Mark the derivation outputs as secret if the derivation file is secret.

src/libstore/build.cc

@@ -2193,16 +2193,17 @@ void DerivationGoal::registerOutputs()
 
     ValidPathInfos infos;
 
+    /* Inherit ownership of outputs from the permission of the derivation
+       file. */
+    SecretMode smode(getOwnerOfSecretFile(drvPath));
+
     /* Check whether the output paths were created, and grep each
        output path to determine what other paths it references.  Also make all
        output paths read-only. */
     foreach (DerivationOutputs::iterator, i, drv.outputs) {
         Path path = i->second.path;
         if (missingPaths.find(path) == missingPaths.end()) continue;
 
-        // :TODO: Transfer the user name down to here.
-        SecretMode smode(publicUserName());
-
         Path actualPath = path;
         if (useChroot) {
             actualPath = chrootRootDir + path;

src/libutil/util.cc

@@ -12,6 +12,7 @@
 
 #include <sys/wait.h>
 #include <unistd.h>
+#include <pwd.h>
 #include <fcntl.h>
 #include <limits.h>
 
@@ -1174,6 +1175,51 @@ const string & getCurrentUserName()
 }
 
 
+string getOwnerOfSecretFile(const Path & path)
+{
+    /* Extract the uid of the file */
+    struct stat st;
+    if (stat(path.c_str(), &st) == -1)
+        throw SysError("statting file");
+
+    /* If the file is readable by the group, then this means this is a
+       public file. */
+    if (st.st_mode & S_IRGRP)
+        return publicUserName();
+
+    /* Map the uid of the private file to the user name */
+    struct passwd pwd;
+    struct passwd *ppwd;
+    char *buf;
+    size_t bufsize;
+    int err;
+
+    bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
+    if (bufsize == size_t(-1))
+        bufsize = 16 * 1024;
+
+    buf = new char[bufsize];
+    if (!buf)
+        throw SysError("allocating passwd entry");
+
+    err = getpwuid_r(st.st_uid, &pwd, buf, bufsize, &ppwd);
+    if (!ppwd) {
+        delete[] buf;
+        if (err)
+            throw SysError("finding owner of a file");
+
+        /* The uid does not match any user name, no need to keep any secret
+           for a non-existing user name. */
+        return publicUserName();
+    }
+
+    string userName(pwd.pw_name);
+    delete[] buf;
+
+    return userName;
+}
+
+
 SecretMode::SecretMode(const string & userName)
   : userName_(userName),
     filterMask_(0),

src/libutil/util.hh

@@ -391,6 +391,10 @@ const string & publicUserName();
 const string & getCurrentUserName();
 
 
+/* Returns the owner of a file if the file is secret */
+string getOwnerOfSecretFile(const Path & path);
+
+
 /* Ensure that files created within this scope are secure by default.  This
    RAI does not protect against doing a chmod of the file. */
 class SecretMode

tests/sec-secretDerivation.sh

@@ -34,8 +34,32 @@ if ! test $publicDrvStat = $expected; then
     exit 1
 fi
 
+expected="dr-xr-xr-x"
+if ! test $publicOutStat = $expected; then
+    echo "Public derivation output director is not only world readbale."
+    exit 1
+fi
+
+expected="-r--r--r--"
+if ! test $publicOutFileStat = $expected; then
+    echo "Public derivation output file is not only world readbale."
+    exit 1
+fi
+
 expected="-r--------"
 if ! test $secretDrvStat = $expected; then
     echo "Secret derivation is not only root readbale."
     exit 1
 fi
+
+expected="dr-x------"
+if ! test $secretOutStat = $expected; then
+    echo "Secret derivation output directory is not only root readbale."
+    exit 1
+fi
+
+expected="-r--------"
+if ! test $secretOutFileStat = $expected; then
+    echo "Secret derivation output file is not only root readbale."
+    exit 1
+fi