diff options
Diffstat (limited to 'src/basic/hostname-util.c')
| -rw-r--r-- | src/basic/hostname-util.c | 209 |
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..e743033 --- /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 = strdupcspn(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; +} |