#pragma once #include "path.hh" #include "hash.hh" #include "content-address.hh" #include "serialise.hh" #include "crypto.hh" #include "lru-cache.hh" #include "sync.hh" #include "globals.hh" #include "config.hh" #include "derivations.hh" #include #include #include #include #include #include #include #include #include namespace nix { MakeError(SubstError, Error); MakeError(BuildError, Error); // denotes a permanent build failure MakeError(InvalidPath, Error); MakeError(Unsupported, Error); MakeError(SubstituteGone, Error); MakeError(SubstituterDisabled, Error); MakeError(NotInStore, Error); class FSAccessor; class NarInfoDiskCache; class Store; class JSONPlaceholder; enum CheckSigsFlag : bool { NoCheckSigs = false, CheckSigs = true }; enum SubstituteFlag : bool { NoSubstitute = false, Substitute = true }; enum AllowInvalidFlag : bool { DisallowInvalid = false, AllowInvalid = true }; /* Magic header of exportPath() output (obsolete). */ const uint32_t exportMagic = 0x4558494e; typedef std::unordered_map> Roots; struct GCOptions { /* Garbage collector operation: - `gcReturnLive': return the set of paths reachable from (i.e. in the closure of) the roots. - `gcReturnDead': return the set of paths not reachable from the roots. - `gcDeleteDead': actually delete the latter set. - `gcDeleteSpecific': delete the paths listed in `pathsToDelete', insofar as they are not reachable. */ typedef enum { gcReturnLive, gcReturnDead, gcDeleteDead, gcDeleteSpecific, } GCAction; GCAction action{gcDeleteDead}; /* If `ignoreLiveness' is set, then reachability from the roots is ignored (dangerous!). However, the paths must still be unreferenced *within* the store (i.e., there can be no other store paths that depend on them). */ bool ignoreLiveness{false}; /* For `gcDeleteSpecific', the paths to delete. */ StorePathSet pathsToDelete; /* Stop after at least `maxFreed' bytes have been freed. */ unsigned long long maxFreed{std::numeric_limits::max()}; }; struct GCResults { /* Depending on the action, the GC roots, or the paths that would be or have been deleted. */ PathSet paths; /* For `gcReturnDead', `gcDeleteDead' and `gcDeleteSpecific', the number of bytes that would be or was freed. */ unsigned long long bytesFreed = 0; }; struct SubstitutablePathInfo { std::optional deriver; StorePathSet references; unsigned long long downloadSize; /* 0 = unknown or inapplicable */ unsigned long long narSize; /* 0 = unknown */ }; typedef std::map SubstitutablePathInfos; struct ValidPathInfo { StorePath path; std::optional deriver; Hash narHash; StorePathSet references; time_t registrationTime = 0; uint64_t narSize = 0; // 0 = unknown uint64_t id; // internal use only /* Whether the path is ultimately trusted, that is, it's a derivation output that was built locally. */ bool ultimate = false; StringSet sigs; // note: not necessarily verified /* If non-empty, an assertion that the path is content-addressed, i.e., that the store path is computed from a cryptographic hash of the contents of the path, plus some other bits of data like the "name" part of the path. Such a path doesn't need signatures, since we don't have to trust anybody's claim that the path is the output of a particular derivation. (In the extensional store model, we have to trust that the *contents* of an output path of a derivation were actually produced by that derivation. In the intensional model, we have to trust that a particular output path was produced by a derivation; the path then implies the contents.) Ideally, the content-addressability assertion would just be a Boolean, and the store path would be computed from the name component, ‘narHash’ and ‘references’. However, we support many types of content addresses. */ std::optional ca; bool operator == (const ValidPathInfo & i) const { return path == i.path && narHash == i.narHash && references == i.references; } /* Return a fingerprint of the store path to be used in binary cache signatures. It contains the store path, the base-32 SHA-256 hash of the NAR serialisation of the path, the size of the NAR, and the sorted references. The size field is strictly speaking superfluous, but might prevent endless/excessive data attacks. */ std::string fingerprint(const Store & store) const; void sign(const Store & store, const SecretKey & secretKey); /* Return true iff the path is verifiably content-addressed. */ bool isContentAddressed(const Store & store) const; static const size_t maxSigs = std::numeric_limits::max(); /* Return the number of signatures on this .narinfo that were produced by one of the specified keys, or