Add "nix copy-sigs" command

This imports signatures from one store into another. E.g.

  $ nix copy-sigs -r /run/current-system -s https://cache.nixos.org/
  imported 595 signatures

src/libstore/binary-cache-store.hh

@@ -170,6 +170,9 @@ public:
 
     ref<FSAccessor> getFSAccessor() override;
 
+    void addSignatures(const Path & storePath, const StringSet & sigs)
+    { notImpl(); }
+
 };
 
 }

src/libstore/local-store.cc

@@ -312,7 +312,7 @@ void LocalStore::openDB(bool create)
     stmtRegisterValidPath.create(db,
         "insert into ValidPaths (path, hash, registrationTime, deriver, narSize, ultimate) values (?, ?, ?, ?, ?, ?);");
     stmtUpdatePathInfo.create(db,
-        "update ValidPaths set narSize = ?, hash = ?, ultimate = ? where path = ?;");
+        "update ValidPaths set narSize = ?, hash = ?, ultimate = ?, sigs = ? where path = ?;");
     stmtAddReference.create(db,
         "insert or replace into Refs (referrer, reference) values (?, ?);");
     stmtQueryPathInfo.create(db,
@@ -683,14 +683,14 @@ ValidPathInfo LocalStore::queryPathInfo(const Path & path)
 }
 
 
-/* Update path info in the database.  Currently only updates the
-   narSize field. */
+/* Update path info in the database. */
 void LocalStore::updatePathInfo(const ValidPathInfo & info)
 {
     stmtUpdatePathInfo.use()
         (info.narSize, info.narSize != 0)
         ("sha256:" + printHash(info.narHash))
         (info.ultimate ? 1 : 0, info.ultimate)
+        (concatStringsSep(" ", info.sigs), !info.sigs.empty())
         (info.path)
         .exec();
 }
@@ -1694,4 +1694,20 @@ void LocalStore::vacuumDB()
 }
 
 
+void LocalStore::addSignatures(const Path & storePath, const StringSet & sigs)
+{
+    retrySQLite<void>([&]() {
+        SQLiteTxn txn(db);
+
+        auto info = queryPathInfo(storePath);
+
+        info.sigs.insert(sigs.begin(), sigs.end());
+
+        updatePathInfo(info);
+
+        txn.commit();
+    });
+}
+
+
 }

src/libstore/local-store.hh

@@ -182,6 +182,8 @@ public:
 
     void setSubstituterEnv();
 
+    void addSignatures(const Path & storePath, const StringSet & sigs) override;
+
 private:
 
     Path schemaPath;

src/libstore/remote-store.cc

@@ -554,6 +554,15 @@ bool RemoteStore::verifyStore(bool checkContents, bool repair)
 }
 
 
+void RemoteStore::addSignatures(const Path & storePath, const StringSet & sigs)
+{
+    auto conn(connections->get());
+    conn->to << wopAddSignatures << storePath << sigs;
+    conn->processStderr();
+    readInt(conn->from);
+}
+
+
 RemoteStore::Connection::~Connection()
 {
     try {

src/libstore/remote-store.hh

@@ -93,6 +93,8 @@ public:
 
     bool verifyStore(bool checkContents, bool repair) override;
 
+    void addSignatures(const Path & storePath, const StringSet & sigs) override;
+
 private:
 
     struct Connection

src/libstore/store-api.hh

@@ -346,6 +346,10 @@ public:
     /* Return an object to access files in the Nix store. */
     virtual ref<FSAccessor> getFSAccessor() = 0;
 
+    /* Add signatures to the specified store path. The signatures are
+       not verified. */
+    virtual void addSignatures(const Path & storePath, const StringSet & sigs) = 0;
+
     /* Utility functions. */
 
     /* Read a derivation, after ensuring its existence through

src/libstore/worker-protocol.hh

@@ -45,6 +45,7 @@ typedef enum {
     wopOptimiseStore = 34,
     wopVerifyStore = 35,
     wopBuildDerivation = 36,
+    wopAddSignatures = 37,
 } WorkerOp;
 
 

src/nix-daemon/nix-daemon.cc

@@ -543,6 +543,18 @@ static void performOp(ref<LocalStore> store, bool trusted, unsigned int clientVe
         break;
     }
 
