diff options
Diffstat (limited to 'src/libexpr/primops/fetchClosure.cc')
| -rw-r--r-- | src/libexpr/primops/fetchClosure.cc | 250 |
1 files changed, 187 insertions, 63 deletions
diff --git a/src/libexpr/primops/fetchClosure.cc b/src/libexpr/primops/fetchClosure.cc index bae849f61..7fe8203f4 100644 --- a/src/libexpr/primops/fetchClosure.cc +++ b/src/libexpr/primops/fetchClosure.cc @@ -5,37 +5,150 @@ namespace nix { +/** + * Handler for the content addressed case. + * + * @param state Evaluator state and store to write to. + * @param fromStore Store containing the path to rewrite. + * @param fromPath Source path to be rewritten. + * @param toPathMaybe Path to write the rewritten path to. If empty, the error shows the actual path. + * @param v Return `Value` + */ +static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, const std::optional<StorePath> & toPathMaybe, Value &v) { + + // establish toPath or throw + + if (!toPathMaybe || !state.store->isValidPath(*toPathMaybe)) { + auto rewrittenPath = makeContentAddressed(fromStore, *state.store, fromPath); + if (toPathMaybe && *toPathMaybe != rewrittenPath) + throw Error({ + .msg = hintfmt("rewriting '%s' to content-addressed form yielded '%s', while '%s' was expected", + state.store->printStorePath(fromPath), + state.store->printStorePath(rewrittenPath), + state.store->printStorePath(*toPathMaybe)), + .errPos = state.positions[pos] + }); + if (!toPathMaybe) + throw Error({ + .msg = hintfmt( + "rewriting '%s' to content-addressed form yielded '%s'\n" + "Use this value for the 'toPath' attribute passed to 'fetchClosure'", + state.store->printStorePath(fromPath), + state.store->printStorePath(rewrittenPath)), + .errPos = state.positions[pos] + }); + } + + auto toPath = *toPathMaybe; + + // check and return + + auto resultInfo = state.store->queryPathInfo(toPath); + + if (!resultInfo->isContentAddressed(*state.store)) { + // We don't perform the rewriting when outPath already exists, as an optimisation. + // However, we can quickly detect a mistake if the toPath is input addressed. + throw Error({ + .msg = hintfmt( + "The 'toPath' value '%s' is input-addressed, so it can't possibly be the result of rewriting to a content-addressed path.\n\n" + "Set 'toPath' to an empty string to make Nix report the correct content-addressed path.", + state.store->printStorePath(toPath)), + .errPos = state.positions[pos] + }); + } + + state.mkStorePathString(toPath, v); +} + +/** + * Fetch the closure and make sure it's content addressed. + */ +static void runFetchClosureWithContentAddressedPath(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, Value & v) { + + if (!state.store->isValidPath(fromPath)) + copyClosure(fromStore, *state.store, RealisedPath::Set { fromPath }); + + auto info = state.store->queryPathInfo(fromPath); + + if (!info->isContentAddressed(*state.store)) { + throw Error({ + .msg = hintfmt( + "The 'fromPath' value '%s' is input-addressed, but 'inputAddressed' is set to 'false' (default).\n\n" + "If you do intend to fetch an input-addressed store path, add\n\n" + " inputAddressed = true;\n\n" + "to the 'fetchClosure' arguments.\n\n" + "Note that to ensure authenticity input-addressed store paths, users must configure a trusted binary cache public key on their systems. This is not needed for content-addressed paths.", + state.store->printStorePath(fromPath)), + .errPos = state.positions[pos] + }); + } + + state.mkStorePathString(fromPath, v); +} + +/** + * Fetch the closure and make sure it's input addressed. + */ +static void runFetchClosureWithInputAddressedPath(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, Value & v) { + + if (!state.store->isValidPath(fromPath)) + copyClosure(fromStore, *state.store, RealisedPath::Set { fromPath }); + + auto info = state.store->queryPathInfo(fromPath); + + if (info->isContentAddressed(*state.store)) { + throw Error({ + .msg = hintfmt( + "The store object referred to by 'fromPath' at '%s' is not input-addressed, but 'inputAddressed' is set to 'true'.