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Systemd/src/shared/specifier.c
Zbigniew Jędrzejewski-Szmek e97708fa3e Add %l as specifier for the hostname without any domain component 
As described in #15603, it is a fairly common setup to use a fqdn as the
configured hostname. But it is often convenient to use just the actual
hostname, i.e. until the first dot. This adds support in tmpfiles, sysusers,
and unit files for %l which expands to that.

Fixes #15603.
2020-05-07 17:36:44 +02:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <errno.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdlib.h>
#include <sys/utsname.h>
#include "sd-id128.h"
#include "alloc-util.h"
#include "architecture.h"
#include "format-util.h"
#include "fs-util.h"
#include "hostname-util.h"
#include "macro.h"
#include "os-util.h"
#include "specifier.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
/*
* Generic infrastructure for replacing %x style specifiers in
* strings. Will call a callback for each replacement.
*/
/* Any ASCII character or digit: our pool of potential specifiers,
* and "%" used for escaping. */
#define POSSIBLE_SPECIFIERS ALPHANUMERICAL "%"
int specifier_printf(const char *text, const Specifier table[], const void *userdata, char **_ret) {
size_t l, allocated = 0;
_cleanup_free_ char *ret = NULL;
char *t;
const char *f;
bool percent = false;
int r;
assert(text);
assert(table);
l = strlen(text);
if (!GREEDY_REALLOC(ret, allocated, l + 1))
return -ENOMEM;
t = ret;
for (f = text; *f; f++, l--)
if (percent) {
if (*f == '%')
*(t++) = '%';
else {
const Specifier *i;
for (i = table; i->specifier; i++)
if (i->specifier == *f)
break;
if (i->lookup) {
_cleanup_free_ char *w = NULL;
size_t k, j;
r = i->lookup(i->specifier, i->data, userdata, &w);
if (r < 0)
return r;
j = t - ret;
k = strlen(w);
if (!GREEDY_REALLOC(ret, allocated, j + k + l + 1))
return -ENOMEM;
memcpy(ret + j, w, k);
t = ret + j + k;
} else if (strchr(POSSIBLE_SPECIFIERS, *f))
/* Oops, an unknown specifier. */
return -EBADSLT;
else {
*(t++) = '%';
*(t++) = *f;
}
}
percent = false;
} else if (*f == '%')
percent = true;
else
*(t++) = *f;
/* If string ended with a stray %, also end with % */
if (percent)
*(t++) = '%';
*(t++) = 0;
/* Try to deallocate unused bytes, but don't sweat it too much */
if ((size_t)(t - ret) < allocated) {
t = realloc(ret, t - ret);
if (t)
ret = t;
}
*_ret = TAKE_PTR(ret);
return 0;
}
/* Generic handler for simple string replacements */
int specifier_string(char specifier, const void *data, const void *userdata, char **ret) {
char *n;
n = strdup(strempty(data));
if (!n)
return -ENOMEM;
*ret = n;
return 0;
}
int specifier_machine_id(char specifier, const void *data, const void *userdata, char **ret) {
sd_id128_t id;
char *n;
int r;
r = sd_id128_get_machine(&id);
if (r < 0)
return r;
n = new(char, 33);
if (!n)
return -ENOMEM;
*ret = sd_id128_to_string(id, n);
return 0;
}
int specifier_boot_id(char specifier, const void *data, const void *userdata, char **ret) {
sd_id128_t id;
char *n;
int r;
r = sd_id128_get_boot(&id);
if (r < 0)
return r;
n = new(char, 33);
if (!n)
return -ENOMEM;
*ret = sd_id128_to_string(id, n);
return 0;
}
int specifier_host_name(char specifier, const void *data, const void *userdata, char **ret) {
char *n;
n = gethostname_malloc();
if (!n)
return -ENOMEM;
*ret = n;
return 0;
}
int specifier_short_host_name(char specifier, const void *data, const void *userdata, char **ret) {
char *n;
n = gethostname_short_malloc();
if (!n)
return -ENOMEM;
*ret = n;
return 0;
}
int specifier_kernel_release(char specifier, const void *data, const void *userdata, char **ret) {
