339 lines
9.1 KiB
C
339 lines
9.1 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include "sd-id128.h"
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "hexdecoct.h"
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#include "id128-util.h"
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#include "io-util.h"
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#include "khash.h"
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#include "macro.h"
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#include "missing.h"
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#include "random-util.h"
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#include "user-util.h"
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#include "util.h"
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_public_ char *sd_id128_to_string(sd_id128_t id, char s[SD_ID128_STRING_MAX]) {
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unsigned n;
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assert_return(s, NULL);
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for (n = 0; n < 16; n++) {
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s[n*2] = hexchar(id.bytes[n] >> 4);
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s[n*2+1] = hexchar(id.bytes[n] & 0xF);
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}
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s[32] = 0;
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return s;
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}
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_public_ int sd_id128_from_string(const char s[], sd_id128_t *ret) {
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unsigned n, i;
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sd_id128_t t;
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bool is_guid = false;
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assert_return(s, -EINVAL);
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for (n = 0, i = 0; n < 16;) {
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int a, b;
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if (s[i] == '-') {
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/* Is this a GUID? Then be nice, and skip over
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* the dashes */
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if (i == 8)
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is_guid = true;
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else if (IN_SET(i, 13, 18, 23)) {
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if (!is_guid)
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return -EINVAL;
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} else
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return -EINVAL;
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i++;
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continue;
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}
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a = unhexchar(s[i++]);
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if (a < 0)
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return -EINVAL;
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b = unhexchar(s[i++]);
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if (b < 0)
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return -EINVAL;
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t.bytes[n++] = (a << 4) | b;
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}
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if (i != (is_guid ? 36 : 32))
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return -EINVAL;
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if (s[i] != 0)
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return -EINVAL;
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if (ret)
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*ret = t;
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return 0;
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}
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_public_ int sd_id128_get_machine(sd_id128_t *ret) {
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static thread_local sd_id128_t saved_machine_id = {};
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int r;
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assert_return(ret, -EINVAL);
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if (sd_id128_is_null(saved_machine_id)) {
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r = id128_read("/etc/machine-id", ID128_PLAIN, &saved_machine_id);
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if (r < 0)
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return r;
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if (sd_id128_is_null(saved_machine_id))
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return -ENOMEDIUM;
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}
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*ret = saved_machine_id;
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return 0;
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}
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_public_ int sd_id128_get_boot(sd_id128_t *ret) {
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static thread_local sd_id128_t saved_boot_id = {};
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int r;
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assert_return(ret, -EINVAL);
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if (sd_id128_is_null(saved_boot_id)) {
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r = id128_read("/proc/sys/kernel/random/boot_id", ID128_UUID, &saved_boot_id);
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if (r < 0)
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return r;
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}
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*ret = saved_boot_id;
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return 0;
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}
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static int get_invocation_from_keyring(sd_id128_t *ret) {
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_cleanup_free_ char *description = NULL;
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char *d, *p, *g, *u, *e;
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unsigned long perms;
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key_serial_t key;
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size_t sz = 256;
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uid_t uid;
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gid_t gid;
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int r, c;
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#define MAX_PERMS ((unsigned long) (KEY_POS_VIEW|KEY_POS_READ|KEY_POS_SEARCH| \
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KEY_USR_VIEW|KEY_USR_READ|KEY_USR_SEARCH))
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assert(ret);
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key = request_key("user", "invocation_id", NULL, 0);
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if (key == -1) {
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/* Keyring support not available? No invocation key stored? */
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if (IN_SET(errno, ENOSYS, ENOKEY))
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return 0;
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return -errno;
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}
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for (;;) {
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description = new(char, sz);
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if (!description)
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return -ENOMEM;
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c = keyctl(KEYCTL_DESCRIBE, key, (unsigned long) description, sz, 0);
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if (c < 0)
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return -errno;
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if ((size_t) c <= sz)
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break;
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sz = c;
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free(description);
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}
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/* The kernel returns a final NUL in the string, verify that. */
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assert(description[c-1] == 0);
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/* Chop off the final description string */
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d = strrchr(description, ';');
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if (!d)
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return -EIO;
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*d = 0;
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/* Look for the permissions */
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p = strrchr(description, ';');
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if (!p)
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return -EIO;
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errno = 0;
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perms = strtoul(p + 1, &e, 16);
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if (errno > 0)
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return -errno;
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if (e == p + 1) /* Read at least one character */