maxSigs if the path is content-addressed. */ size_t checkSignatures(const Store & store, const PublicKeys & publicKeys) const; /* Verify a single signature. */ bool checkSignature(const Store & store, const PublicKeys & publicKeys, const std::string & sig) const; Strings shortRefs() const; ValidPathInfo(const ValidPathInfo & other) = default; ValidPathInfo(StorePath && path) : path(std::move(path)) { }; ValidPathInfo(const StorePath & path) : path(path) { }; virtual ~ValidPathInfo() { } }; typedef list ValidPathInfos; enum BuildMode { bmNormal, bmRepair, bmCheck }; struct BuildResult { /* Note: don't remove status codes, and only add new status codes at the end of the list, to prevent client/server incompatibilities in the nix-store --serve protocol. */ enum Status { Built = 0, Substituted, AlreadyValid, PermanentFailure, InputRejected, OutputRejected, TransientFailure, // possibly transient CachedFailure, // no longer used TimedOut, MiscFailure, DependencyFailed, LogLimitExceeded, NotDeterministic, } status = MiscFailure; std::string errorMsg; /* How many times this build was performed. */ unsigned int timesBuilt = 0; /* If timesBuilt > 1, whether some builds did not produce the same result. (Note that 'isNonDeterministic = false' does not mean the build is deterministic, just that we don't have evidence of non-determinism.) */ bool isNonDeterministic = false; /* The start/stop times of the build (or one of the rounds, if it was repeated). */ time_t startTime = 0, stopTime = 0; bool success() { return status == Built || status == Substituted || status == AlreadyValid; } }; class Store : public std::enable_shared_from_this, public Config { public: typedef std::map Params; const PathSetting storeDir_{this, false, settings.nixStore, "store", "path to the Nix store"}; const Path storeDir = storeDir_; const Setting pathInfoCacheSize{this, 65536, "path-info-cache-size", "size of the in-memory store path information cache"}; const Setting isTrusted{this, false, "trusted", "whether paths from this store can be used as substitutes even when they lack trusted signatures"}; Setting priority{this, 0, "priority", "priority of this substituter (lower value means higher priority)"}; Setting wantMassQuery{this, false, "want-mass-query", "whether this substituter can be queried efficiently for path validity"}; protected: struct PathInfoCacheValue { // Time of cache entry creation or update std::chrono::time_point time_point = std::chrono::steady_clock::now(); // Null if missing std::shared_ptr value; // Whether the value is valid as a cache entry. The path may not exist. bool isKnownNow(); // Past tense, because a path can only be assumed to exists when // isKnownNow() && didExist() inline bool didExist() { return value != nullptr; } }; struct State { // FIXME: fix key LRUCache pathInfoCache; }; Sync state; std::shared_ptr diskCache; Store(const Params & params); public: virtual ~Store() { } virtual std::string getUri() = 0; StorePath parseStorePath(std::string_view path) const; std::optional maybeParseStorePath(std::string_view path) const; std::string printStorePath(const StorePath & path) const; // FIXME: remove StorePathSet parseStorePathSet(const PathSet & paths) const; PathSet printStorePathSet(const StorePathSet & path) const; /* Split a string specifying a derivation and a set of outputs (/nix/store/hash-foo!out1,out2,...) into the derivation path and the outputs. */ StorePathWithOutputs parsePathWithOutputs(const string & s); /* Display a set of paths in human-readable form (i.e., between quotes and separated by commas). */ std::string showPaths(const StorePathSet & paths); /* Return true if ‘path’ is in the Nix store (but not the Nix store itself). */ bool isInStore(const Path & path) const; /* Return true if ‘path’ is a store path, i.e. a direct child of the Nix store. */ bool isStorePath(std::string_view path) const; /* Chop off the parts after the top-level store name, e.g., /nix/store/abcd-foo/bar => /nix/store/abcd-foo. */ Path toStorePath(const Path & path) const; /* Follow symlinks until we end up with a path in the Nix store. */ Path followLinksToStore(std::string_view path) const; /* Same as followLinksToStore(), but apply toStorePath() to the result. */ StorePath followLinksToStorePath(std::string_view path) const; StorePathWithOutputs followLinksToStorePathWithOutputs(std::string_view path) const; /* Constructs a unique store path name. */ StorePath makeStorePath(const string & type, const Hash & hash, std::string_view name) const; StorePath makeOutputPath(const string & id, const