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Merge pull request #8477 from edolstra/tarball-flake-redirects

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Tarball flake improvements
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Eelco Dolstra 2023-06-16 18:03:50 +02:00 committed by GitHub
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15 changed files with 231 additions and 30 deletions
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2
doc/manual/src/SUMMARY.md.in
View file

@ -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)

4
doc/manual/src/protocols/protocols.md Normal file
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@ -0,0 +1,4 @@
# Protocols
This chapter documents various developer-facing interfaces provided by
Nix.

42
doc/manual/src/protocols/tarball-fetcher.md Normal file
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@ -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/<revision>.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: <flakeref>; 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: <https://example.org/hello/442793d9ec0584f6a6e82fa253850c8085bb150a.tar.gz
?rev=442793d9ec0584f6a6e82fa253850c8085bb150a
&revCount=835
&narHash=sha256-GUm8Uh/U74zFCwkvt9Mri4DSM%2BmHj3tYhXUkYpiv31M%3D>; 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.

2
flake.nix
View file

@ -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

2
src/libcmd/common-eval-args.cc
View file

@ -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)));
}

2
src/libexpr/parser.y
View file

@ -793,7 +793,7 @@ std::pair<bool, std::string> 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({

2
src/libexpr/primops/fetchTree.cc
View file

@ -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) {

1
src/libfetchers/attrs.hh
View file

@ -2,6 +2,7 @@
///@file
#include "types.hh"
#include "hash.hh"
#include <variant>

6
src/libfetchers/fetchers.cc
View file

@ -159,6 +159,12 @@ std::pair<Tree, Input> Input::fetch(ref<Store> 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",

10
src/libfetchers/fetchers.hh
View file

@ -158,6 +158,7 @@ struct DownloadFileResult
StorePath storePath;
std::string etag;
std::string effectiveUrl;
std::optional<std::string> immutableUrl;
};
DownloadFileResult downloadFile(
@ -167,7 +168,14 @@ DownloadFileResult downloadFile(
bool locked,
const Headers & headers = {});
std::pair<Tree, time_t> downloadTarball(
struct DownloadTarballResult
{
Tree tree;
time_t lastModified;
std::optional<std::string> immutableUrl;
};
DownloadTarballResult downloadTarball(
ref<Store> store,
const std::string & url,
const std::string & name,

10
src/libfetchers/github.cc
View file

@ -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};
}
};

68
src/libfetchers/tarball.cc
View file

@ -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> 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<Tree, time_t> downloadTarball(
DownloadTarballResult downloadTarball(
ref<Store> store,
const std::string & url,
const std::string & name,
@ -131,8 +135,9 @@ std::pair<Tree, time_t> 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<Tree, time_t> downloadTarball(
{"etag", res.etag},
});
if (res.immutableUrl)
infoAttrs.emplace("immutableUrl", *res.immutableUrl);
getCache()->add(
store,
inAttrs,
@ -168,8 +176,9 @@ std::pair<Tree, time_t> 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<Input> inputFromURL(const ParsedURL & url) const override
std::optional<Input> 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<uint64_t>(*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<std::string> allowedNames = {"type", "url", "narHash", "name", "unpack"};
// FIXME: some of these only apply to TarballInputScheme.
std::set<std::string> 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<StorePath, Input> fetch(ref<Store> store, const Input & input) override
std::pair<StorePath, Input> fetch(ref<Store> 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)};
}
};

22
src/libstore/filetransfer.cc
View file

@ -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;

4
src/libstore/filetransfer.hh
View file

@ -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: <url>;
rel="immutable"` header. */
std::optional<std::string> immutableUrl;
};
class Store;

84
tests/nixos/tarball-flakes.nix Normal file
View file

@ -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"' > $out/.htaccess
echo 'Header set Link "<http://localhost/stable/${nixpkgs.rev}.tar.gz?rev=${nixpkgs.rev}&revCount=1234>; 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=")
'';
}