lix/src/libstore/derivations.cc

#include "derivations.hh"
#include "store-api.hh"
#include "globals.hh"
#include "util.hh"
#include "worker-protocol.hh"
#include "fs-accessor.hh"

namespace nix {

std::optional<StorePath> DerivationOutput::pathOpt(const Store & store, std::string_view drvName) const
{
    return std::visit(overloaded {
        [](DerivationOutputInputAddressed doi) -> std::optional<StorePath> {
            return { doi.path };
        },
        [&](DerivationOutputFixed dof) -> std::optional<StorePath> {
            return {
                store.makeFixedOutputPath(dof.hash.method, dof.hash.hash, drvName)
            };
        },
        [](DerivationOutputFloating dof) -> std::optional<StorePath> {
            return std::nullopt;
        },
    }, output);
}

const StorePath BasicDerivation::findOutput(const Store & store, const string & id) const
{
    auto i = outputs.find(id);
    if (i == outputs.end())
        throw Error("derivation has no output '%s'", id);
    return i->second.path(store, name);
}


bool BasicDerivation::isBuiltin() const
{
    return string(builder, 0, 8) == "builtin:";
}


StorePath writeDerivation(ref<Store> store,
    const Derivation & drv, std::string_view name, RepairFlag repair)
{
    auto references = drv.inputSrcs;
    for (auto & i : drv.inputDrvs)
        references.insert(i.first);
    /* Note that the outputs of a derivation are *not* references
       (that can be missing (of course) and should not necessarily be
       held during a garbage collection). */
    auto suffix = std::string(name) + drvExtension;
    auto contents = drv.unparse(*store, false);
    return settings.readOnlyMode
        ? store->computeStorePathForText(suffix, contents, references)
        : store->addTextToStore(suffix, contents, references, repair);
}


/* Read string `s' from stream `str'. */
static void expect(std::istream & str, const string & s)
{
    char s2[s.size()];
    str.read(s2, s.size());
    if (string(s2, s.size()) != s)
        throw FormatError("expected string '%1%'", s);
}


/* Read a C-style string from stream `str'. */
static string parseString(std::istream & str)
{
    string res;
    expect(str, "\"");
    int c;
    while ((c = str.get()) != '"')
        if (c == '\\') {
            c = str.get();
            if (c == 'n') res += '\n';
            else if (c == 'r') res += '\r';
            else if (c == 't') res += '\t';
            else res += c;
        }
        else res += c;
    return res;
}


static Path parsePath(std::istream & str)
{
    string s = parseString(str);
    if (s.size() == 0 || s[0] != '/')
        throw FormatError("bad path '%1%' in derivation", s);
    return s;
}


static bool endOfList(std::istream & str)
{
    if (str.peek() == ',') {
        str.get();
        return false;
    }
    if (str.peek() == ']') {
        str.get();
        return true;
    }
    return false;
}


static StringSet parseStrings(std::istream & str, bool arePaths)
{
    StringSet res;
    while (!endOfList(str))
        res.insert(arePaths ? parsePath(str) : parseString(str));
    return res;
}


static DerivationOutput parseDerivationOutput(const Store & store, std::istringstream & str)
{
    expect(str, ","); auto path = store.parseStorePath(parsePath(str));
    expect(str, ","); auto hashAlgo = parseString(str);
    expect(str, ","); const auto hash = parseString(str);
    expect(str, ")");

    if (hashAlgo != "") {
        auto method = FileIngestionMethod::Flat;
        if (string(hashAlgo, 0, 2) == "r:") {
            method = FileIngestionMethod::Recursive;
            hashAlgo = string(hashAlgo, 2);
        }
        const HashType hashType = parseHashType(hashAlgo);

        return hash != ""
            ? DerivationOutput {
                  .output = DerivationOutputFixed {
                      .hash = FixedOutputHash {
                          .method = std::move(method),
                          .hash = Hash(hash, hashType),
                      },
                  }
               }
            : DerivationOutput {
                  .output = DerivationOutputFloating {
                      .method = std::move(method),
                      .hashType = std::move(hashType),
                  },
              };
    } else
        return DerivationOutput {
            .output = DerivationOutputInputAddressed {
                .path = std::move(path),
            }
        };
}


static Derivation parseDerivation(const Store & store, std::string && s, std::string_view name)
{
    Derivation drv;
    drv.name = name;

    std::istringstream str(std::move(s));
    expect(str, "Derive([");