Hash & hash, std::string_view name) const; StorePath makeFixedOutputPath(FileIngestionMethod method, const Hash & hash, std::string_view name, const StorePathSet & references = {}, bool hasSelfReference = false) const; StorePath makeTextPath(std::string_view name, const Hash & hash, const StorePathSet & references = {}) const; StorePath makeFixedOutputPathFromCA(std::string_view name, ContentAddress ca, const StorePathSet & references = {}, bool hasSelfReference = false) const; /* This is the preparatory part of addToStore(); it computes the store path to which srcPath is to be copied. Returns the store path and the cryptographic hash of the contents of srcPath. */ std::pair computeStorePathForPath(std::string_view name, const Path & srcPath, FileIngestionMethod method = FileIngestionMethod::Recursive, HashType hashAlgo = htSHA256, PathFilter & filter = defaultPathFilter) const; /* Preparatory part of addTextToStore(). !!! Computation of the path should take the references given to addTextToStore() into account, otherwise we have a (relatively minor) security hole: a caller can register a source file with bogus references. If there are too many references, the path may not be garbage collected when it has to be (not really a problem, the caller could create a root anyway), or it may be garbage collected when it shouldn't be (more serious). Hashing the references would solve this (bogus references would simply yield a different store path, so other users wouldn't be affected), but it has some backwards compatibility issues (the hashing scheme changes), so I'm not doing that for now. */ StorePath computeStorePathForText(const string & name, const string & s, const StorePathSet & references) const; /* Check whether a path is valid. */ bool isValidPath(const StorePath & path); protected: virtual bool isValidPathUncached(const StorePath & path); public: /* Query which of the given paths is valid. Optionally, try to substitute missing paths. */ virtual StorePathSet queryValidPaths(const StorePathSet & paths, SubstituteFlag maybeSubstitute = NoSubstitute); /* Query the set of all valid paths. Note that for some store backends, the name part of store paths may be omitted (i.e. you'll get /nix/store/ rather than /nix/store/-). Use queryPathInfo() to obtain the full store path. */ virtual StorePathSet queryAllValidPaths() { unsupported("queryAllValidPaths"); } /* Query information about a valid path. It is permitted to omit the name part of the store path. */ ref queryPathInfo(const StorePath & path); /* Asynchronous version of queryPathInfo(). */ void queryPathInfo(const StorePath & path, Callback> callback) noexcept; protected: virtual void queryPathInfoUncached(const StorePath & path, Callback> callback) noexcept = 0; public: /* Queries the set of incoming FS references for a store path. The result is not cleared. */ virtual void queryReferrers(const StorePath & path, StorePathSet & referrers) { unsupported("queryReferrers"); } /* Return all currently valid derivations that have `path' as an output. (Note that the result of `queryDeriver()' is the derivation that was actually used to produce `path', which may not exist anymore.) */ virtual StorePathSet queryValidDerivers(const StorePath & path) { return {}; }; /* Query the outputs of the derivation denoted by `path'. */ virtual StorePathSet queryDerivationOutputs(const StorePath & path); /* Query the mapping outputName=>outputPath for the given derivation */ virtual OutputPathMap queryDerivationOutputMap(const StorePath & path) { unsupported("queryDerivationOutputMap"); } /* Query the full store path given the hash part of a valid store path, or empty if the path doesn't exist. */ virtual std::optional queryPathFromHashPart(const std::string & hashPart) = 0; /* Query which of the given paths have substitutes. */ virtual StorePathSet querySubstitutablePaths(const StorePathSet & paths) { return {}; }; /* Query substitute info (i.e. references, derivers and download sizes) of a map of paths to their optional ca values. If a path does not have substitute info, it's omitted from the resulting ‘infos’ map. */ virtual void querySubstitutablePathInfos(const StorePathCAMap & paths, SubstitutablePathInfos & infos) { return; }; /* Import a path into the store. */ virtual void addToStore(const ValidPathInfo & info, Source & narSource, RepairFlag repair = NoRepair, CheckSigsFlag checkSigs = CheckSigs, std::shared_ptr accessor = 0) = 0; /* Copy the contents of a path to the store and register the validity the resulting path. The resulting path is returned. The