1 files changed, 316 insertions, 0 deletions
diff --git a/src/resolve/dns-type.c b/src/resolve/dns-type.c
new file mode 100644
index 0000000..da68b41
--- /dev/null
+++ b/src/resolve/dns-type.c
@@ -0,0 +1,316 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/socket.h>
+#include <errno.h>
+
+#include "dns-type.h"
+#include "parse-util.h"
+#include "string-util.h"
+
+typedef const struct {
+        uint16_t type;
+        const char *name;
+} dns_type;
+
+static const struct dns_type_name *
+lookup_dns_type (register const char *str, register GPERF_LEN_TYPE len);
+
+#include "dns_type-from-name.h"
+#include "dns_type-to-name.h"
+
+int dns_type_from_string(const char *s) {
+        const struct dns_type_name *sc;
+
+        assert(s);
+
+        sc = lookup_dns_type(s, strlen(s));
+        if (sc)
+                return sc->id;
+
+        s = startswith_no_case(s, "TYPE");
+        if (s) {
+                unsigned x;
+
+                if (safe_atou(s, &x) >= 0 &&
+                    x <= UINT16_MAX)
+                        return (int) x;
+        }
+
+        return _DNS_TYPE_INVALID;
+}
+
+bool dns_type_is_pseudo(uint16_t type) {
+
+        /* Checks whether the specified type is a "pseudo-type". What
+         * a "pseudo-type" precisely is, is defined only very weakly,
+         * but apparently entails all RR types that are not actually
+         * stored as RRs on the server and should hence also not be
+         * cached. We use this list primarily to validate NSEC type
+         * bitfields, and to verify what to cache. */
+
+        return IN_SET(type,
+                      0, /* A Pseudo RR type, according to RFC 2931 */
+                      DNS_TYPE_ANY,
+                      DNS_TYPE_AXFR,
+                      DNS_TYPE_IXFR,
+                      DNS_TYPE_OPT,
+                      DNS_TYPE_TSIG,
+                      DNS_TYPE_TKEY
+        );
+}
+
+bool dns_class_is_pseudo(uint16_t class) {
+        return class == DNS_CLASS_ANY;
+}
+
+bool dns_type_is_valid_query(uint16_t type) {
+
+        /* The types valid as questions in packets */
+
+        return !IN_SET(type,
+                       0,
+                       DNS_TYPE_OPT,
+                       DNS_TYPE_TSIG,
+                       DNS_TYPE_TKEY,
+
+                       /* RRSIG are technically valid as questions, but we refuse doing explicit queries for them, as
+                        * they aren't really payload, but signatures for payload, and cannot be validated on their
+                        * own. After all they are the signatures, and have no signatures of their own validating
+                        * them. */
+                       DNS_TYPE_RRSIG);
+}
+
+bool dns_type_is_zone_transer(uint16_t type) {
+
+        /* Zone transfers, either normal or incremental */
+
+        return IN_SET(type,
+                      DNS_TYPE_AXFR,
+                      DNS_TYPE_IXFR);
+}
+
+bool dns_type_is_valid_rr(uint16_t type) {
+
+        /* The types valid as RR in packets (but not necessarily
+         * stored on servers). */
+
+        return !IN_SET(type,
+                       DNS_TYPE_ANY,
+                       DNS_TYPE_AXFR,
+                       DNS_TYPE_IXFR);
+}
+
+bool dns_class_is_valid_rr(uint16_t class) {
+        return class != DNS_CLASS_ANY;
+}
+
+bool dns_type_may_redirect(uint16_t type) {
+        /* The following record types should never be redirected using
+         * CNAME/DNAME RRs. See
+         * <https://tools.ietf.org/html/rfc4035#section-2.5>. */
+
+        if (dns_type_is_pseudo(type))
+                return false;
+
+        return !IN_SET(type,
+                       DNS_TYPE_CNAME,
+                       DNS_TYPE_DNAME,
+                       DNS_TYPE_NSEC3,
+                       DNS_TYPE_NSEC,
+                       DNS_TYPE_RRSIG,
+                       DNS_TYPE_NXT,
+                       DNS_TYPE_SIG,
+                       DNS_TYPE_KEY);
+}
+
+bool dns_type_may_wildcard(uint16_t type) {
+
+        /* The following records may not be expanded from wildcard RRsets */
+
+        if (dns_type_is_pseudo(type))
+                return false;
+
+        return !IN_SET(type,
+                       DNS_TYPE_NSEC3,
+                       DNS_TYPE_SOA,
+
+                       /* Prohibited by https://tools.ietf.org/html/rfc4592#section-4.4 */
+                       DNS_TYPE_DNAME);
+}
+
+bool dns_type_apex_only(uint16_t type) {
+
