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Diffstat (limited to 'src/lib/dns/zone_checker.h')
| -rw-r--r-- | src/lib/dns/zone_checker.h | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/src/lib/dns/zone_checker.h b/src/lib/dns/zone_checker.h new file mode 100644 index 0000000..be36a32 --- /dev/null +++ b/src/lib/dns/zone_checker.h @@ -0,0 +1,153 @@ +// Copyright (C) 2012-2020 Internet Systems Consortium, Inc. ("ISC") +// +// This Source Code Form is subject to the terms of the Mozilla Public +// License, v. 2.0. If a copy of the MPL was not distributed with this +// file, You can obtain one at http://mozilla.org/MPL/2.0/. + +#ifndef ZONE_CHECKER_H +#define ZONE_CHECKER_H 1 + +#include <dns/dns_fwd.h> + +#include <functional> +#include <string> + +namespace isc { +namespace dns { + +/// \brief Set of callbacks used in zone checks. +/// +/// Objects of this class are expected to be passed to \c checkZone(). +class ZoneCheckerCallbacks { +public: + /// \brief Functor type of the callback on some issue (error or warning). + /// + /// Its parameter indicates the reason for the corresponding issue. + typedef std::function<void(const std::string& reason)> IssueCallback; + + /// \brief Constructor. + /// + /// Either or both of the callbacks can be empty, in which case the + /// corresponding callback will be effectively no-operation. This can be + /// used, for example, when the caller of \c checkZone() is only + /// interested in the final result. Note that a \c NULL pointer will be + /// implicitly converted to an empty functor object, so passing \c NULL + /// suffices. + /// + /// \throw none + /// + /// \param error_callback Callback functor to be called on critical errors. + /// \param warn_callback Callback functor to be called on non critical + /// issues. + ZoneCheckerCallbacks(const IssueCallback& error_callback, + const IssueCallback& warn_callback) : + error_callback_(error_callback), warn_callback_(warn_callback) + {} + + /// \brief Call the callback for a critical error. + /// + /// This method itself is exception free, but propagates any exception + /// thrown from the callback. + /// + /// \param reason Textual representation of the reason for the error. + void error(const std::string& reason) const { + if (error_callback_) { + error_callback_(reason); + } + } + + /// \brief Call the callback for a non critical issue. + /// + /// This method itself is exception free, but propagates any exception + /// thrown from the callback. + /// + /// \param reason Textual representation of the reason for the issue. + void warn(const std::string& reason) const { + if (warn_callback_) + warn_callback_(reason); + } + +private: + IssueCallback error_callback_; + IssueCallback warn_callback_; +}; + +/// \brief Perform basic integrity checks on zone RRsets. +/// +/// This function performs some lightweight checks on zone's SOA and (apex) +/// NS records. Here, lightweight means it doesn't require traversing +/// the entire zone, and should be expected to complete reasonably quickly +/// regardless of the size of the zone. +/// +/// It distinguishes "critical" errors and other undesirable issues: +/// the former should be interpreted as the resulting zone shouldn't be used +/// further, e.g, by an authoritative server implementation; the latter means +/// the issues are better to be addressed but are not necessarily considered +/// to make the zone invalid. Critical errors are reported via the +/// \c error() method of \c callbacks, and non critical issues are reported +/// via its \c warn() method. +/// +/// Specific checks performed by this function is as follows. Failure of +/// a check is considered a critical error unless noted otherwise: +/// - There is exactly one SOA RR at the zone apex. +/// - There is at least one NS RR at the zone apex. +/// - For each apex NS record, if the NS name (the RDATA of the record) is +/// in the zone (i.e., it's a subdomain of the zone origin and above any +/// zone cut due to delegation), check the following: +/// - the NS name should have an address record (AAAA or A). Failure of +/// this check is considered a non critical issue. +/// - the NS name does not have a CNAME. This is prohibited by Section +/// 10.3 of RFC 2181. +/// - the NS name is not subject to DNAME substitution. This is prohibited +/// by Section 4 of RFC 6672. +/// . +/// +/// In addition, when the check is completed without any critical error, this +/// function guarantees that RRsets for the SOA and (apex) NS stored in the +/// passed RRset collection have the expected type of Rdata objects, +/// i.e., generic::SOA and generic::NS, respectively. (This is normally +/// expected to be the case, but not guaranteed by the API). +/// +/// As for the check on the existence of AAAA or A records for NS names, +/// it should be noted that BIND 9 treats this as a critical error. +/// It's not clear whether it's an implementation dependent behavior or +/// based on the protocol standard (it looks like the former), but to make +/// it sure we need to confirm there is even no wildcard match for the names. +/// This should be a very rare configuration, and more expensive to detect, +/// so we do not check this condition, and treat this case as a non critical +/// issue. +/// +/// This function indicates the result of the checks (whether there is a +/// critical error) via the return value: It returns \c true if there is no +/// critical error and returns \c false otherwise. It doesn't throw an +/// exception on encountering an error so that it can report as many errors +/// as possible in a single call. If an exception is a better way to signal +/// the error, the caller can pass a callback object that throws from its +/// \c error() method. +/// +/// This function can still throw an exception if it finds a really bogus +/// condition that is most likely to be an implementation bug of the caller. +/// Such cases include when an RRset contained in the RRset collection is +/// empty. +/// +/// \throw Unexpected Conditions that suggest a caller's bug (see the +/// description) +/// +/// \param zone_name The name of the zone to be checked +/// \param zone_class The RR class of the zone to be checked +/// \param zone_rrsets The collection of RRsets of the zone +/// \param callbacks Callback object used to report errors and issues +/// +/// \return \c true if no critical errors are found; \c false otherwise. +bool +checkZone(const Name& zone_name, const RRClass& zone_class, + const RRsetCollectionBase& zone_rrsets, + const ZoneCheckerCallbacks& callbacks); + +} // namespace dns +} // namespace isc +#endif // ZONE_CHECKER_H + +// Local Variables: +// mode: c++ +// End: |