diff --git a/doc/manual/src/SUMMARY.md.in b/doc/manual/src/SUMMARY.md.in index 69c721b57..cfbb38be8 100644 --- a/doc/manual/src/SUMMARY.md.in +++ b/doc/manual/src/SUMMARY.md.in @@ -98,6 +98,8 @@ - [Channels](command-ref/files/channels.md) - [Default Nix expression](command-ref/files/default-nix-expression.md) - [Architecture](architecture/architecture.md) +- [Protocols](protocols/protocols.md) + - [Serving Tarball Flakes](protocols/tarball-fetcher.md) - [Glossary](glossary.md) - [Contributing](contributing/contributing.md) - [Hacking](contributing/hacking.md) diff --git a/doc/manual/src/protocols/protocols.md b/doc/manual/src/protocols/protocols.md new file mode 100644 index 000000000..d6bf1d809 --- /dev/null +++ b/doc/manual/src/protocols/protocols.md @@ -0,0 +1,4 @@ +# Protocols + +This chapter documents various developer-facing interfaces provided by +Nix. diff --git a/doc/manual/src/protocols/tarball-fetcher.md b/doc/manual/src/protocols/tarball-fetcher.md new file mode 100644 index 000000000..0d3212303 --- /dev/null +++ b/doc/manual/src/protocols/tarball-fetcher.md @@ -0,0 +1,42 @@ +# Lockable HTTP Tarball Protocol + +Tarball flakes can be served as regular tarballs via HTTP or the file +system (for `file://` URLs). Unless the server implements the Lockable +HTTP Tarball protocol, it is the responsibility of the user to make sure that +the URL always produces the same tarball contents. + +An HTTP server can return an "immutable" HTTP URL appropriate for lock +files. This allows users to specify a tarball flake input in +`flake.nix` that requests the latest version of a flake +(e.g. `https://example.org/hello/latest.tar.gz`), while `flake.lock` +will record a URL whose contents will not change +(e.g. `https://example.org/hello/.tar.gz`). To do so, the +server must return an [HTTP `Link` header](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Link) with the `rel` attribute set to +`immutable`, as follows: + +``` +Link: ; rel="immutable" +``` + +(Note the required `<` and `>` characters around *flakeref*.) + +*flakeref* must be a tarball flakeref. It can contain flake attributes +such as `narHash`, `rev` and `revCount`. If `narHash` is included, its +value must be the NAR hash of the unpacked tarball (as computed via +`nix hash path`). Nix checks the contents of the returned tarball +against the `narHash` attribute. The `rev` and `revCount` attributes +are useful when the tarball flake is a mirror of a fetcher type that +has those attributes, such as Git or GitHub. They are not checked by +Nix. + +``` +Link: ; rel="immutable" +``` + +(The linebreaks in this example are for clarity and must not be included in the actual response.) + +For tarball flakes, the value of the `lastModified` flake attribute is +defined as the timestamp of the newest file inside the tarball. diff --git a/flake.nix b/flake.nix index a4ee80b32..bdbf54169 100644 --- a/flake.nix +++ b/flake.nix @@ -590,6 +590,8 @@ tests.sourcehutFlakes = runNixOSTestFor "x86_64-linux" ./tests/nixos/sourcehut-flakes.nix; + tests.tarballFlakes = runNixOSTestFor "x86_64-linux" ./tests/nixos/tarball-flakes.nix; + tests.containers = runNixOSTestFor "x86_64-linux" ./tests/nixos/containers/containers.nix; tests.setuid = lib.genAttrs diff --git a/src/libcmd/common-eval-args.cc b/src/libcmd/common-eval-args.cc index ff3abd534..7f97364a1 100644 --- a/src/libcmd/common-eval-args.cc +++ b/src/libcmd/common-eval-args.cc @@ -165,7 +165,7 @@ SourcePath lookupFileArg(EvalState & state, std::string_view s) { if (EvalSettings::isPseudoUrl(s)) { auto storePath = fetchers::downloadTarball( - state.store, EvalSettings::resolvePseudoUrl(s), "source", false).first.storePath; + state.store, EvalSettings::resolvePseudoUrl(s), "source", false).tree.storePath; return state.rootPath(CanonPath(state.store->toRealPath(storePath))); } diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y index 4d981712a..3b545fd84 100644 --- a/src/libexpr/parser.y +++ b/src/libexpr/parser.y @@ -793,7 +793,7 @@ std::pair EvalState::resolveSearchPathElem(const SearchPathEl if (EvalSettings::isPseudoUrl(elem.second)) { try { auto storePath = fetchers::downloadTarball( - store, EvalSettings::resolvePseudoUrl(elem.second), "source", false).first.storePath; + store, EvalSettings::resolvePseudoUrl(elem.second), "source", false).tree.storePath; res = { true, store->toRealPath(storePath) }; } catch (FileTransferError & e) { logWarning({ diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc index be8159cc8..1d23ef53b 100644 --- a/src/libexpr/primops/fetchTree.cc +++ b/src/libexpr/primops/fetchTree.cc @@ -266,7 +266,7 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v // https://github.com/NixOS/nix/issues/4313 auto storePath = unpack - ? fetchers::downloadTarball(state.store, *url, name, (bool) expectedHash).first.storePath + ? fetchers::downloadTarball(state.store, *url, name, (bool) expectedHash).tree.storePath : fetchers::downloadFile(state.store, *url, name, (bool) expectedHash).storePath; if (expectedHash) { diff --git a/src/libfetchers/attrs.hh b/src/libfetchers/attrs.hh index 1a14bb023..9f885a793 100644 --- a/src/libfetchers/attrs.hh +++ b/src/libfetchers/attrs.hh @@ -2,6 +2,7 @@ ///@file #include "types.hh" +#include "hash.hh" #include diff --git a/src/libfetchers/fetchers.cc b/src/libfetchers/fetchers.cc index 91db3a9eb..2860c1ceb 100644 --- a/src/libfetchers/fetchers.cc +++ b/src/libfetchers/fetchers.cc @@ -159,6 +159,12 @@ std::pair Input::fetch(ref store) const input.to_string(), *prevLastModified); } + if (auto prevRev = getRev()) { + if (input.getRev() != prevRev) + throw Error("'rev' attribute mismatch in input '%s', expected %s", + input.to_string(), prevRev->gitRev()); + } + if (auto prevRevCount = getRevCount()) { if (input.getRevCount() != prevRevCount) throw Error("'revCount' attribute mismatch in input '%s', expected %d", diff --git a/src/libfetchers/fetchers.hh b/src/libfetchers/fetchers.hh index 498ad7e4d..d0738f619 100644 --- a/src/libfetchers/fetchers.hh +++ b/src/libfetchers/fetchers.hh @@ -158,6 +158,7 @@ struct DownloadFileResult StorePath storePath; std::string etag; std::string effectiveUrl; + std::optional immutableUrl; }; DownloadFileResult downloadFile( @@ -167,7 +168,14 @@ DownloadFileResult downloadFile( bool locked, const Headers & headers = {}); -std::pair downloadTarball( +struct DownloadTarballResult +{ + Tree tree; + time_t lastModified; + std::optional immutableUrl; +}; + +DownloadTarballResult downloadTarball( ref store, const std::string & url, const std::string & name, diff --git a/src/libfetchers/github.cc b/src/libfetchers/github.cc index 6c1d573ce..80598e7f8 100644 --- a/src/libfetchers/github.cc +++ b/src/libfetchers/github.cc @@ -207,21 +207,21 @@ struct GitArchiveInputScheme : InputScheme auto url = getDownloadUrl(input); - auto [tree, lastModified] = downloadTarball(store, url.url, input.getName(), true, url.headers); + auto result = downloadTarball(store, url.url, input.getName(), true, url.headers); - input.attrs.insert_or_assign("lastModified", uint64_t(lastModified)); + input.attrs.insert_or_assign("lastModified", uint64_t(result.lastModified)); getCache()->add( store, lockedAttrs, { {"rev", rev->gitRev()}, - {"lastModified", uint64_t(lastModified)} + {"lastModified", uint64_t(result.lastModified)} }, - tree.storePath, + result.tree.storePath, true); - return {std::move(tree.storePath), input}; + return {result.tree.storePath, input}; } }; diff --git a/src/libfetchers/tarball.cc b/src/libfetchers/tarball.cc index 96fe5faca..e42aca6db 100644 --- a/src/libfetchers/tarball.cc +++ b/src/libfetchers/tarball.cc @@ -32,7 +32,8 @@ DownloadFileResult downloadFile( return { .storePath = std::move(cached->storePath), .etag = getStrAttr(cached->infoAttrs, "etag"), - .effectiveUrl = getStrAttr(cached->infoAttrs, "url") + .effectiveUrl = getStrAttr(cached->infoAttrs, "url"), + .immutableUrl = maybeGetStrAttr(cached->infoAttrs, "immutableUrl"), }; }; @@ -55,12 +56,14 @@ DownloadFileResult downloadFile( } // FIXME: write to temporary file. - Attrs infoAttrs({ {"etag", res.etag}, {"url", res.effectiveUri}, }); + if (res.immutableUrl) + infoAttrs.emplace("immutableUrl", *res.immutableUrl); + std::optional storePath; if (res.cached) { @@ -111,10 +114,11 @@ DownloadFileResult downloadFile( .storePath = std::move(*storePath), .etag = res.etag, .effectiveUrl = res.effectiveUri, + .immutableUrl = res.immutableUrl, }; } -std::pair downloadTarball( +DownloadTarballResult downloadTarball( ref store, const std::string & url, const std::string & name, @@ -131,8 +135,9 @@ std::pair downloadTarball( if (cached && !cached->expired) return { - Tree { .actualPath = store->toRealPath(cached->storePath), .storePath = std::move(cached->storePath) }, - getIntAttr(cached->infoAttrs, "lastModified") + .tree = Tree { .actualPath = store->toRealPath(cached->storePath), .storePath = std::move(cached->storePath) }, + .lastModified = (time_t) getIntAttr(cached->infoAttrs, "lastModified"), + .immutableUrl = maybeGetStrAttr(cached->infoAttrs, "immutableUrl"), }; auto res = downloadFile(store, url, name, locked, headers); @@ -160,6 +165,9 @@ std::pair downloadTarball( {"etag", res.etag}, }); + if (res.immutableUrl) + infoAttrs.emplace("immutableUrl", *res.immutableUrl); + getCache()->add( store, inAttrs, @@ -168,8 +176,9 @@ std::pair downloadTarball( locked); return { - Tree { .actualPath = store->toRealPath(*unpackedStorePath), .storePath = std::move(*unpackedStorePath) }, - lastModified, + .tree = Tree { .actualPath = store->toRealPath(*unpackedStorePath), .storePath = std::move(*unpackedStorePath) }, + .lastModified = lastModified, + .immutableUrl = res.immutableUrl, }; } @@ -189,21 +198,33 @@ struct CurlInputScheme : InputScheme virtual bool isValidURL(const ParsedURL & url) const = 0; - std::optional inputFromURL(const ParsedURL & url) const override + std::optional inputFromURL(const ParsedURL & _url) const override { - if (!isValidURL(url)) + if (!isValidURL(_url)) return std::nullopt; Input input; - auto urlWithoutApplicationScheme = url; - urlWithoutApplicationScheme.scheme = parseUrlScheme(url.scheme).transport; + auto url = _url; + + url.scheme = parseUrlScheme(url.scheme).transport; - input.attrs.insert_or_assign("type", inputType()); - input.attrs.insert_or_assign("url", urlWithoutApplicationScheme.to_string()); auto narHash = url.query.find("narHash"); if (narHash != url.query.end()) input.attrs.insert_or_assign("narHash", narHash->second); + + if (auto i = get(url.query, "rev")) + input.attrs.insert_or_assign("rev", *i); + + if (auto i = get(url.query, "revCount")) + if (auto