lix/src/libstore/store-api.cc

#include "crypto.hh"
#include "globals.hh"
#include "store-api.hh"
#include "util.hh"
#include "nar-info-disk-cache.hh"

#include <future>


namespace nix {


bool Store::isInStore(const Path & path) const
{
    return isInDir(path, storeDir);
}


bool Store::isStorePath(const Path & path) const
{
    return isInStore(path)
        && path.size() >= storeDir.size() + 1 + storePathHashLen
        && path.find('/', storeDir.size() + 1) == Path::npos;
}


void Store::assertStorePath(const Path & path) const
{
    if (!isStorePath(path))
        throw Error(format("path ‘%1%’ is not in the Nix store") % path);
}


Path Store::toStorePath(const Path & path) const
{
    if (!isInStore(path))
        throw Error(format("path ‘%1%’ is not in the Nix store") % path);
    Path::size_type slash = path.find('/', storeDir.size() + 1);
    if (slash == Path::npos)
        return path;
    else
        return Path(path, 0, slash);
}


Path Store::followLinksToStore(const Path & _path) const
{
    Path path = absPath(_path);
    while (!isInStore(path)) {
        if (!isLink(path)) break;
        string target = readLink(path);
        path = absPath(target, dirOf(path));
    }
    if (!isInStore(path))
        throw Error(format("path ‘%1%’ is not in the Nix store") % path);
    return path;
}


Path Store::followLinksToStorePath(const Path & path) const
{
    return toStorePath(followLinksToStore(path));
}


string storePathToName(const Path & path)
{
    auto base = baseNameOf(path);
    assert(base.size() == storePathHashLen || (base.size() > storePathHashLen && base[storePathHashLen] == '-'));
    return base.size() == storePathHashLen ? "" : string(base, storePathHashLen + 1);
}


string storePathToHash(const Path & path)
{
    auto base = baseNameOf(path);
    assert(base.size() >= storePathHashLen);
    return string(base, 0, storePathHashLen);
}


void checkStoreName(const string & name)
{
    string validChars = "+-._?=";
    /* Disallow names starting with a dot for possible security
       reasons (e.g., "." and ".."). */
    if (string(name, 0, 1) == ".")
        throw Error(format("illegal name: ‘%1%’") % name);
    for (auto & i : name)
        if (!((i >= 'A' && i <= 'Z') ||
              (i >= 'a' && i <= 'z') ||
              (i >= '0' && i <= '9') ||
              validChars.find(i) != string::npos))
        {
            throw Error(format("invalid character ‘%1%’ in name ‘%2%’")
                % i % name);
        }
}


/* Store paths have the following form:

   <store>/<h>-<name>

   where

   <store> = the location of the Nix store, usually /nix/store

   <name> = a human readable name for the path, typically obtained
     from the name attribute of the derivation, or the name of the
     source file from which the store path is created.  For derivation
     outputs other than the default "out" output, the string "-<id>"
     is suffixed to <name>.

   <h> = base-32 representation of the first 160 bits of a SHA-256
     hash of <s>; the hash part of the store name

   <s> = the string "<type>:sha256:<h2>:<store>:<name>";
     note that it includes the location of the store as well as the
     name to make sure that changes to either of those are reflected
     in the hash (e.g. you won't get /nix/store/<h>-name1 and
     /nix/store/<h>-name2 with equal hash parts).

   <type> = one of:
     "text:<r1>:<r2>:...<rN>"
       for plain text files written to the store using
       addTextToStore(); <r1> ... <rN> are the references of the
       path.
     "source"
       for paths copied to the store using addToStore() when recursive
       = true and hashAlgo = "sha256"
     "output:<id>"
       for either the outputs created by derivations, OR paths copied
       to the store using addToStore() with recursive != true or
       hashAlgo != "sha256" (in that case "source" is used; it's
       silly, but it's done that way for compatibility).  <id> is the
       name of the output (usually, "out").

   <h2> = base-16 representation of a SHA-256 hash of:
     if <type> = "text:...":
       the string written to the resulting store path
     if <type> = "source":
       the serialisation of the path from which this store path is
       copied, as returned by hashPath()
     if <type> = "output:<id>":
       for non-fixed derivation outputs:
         the derivation (see hashDerivationModulo() in
         primops.cc)
       for paths copied by addToStore() or produced by fixed-output
       derivations:
         the string "fixed:out:<rec><algo>:<hash>:", where
           <rec> = "r:" for recursive (path) hashes, or "" for flat
             (file) hashes
           <algo> = "md5", "sha1" or "sha256"
           <hash> = base-16 representation of the path or flat hash of
             the contents of the path (or expected contents of the
             path for fixed-output derivations)

   It would have been nicer to handle fixed-output derivations under
   "source", e.g. have something like "source:<rec><algo>", but we're
   stuck with this for now...

