Disallow empty store path names

Fixes #3239.

src/libstore/local-store.cc

@@ -585,6 +585,8 @@ void LocalStore::checkDerivationOutputs(const Path & drvPath, const Derivation &
 uint64_t LocalStore::addValidPath(State & state,
     const ValidPathInfo & info, bool checkOutputs)
 {
+    checkStoreName(storePathToName(info.path));
+
     if (info.ca != "" && !info.isContentAddressed(*this))
         throw Error("cannot add path '%s' to the Nix store because it claims to be content-addressed but isn't", info.path);
 

src/libstore/store-api.cc

@@ -90,17 +90,22 @@ void checkStoreName(const string & name)
         "Path names are alphanumeric and can include the symbols %1% "
         "and must not begin with a period. "
         "Note: If '%2%' is a source file and you cannot rename it on "
-        "disk, builtins.path { name = ... } can be used to give it an "
+        "disk, 'builtins.path { name = ... }' can be used to give it an "
         "alternative name.") % validChars % name;
 
+    if (name.empty())
+        throw Error(baseError % "it is an empty string");
+
     /* Disallow names starting with a dot for possible security
        reasons (e.g., "." and ".."). */
-    if (string(name, 0, 1) == ".")
+    if (name[0] == '.')
         throw Error(baseError % "it is illegal to start the name with a period");
+
     /* Disallow names longer than 211 characters. ext4’s max is 256,
        but we need extra space for the hash and .chroot extensions. */
     if (name.length() > 211)
         throw Error(baseError % "name must be less than 212 characters");
+
     for (auto & i : name)
         if (!((i >= 'A' && i <= 'Z') ||
               (i >= 'a' && i <= 'z') ||

tests/referrers.sh

@@ -4,7 +4,7 @@ clearStore
 
 max=500
 
-reference=$NIX_STORE_DIR/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+reference=$NIX_STORE_DIR/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-bla
 touch $reference
 (echo $reference && echo && echo 0) | nix-store --register-validity