\n\n" + "Remove the 'inputAddressed' attribute (it defaults to 'false') to expect 'fromPath' to be content-addressed", + state.store->printStorePath(fromPath)), + .errPos = state.positions[pos] + }); + } + + state.mkStorePathString(fromPath, v); +} + +typedef std::optional<StorePath> StorePathOrGap; + static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * args, Value & v) { state.forceAttrs(*args[0], pos, "while evaluating the argument passed to builtins.fetchClosure"); std::optional<std::string> fromStoreUrl; std::optional<StorePath> fromPath; - bool toCA = false; - std::optional<StorePath> toPath; + std::optional<StorePathOrGap> toPath; + std::optional<bool> inputAddressedMaybe; for (auto & attr : *args[0]->attrs) { const auto & attrName = state.symbols[attr.name]; + auto attrHint = [&]() -> std::string { + return "while evaluating the '" + attrName + "' attribute passed to builtins.fetchClosure"; + }; if (attrName == "fromPath") { NixStringContext context; - fromPath = state.coerceToStorePath(attr.pos, *attr.value, context, - "while evaluating the 'fromPath' attribute passed to builtins.fetchClosure"); + fromPath = state.coerceToStorePath(attr.pos, *attr.value, context, attrHint()); } else if (attrName == "toPath") { state.forceValue(*attr.value, attr.pos); - toCA = true; - if (attr.value->type() != nString || attr.value->string.s != std::string("")) { + bool isEmptyString = attr.value->type() == nString && attr.value->string.s == std::string(""); + if (isEmptyString) { + toPath = StorePathOrGap {}; + } + else { NixStringContext context; - toPath = state.coerceToStorePath(attr.pos, *attr.value, context, - "while evaluating the 'toPath' attribute passed to builtins.fetchClosure"); + toPath = state.coerceToStorePath(attr.pos, *attr.value, context, attrHint()); } } else if (attrName == "fromStore") fromStoreUrl = state.forceStringNoCtx(*attr.value, attr.pos, - "while evaluating the 'fromStore' attribute passed to builtins.fetchClosure"); + attrHint()); + + else if (attrName == "inputAddressed") + inputAddressedMaybe = state.forceBool(*attr.value, attr.pos, attrHint()); else throw Error({ @@ -50,6 +163,18 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg .errPos = state.positions[pos] }); + bool inputAddressed = inputAddressedMaybe.value_or(false); + + if (inputAddressed) { + if (toPath) + throw Error({ + .msg = hintfmt("attribute '%s' is set to true, but '%s' is also set. Please remove one of them", + "inputAddressed", + "toPath"), + .errPos = state.positions[pos] + }); + } + if (!fromStoreUrl) throw Error({ .msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromStore"), @@ -74,55 +199,40 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg auto fromStore = openStore(parsedURL.to_string()); - if (toCA) { - if (!toPath || !state.store->isValidPath(*toPath)) { - auto remappings = makeContentAddressed(*fromStore, *state.store, { *fromPath }); - auto i = remappings.find(*fromPath); - assert(i != remappings.end()); - if (toPath && *toPath != i->second) - throw Error({ - .msg = hintfmt("rewriting '%s' to content-addressed form yielded '%s', while '%s' was expected", - state.store->printStorePath(*fromPath), - state.store->printStorePath(i->second), - state.store->printStorePath(*toPath)), - .errPos = state.positions[pos] - }); - if (!toPath) - throw Error({ - .msg = hintfmt( - "rewriting '%s' to content-addressed form yielded '%s'; " - "please set this in the 'toPath' attribute passed to 'fetchClosure'", - state.store->printStorePath(*fromPath), - state.store->printStorePath(i->second)), - .errPos = state.positions[pos] - }); - } - } else { - if (!state.store->isValidPath(*fromPath)) - copyClosure(*fromStore, *state.store, RealisedPath::Set { *fromPath }); - toPath = fromPath; - } - - /* In pure mode, require a CA path. */ - if (evalSettings.pureEval) { - auto info = state.store->queryPathInfo(*toPath); - if (!info->isContentAddressed(*state.store)) - throw Error({ - .msg = hintfmt("in pure mode, 'fetchClosure' requires a content-addressed path, which '%s' isn't", - state.store->printStorePath(*toPath)), - .errPos = state.positions[pos] - }); - } - - state.mkStorePathString(*toPath, v); + if (toPath) + runFetchClosureWithRewrite(state, pos, *fromStore, *fromPath, *toPath, v); + else if (inputAddressed) + runFetchClosureWithInputAddressedPath(state, pos, *fromStore, *fromPath, v); + else + runFetchClosureWithContentAddressedPath(state, pos, *fromStore, *fromPath, v); } static RegisterPrimOp primop_fetchClosure({ .name = "__fetchClosure", .args = {"args"}, .doc = R"( - Fetch a Nix store closure from a binary cache, rewriting it into - content-addressed form. For example, + Fetch a store path [closure](@docroot@/glossary.md#gloss-closure) from a binary cache, and return the store path as a string with context. + + This function can be invoked in three ways, that we will discuss in order of preference. + + **Fetch a content-addressed store path** + + Example: + + ```nix + builtins.fetchClosure { + fromStore = "https://cache.nixos.org"; + fromPath = /nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1; + } + ``` + + This is the simplest invocation, and it does not require the user of the expression to configure [`trusted-public-keys`](@docroot@/command-ref/conf-file.md#conf-trusted-public-keys) to ensure their authenticity. + + If your store path is [input addressed](@docroot@/glossary.md#gloss-input-addressed-store-object) instead of content addressed, consider the other two invocations. + + **Fetch any store path and rewrite it to a fully content-addressed store path** + + Example: ```nix builtins.fetchClosure { @@ -132,28 +242,42 @@ static RegisterPrimOp primop_fetchClosure({ } ``` - fetches `/nix/store/r2jd...` from the specified binary cache, + This example fetches `/nix/store/r2jd...` from the specified binary cache, and rewrites it into the content-addressed store path `/nix/store/ldbh...`. - If `fromPath` is already content-addressed, or if you are - allowing impure evaluation (`--impure`), then `toPath` may be - omitted. + Like the previous example, no extra configuration or privileges are required. To find out the correct value for `toPath` given a `fromPath`, - you can use `nix store make-content-addressed`: + use [`nix store make-content-addressed`](@docroot@/command-ref/new-cli/nix3-store-make-content-addressed.md): ```console # nix store make-content-addressed --from https://cache.nixos.org /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1 rewrote '/nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1' to '/nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1' ``` - This function is similar to `builtins.storePath` in that it - allows you to use a previously built store path in a Nix - expression. However, it is more reproducible because it requires - specifying a binary cache from which the path can be fetched. - Also, requiring a content-addressed final store path avoids the - need for users to configure binary cache public keys. + Alternatively, set `toPath = ""` and find the correct `toPath` in the error message. + + **Fetch an input-addressed store path as is** + + Example: + + ```nix + builtins.fetchClosure { + fromStore = "https://cache.nixos.org"; + fromPath = /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1; + inputAddressed = true; + } + ``` + + It is possible to fetch an [input-addressed store path](@docroot@/glossary.md#gloss-input-addressed-store-object) and return it as is. + However, this is the least preferred way of invoking `fetchClosure`, because it requires that the input-addressed paths are trusted by the Nix configuration. + + **`builtins.storePath`** + + `fetchClosure` is similar to [`builtins.storePath`](#builtins-storePath) in that it allows you to use a previously built store path in a Nix expression. + However, `fetchClosure` is more reproducible because it specifies a binary cache from which the path can be fetched. + Also, using content-addressed store paths does not require users to configure [`trusted-public-keys`](@docroot@/command-ref/conf-file.md#conf-trusted-public-keys) to ensure their authenticity. )", .fun = prim_fetchClosure, .experimentalFeature = Xp::FetchClosure, |