   The main reason for this way of computing names is to prevent name
   collisions (for security).  For instance, it shouldn't be feasible
   to come up with a derivation whose output path collides with the
   path for a copied source.  The former would have a <s> starting with
   "output:out:", while the latter would have a <2> starting with
   "source:".
*/


Path Store::makeStorePath(const string & type,
    const Hash & hash, const string & name) const
{
    /* e.g., "source:sha256:1abc...:/nix/store:foo.tar.gz" */
    string s = type + ":sha256:" + printHash(hash) + ":"
        + storeDir + ":" + name;

    checkStoreName(name);

    return storeDir + "/"
        + printHash32(compressHash(hashString(htSHA256, s), 20))
        + "-" + name;
}


Path Store::makeOutputPath(const string & id,
    const Hash & hash, const string & name) const
{
    return makeStorePath("output:" + id, hash,
        name + (id == "out" ? "" : "-" + id));
}


Path Store::makeFixedOutputPath(bool recursive,
    const Hash & hash, const string & name) const
{
    return hash.type == htSHA256 && recursive
        ? makeStorePath("source", hash, name)
        : makeStorePath("output:out", hashString(htSHA256,
                "fixed:out:" + (recursive ? (string) "r:" : "") +
                printHashType(hash.type) + ":" + printHash(hash) + ":"),
            name);
}


Path Store::makeTextPath(const string & name, const Hash & hash,
    const PathSet & references) const
{
    assert(hash.type == htSHA256);
    /* Stuff the references (if any) into the type.  This is a bit
       hacky, but we can't put them in `s' since that would be
       ambiguous. */
    string type = "text";
    for (auto & i : references) {
        type += ":";
        type += i;
    }
    return makeStorePath(type, hash, name);
}


std::pair<Path, Hash> Store::computeStorePathForPath(const Path & srcPath,
    bool recursive, HashType hashAlgo, PathFilter & filter) const
{
    Hash h = recursive ? hashPath(hashAlgo, srcPath, filter).first : hashFile(hashAlgo, srcPath);
    string name = baseNameOf(srcPath);
    Path dstPath = makeFixedOutputPath(recursive, h, name);
    return std::pair<Path, Hash>(dstPath, h);
}


Path Store::computeStorePathForText(const string & name, const string & s,
    const PathSet & references) const
{
    return makeTextPath(name, hashString(htSHA256, s), references);
}


Store::Store(const Params & params)
    : storeDir(get(params, "store", settings.nixStore))
{
}


std::string Store::getUri()
{
    return "";
}


bool Store::isValidPath(const Path & storePath)
{
    auto hashPart = storePathToHash(storePath);

    {
        auto state_(state.lock());
        auto res = state_->pathInfoCache.get(hashPart);
        if (res) {
            stats.narInfoReadAverted++;
            return *res != 0;
        }
    }

    if (diskCache) {
        auto res = diskCache->lookupNarInfo(getUri(), hashPart);
        if (res.first != NarInfoDiskCache::oUnknown) {
            stats.narInfoReadAverted++;
            auto state_(state.lock());
            state_->pathInfoCache.upsert(hashPart,
                res.first == NarInfoDiskCache::oInvalid ? 0 : res.second);
            return res.first == NarInfoDiskCache::oValid;
        }
    }

    bool valid = isValidPathUncached(storePath);

    if (diskCache && !valid)
        // FIXME: handle valid = true case.
        diskCache->upsertNarInfo(getUri(), hashPart, 0);

    return valid;
}


ref<const ValidPathInfo> Store::queryPathInfo(const Path & storePath)
{
    std::promise<ref<ValidPathInfo>> promise;

    queryPathInfo(storePath,
        [&](ref<ValidPathInfo> info) {
            promise.set_value(info);
        },
        [&](std::exception_ptr exc) {
            promise.set_exception(exc);
        });

    return promise.get_future().get();
}


void Store::queryPathInfo(const Path & storePath,
    std::function<void(ref<ValidPathInfo>)> success,
    std::function<void(std::exception_ptr exc)> failure)
{
    auto hashPart = storePathToHash(storePath);

    try {

        {
            auto res = state.lock()->pathInfoCache.get(hashPart);
            if (res) {
                stats.narInfoReadAverted++;
                if (!*res)
                    throw InvalidPath(format("path ‘%s’ is not valid") % storePath);
                return success(ref<ValidPathInfo>(*res));
            }
        }

        if (diskCache) {
            auto res = diskCache->lookupNarInfo(getUri(), hashPart);
            if (res.first != NarInfoDiskCache::oUnknown) {
                stats.narInfoReadAverted++;
                {
                    auto state_(state.lock());
                    state_->pathInfoCache.upsert(hashPart,
                        res.first == NarInfoDiskCache::oInvalid ? 0 : res.second);
                    if (res.first == NarInfoDiskCache::oInvalid ||
                        (res.second->path != storePath && storePathToName(storePath) != ""))
                        throw InvalidPath(format("path ‘%s’ is not valid") % storePath);
                }
                return success(ref<ValidPathInfo>(res.second));
            }
        }