function object `filter' can be used to exclude files (see libutil/archive.hh). */ virtual StorePath addToStore(const string & name, const Path & srcPath, FileIngestionMethod method = FileIngestionMethod::Recursive, HashType hashAlgo = htSHA256, PathFilter & filter = defaultPathFilter, RepairFlag repair = NoRepair) = 0; /* Copy the contents of a path to the store and register the validity the resulting path, using a constant amount of memory. */ ValidPathInfo addToStoreSlow(std::string_view name, const Path & srcPath, FileIngestionMethod method = FileIngestionMethod::Recursive, HashType hashAlgo = htSHA256, std::optional expectedCAHash = {}); // FIXME: remove? virtual StorePath addToStoreFromDump(const string & dump, const string & name, FileIngestionMethod method = FileIngestionMethod::Recursive, HashType hashAlgo = htSHA256, RepairFlag repair = NoRepair) { throw Error("addToStoreFromDump() is not supported by this store"); } /* Like addToStore, but the contents written to the output path is a regular file containing the given string. */ virtual StorePath addTextToStore(const string & name, const string & s, const StorePathSet & references, RepairFlag repair = NoRepair) = 0; /* Write a NAR dump of a store path. */ virtual void narFromPath(const StorePath & path, Sink & sink) = 0; /* For each path, if it's a derivation, build it. Building a derivation means ensuring that the output paths are valid. If they are already valid, this is a no-op. Otherwise, validity can be reached in two ways. First, if the output paths is substitutable, then build the path that way. Second, the output paths can be created by running the builder, after recursively building any sub-derivations. For inputs that are not derivations, substitute them. */ virtual void buildPaths( const std::vector & paths, BuildMode buildMode = bmNormal); /* Build a single non-materialized derivation (i.e. not from an on-disk .drv file). Note that ‘drvPath’ is only used for informational purposes. */ virtual BuildResult buildDerivation(const StorePath & drvPath, const BasicDerivation & drv, BuildMode buildMode = bmNormal) = 0; /* Ensure that a path is valid. If it is not currently valid, it may be made valid by running a substitute (if defined for the path). */ virtual void ensurePath(const StorePath & path) = 0; /* Add a store path as a temporary root of the garbage collector. The root disappears as soon as we exit. */ virtual void addTempRoot(const StorePath & path) { unsupported("addTempRoot"); } /* Add an indirect root, which is merely a symlink to `path' from /nix/var/nix/gcroots/auto/. `path' is supposed to be a symlink to a store path. The garbage collector will automatically remove the indirect root when it finds that `path' has disappeared. */ virtual void addIndirectRoot(const Path & path) { unsupported("addIndirectRoot"); } /* Acquire the global GC lock, then immediately release it. This function must be called after registering a new permanent root, but before exiting. Otherwise, it is possible that a running garbage collector doesn't see the new root and deletes the stuff we've just built. By acquiring the lock briefly, we ensure that either: - The collector is already running, and so we block until the collector is finished. The collector will know about our *temporary* locks, which should include whatever it is we want to register as a permanent lock. - The collector isn't running, or it's just started but hasn't acquired the GC lock yet. In that case we get and release the lock right away, then exit. The collector scans the permanent root and sees our's. In either case the permanent root is seen by the collector. */ virtual void syncWithGC() { }; /* Find the roots of the garbage collector. Each root is a pair (link, storepath) where `link' is the path of the symlink outside of the Nix store that point to `storePath'. If 'censor' is true, privacy-sensitive information about roots found in /proc is censored. */ virtual Roots findRoots(bool censor) { unsupported("findRoots"); } /* Perform a garbage collection. */ virtual void collectGarbage(const GCOptions & options, GCResults & results) { unsupported("collectGarbage"); } /* Return a string representing information about the path that can be loaded into the database using `nix-store --load-db' or `nix-store --register-validity'. */ string makeValidityRegistration(const StorePathSet & paths, bool showDerivers, bool showHash); /* Write a JSON representation of store path metadata, such as the hash and the references. If ‘includeImpureInfo’ is true, variable elements such