Use libsodium instead of OpenSSL for binary cache signing

Sodium's Ed25519 signatures are much shorter than OpenSSL's RSA
signatures. Public keys are also much shorter, so they're now
specified directly in the nix.conf option ‘binary-cache-public-keys’.

The new command ‘nix-store --generate-binary-cache-key’ generates and
prints a public and secret key.

2 files changed, 33 insertions, 3 deletions

diff --git a/src/nix-store/local.mk b/src/nix-store/local.mk
index b887fe03389b..84ff15b241f3 100644
--- a/src/nix-store/local.mk
+++ b/src/nix-store/local.mk
@@ -6,6 +6,6 @@ nix-store_SOURCES := $(wildcard $(d)/*.cc)
 
 nix-store_LIBS = libmain libstore libutil libformat
 
-nix-store_LDFLAGS = -lbz2 -pthread
+nix-store_LDFLAGS = -lbz2 -pthread $(SODIUM_LIBS)
 
 nix-store_CXXFLAGS = -DCURL=\"$(curl)\"
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 87bc8c379de5..18739736838e 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -20,6 +20,8 @@
 
 #include <bzlib.h>
 
+#include <sodium.h>
+
 
 using namespace nix;
 using std::cin;
@@ -1006,6 +1008,32 @@ static void opServe(Strings opFlags, Strings opArgs)
 }
 
 
+static void opGenerateBinaryCacheKey(Strings opFlags, Strings opArgs)
+{
+    foreach (Strings::iterator, i, opFlags)
+        throw UsageError(format("unknown flag ‘%1%’") % *i);
+
+    if (opArgs.size() != 1) throw UsageError("one argument expected");
+    string keyName = opArgs.front();
+
+    sodium_init();
+
+    unsigned char pk[crypto_sign_PUBLICKEYBYTES];
+    unsigned char sk[crypto_sign_SECRETKEYBYTES];
+    if (crypto_sign_keypair(pk, sk) != 0)
+        throw Error("key generation failed");
+
+    // FIXME: super ugly way to do base64 encoding.
+    auto args = Strings({"-MMIME::Base64", "-0777", "-ne", "print encode_base64($_, '')"});
+
+    string pk64 = runProgram("perl", true, args, string((char *) pk, crypto_sign_PUBLICKEYBYTES));
+    std::cout << keyName << ":" << pk64 << std::endl;
+
+    string sk64 = runProgram("perl", true, args, string((char *) sk, crypto_sign_SECRETKEYBYTES));
+    std::cout << keyName << ":" << sk64 << std::endl;
+}
+
+
 /* Scan the arguments; find the operation, set global flags, put all
    other flags in a list, and put all other arguments in another
    list. */
@@ -1072,14 +1100,16 @@ int main(int argc, char * * argv)
                 op = opQueryFailedPaths;
             else if (*arg == "--clear-failed-paths")
                 op = opClearFailedPaths;
+            else if (*arg == "--serve")
+                op = opServe;
+            else if (*arg == "--generate-binary-cache-key")
+                op = opGenerateBinaryCacheKey;
             else if (*arg == "--add-root")
                 gcRoot = absPath(getArg(*arg, arg, end));
             else if (*arg == "--indirect")
                 indirectRoot = true;
             else if (*arg == "--no-output")
                 noOutput = true;
-            else if (*arg == "--serve")
-                op = opServe;
             else if (*arg != "" && arg->at(0) == '-') {
                 opFlags.push_back(*arg);
                 if (*arg == "--max-freed" || *arg == "--max-links" || *arg == "--max-atime") /* !!! hack */