    /* Parse the list of outputs. */
    while (!endOfList(str)) {
        expect(str, "("); std::string id = parseString(str);
        auto output = parseDerivationOutput(store, str);
        drv.outputs.emplace(std::move(id), std::move(output));
    }

    /* Parse the list of input derivations. */
    expect(str, ",[");
    while (!endOfList(str)) {
        expect(str, "(");
        Path drvPath = parsePath(str);
        expect(str, ",[");
        drv.inputDrvs.insert_or_assign(store.parseStorePath(drvPath), parseStrings(str, false));
        expect(str, ")");
    }

    expect(str, ",["); drv.inputSrcs = store.parseStorePathSet(parseStrings(str, true));
    expect(str, ","); drv.platform = parseString(str);
    expect(str, ","); drv.builder = parseString(str);

    /* Parse the builder arguments. */
    expect(str, ",[");
    while (!endOfList(str))
        drv.args.push_back(parseString(str));

    /* Parse the environment variables. */
    expect(str, ",[");
    while (!endOfList(str)) {
        expect(str, "("); string name = parseString(str);
        expect(str, ","); string value = parseString(str);
        expect(str, ")");
        drv.env[name] = value;
    }

    expect(str, ")");
    return drv;
}


Derivation readDerivation(const Store & store, const Path & drvPath, std::string_view name)
{
    try {
        return parseDerivation(store, readFile(drvPath), name);
    } catch (FormatError & e) {
        throw Error("error parsing derivation '%1%': %2%", drvPath, e.msg());
    }
}


Derivation Store::derivationFromPath(const StorePath & drvPath)
{
    ensurePath(drvPath);
    return readDerivation(drvPath);
}


Derivation Store::readDerivation(const StorePath & drvPath)
{
    auto accessor = getFSAccessor();
    try {
        return parseDerivation(*this, accessor->readFile(printStorePath(drvPath)), Derivation::nameFromPath(drvPath));
    } catch (FormatError & e) {
        throw Error("error parsing derivation '%s': %s", printStorePath(drvPath), e.msg());
    }
}


static void printString(string & res, std::string_view s)
{
    char buf[s.size() * 2 + 2];
    char * p = buf;
    *p++ = '"';
    for (auto c : s)
        if (c == '\"' || c == '\\') { *p++ = '\\'; *p++ = c; }
        else if (c == '\n') { *p++ = '\\'; *p++ = 'n'; }
        else if (c == '\r') { *p++ = '\\'; *p++ = 'r'; }
        else if (c == '\t') { *p++ = '\\'; *p++ = 't'; }
        else *p++ = c;
    *p++ = '"';
    res.append(buf, p - buf);
}


static void printUnquotedString(string & res, std::string_view s)
{
    res += '"';
    res.append(s);
    res += '"';
}


template<class ForwardIterator>
static void printStrings(string & res, ForwardIterator i, ForwardIterator j)
{
    res += '[';
    bool first = true;
    for ( ; i != j; ++i) {
        if (first) first = false; else res += ',';
        printString(res, *i);
    }
    res += ']';
}


template<class ForwardIterator>
static void printUnquotedStrings(string & res, ForwardIterator i, ForwardIterator j)
{
    res += '[';
    bool first = true;
    for ( ; i != j; ++i) {
        if (first) first = false; else res += ',';
        printUnquotedString(res, *i);
    }
    res += ']';
}


string Derivation::unparse(const Store & store, bool maskOutputs,
    std::map<std::string, StringSet> * actualInputs) const
{
    string s;
    s.reserve(65536);
    s += "Derive([";

    bool first = true;
    for (auto & i : outputs) {
        if (first) first = false; else s += ',';
        s += '('; printUnquotedString(s, i.first);
        s += ','; printUnquotedString(s, maskOutputs ? "" : store.printStorePath(i.second.path(store, name)));
        std::visit(overloaded {
            [&](DerivationOutputInputAddressed doi) {
                s += ','; printUnquotedString(s, "");
                s += ','; printUnquotedString(s, "");
            },
            [&](DerivationOutputFixed dof) {
                s += ','; printUnquotedString(s, dof.hash.printMethodAlgo());
                s += ','; printUnquotedString(s, dof.hash.hash.to_string(Base16, false));
            },
            [&](DerivationOutputFloating dof) {
                s += ','; printUnquotedString(s, makeFileIngestionPrefix(dof.method) + printHashType(dof.hashType));
                s += ','; printUnquotedString(s, "");
            },
        }, i.second.output);
        s += ')';
    }