n = string2Int(*i)) + input.attrs.insert_or_assign("revCount", *n); + + url.query.erase("rev"); + url.query.erase("revCount"); + + input.attrs.insert_or_assign("type", inputType()); + input.attrs.insert_or_assign("url", url.to_string()); return input; } @@ -212,7 +233,8 @@ struct CurlInputScheme : InputScheme auto type = maybeGetStrAttr(attrs, "type"); if (type != inputType()) return {}; - std::set allowedNames = {"type", "url", "narHash", "name", "unpack"}; + // FIXME: some of these only apply to TarballInputScheme. + std::set allowedNames = {"type", "url", "narHash", "name", "unpack", "rev", "revCount"}; for (auto & [name, value] : attrs) if (!allowedNames.count(name)) throw Error("unsupported %s input attribute '%s'", *type, name); @@ -275,10 +297,22 @@ struct TarballInputScheme : CurlInputScheme : hasTarballExtension(url.path)); } - std::pair fetch(ref store, const Input & input) override + std::pair fetch(ref store, const Input & _input) override { - auto tree = downloadTarball(store, getStrAttr(input.attrs, "url"), input.getName(), false).first; - return {std::move(tree.storePath), input}; + Input input(_input); + auto url = getStrAttr(input.attrs, "url"); + auto result = downloadTarball(store, url, input.getName(), false); + + if (result.immutableUrl) { + auto immutableInput = Input::fromURL(*result.immutableUrl); + // FIXME: would be nice to support arbitrary flakerefs + // here, e.g. git flakes. + if (immutableInput.getType() != "tarball") + throw Error("tarball 'Link' headers that redirect to non-tarball URLs are not supported"); + input = immutableInput; + } + + return {result.tree.storePath, std::move(input)}; } }; diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc index 2346accbe..38b691279 100644 --- a/src/libstore/filetransfer.cc +++ b/src/libstore/filetransfer.cc @@ -186,9 +186,9 @@ struct curlFileTransfer : public FileTransfer size_t realSize = size * nmemb; std::string line((char *) contents, realSize); printMsg(lvlVomit, "got header for '%s': %s", request.uri, trim(line)); + static std::regex statusLine("HTTP/[^ ]+ +[0-9]+(.*)", std::regex::extended | std::regex::icase); - std::smatch match; - if (std::regex_match(line, match, statusLine)) { + if (std::smatch match; std::regex_match(line, match, statusLine)) { result.etag = ""; result.data.clear(); result.bodySize = 0; @@ -196,9 +196,11 @@ struct curlFileTransfer : public FileTransfer acceptRanges = false; encoding = ""; } else { + auto i = line.find(':'); if (i != std::string::npos) { std::string name = toLower(trim(line.substr(0, i))); + if (name == "etag") { result.etag = trim(line.substr(i + 1)); /* Hack to work around a GitHub bug: it sends @@ -212,10 +214,22 @@ struct curlFileTransfer : public FileTransfer debug("shutting down on 200 HTTP response with expected ETag"); return 0; } - } else if (name == "content-encoding") + } + + else if (name == "content-encoding") encoding = trim(line.substr(i + 1)); + else if (name == "accept-ranges" && toLower(trim(line.substr(i + 1))) == "bytes") acceptRanges = true; + + else if (name == "link" || name == "x-amz-meta-link") { + auto value = trim(line.substr(i + 1)); + static std::regex linkRegex("<([^>]*)>; rel=\"immutable\"", std::regex::extended | std::regex::icase); + if (std::smatch match; std::regex_match(value, match, linkRegex)) + result.immutableUrl = match.str(1); + else + debug("got invalid link header '%s'", value); + } } } return realSize; @@ -345,7 +359,7 @@ struct curlFileTransfer : public FileTransfer { auto httpStatus = getHTTPStatus(); - char * effectiveUriCStr; + char * effectiveUriCStr = nullptr; curl_easy_getinfo(req, CURLINFO_EFFECTIVE_URL, &effectiveUriCStr); if (effectiveUriCStr) result.effectiveUri = effectiveUriCStr; diff --git a/src/libstore/filetransfer.hh b/src/libstore/filetransfer.hh index 378c6ff78..a3b0dde1f 100644 --- a/src/libstore/filetransfer.hh +++ b/src/libstore/filetransfer.hh @@ -80,6 +80,10 @@ struct FileTransferResult std::string effectiveUri; std::string data; uint64_t bodySize = 0; + /* An "immutable" URL for this resource (i.e. one whose contents + will never change), as returned by the `Link: ; + rel="immutable"` header. */ + std::optional immutableUrl; }; class Store; diff --git a/tests/nixos/tarball-flakes.nix b/tests/nixos/tarball-flakes.nix new file mode 100644 index 000000000..1d43a5d04 --- /dev/null +++ b/tests/nixos/tarball-flakes.nix @@ -0,0 +1,84 @@ +{ lib, config, nixpkgs, ... }: + +let + pkgs = config.nodes.machine.nixpkgs.pkgs; + + root = pkgs.runCommand "nixpkgs-flake" {} + '' + mkdir -p $out/stable + + set -x + dir=nixpkgs-${nixpkgs.shortRev} + cp -prd ${nixpkgs} $dir + # Set the correct timestamp in the tarball. + find $dir -print0 | xargs -0 touch -t ${builtins.substring 0 12 nixpkgs.lastModifiedDate}.${builtins.substring 12 2 nixpkgs.lastModifiedDate} -- + tar cfz $out/stable/${nixpkgs.rev}.tar.gz $dir --hard-dereference + + echo 'Redirect "/latest.tar.gz" "/stable/${nixpkgs.rev}.tar.gz"' > $out/.htaccess + + echo 'Header set Link "; rel=\"immutable\""' > $out/stable/.htaccess + ''; +in + +{ + name = "tarball-flakes"; + + nodes = + { + machine = + { config, pkgs, ... }: + { networking.firewall.allowedTCPPorts = [ 80 ]; + + services.httpd.enable = true; + services.httpd.adminAddr = "foo@example.org"; + services.httpd.extraConfig = '' + ErrorLog syslog:local6 + ''; + services.httpd.virtualHosts."localhost" = + { servedDirs = + [ { urlPath = "/"; + dir = root; + } + ]; + }; + + virtualisation.writableStore = true; + virtualisation.diskSize = 2048; + virtualisation.additionalPaths = [ pkgs.hello pkgs.fuse ]; + virtualisation.memorySize = 4096; + nix.settings.substituters = lib.mkForce [ ]; + nix.extraOptions = "experimental-features = nix-command flakes"; + }; + }; + + testScript = { nodes }: '' + # fmt: off + import json + + start_all() + + machine.wait_for_unit("httpd.service") + + out = machine.succeed("nix flake metadata --json http://localhost/latest.tar.gz") + print(out) + info = json.loads(out) + + # Check that we got redirected to the immutable URL. + assert info["locked"]["url"] == "http://localhost/stable/${nixpkgs.rev}.tar.gz" + + # Check that we got the rev and revCount attributes. + assert info["revision"] == "${nixpkgs.rev}" + assert info["revCount"] == 1234 + + # Check that fetching with rev/revCount/narHash succeeds. + machine.succeed("nix flake metadata --json http://localhost/latest.tar.gz?rev=" + info["revision"]) + machine.succeed("nix flake metadata --json http://localhost/latest.tar.gz?revCount=" + str(info["revCount"])) + machine.succeed("nix flake metadata --json http://localhost/latest.tar.gz?narHash=" + info["locked"]["narHash"]) + + # Check that fetching fails if we provide incorrect attributes. + machine.fail("nix flake metadata --json http://localhost/latest.tar.gz?rev=493300eb13ae6fb387fbd47bf54a85915acc31c0") + machine.fail("nix flake metadata --json http://localhost/latest.tar.gz?revCount=789") + machine.fail("nix flake metadata --json http://localhost/latest.tar.gz?narHash=sha256-tbudgBSg+bHWHiHnlteNzN8TUvI80ygS9IULh4rklEw=") + ''; + +}