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return -EIO;
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if (e != d) /* Must reached the end */
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return -EIO;
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if ((perms & ~MAX_PERMS) != 0)
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return -EPERM;
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*p = 0;
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/* Look for the group ID */
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g = strrchr(description, ';');
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if (!g)
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return -EIO;
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r = parse_gid(g + 1, &gid);
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if (r < 0)
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return r;
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if (gid != 0)
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return -EPERM;
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*g = 0;
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/* Look for the user ID */
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u = strrchr(description, ';');
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if (!u)
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return -EIO;
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r = parse_uid(u + 1, &uid);
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if (r < 0)
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return r;
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if (uid != 0)
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return -EPERM;
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c = keyctl(KEYCTL_READ, key, (unsigned long) ret, sizeof(sd_id128_t), 0);
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if (c < 0)
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return -errno;
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if (c != sizeof(sd_id128_t))
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return -EIO;
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return 1;
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}
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_public_ int sd_id128_get_invocation(sd_id128_t *ret) {
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static thread_local sd_id128_t saved_invocation_id = {};
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int r;
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assert_return(ret, -EINVAL);
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if (sd_id128_is_null(saved_invocation_id)) {
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/* We first try to read the invocation ID from the kernel keyring. This has the benefit that it is not
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* fakeable by unprivileged code. If the information is not available in the keyring, we use
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* $INVOCATION_ID but ignore the data if our process was called by less privileged code
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* (i.e. secure_getenv() instead of getenv()).
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*
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* The kernel keyring is only relevant for system services (as for user services we don't store the
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* invocation ID in the keyring, as there'd be no trust benefit in that). The environment variable is
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* primarily relevant for user services, and sufficiently safe as no privilege boundary is involved. */
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r = get_invocation_from_keyring(&saved_invocation_id);
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if (r < 0)
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return r;
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if (r == 0) {
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const char *e;
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e = secure_getenv("INVOCATION_ID");
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if (!e)
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return -ENXIO;
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r = sd_id128_from_string(e, &saved_invocation_id);
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if (r < 0)
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return r;
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}
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}
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*ret = saved_invocation_id;
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return 0;
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}
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static sd_id128_t make_v4_uuid(sd_id128_t id) {
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/* Stolen from generate_random_uuid() of drivers/char/random.c
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* in the kernel sources */
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/* Set UUID version to 4 --- truly random generation */
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id.bytes[6] = (id.bytes[6] & 0x0F) | 0x40;
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/* Set the UUID variant to DCE */
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id.bytes[8] = (id.bytes[8] & 0x3F) | 0x80;
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return id;
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}
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_public_ int sd_id128_randomize(sd_id128_t *ret) {
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sd_id128_t t;
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int r;
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assert_return(ret, -EINVAL);
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r = acquire_random_bytes(&t, sizeof t, true);
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if (r < 0)
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return r;
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/* Turn this into a valid v4 UUID, to be nice. Note that we
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* only guarantee this for newly generated UUIDs, not for
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* pre-existing ones. */
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*ret = make_v4_uuid(t);
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return 0;
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}
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static int get_app_specific(sd_id128_t base, sd_id128_t app_id, sd_id128_t *ret) {
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_cleanup_(khash_unrefp) khash *h = NULL;
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sd_id128_t result;
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const void *p;
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int r;
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assert(ret);
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r = khash_new_with_key(&h, "hmac(sha256)", &base, sizeof(base));
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if (r < 0)
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return r;
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r = khash_put(h, &app_id, sizeof(app_id));
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if (r < 0)
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return r;
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r = khash_digest_data(h, &p);
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if (r < 0)
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return r;
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/* We chop off the trailing 16 bytes */
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memcpy(&result, p, MIN(khash_get_size(h), sizeof(result)));
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*ret = make_v4_uuid(result);
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return 0;
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}
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_public_ int sd_id128_get_machine_app_specific(sd_id128_t app_id, sd_id128_t *ret) {
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sd_id128_t id;
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int r;
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assert_return(ret, -EINVAL);
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r = sd_id128_get_machine(&id);
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if (r < 0)
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return r;
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return get_app_specific(id, app_id, ret);
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}
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_public_ int sd_id128_get_boot_app_specific(sd_id128_t app_id, sd_id128_t *ret) {
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sd_id128_t id;
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int r;
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assert_return(ret, -EINVAL);
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r = sd_id128_get_boot(&id);
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if (r < 0)
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return r;
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return get_app_specific(id, app_id, ret);
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}
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