Make <nix/fetchurl.nix> a builtin builder

This ensures that 1) the derivation doesn't change when Nix changes;
2) the derivation closure doesn't contain Nix and its dependencies; 3)
we don't have to rely on ugly chroot hacks.

9 files changed, 61 insertions, 20 deletions

diff --git a/corepkgs/config.nix.in b/corepkgs/config.nix.in
index 8918f4ddde..90e8edbea8 100644
--- a/corepkgs/config.nix.in
+++ b/corepkgs/config.nix.in
@@ -12,7 +12,6 @@ in rec {
   tar = "@tar@";
   tarFlags = "@tarFlags@";
   tr = "@tr@";
-  curl = "@curl@";
   nixBinDir = fromEnv "NIX_BIN_DIR" "@bindir@";
   nixPrefix = "@prefix@";
 
diff --git a/corepkgs/fetchurl.nix b/corepkgs/fetchurl.nix
index 1ce88593cf..64d1f121f8 100644
--- a/corepkgs/fetchurl.nix
+++ b/corepkgs/fetchurl.nix
@@ -5,20 +5,9 @@ with import <nix/config.nix>;
 assert (outputHash != "" && outputHashAlgo != "")
     || md5 != "" || sha1 != "" || sha256 != "";
 
-let
-
-  builder = builtins.toFile "fetchurl.sh"
-    (''
-      echo "downloading $url into $out"
-      ${curl} --fail --location --max-redirs 20 --insecure "$url" > "$out"
-    '' + (if executable then "${coreutils}/chmod +x $out" else ""));
-
-in
-
 derivation {
   name = baseNameOf (toString url);
-  builder = shell;
-  args = [ "-e" builder ];
+  builder = "builtin:fetchurl";
 
   # New-style output content requirements.
   outputHashAlgo = if outputHashAlgo != "" then outputHashAlgo else
@@ -39,6 +28,4 @@ derivation {
     # by definition pure.
     "http_proxy" "https_proxy" "ftp_proxy" "all_proxy" "no_proxy"
   ];
-
-  inherit chrootDeps;
 }
diff --git a/src/libexpr/local.mk b/src/libexpr/local.mk
index 35e84980a6..4c1f4de191 100644
--- a/src/libexpr/local.mk
+++ b/src/libexpr/local.mk
@@ -8,7 +8,7 @@ libexpr_SOURCES := $(wildcard $(d)/*.cc) $(d)/lexer-tab.cc $(d)/parser-tab.cc
 
 libexpr_LIBS = libutil libstore libformat
 
-libexpr_LDFLAGS = -ldl -lcurl
+libexpr_LDFLAGS = -ldl
 
 # The dependency on libgc must be propagated (i.e. meaning that
 # programs/libraries that use libexpr must explicitly pass -lgc),
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 61677d1eb5..46d2841dc9 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -8,6 +8,7 @@
 #include "util.hh"
 #include "archive.hh"
 #include "affinity.hh"
+#include "builtins.hh"
 
 #include <map>
 #include <sstream>
@@ -1269,6 +1270,12 @@ bool substitutesAllowed(const BasicDerivation & drv)
 }
 
 
+static bool isBuiltin(const BasicDerivation & drv)
+{
+    return string(drv.builder, 0, 8) == "builtin:";
+}
+
+
 void DerivationGoal::tryToBuild()
 {
     trace("trying to build");
@@ -2139,7 +2146,7 @@ void DerivationGoal::startBuilder()
 #endif
     {
         ProcessOptions options;
-        options.allowVfork = !buildUser.enabled();
+        options.allowVfork = !buildUser.enabled() && !isBuiltin(*drv);
         pid = startProcess([&]() {
             runChild();
         }, options);
@@ -2386,7 +2393,9 @@ void DerivationGoal::runChild()
         const char *builder = "invalid";
 
         string sandboxProfile;
-        if (useChroot && SANDBOX_ENABLED) {
+        if (isBuiltin(*drv))
+            ;
+        else if (useChroot && SANDBOX_ENABLED) {
             /* Lots and lots and lots of file functions freak out if they can't stat their full ancestry */
             PathSet ancestry;
 
