308 lines
8.2 KiB
C
308 lines
8.2 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#include <errno.h>
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#include <limits.h>
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#include <stdio.h>
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#include <sys/utsname.h>
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#include <unistd.h>
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#include "alloc-util.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "hostname-util.h"
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#include "macro.h"
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#include "string-util.h"
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bool hostname_is_set(void) {
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struct utsname u;
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assert_se(uname(&u) >= 0);
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if (isempty(u.nodename))
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return false;
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/* This is the built-in kernel default hostname */
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if (streq(u.nodename, "(none)"))
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return false;
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return true;
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}
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char* gethostname_malloc(void) {
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struct utsname u;
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/* This call tries to return something useful, either the actual hostname
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* or it makes something up. The only reason it might fail is OOM.
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* It might even return "localhost" if that's set. */
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assert_se(uname(&u) >= 0);
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if (isempty(u.nodename) || streq(u.nodename, "(none)"))
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return strdup(FALLBACK_HOSTNAME);
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return strdup(u.nodename);
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}
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int gethostname_strict(char **ret) {
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struct utsname u;
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char *k;
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/* This call will rather fail than make up a name. It will not return "localhost" either. */
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assert_se(uname(&u) >= 0);
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if (isempty(u.nodename))
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return -ENXIO;
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if (streq(u.nodename, "(none)"))
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return -ENXIO;
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if (is_localhost(u.nodename))
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return -ENXIO;
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k = strdup(u.nodename);
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if (!k)
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return -ENOMEM;
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*ret = k;
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return 0;
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}
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bool valid_ldh_char(char c) {
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return
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(c >= 'a' && c <= 'z') ||
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(c >= 'A' && c <= 'Z') ||
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(c >= '0' && c <= '9') ||
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c == '-';
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}
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/**
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* Check if s looks like a valid hostname or FQDN. This does not do
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* full DNS validation, but only checks if the name is composed of
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* allowed characters and the length is not above the maximum allowed
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* by Linux (c.f. dns_name_is_valid()). Trailing dot is allowed if
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* allow_trailing_dot is true and at least two components are present
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* in the name. Note that due to the restricted charset and length
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* this call is substantially more conservative than
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* dns_name_is_valid().
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*/
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bool hostname_is_valid(const char *s, bool allow_trailing_dot) {
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unsigned n_dots = 0;
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const char *p;
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bool dot, hyphen;
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if (isempty(s))
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return false;
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/* Doesn't accept empty hostnames, hostnames with
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* leading dots, and hostnames with multiple dots in a
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* sequence. Also ensures that the length stays below
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* HOST_NAME_MAX. */
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for (p = s, dot = hyphen = true; *p; p++)
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if (*p == '.') {
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if (dot || hyphen)
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return false;
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dot = true;
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hyphen = false;
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n_dots++;
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} else if (*p == '-') {
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if (dot)
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return false;
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dot = false;
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hyphen = true;
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} else {
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if (!valid_ldh_char(*p))
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return false;
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dot = false;
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hyphen = false;
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}
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if (dot && (n_dots < 2 || !allow_trailing_dot))
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return false;
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if (hyphen)
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return false;
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if (p-s > HOST_NAME_MAX) /* Note that HOST_NAME_MAX is 64 on
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* Linux, but DNS allows domain names
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* up to 255 characters */
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return false;
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return true;
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}
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char* hostname_cleanup(char *s) {
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char *p, *d;
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bool dot, hyphen;
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assert(s);
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for (p = s, d = s, dot = hyphen = true; *p && d - s < HOST_NAME_MAX; p++)
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if (*p == '.') {
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if (dot || hyphen)
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continue;
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*(d++) = '.';
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dot = true;
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hyphen = false;
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} else if (*p == '-') {
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if (dot)
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continue;
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*(d++) = '-';
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dot = false;
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hyphen = true;
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} else if (valid_ldh_char(*p)) {
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*(d++) = *p;
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dot = false;
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hyphen = false;
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}
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if (d > s && IN_SET(d[-1], '-', '.'))
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/* The dot can occur at most once, but we might have multiple
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* hyphens, hence the loop */
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d--;
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*d = 0;
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return s;
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}
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bool is_localhost(const char *hostname) {
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assert(hostname);
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/* This tries to identify local host and domain names
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* described in RFC6761 plus the redhatism of localdomain */
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return strcaseeq(hostname, "localhost") ||
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strcaseeq(hostname, "localhost.") ||
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strcaseeq(hostname, "localhost.localdomain") ||
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strcaseeq(hostname, "localhost.localdomain.") ||
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endswith_no_case(hostname, ".localhost") ||
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endswith_no_case(hostname, ".localhost.") ||
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endswith_no_case(hostname, ".localhost.localdomain") ||
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endswith_no_case(hostname, ".localhost.localdomain.");
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}
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bool is_gateway_hostname(const char *hostname) {
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assert(hostname);
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/* This tries to identify the valid syntaxes for the our
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* synthetic "gateway" host. */
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return
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strcaseeq(hostname, "_gateway") || strcaseeq(hostname, "_gateway.")
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#if ENABLE_COMPAT_GATEWAY_HOSTNAME
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|| strcaseeq(hostname, "gateway") || strcaseeq(hostname, "gateway.")
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#endif
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;
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}
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int sethostname_idempotent(const char *s) {
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char buf[HOST_NAME_MAX + 1] = {};
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assert(s);
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if (gethostname(buf, sizeof(buf)) < 0)
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return -errno;
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if (streq(buf, s))
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return 0;
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if (sethostname(s, strlen(s)) < 0)
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return -errno;
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return 1;
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}
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int shorten_overlong(const char *s, char **ret) {
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char *h, *p;
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/* Shorten an overlong name to HOST_NAME_MAX or to the first dot,
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* whatever comes earlier. */
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assert(s);
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h = strdup(s);
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if (!h)
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return -ENOMEM;
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if (hostname_is_valid(h, false)) {
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*ret = h;
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return 0;
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}
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p = strchr(h, '.');
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if (p)
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*p = 0;
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strshorten(h, HOST_NAME_MAX);
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if (!hostname_is_valid(h, false)) {
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free(h);
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return -EDOM;
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}
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*ret = h;
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return 1;
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}
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int read_etc_hostname_stream(FILE *f, char **ret) {
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int r;
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assert(f);
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assert(ret);
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for (;;) {
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_cleanup_free_ char *line = NULL;
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char *p;
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r = read_line(f, LONG_LINE_MAX, &line);
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if (r < 0)
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return r;
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if (r == 0) /* EOF without any hostname? the file is empty, let's treat that exactly like no file at all: ENOENT */
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return -ENOENT;
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p = strstrip(line);
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/* File may have empty lines or comments, ignore them */
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if (!IN_SET(*p, '\0', '#')) {
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char *copy;
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hostname_cleanup(p); /* normalize the hostname */
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if (!hostname_is_valid(p, true)) /* check that the hostname we return is valid */
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return -EBADMSG;
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copy = strdup(p);
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if (!copy)
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return -ENOMEM;
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*ret = copy;
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return 0;
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}
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}
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}
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int read_etc_hostname(const char *path, char **ret) {
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_cleanup_fclose_ FILE *f = NULL;
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assert(ret);
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if (!path)
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path = "/etc/hostname";
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f = fopen(path, "re");
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if (!f)
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return -errno;
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return read_etc_hostname_stream(f, ret);
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}
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