    s += "],[";
    first = true;
    if (actualInputs) {
        for (auto & i : *actualInputs) {
            if (first) first = false; else s += ',';
            s += '('; printUnquotedString(s, i.first);
            s += ','; printUnquotedStrings(s, i.second.begin(), i.second.end());
            s += ')';
        }
    } else {
        for (auto & i : inputDrvs) {
            if (first) first = false; else s += ',';
            s += '('; printUnquotedString(s, store.printStorePath(i.first));
            s += ','; printUnquotedStrings(s, i.second.begin(), i.second.end());
            s += ')';
        }
    }

    s += "],";
    auto paths = store.printStorePathSet(inputSrcs); // FIXME: slow
    printUnquotedStrings(s, paths.begin(), paths.end());

    s += ','; printUnquotedString(s, platform);
    s += ','; printString(s, builder);
    s += ','; printStrings(s, args.begin(), args.end());

    s += ",[";
    first = true;
    for (auto & i : env) {
        if (first) first = false; else s += ',';
        s += '('; printString(s, i.first);
        s += ','; printString(s, maskOutputs && outputs.count(i.first) ? "" : i.second);
        s += ')';
    }

    s += "])";

    return s;
}


// FIXME: remove
bool isDerivation(const string & fileName)
{
    return hasSuffix(fileName, drvExtension);
}


bool BasicDerivation::isFixedOutput() const
{
    return outputs.size() == 1 &&
        outputs.begin()->first == "out" &&
        std::holds_alternative<DerivationOutputFixed>(outputs.begin()->second.output);
}


DrvHashes drvHashes;

/* pathDerivationModulo and hashDerivationModulo are mutually recursive
 */

/* Look up the derivation by value and memoize the
   `hashDerivationModulo` call.
 */
static const DrvHashModulo & pathDerivationModulo(Store & store, const StorePath & drvPath)
{
    auto h = drvHashes.find(drvPath);
    if (h == drvHashes.end()) {
        assert(store.isValidPath(drvPath));
        // Cache it
        h = drvHashes.insert_or_assign(
            drvPath,
            hashDerivationModulo(
                store,
                store.readDerivation(drvPath),
                false)).first;
    }
    return h->second;
}

/* See the header for interface details. These are the implementation details.

   For fixed-output derivations, each hash in the map is not the
   corresponding output's content hash, but a hash of that hash along
   with other constant data. The key point is that the value is a pure
   function of the output's contents, and there are no preimage attacks
   either spoofing an output's contents for a derivation, or
   spoofing a derivation for an output's contents.

   For regular derivations, it looks up each subderivation from its hash
   and recurs. If the subderivation is also regular, it simply
   substitutes the derivation path with its hash. If the subderivation
   is fixed-output, however, it takes each output hash and pretends it
   is a derivation hash producing a single "out" output. This is so we
   don't leak the provenance of fixed outputs, reducing pointless cache
   misses as the build itself won't know this.
 */
DrvHashModulo hashDerivationModulo(Store & store, const Derivation & drv, bool maskOutputs)
{
    /* Return a fixed hash for fixed-output derivations. */
    if (drv.isFixedOutput()) {
        std::map<std::string, Hash> outputHashes;
        for (const auto & i : drv.outputs) {
            auto & dof = std::get<DerivationOutputFixed>(i.second.output);
            auto hash = hashString(htSHA256, "fixed:out:"
                + dof.hash.printMethodAlgo() + ":"
                + dof.hash.hash.to_string(Base16, false) + ":"
                + store.printStorePath(i.second.path(store, drv.name)));
            outputHashes.insert_or_assign(i.first, std::move(hash));
        }
        return outputHashes;
    }

