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Diffstat (limited to '')
| -rw-r--r-- | src/basic/hostname-util.c | 308 |
1 files changed, 308 insertions, 0 deletions
diff --git a/src/basic/hostname-util.c b/src/basic/hostname-util.c new file mode 100644 index 0000000..5bfa028 --- /dev/null +++ b/src/basic/hostname-util.c @@ -0,0 +1,308 @@ +/* SPDX-License-Identifier: LGPL-2.1+ */ + +#include <errno.h> +#include <limits.h> +#include <stdio.h> +#include <string.h> +#include <sys/utsname.h> +#include <unistd.h> + +#include "alloc-util.h" +#include "fd-util.h" +#include "fileio.h" +#include "hostname-util.h" +#include "macro.h" +#include "string-util.h" + +bool hostname_is_set(void) { + struct utsname u; + + assert_se(uname(&u) >= 0); + + if (isempty(u.nodename)) + return false; + + /* This is the built-in kernel default host name */ + if (streq(u.nodename, "(none)")) + return false; + + return true; +} + +char* gethostname_malloc(void) { + struct utsname u; + + /* This call tries to return something useful, either the actual hostname + * or it makes something up. The only reason it might fail is OOM. + * It might even return "localhost" if that's set. */ + + assert_se(uname(&u) >= 0); + + if (isempty(u.nodename) || streq(u.nodename, "(none)")) + return strdup(FALLBACK_HOSTNAME); + + return strdup(u.nodename); +} + +int gethostname_strict(char **ret) { + struct utsname u; + char *k; + + /* This call will rather fail than make up a name. It will not return "localhost" either. */ + + assert_se(uname(&u) >= 0); + + if (isempty(u.nodename)) + return -ENXIO; + + if (streq(u.nodename, "(none)")) + return -ENXIO; + + if (is_localhost(u.nodename)) + return -ENXIO; + + k = strdup(u.nodename); + if (!k) + return -ENOMEM; + + *ret = k; + return 0; +} + +bool valid_ldh_char(char c) { + return + (c >= 'a' && c <= 'z') || + (c >= 'A' && c <= 'Z') || + (c >= '0' && c <= '9') || + c == '-'; +} + +/** + * Check if s looks like a valid host name 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()). Trailing dot is allowed if + * allow_trailing_dot is true 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(). + */ +bool hostname_is_valid(const char *s, bool allow_trailing_dot) { + unsigned n_dots = 0; + const char *p; + bool dot, hyphen; + + if (isempty(s)) + return false; + + /* Doesn't accept empty hostnames, hostnames with + * leading dots, and hostnames with multiple dots in a + * sequence. Also ensures that the length stays below + * HOST_NAME_MAX. */ + + 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 || !allow_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 strcaseeq(hostname, "localhost") || + strcaseeq(hostname, "localhost.") || + strcaseeq(hostname, "localhost.localdomain") || + strcaseeq(hostname, "localhost.localdomain.") || + endswith_no_case(hostname, ".localhost") || + endswith_no_case(hostname, ".localhost.") || + endswith_no_case(hostname, ".localhost.localdomain") || + endswith_no_case(hostname, ".localhost.localdomain."); +} + +bool is_gateway_hostname(const char *hostname) { + assert(hostname); + + /* This tries to identify the valid syntaxes for the our + * synthetic "gateway" host. */ + + return + strcaseeq(hostname, "_gateway") || strcaseeq(hostname, "_gateway.") +#if ENABLE_COMPAT_GATEWAY_HOSTNAME + || strcaseeq(hostname, "gateway") || strcaseeq(hostname, "gateway.") +#endif + ; +} + +int sethostname_idempotent(const char *s) { + char buf[HOST_NAME_MAX + 1] = {}; + + assert(s); + + if (gethostname(buf, sizeof(buf)) < 0) + return -errno; + + if (streq(buf, s)) + return 0; + + if (sethostname(s, strlen(s)) < 0) + return -errno; + + return 1; +} + +int shorten_overlong(const char *s, char **ret) { + char *h, *p; + + /* Shorten an overlong name to HOST_NAME_MAX or to the first dot, + * whatever comes earlier. */ + + assert(s); + + h = strdup(s); + if (!h) + return -ENOMEM; + + if (hostname_is_valid(h, false)) { + *ret = h; + return 0; + } + + p = strchr(h, '.'); + if (p) + *p = 0; + + strshorten(h, HOST_NAME_MAX); + + if (!hostname_is_valid(h, false)) { + free(h); + return -EDOM; + } + + *ret = h; + return 1; +} + +int read_etc_hostname_stream(FILE *f, char **ret) { + int r; + + assert(f); + assert(ret); + + for (;;) { + _cleanup_free_ char *line = NULL; + char *p; + + r = read_line(f, LONG_LINE_MAX, &line); + if (r < 0) + return r; + if (r == 0) /* EOF without any hostname? the file is empty, let's treat that exactly like no file at all: ENOENT */ + return -ENOENT; + + p = strstrip(line); + + /* File may have empty lines or comments, ignore them */ + if (!IN_SET(*p, '\0', '#')) { + char *copy; + + hostname_cleanup(p); /* normalize the hostname */ + + if (!hostname_is_valid(p, true)) /* check that the hostname we return is valid */ + return -EBADMSG; + + copy = strdup(p); + if (!copy) + return -ENOMEM; + + *ret = copy; + return 0; + } + } +} + +int read_etc_hostname(const char *path, char **ret) { + _cleanup_fclose_ FILE *f = NULL; + + assert(ret); + + if (!path) + path = "/etc/hostname"; + + f = fopen(path, "re"); + if (!f) + return -errno; + + return read_etc_hostname_stream(f, ret); + +} |