struct utsname uts;
char *n;
int r;
r = uname(&uts);
if (r < 0)
return -errno;
n = strdup(uts.release);
if (!n)
return -ENOMEM;
*ret = n;
return 0;
}
int specifier_architecture(char specifier, const void *data, const void *userdata, char **ret) {
char *t;
t = strdup(architecture_to_string(uname_architecture()));
if (!t)
return -ENOMEM;
*ret = t;
return 0;
}
static int specifier_os_release_common(const char *field, char **ret) {
char *t = NULL;
int r;
r = parse_os_release(NULL, field, &t, NULL);
if (r < 0)
return r;
if (!t) {
/* fields in /etc/os-release might quite possibly be missing, even if everything is entirely
* valid otherwise. Let's hence return "" in that case. */
t = strdup("");
if (!t)
return -ENOMEM;
}
*ret = t;
return 0;
}
int specifier_os_id(char specifier, const void *data, const void *userdata, char **ret) {
return specifier_os_release_common("ID", ret);
}
int specifier_os_version_id(char specifier, const void *data, const void *userdata, char **ret) {
return specifier_os_release_common("VERSION_ID", ret);
}
int specifier_os_build_id(char specifier, const void *data, const void *userdata, char **ret) {
return specifier_os_release_common("BUILD_ID", ret);
}
int specifier_os_variant_id(char specifier, const void *data, const void *userdata, char **ret) {
return specifier_os_release_common("VARIANT_ID", ret);
}
int specifier_group_name(char specifier, const void *data, const void *userdata, char **ret) {
char *t;
t = gid_to_name(getgid());
if (!t)
return -ENOMEM;
*ret = t;
return 0;
}
int specifier_group_id(char specifier, const void *data, const void *userdata, char **ret) {
if (asprintf(ret, UID_FMT, getgid()) < 0)
return -ENOMEM;
return 0;
}
int specifier_user_name(char specifier, const void *data, const void *userdata, char **ret) {
char *t;
/* If we are UID 0 (root), this will not result in NSS, otherwise it might. This is good, as we want to be able
* to run this in PID 1, where our user ID is 0, but where NSS lookups are not allowed.
* We don't use getusername_malloc() here, because we don't want to look at $USER, to remain consistent with
* specifer_user_id() below.
*/
t = uid_to_name(getuid());
if (!t)
return -ENOMEM;
*ret = t;
return 0;
}
int specifier_user_id(char specifier, const void *data, const void *userdata, char **ret) {
if (asprintf(ret, UID_FMT, getuid()) < 0)
return -ENOMEM;
return 0;
}
int specifier_user_home(char specifier, const void *data, const void *userdata, char **ret) {
/* On PID 1 (which runs as root) this will not result in NSS,
* which is good. See above */
return get_home_dir(ret);
}
int specifier_user_shell(char specifier, const void *data, const void *userdata, char **ret) {
/* On PID 1 (which runs as root) this will not result in NSS,
* which is good. See above */
return get_shell(ret);
}
int specifier_tmp_dir(char specifier, const void *data, const void *userdata, char **ret) {
const char *p;
char *copy;
int r;
r = tmp_dir(&p);
if (r < 0)
return r;
copy = strdup(p);
if (!copy)
return -ENOMEM;
*ret = copy;
return 0;
}
int specifier_var_tmp_dir(char specifier, const void *data, const void *userdata, char **ret) {
const char *p;
char *copy;
int r;
r = var_tmp_dir(&p);
if (r < 0)
return r;
copy = strdup(p);
if (!copy)
return -ENOMEM;
*ret = copy;
return 0;
}
int specifier_escape_strv(char **l, char ***ret) {
char **z, **p, **q;
assert(ret);
if (strv_isempty(l)) {
*ret = NULL;
return 0;
}
z = new(char*, strv_length(l)+1);
if (!z)
return -ENOMEM;
for (p = l, q = z; *p; p++, q++) {
*q = specifier_escape(*p);
if (!*q) {
strv_free(z);
return -ENOMEM;
}
}
*q = NULL;
*ret = z;
return 0;
}
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