7470cc4c73
https://tools.ietf.org/html/rfc1035#section-2.3.1 says (approximately) that only letters, numbers, and non-leading non-trailing dashes are allowed (for entries with A/AAAA records). We set no restrictions. hosts(5) says: > Host names may contain only alphanumeric characters, minus signs ("-"), and > periods ("."). They must begin with an alphabetic character and end with an > alphanumeric character. nss-files follows those rules, and will ignore names in /etc/hosts that do not follow this rule. Let's follow the documented rules for /etc/hosts. In particular, this makes us consitent with nss-files, reducing surprises for the user. I'm pretty sure we should apply stricter filtering to names received over DNS and LLMNR and MDNS, but it's a bigger project, because the rules differ depepending on which level the label appears (rules for top-level names are stricter), and this patch takes the minimalistic approach and only changes behaviour for /etc/hosts. Escape syntax is also disallowed in /etc/hosts, even if the resulting character would be allowed. Other tools that parse /etc/hosts do not support this, and there is no need to use it because no allowed characters benefit from escaping.
113 lines
4.1 KiB
C
113 lines
4.1 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#pragma once
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#include <errno.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#include "hashmap.h"
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#include "in-addr-util.h"
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/* Length of a single label, with all escaping removed, excluding any trailing dot or NUL byte */
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#define DNS_LABEL_MAX 63
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/* Worst case length of a single label, with all escaping applied and room for a trailing NUL byte. */
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#define DNS_LABEL_ESCAPED_MAX (DNS_LABEL_MAX*4+1)
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/* Maximum length of a full hostname, consisting of a series of unescaped labels, and no trailing dot or NUL byte */
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#define DNS_HOSTNAME_MAX 253
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/* Maximum length of a full hostname, on the wire, including the final NUL byte */
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#define DNS_WIRE_FORMAT_HOSTNAME_MAX 255
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/* Maximum number of labels per valid hostname */
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#define DNS_N_LABELS_MAX 127
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typedef enum DNSLabelFlags {
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DNS_LABEL_LDH = 1 << 0, /* Follow the "LDH" rule — only letters, digits, and internal hyphens. */
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DNS_LABEL_NO_ESCAPES = 1 << 1, /* Do not treat backslashes specially */
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} DNSLabelFlags;
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int dns_label_unescape(const char **name, char *dest, size_t sz, DNSLabelFlags flags);
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int dns_label_unescape_suffix(const char *name, const char **label_end, char *dest, size_t sz);
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int dns_label_escape(const char *p, size_t l, char *dest, size_t sz);
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int dns_label_escape_new(const char *p, size_t l, char **ret);
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static inline int dns_name_parent(const char **name) {
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return dns_label_unescape(name, NULL, DNS_LABEL_MAX, 0);
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}
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#if HAVE_LIBIDN
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int dns_label_apply_idna(const char *encoded, size_t encoded_size, char *decoded, size_t decoded_max);
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int dns_label_undo_idna(const char *encoded, size_t encoded_size, char *decoded, size_t decoded_max);
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#endif
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int dns_name_concat(const char *a, const char *b, DNSLabelFlags flags, char **ret);
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static inline int dns_name_normalize(const char *s, DNSLabelFlags flags, char **ret) {
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/* dns_name_concat() normalizes as a side-effect */
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return dns_name_concat(s, NULL, flags, ret);
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}
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static inline int dns_name_is_valid(const char *s) {
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int r;
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/* dns_name_normalize() verifies as a side effect */
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r = dns_name_normalize(s, 0, NULL);
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if (r == -EINVAL)
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return 0;
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if (r < 0)
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return r;
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return 1;
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}
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static inline int dns_name_is_valid_ldh(const char *s) {
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int r;
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r = dns_name_concat(s, NULL, DNS_LABEL_LDH|DNS_LABEL_NO_ESCAPES, NULL);
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if (r == -EINVAL)
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return 0;
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if (r < 0)
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return r;
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return 1;
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}
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void dns_name_hash_func(const char *s, struct siphash *state);
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int dns_name_compare_func(const char *a, const char *b);
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extern const struct hash_ops dns_name_hash_ops;
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int dns_name_between(const char *a, const char *b, const char *c);
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int dns_name_equal(const char *x, const char *y);
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int dns_name_endswith(const char *name, const char *suffix);
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int dns_name_startswith(const char *name, const char *prefix);
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int dns_name_change_suffix(const char *name, const char *old_suffix, const char *new_suffix, char **ret);
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int dns_name_reverse(int family, const union in_addr_union *a, char **ret);
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int dns_name_address(const char *p, int *family, union in_addr_union *a);
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bool dns_name_is_root(const char *name);
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bool dns_name_is_single_label(const char *name);
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int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len, bool canonical);
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bool dns_srv_type_is_valid(const char *name);
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bool dnssd_srv_type_is_valid(const char *name);
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bool dns_service_name_is_valid(const char *name);
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int dns_service_join(const char *name, const char *type, const char *domain, char **ret);
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int dns_service_split(const char *joined, char **name, char **type, char **domain);
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int dns_name_suffix(const char *name, unsigned n_labels, const char **ret);
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int dns_name_count_labels(const char *name);
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int dns_name_skip(const char *a, unsigned n_labels, const char **ret);
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int dns_name_equal_skip(const char *a, unsigned n_labels, const char *b);
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int dns_name_common_suffix(const char *a, const char *b, const char **ret);
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int dns_name_apply_idna(const char *name, char **ret);
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int dns_name_is_valid_or_address(const char *name);
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