    } catch (std::exception & e) {
        return callFailure(failure);
    }

    queryPathInfoUncached(storePath,
        [this, storePath, hashPart, success, failure](std::shared_ptr<ValidPathInfo> info) {

            if (diskCache)
                diskCache->upsertNarInfo(getUri(), hashPart, info);

            {
                auto state_(state.lock());
                state_->pathInfoCache.upsert(hashPart, info);
            }

            if (!info
                || (info->path != storePath && storePathToName(storePath) != ""))
            {
                stats.narInfoMissing++;
                return failure(std::make_exception_ptr(InvalidPath(format("path ‘%s’ is not valid") % storePath)));
            }

            callSuccess(success, failure, ref<ValidPathInfo>(info));

        }, failure);
}


PathSet Store::queryValidPaths(const PathSet & paths)
{
    struct State
    {
        size_t left;
        PathSet valid;
        std::exception_ptr exc;
    };

    Sync<State> state_(State{paths.size(), PathSet()});

    std::condition_variable wakeup;

    for (auto & path : paths)
        queryPathInfo(path,
            [path, &state_, &wakeup](ref<ValidPathInfo> info) {
                auto state(state_.lock());
                state->valid.insert(path);
                assert(state->left);
                if (!--state->left)
                    wakeup.notify_one();
            },
            [path, &state_, &wakeup](std::exception_ptr exc) {
                auto state(state_.lock());
                try {
                    std::rethrow_exception(exc);
                } catch (InvalidPath &) {
                } catch (...) {
                    state->exc = exc;
                }
                assert(state->left);
                if (!--state->left)
                    wakeup.notify_one();
            });

    while (true) {
        auto state(state_.lock());
        if (!state->left) {
            if (state->exc) std::rethrow_exception(state->exc);
            return state->valid;
        }
        state.wait(wakeup);
    }
}


/* Return a string accepted by decodeValidPathInfo() that
   registers the specified paths as valid.  Note: it's the
   responsibility of the caller to provide a closure. */
string Store::makeValidityRegistration(const PathSet & paths,
    bool showDerivers, bool showHash)
{
    string s = "";

    for (auto & i : paths) {
        s += i + "\n";

        auto info = queryPathInfo(i);

        if (showHash) {
            s += printHash(info->narHash) + "\n";
            s += (format("%1%\n") % info->narSize).str();
        }

        Path deriver = showDerivers ? info->deriver : "";
        s += deriver + "\n";

        s += (format("%1%\n") % info->references.size()).str();

        for (auto & j : info->references)
            s += j + "\n";
    }

    return s;
}


const Store::Stats & Store::getStats()
{
    {
        auto state_(state.lock());
        stats.pathInfoCacheSize = state_->pathInfoCache.size();
    }
    return stats;
}


void copyStorePath(ref<Store> srcStore, ref<Store> dstStore,
    const Path & storePath, bool repair)
{
    auto info = srcStore->queryPathInfo(storePath);

    StringSink sink;
    srcStore->narFromPath({storePath}, sink);

    dstStore->addToStore(*info, *sink.s, repair);
}


void copyClosure(ref<Store> srcStore, ref<Store> dstStore,
    const PathSet & storePaths, bool repair)
{
    PathSet closure;
    for (auto & path : storePaths)
        srcStore->computeFSClosure(path, closure);

    PathSet valid = dstStore->queryValidPaths(closure);

    if (valid.size() == closure.size()) return;

    Paths sorted = srcStore->topoSortPaths(closure);

    Paths missing;
    for (auto i = sorted.rbegin(); i != sorted.rend(); ++i)
        if (!valid.count(*i)) missing.push_back(*i);

    printMsg(lvlDebug, format("copying %1% missing paths") % missing.size());

    for (auto & i : missing)
        copyStorePath(srcStore, dstStore, i, repair);
}


ValidPathInfo decodeValidPathInfo(std::istream & str, bool hashGiven)
{
    ValidPathInfo info;
    getline(str, info.path);
    if (str.eof()) { info.path = ""; return info; }
    if (hashGiven) {
        string s;
        getline(str, s);
        info.narHash = parseHash(htSHA256, s);
        getline(str, s);
        if (!string2Int(s, info.narSize)) throw Error("number expected");
    }
    getline(str, info.deriver);
    string s; int n;
    getline(str, s);
    if (!string2Int(s, n)) throw Error("number expected");
    while (n--) {
        getline(str, s);
        info.references.insert(s);
    }
    if (!str || str.eof()) throw Error("missing input");
    return info;
}


