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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/utsname.h>
#include <unistd.h>
#include "alloc-util.h"
#include "hostname-util.h"
#include "os-util.h"
#include "string-util.h"
#include "strv.h"
char* get_default_hostname(void) {
int r;
const char *e = secure_getenv("SYSTEMD_DEFAULT_HOSTNAME");
if (e) {
if (hostname_is_valid(e, 0))
return strdup(e);
log_debug("Invalid hostname in $SYSTEMD_DEFAULT_HOSTNAME, ignoring: %s", e);
}
_cleanup_free_ char *f = NULL;
r = parse_os_release(NULL, "DEFAULT_HOSTNAME", &f);
if (r < 0)
log_debug_errno(r, "Failed to parse os-release, ignoring: %m");
else if (f) {
if (hostname_is_valid(f, 0))
return TAKE_PTR(f);
log_debug("Invalid hostname in os-release, ignoring: %s", f);
}
return strdup(FALLBACK_HOSTNAME);
}
int gethostname_full(GetHostnameFlags flags, char **ret) {
_cleanup_free_ char *buf = NULL, *fallback = NULL;
struct utsname u;
const char *s;
assert(ret);
assert_se(uname(&u) >= 0);
s = u.nodename;
if (isempty(s) ||
(!FLAGS_SET(flags, GET_HOSTNAME_ALLOW_NONE) && streq(s, "(none)")) ||
(!FLAGS_SET(flags, GET_HOSTNAME_ALLOW_LOCALHOST) && is_localhost(s)) ||
(FLAGS_SET(flags, GET_HOSTNAME_SHORT) && s[0] == '.')) {
if (!FLAGS_SET(flags, GET_HOSTNAME_FALLBACK_DEFAULT))
return -ENXIO;
s = fallback = get_default_hostname();
if (!s)
return -ENOMEM;
if (FLAGS_SET(flags, GET_HOSTNAME_SHORT) && s[0] == '.')
return -ENXIO;
}
if (FLAGS_SET(flags, GET_HOSTNAME_SHORT))
buf = strndup(s, strcspn(s, "."));
else
buf = strdup(s);
if (!buf)
return -ENOMEM;
*ret = TAKE_PTR(buf);
return 0;
}
bool valid_ldh_char(char c) {
/* "LDH" → "Letters, digits, hyphens", as per RFC 5890, Section 2.3.1 */
return
(c >= 'a' && c <= 'z') ||
(c >= 'A' && c <= 'Z') ||
(c >= '0' && c <= '9') ||
c == '-';
}
bool hostname_is_valid(const char *s, ValidHostnameFlags flags) {
unsigned n_dots = 0;
const char *p;
bool dot, hyphen;
/* Check if s looks like a valid hostname or FQDN. This does not do full DNS validation, but only
* checks if the name is composed of allowed characters and the length is not above the maximum
* allowed by Linux (c.f. dns_name_is_valid()). A trailing dot is allowed if
* VALID_HOSTNAME_TRAILING_DOT flag is set and at least two components are present in the name. Note
* that due to the restricted charset and length this call is substantially more conservative than
* dns_name_is_valid(). Doesn't accept empty hostnames, hostnames with leading dots, and hostnames
* with multiple dots in a sequence. Doesn't allow hyphens at the beginning or end of label. */
if (isempty(s))
return false;
if (streq(s, ".host")) /* Used by the container logic to denote the "root container" */
return FLAGS_SET(flags, VALID_HOSTNAME_DOT_HOST);
for (p = s, dot = hyphen = true; *p; p++)
if (*p == '.') {
if (dot || hyphen)
return false;
dot = true;
hyphen = false;
n_dots++;
} else if (*p == '-') {
if (dot)
return false;
dot = false;
hyphen = true;
} else {
if (!valid_ldh_char(*p))
return false;
dot = false;
hyphen = false;
}
if (dot && (n_dots < 2 || !FLAGS_SET(flags, VALID_HOSTNAME_TRAILING_DOT)))
return false;
if (hyphen)
return false;
if (p-s > HOST_NAME_MAX) /* Note that HOST_NAME_MAX is 64 on Linux, but DNS allows domain names up to
* 255 characters */
return false;
return true;
}
char* hostname_cleanup(char *s) {
char *p, *d;
bool dot, hyphen;
assert(s);
for (p = s, d = s, dot = hyphen = true; *p && d - s < HOST_NAME_MAX; p++)
if (*p == '.') {
if (dot || hyphen)
continue;
*(d++) = '.';
dot = true;
hyphen = false;
} else if (*p == '-') {
if (dot)
continue;
*(d++) = '-';
dot = false;
hyphen = true;
} else if (valid_ldh_char(*p)) {
*(d++) = *p;
dot = false;
hyphen = false;
}
if (d > s && IN_SET(d[-1], '-', '.'))
/* The dot can occur at most once, but we might have multiple
* hyphens, hence the loop */
d--;
*d = 0;
return s;
}
bool is_localhost(const char *hostname) {
assert(hostname);
/* This tries to identify local host and domain names
* described in RFC6761 plus the redhatism of localdomain */
return STRCASE_IN_SET(
hostname,
"localhost",
"localhost.",
"localhost.localdomain",
"localhost.localdomain.") ||
endswith_no_case(hostname, ".localhost") ||
endswith_no_case(hostname, ".localhost.") ||
endswith_no_case(hostname, ".localhost.localdomain") ||
endswith_no_case(hostname, ".localhost.localdomain.");
}
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