@@ -2413,7 +2422,6 @@ void DerivationGoal::runChild()
             for (auto & i : inputPaths)
                 dirsInChroot[i] = i;
 
-
             /* TODO: we should factor out the policy cleanly, so we don't have to repeat the constants every time... */
             sandboxProfile += "(version 1)\n";
 
@@ -2517,6 +2525,20 @@ void DerivationGoal::runChild()
         }
 
         /* Execute the program.  This should not return. */
+        if (isBuiltin(*drv)) {
+            try {
+                logType = ltFlat;
+                if (drv->builder == "builtin:fetchurl")
+                    builtinFetchurl(*drv);
+                else
+                    throw Error(format("unsupported builtin function ‘%1%’") % string(drv->builder, 8));
+                _exit(0);
+            } catch (std::exception & e) {
+                writeFull(STDERR_FILENO, "error: " + string(e.what()) + "\n");
+                _exit(1);
+            }
+        }
+
         execve(builder, stringsToCharPtrs(args).data(), stringsToCharPtrs(envStrs).data());
 
         throw SysError(format("executing ‘%1%’") % drv->builder);
diff --git a/src/libstore/builtins.cc b/src/libstore/builtins.cc
new file mode 100644
index 0000000000..97d6cb9434
--- /dev/null
+++ b/src/libstore/builtins.cc
@@ -0,0 +1,24 @@
+#include "builtins.hh"
+#include "download.hh"
+
+namespace nix {
+
+void builtinFetchurl(const BasicDerivation & drv)
+{
+    auto url = drv.env.find("url");
+    if (url == drv.env.end()) throw Error("attribute ‘url’ missing");
+    printMsg(lvlInfo, format("downloading ‘%1%’...") % url->second);
+    auto data = downloadFile(url->second); // FIXME: show progress
+
+    auto out = drv.env.find("out");
+    if (out == drv.env.end()) throw Error("attribute ‘url’ missing");
+    writeFile(out->second, data.data);
+
+    auto executable = drv.env.find("out");
+    if (executable != drv.env.end() && executable->second == "1") {
+        if (chmod(out->second.c_str(), 0755) == -1)
+            throw SysError(format("making ‘%1%’ executable") % out->second);
+    }
+}
+
+}
diff --git a/src/libstore/builtins.hh b/src/libstore/builtins.hh
new file mode 100644
index 0000000000..4b2431aa08
--- /dev/null
+++ b/src/libstore/builtins.hh
@@ -0,0 +1,9 @@
+#pragma once
+
+#include "derivations.hh"
+
+namespace nix {
+
+void builtinFetchurl(const BasicDerivation & drv);
+
+}
diff --git a/src/libexpr/download.cc b/src/libstore/download.cc
index 9bf3e13aa9..9bf3e13aa9 100644
--- a/src/libexpr/download.cc
+++ b/src/libstore/download.cc
diff --git a/src/libexpr/download.hh b/src/libstore/download.hh
index 28c9117e42..28c9117e42 100644
--- a/src/libexpr/download.hh
+++ b/src/libstore/download.hh
diff --git a/src/libstore/local.mk b/src/libstore/local.mk
index 771c06753a..bf5c256c94 100644
--- a/src/libstore/local.mk
+++ b/src/libstore/local.mk
@@ -8,7 +8,7 @@ libstore_SOURCES := $(wildcard $(d)/*.cc)
 
 libstore_LIBS = libutil libformat
 
-libstore_LDFLAGS = -lsqlite3 -lbz2
+libstore_LDFLAGS = -lsqlite3 -lbz2 -lcurl
 
 ifeq ($(OS), SunOS)
 	libstore_LDFLAGS += -lsocket