-id-setup.c
+++ b/src/machine-id-setup.c
@@ -32,16 +32,28 @@
#include "util.h"
#include "log.h"
+static void make_v4_uuid(unsigned char *id) {
+ /* Stolen from generate_random_uuid() of drivers/char/random.c
+ * in the kernel sources */
+
+ /* Set UUID version to 4 --- truly random generation */
+ id[6] = (id[6] & 0x0F) | 0x40;
+
+ /* Set the UUID variant to DCE */
+ id[8] = (id[8] & 0x3F) | 0x80;
+}
+
static int generate(char id[34]) {
int fd;
- char buf[16];
- char *p, *q;
+ unsigned char buf[16], *p;
+ char *q;
ssize_t k;
assert(id);
/* First, try reading the D-Bus machine id, unless it is a symlink */
- if ((fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW)) >= 0) {
+ fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+ if (fd >= 0) {
k = loop_read(fd, id, 33, false);
close_nointr_nofail(fd);
@@ -56,7 +68,8 @@ static int generate(char id[34]) {
}
/* If that didn't work, generate a random machine id */
- if ((fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
+ fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+ if (fd < 0) {
log_error("Failed to open /dev/urandom: %m");
return -errno;
}
@@ -69,6 +82,11 @@ static int generate(char id[34]) {
return k < 0 ? (int) k : -EIO;
}
+ /* Turn this into a valid v4 UUID, to be nice. Note that we
+ * only guarantee this for newly generated UUIDs, not for
+ * pre-existing ones.*/
+ make_v4_uuid(buf);
+
for (p = buf, q = id; p < buf + sizeof(buf); p++, q += 2) {
q[0] = hexchar(*p >> 4);
q[1] = hexchar(*p & 15);
@@ -96,10 +114,12 @@ int machine_id_setup(void) {
* will be owned by root it doesn't matter much, but maybe
* people look. */
- if ((fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444)) >= 0)
+ fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
+ if (fd >= 0)
writable = true;
else {
- if ((fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
+ fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+ if (fd < 0) {
umask(m);
log_error("Cannot open /etc/machine-id: %m");
return -errno;
@@ -126,7 +146,8 @@ int machine_id_setup(void) {
/* Hmm, so, the id currently stored is not useful, then let's
* generate one */
- if ((r = generate(id)) < 0)
+ r = generate(id);
+ if (r < 0)
goto finish;
if (S_ISREG(st.st_mode) && writable) {
@@ -146,7 +167,8 @@ int machine_id_setup(void) {
mkdir_p("/run/systemd", 0755);
- if ((r = write_one_line_file("/run/systemd/machine-id", id)) < 0) {
+ r = write_one_line_file("/run/systemd/machine-id", id);
+ if (r < 0) {
log_error("Cannot write /run/systemd/machine-id: %s", strerror(-r));
unlink("/run/systemd/machine-id");