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-rw-r--r--src/basic/hostname-util.c209
1 files changed, 209 insertions, 0 deletions
diff --git a/src/basic/hostname-util.c b/src/basic/hostname-util.c
new file mode 100644
index 0000000..b710f07
--- /dev/null
+++ b/src/basic/hostname-util.c
@@ -0,0 +1,209 @@
+/* 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 "env-file.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) || 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 ascii_isalpha(c) ||
+ ascii_isdigit(c) ||
+ 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.");
+}
+
+int get_pretty_hostname(char **ret) {
+ _cleanup_free_ char *n = NULL;
+ int r;
+
+ assert(ret);
+
+ r = parse_env_file(NULL, "/etc/machine-info", "PRETTY_HOSTNAME", &n);
+ if (r < 0)
+ return r;
+
+ if (isempty(n))
+ return -ENXIO;
+
+ *ret = TAKE_PTR(n);
+ return 0;
+}