+        /* Returns true for all RR types that may only appear signed in a zone apex */
+
+        return IN_SET(type,
+                      DNS_TYPE_SOA,
+                      DNS_TYPE_NS,            /* this one can appear elsewhere, too, but not signed */
+                      DNS_TYPE_DNSKEY,
+                      DNS_TYPE_NSEC3PARAM);
+}
+
+bool dns_type_is_dnssec(uint16_t type) {
+        return IN_SET(type,
+                      DNS_TYPE_DS,
+                      DNS_TYPE_DNSKEY,
+                      DNS_TYPE_RRSIG,
+                      DNS_TYPE_NSEC,
+                      DNS_TYPE_NSEC3,
+                      DNS_TYPE_NSEC3PARAM);
+}
+
+bool dns_type_is_obsolete(uint16_t type) {
+        return IN_SET(type,
+                      /* Obsoleted by RFC 973 */
+                      DNS_TYPE_MD,
+                      DNS_TYPE_MF,
+                      DNS_TYPE_MAILA,
+
+                      /* Kinda obsoleted by RFC 2505 */
+                      DNS_TYPE_MB,
+                      DNS_TYPE_MG,
+                      DNS_TYPE_MR,
+                      DNS_TYPE_MINFO,
+                      DNS_TYPE_MAILB,
+
+                      /* RFC1127 kinda obsoleted this by recommending against its use */
+                      DNS_TYPE_WKS,
+
+                      /* Declared historical by RFC 6563 */
+                      DNS_TYPE_A6,
+
+                      /* Obsoleted by DNSSEC-bis */
+                      DNS_TYPE_NXT,
+
+                      /* RFC 1035 removed support for concepts that needed this from RFC 883 */
+                      DNS_TYPE_NULL);
+}
+
+bool dns_type_needs_authentication(uint16_t type) {
+
+        /* Returns true for all (non-obsolete) RR types where records are not useful if they aren't
+         * authenticated. I.e. everything that contains crypto keys. */
+
+        return IN_SET(type,
+                      DNS_TYPE_CERT,
+                      DNS_TYPE_SSHFP,
+                      DNS_TYPE_IPSECKEY,
+                      DNS_TYPE_DS,
+                      DNS_TYPE_DNSKEY,
+                      DNS_TYPE_TLSA,
+                      DNS_TYPE_CDNSKEY,
+                      DNS_TYPE_OPENPGPKEY,
+                      DNS_TYPE_CAA);
+}
+
+int dns_type_to_af(uint16_t t) {
+        switch (t) {
+
+        case DNS_TYPE_A:
+                return AF_INET;
+
+        case DNS_TYPE_AAAA:
+                return AF_INET6;
+
+        case DNS_TYPE_ANY:
+                return AF_UNSPEC;
+
+        default:
+                return -EINVAL;
+        }
+}
+
+const char *dns_class_to_string(uint16_t class) {
+
+        switch (class) {
+
+        case DNS_CLASS_IN:
+                return "IN";
+
+        case DNS_CLASS_ANY:
+                return "ANY";
+        }
+
+        return NULL;
+}
+
+int dns_class_from_string(const char *s) {
+
+        if (!s)
+                return _DNS_CLASS_INVALID;
+
+        if (strcaseeq(s, "IN"))
+                return DNS_CLASS_IN;
+        else if (strcaseeq(s, "ANY"))
+                return DNS_CLASS_ANY;
+
+        return _DNS_CLASS_INVALID;
+}
+
+const char* tlsa_cert_usage_to_string(uint8_t cert_usage) {
+
+        switch (cert_usage) {
+
+        case 0:
+                return "CA constraint";
+
+        case 1:
+                return "Service certificate constraint";
+
+        case 2:
+                return "Trust anchor assertion";
+
+        case 3:
+                return "Domain-issued certificate";
+
+        case 4 ... 254:
+                return "Unassigned";
+
+        case 255:
+                return "Private use";
+        }
+
+        return NULL;  /* clang cannot count that we covered everything */
+}
+
+const char* tlsa_selector_to_string(uint8_t selector) {
+        switch (selector) {
+
+        case 0:
+                return "Full Certificate";
+
+        case 1:
+                return "SubjectPublicKeyInfo";
+
+        case 2 ... 254:
+                return "Unassigned";
+
+        case 255:
+                return "Private use";
+        }
+
+        return NULL;
+}
+
+const char* tlsa_matching_type_to_string(uint8_t selector) {
+
+        switch (selector) {
+
+        case 0:
+                return "No hash used";
+
+        case 1:
+                return "SHA-256";
+
+        case 2:
+                return "SHA-512";
+
+        case 3 ... 254:
+                return "Unassigned";
+
+        case 255:
+                return "Private use";
+        }
+
+        return NULL;
+}