string showPaths(const PathSet & paths)
{
    string s;
    for (auto & i : paths) {
        if (s.size() != 0) s += ", ";
        s += "‘" + i + "’";
    }
    return s;
}


std::string ValidPathInfo::fingerprint() const
{
    if (narSize == 0 || !narHash)
        throw Error(format("cannot calculate fingerprint of path ‘%s’ because its size/hash is not known")
            % path);
    return
        "1;" + path + ";"
        + printHashType(narHash.type) + ":" + printHash32(narHash) + ";"
        + std::to_string(narSize) + ";"
        + concatStringsSep(",", references);
}


void ValidPathInfo::sign(const SecretKey & secretKey)
{
    sigs.insert(secretKey.signDetached(fingerprint()));
}


bool ValidPathInfo::isContentAddressed(const Store & store) const
{
    auto warn = [&]() {
        printError(format("warning: path ‘%s’ claims to be content-addressed but isn't") % path);
    };

    if (hasPrefix(ca, "text:")) {
        auto hash = parseHash(std::string(ca, 5));
        if (store.makeTextPath(storePathToName(path), hash, references) == path)
            return true;
        else
            warn();
    }

    else if (hasPrefix(ca, "fixed:")) {
        bool recursive = ca.compare(6, 2, "r:") == 0;
        auto hash = parseHash(std::string(ca, recursive ? 8 : 6));
        if (store.makeFixedOutputPath(recursive, hash, storePathToName(path)) == path)
            return true;
        else
            warn();
    }

    return false;
}


size_t ValidPathInfo::checkSignatures(const Store & store, const PublicKeys & publicKeys) const
{
    if (isContentAddressed(store)) return maxSigs;

    size_t good = 0;
    for (auto & sig : sigs)
        if (checkSignature(publicKeys, sig))
            good++;
    return good;
}


bool ValidPathInfo::checkSignature(const PublicKeys & publicKeys, const std::string & sig) const
{
    return verifyDetached(fingerprint(), sig, publicKeys);
}


Strings ValidPathInfo::shortRefs() const
{
    Strings refs;
    for (auto & r : references)
        refs.push_back(baseNameOf(r));
    return refs;
}


}


#include "local-store.hh"
#include "remote-store.hh"


namespace nix {


RegisterStoreImplementation::Implementations * RegisterStoreImplementation::implementations = 0;


ref<Store> openStoreAt(const std::string & uri_)
{
    auto uri(uri_);
    Store::Params params;
    auto q = uri.find('?');
    if (q != std::string::npos) {
        for (auto s : tokenizeString<Strings>(uri.substr(q + 1), "&")) {
            auto e = s.find('=');
            if (e != std::string::npos)
                params[s.substr(0, e)] = s.substr(e + 1);
        }
        uri = uri_.substr(0, q);
    }

    for (auto fun : *RegisterStoreImplementation::implementations) {
        auto store = fun(uri, params);
        if (store) return ref<Store>(store);
    }

    throw Error(format("don't know how to open Nix store ‘%s’") % uri);
}


ref<Store> openStore()
{
    return openStoreAt(getEnv("NIX_REMOTE"));
}


static RegisterStoreImplementation regStore([](
    const std::string & uri, const Store::Params & params)
    -> std::shared_ptr<Store>
{
    enum { mDaemon, mLocal, mAuto } mode;

    if (uri == "daemon") mode = mDaemon;
    else if (uri == "local") mode = mLocal;
    else if (uri == "") mode = mAuto;
    else return 0;

    if (mode == mAuto) {
        auto stateDir = get(params, "state", settings.nixStateDir);
        if (access(stateDir.c_str(), R_OK | W_OK) == 0)
            mode = mLocal;
        else if (pathExists(settings.nixDaemonSocketFile))
            mode = mDaemon;
        else
            mode = mLocal;
    }

    return mode == mDaemon
        ? std::shared_ptr<Store>(std::make_shared<RemoteStore>(params))
        : std::shared_ptr<Store>(std::make_shared<LocalStore>(params));
});


std::list<ref<Store>> getDefaultSubstituters()
{
    struct State {
        bool done = false;
        std::list<ref<Store>> stores;
    };
    static Sync<State> state_;

    auto state(state_.lock());

    if (state->done) return state->stores;

    StringSet done;

    auto addStore = [&](const std::string & uri) {
        if (done.count(uri)) return;
        done.insert(uri);
        state->stores.push_back(openStoreAt(uri));
    };

    for (auto uri : settings.get("substituters", Strings()))
        addStore(uri);

    for (auto uri : settings.get("binary-caches", Strings()))
        addStore(uri);

    for (auto uri : settings.get("extra-binary-caches", Strings()))
        addStore(uri);

    state->done = true;

    return state->stores;
}


}