    /* For other derivations, replace the inputs paths with recursive
       calls to this function. */
    std::map<std::string, StringSet> inputs2;
    for (auto & i : drv.inputDrvs) {
        const auto & res = pathDerivationModulo(store, i.first);
        std::visit(overloaded {
            // Regular non-CA derivation, replace derivation
            [&](Hash drvHash) {
                inputs2.insert_or_assign(drvHash.to_string(Base16, false), i.second);
            },
            // CA derivation's output hashes
            [&](CaOutputHashes outputHashes) {
                std::set<std::string> justOut = { "out" };
                for (auto & output : i.second) {
                    /* Put each one in with a single "out" output.. */
                    const auto h = outputHashes.at(output);
                    inputs2.insert_or_assign(
                        h.to_string(Base16, false),
                        justOut);
                }
            },
        }, res);
    }

    return hashString(htSHA256, drv.unparse(store, maskOutputs, &inputs2));
}


std::string StorePathWithOutputs::to_string(const Store & store) const
{
    return outputs.empty()
        ? store.printStorePath(path)
        : store.printStorePath(path) + "!" + concatStringsSep(",", outputs);
}


bool wantOutput(const string & output, const std::set<string> & wanted)
{
    return wanted.empty() || wanted.find(output) != wanted.end();
}


StorePathSet BasicDerivation::outputPaths(const Store & store) const
{
    StorePathSet paths;
    for (auto & i : outputs)
        paths.insert(i.second.path(store, name));
    return paths;
}

static DerivationOutput readDerivationOutput(Source & in, const Store & store)
{
    auto path = store.parseStorePath(readString(in));
    auto hashAlgo = readString(in);
    auto hash = readString(in);

    if (hashAlgo != "") {
        auto method = FileIngestionMethod::Flat;
        if (string(hashAlgo, 0, 2) == "r:") {
            method = FileIngestionMethod::Recursive;
            hashAlgo = string(hashAlgo, 2);
        }
        auto hashType = parseHashType(hashAlgo);
        return hash != ""
            ? DerivationOutput {
                  .output = DerivationOutputFixed {
                      .hash = FixedOutputHash {
                          .method = std::move(method),
                          .hash = Hash(hash, hashType),
                      },
                  }
               }
            : DerivationOutput {
                  .output = DerivationOutputFloating {
                      .method = std::move(method),
                      .hashType = std::move(hashType),
                  },
              };
    } else
        return DerivationOutput {
            .output = DerivationOutputInputAddressed {
                .path = std::move(path),
            }
        };
}

StringSet BasicDerivation::outputNames() const
{
    StringSet names;
    for (auto & i : outputs)
        names.insert(i.first);
    return names;
}


std::string_view BasicDerivation::nameFromPath(const StorePath & drvPath) {
    auto nameWithSuffix = drvPath.name();
    constexpr std::string_view extension = ".drv";
    assert(hasSuffix(nameWithSuffix, extension));
    nameWithSuffix.remove_suffix(extension.size());
    return nameWithSuffix;
}


Source & readDerivation(Source & in, const Store & store, BasicDerivation & drv, std::string_view name)
{
    drv.name = name;

    drv.outputs.clear();
    auto nr = readNum<size_t>(in);
    for (size_t n = 0; n < nr; n++) {
        auto name = readString(in);
        auto output = readDerivationOutput(in, store);
        drv.outputs.emplace(std::move(name), std::move(output));
    }

    drv.inputSrcs = readStorePaths<StorePathSet>(store, in);
    in >> drv.platform >> drv.builder;
    drv.args = readStrings<Strings>(in);

    nr = readNum<size_t>(in);
    for (size_t n = 0; n < nr; n++) {
        auto key = readString(in);
        auto value = readString(in);
        drv.env[key] = value;
    }

    return in;
}


void writeDerivation(Sink & out, const Store & store, const BasicDerivation & drv)
{
    out << drv.outputs.size();
    for (auto & i : drv.outputs) {
        out << i.first
            << store.printStorePath(i.second.path(store, drv.name));
        std::visit(overloaded {
            [&](DerivationOutputInputAddressed doi) {
                out << "" << "";
            },
            [&](DerivationOutputFixed dof) {
                out << dof.hash.printMethodAlgo()
                    << dof.hash.hash.to_string(Base16, false);
            },
            [&](DerivationOutputFloating dof) {
                out << (makeFileIngestionPrefix(dof.method) + printHashType(dof.hashType))
                    << "";
            },
        }, i.second.output);
    }
    writeStorePaths(store, out, drv.inputSrcs);
    out << drv.platform << drv.builder << drv.args;
    out << drv.env.size();
    for (auto & i : drv.env)
        out << i.first << i.second;
}


std::string hashPlaceholder(const std::string & outputName)
{
    // FIXME: memoize?
    return "/" + hashString(htSHA256, "nix-output:" + outputName).to_string(Base32, false);
}


}