+    case wopAddSignatures: {
+        Path path = readStorePath(from);
+        StringSet sigs = readStrings<StringSet>(from);
+        startWork();
+        if (!trusted)
+            throw Error("you are not privileged to add signatures");
+        store->addSignatures(path, sigs);
+        stopWork();
+        to << 1;
+        break;
+    }
+
     default:
         throw Error(format("invalid operation %1%") % op);
     }

src/nix/sigs.cc

@@ -0,0 +1,133 @@
+#include "affinity.hh" // FIXME
+#include "command.hh"
+#include "progress-bar.hh"
+#include "shared.hh"
+#include "store-api.hh"
+#include "thread-pool.hh"
+
+#include <atomic>
+
+using namespace nix;
+
+struct CmdCopySigs : StorePathsCommand
+{
+    Strings substituterUris;
+
+    CmdCopySigs()
+    {
+        mkFlag('s', "substituter", {"store-uri"}, "use signatures from specified store", 1,
+            [&](Strings ss) { substituterUris.push_back(ss.front()); });
+    }
+
+    std::string name() override
+    {
+        return "copy-sigs";
+    }
+
+    std::string description() override
+    {
+        return "copy path signatures from substituters (like binary caches)";
+    }
+
+    void run(ref<Store> store, Paths storePaths) override
+    {
+        restoreAffinity(); // FIXME
+
+        if (substituterUris.empty())
+            throw UsageError("you must specify at least one subtituter using ‘-s’");
+
+        // FIXME: factor out commonality with MixVerify.
+        std::vector<ref<Store>> substituters;
+        for (auto & s : substituterUris)
+            substituters.push_back(openStoreAt(s));
+
+        ProgressBar progressBar;
+
+        ThreadPool pool;
+
+        std::atomic<size_t> done{0};
+        std::atomic<size_t> added{0};
+
+        auto showProgress = [&]() {
+            return (format("[%d/%d done]") % done % storePaths.size()).str();
+        };
+
+        progressBar.updateStatus(showProgress());
+
+        auto doPath = [&](const Path & storePath) {
+            auto activity(progressBar.startActivity(format("getting signatures for ‘%s’") % storePath));
+
+            checkInterrupt();
+
+            auto info = store->queryPathInfo(storePath);
+
+            StringSet newSigs;
+
+            for (auto & store2 : substituters) {
+                if (!store2->isValidPath(storePath)) continue;
+                auto info2 = store2->queryPathInfo(storePath);
+
+                /* Don't import signatures that don't match this
+                   binary. */
+                if (info.narHash != info2.narHash ||
+                    info.narSize != info2.narSize ||
+                    info.references != info2.references)
+                    continue;
+
+                for (auto & sig : info2.sigs)
+                    if (!info.sigs.count(sig))
+                        newSigs.insert(sig);
+            }
+
+            if (!newSigs.empty()) {
+                store->addSignatures(storePath, newSigs);
+                added += newSigs.size();
+            }
+
+            done++;
+            progressBar.updateStatus(showProgress());
+        };
+
+        for (auto & storePath : storePaths)
+            pool.enqueue(std::bind(doPath, storePath));
+
+        pool.process();
+
+        progressBar.done();
+
+        printMsg(lvlInfo, format("imported %d signatures") % added);
+    }
+};
+
+static RegisterCommand r1(make_ref<CmdCopySigs>());
+
+struct CmdQueryPathSigs : StorePathsCommand
+{
+    CmdQueryPathSigs()
+    {
+    }
+
+    std::string name() override
+    {
+        return "query-path-sigs";
+    }
+
+    std::string description() override
+    {
+        return "print store path signatures";
+    }
+
+    void run(ref<Store> store, Paths storePaths) override
+    {
+        for (auto & storePath : storePaths) {
+            auto info = store->queryPathInfo(storePath);
+            std::cout << storePath << " ";
+            if (info.ultimate) std::cout << "ultimate ";
+            for (auto & sig : info.sigs)
+                std::cout << sig << " ";
+            std::cout << "\n";
+        }
+    }
+};
+
+static RegisterCommand r2(make_ref<CmdQueryPathSigs>());