as the registration time are included. If ‘showClosureSize’ is true, the closure size of each path is included. */ void pathInfoToJSON(JSONPlaceholder & jsonOut, const StorePathSet & storePaths, bool includeImpureInfo, bool showClosureSize, Base hashBase = Base32, AllowInvalidFlag allowInvalid = DisallowInvalid); /* Return the size of the closure of the specified path, that is, the sum of the size of the NAR serialisation of each path in the closure. */ std::pair getClosureSize(const StorePath & storePath); /* Optimise the disk space usage of the Nix store by hard-linking files with the same contents. */ virtual void optimiseStore() { }; /* Check the integrity of the Nix store. Returns true if errors remain. */ virtual bool verifyStore(bool checkContents, RepairFlag repair = NoRepair) { return false; }; /* Return an object to access files in the Nix store. */ virtual ref getFSAccessor() { unsupported("getFSAccessor"); } /* Add signatures to the specified store path. The signatures are not verified. */ virtual void addSignatures(const StorePath & storePath, const StringSet & sigs) { unsupported("addSignatures"); } /* Utility functions. */ /* Read a derivation, after ensuring its existence through ensurePath(). */ Derivation derivationFromPath(const StorePath & drvPath); /* Read a derivation (which must already be valid). */ Derivation readDerivation(const StorePath & drvPath); /* Place in `out' the set of all store paths in the file system closure of `storePath'; that is, all paths than can be directly or indirectly reached from it. `out' is not cleared. If `flipDirection' is true, the set of paths that can reach `storePath' is returned; that is, the closures under the `referrers' relation instead of the `references' relation is returned. */ virtual void computeFSClosure(const StorePathSet & paths, StorePathSet & out, bool flipDirection = false, bool includeOutputs = false, bool includeDerivers = false); void computeFSClosure(const StorePath & path, StorePathSet & out, bool flipDirection = false, bool includeOutputs = false, bool includeDerivers = false); /* Given a set of paths that are to be built, return the set of derivations that will be built, and the set of output paths that will be substituted. */ virtual void queryMissing(const std::vector & targets, StorePathSet & willBuild, StorePathSet & willSubstitute, StorePathSet & unknown, unsigned long long & downloadSize, unsigned long long & narSize); /* Sort a set of paths topologically under the references relation. If p refers to q, then p precedes q in this list. */ StorePaths topoSortPaths(const StorePathSet & paths); /* Export multiple paths in the format expected by ‘nix-store --import’. */ void exportPaths(const StorePathSet & paths, Sink & sink); void exportPath(const StorePath & path, Sink & sink); /* Import a sequence of NAR dumps created by exportPaths() into the Nix store. Optionally, the contents of the NARs are preloaded into the specified FS accessor to speed up subsequent access. */ StorePaths importPaths(Source & source, std::shared_ptr accessor, CheckSigsFlag checkSigs = CheckSigs); struct Stats { std::atomic narInfoRead{0}; std::atomic narInfoReadAverted{0}; std::atomic narInfoMissing{0}; std::atomic narInfoWrite{0}; std::atomic pathInfoCacheSize{0}; std::atomic narRead{0}; std::atomic narReadBytes{0}; std::atomic narReadCompressedBytes{0}; std::atomic narWrite{0}; std::atomic narWriteAverted{0}; std::atomic narWriteBytes{0}; std::atomic narWriteCompressedBytes{0}; std::atomic narWriteCompressionTimeMs{0}; }; const Stats & getStats(); /* Return the build log of the specified store path, if available, or null otherwise. */ virtual std::shared_ptr getBuildLog(const StorePath & path) { return nullptr; } /* Hack to allow long-running processes like hydra-queue-runner to occasionally flush their path info cache. */ void clearPathInfoCache() { state.lock()->pathInfoCache.clear(); } /* Establish a connection to the store, for store types that have a notion of connection. Otherwise this is a no-op. */ virtual void connect() { }; /* Get the protocol version of this store or it's connection. */ virtual unsigned int getProtocol() { return 0; }; virtual Path toRealPath(const Path & storePath) { return storePath; } Path toRealPath(const StorePath & storePath) { return toRealPath(printStorePath(storePath)); } virtual void createUser(const std::string & userName, uid_t userId) { } protected: Stats stats; /* Unsupported methods. */ [[noreturn]] void unsupported(const std::string & op) { throw Unsupported("operation '%s' is not supported by store '%s'", op, getUri()); } }; class LocalFSStore : public virtual Store { public: // FIXME: the (Store*) cast works around a bug in gcc that causes // it to omit the call to the Setting constructor. Clang works fine // either way. const PathSetting rootDir{(Store*) this, true, "", "root", "directory prefixed to all other paths"}; const PathSetting stateDir{(Store*) this, false, rootDir != "" ? rootDir + "/nix/var/nix" : settings.nixStateDir, "state", "directory where Nix will store state"}; const PathSetting logDir{(Store*) this, false, rootDir != "" ? rootDir + "/nix/var/log/nix" : settings.nixLogDir, "log", "directory where Nix will store state"}; const static string drvsLogDir; LocalFSStore(const Params & params); void narFromPath(const StorePath & path, Sink & sink) override; ref getFSAccessor() override; /* Register a permanent GC root. */ Path addPermRoot(const StorePath & storePath, const Path & gcRoot, bool indirect, bool allowOutsideRootsDir = false); virtual Path getRealStoreDir() { return storeDir; } Path toRealPath(const Path & storePath) override { assert(isInStore(storePath)); return getRealStoreDir() + "/" + std::string(storePath, storeDir.size() + 1); } std::shared_ptr getBuildLog(const StorePath & path) override; }; /* Copy a path from one store to another. */ void copyStorePath(ref srcStore, ref dstStore, const StorePath & storePath, RepairFlag repair = NoRepair, CheckSigsFlag checkSigs = CheckSigs); /* Copy store paths from one store to another. The paths may be copied in parallel. They are copied in a topologically sorted order (i.e. if A is a reference of B, then A is copied before B), but the set of store paths is not automatically closed; use copyClosure() for that. Returns a map of what each path was copied to the dstStore as. */ std::map copyPaths(ref srcStore, ref dstStore, const StorePathSet & storePaths, RepairFlag repair = NoRepair, CheckSigsFlag checkSigs = CheckSigs, SubstituteFlag substitute = NoSubstitute); /* Copy the closure of the specified paths from one store to another. */ void copyClosure(ref srcStore, ref dstStore, const StorePathSet & storePaths, RepairFlag repair = NoRepair, CheckSigsFlag checkSigs = CheckSigs, SubstituteFlag substitute = NoSubstitute); /* Remove the temporary roots file for this process. Any temporary root becomes garbage after this point unless it has been registered as a (permanent) root. */ void removeTempRoots(); /* Return a Store object to access the Nix store denoted by ‘uri’ (slight misnomer...). Supported values are: * ‘local’: The Nix store in /nix/store and database in /nix/var/nix/db, accessed directly. * ‘daemon’: The Nix store accessed via a Unix domain socket connection to nix-daemon. * ‘unix://’: The Nix store accessed via a Unix domain socket connection to nix-daemon, with the socket located at . * ‘auto’ or ‘’: Equivalent to ‘local’ or ‘daemon’ depending on whether the user has write access to the local Nix store/database. * ‘file://’: A binary cache stored in . * ‘https://’: A binary cache accessed via HTTP. * ‘s3://’: A writable binary cache stored on Amazon's Simple Storage Service. * ‘ssh://[user@]’: A remote Nix store accessed by running ‘nix-store --serve’ via SSH. You can pass parameters to the store implementation by appending ‘?key=value&key=value&...’ to the URI. */ ref openStore(const std::string & uri = settings.storeUri.get(), const Store::Params & extraParams = Store::Params()); enum StoreType { tDaemon, tLocal, tOther }; StoreType getStoreType(const std::string & uri = settings.storeUri.get(), const std::string & stateDir = settings.nixStateDir); /* Return the default substituter stores, defined by the ‘substituters’ option and various legacy options. */ std::list> getDefaultSubstituters(); /* Store implementation registration. */ typedef std::function( const std::string & uri, const Store::Params & params)> OpenStore; struct RegisterStoreImplementation { typedef std::vector Implementations; static Implementations * implementations; RegisterStoreImplementation(OpenStore fun) { if (!implementations) implementations = new Implementations; implementations->push_back(fun); } }; /* Display a set of paths in human-readable form (i.e., between quotes and separated by commas). */ string showPaths(const PathSet & paths); std::optional decodeValidPathInfo( const Store & store, std::istream & str, bool hashGiven = false); /* Split URI into protocol+hierarchy part and its parameter set. */ std::pair splitUriAndParams(const std::string & uri); std::optional getDerivationCA(const BasicDerivation & drv); }