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authorMatthew Bauer <mjbauer95@gmail.com>2019-08-28T16·26-0400
committerMatthew Bauer <mjbauer95@gmail.com>2019-08-28T16·32-0400
commit693e68e09c9a17ca72b074bd2e575bf435647b45 (patch)
tree8d38503b1f9095912900c7faaf2f6daabcffcdba /src
parentf435634a29551754d5f7303b0a60cd8fe2df2079 (diff)
Set maximum name length in Nix
Previously we allowed any length of name for Nix derivations. This is
bad because different file systems have different max lengths. To make
things predictable, I have picked a max. This was done by trying to
build this derivation:

  derivation {
    name = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
    builder = "/no-such-path";
    system = "x86_64-linux";
  }

Take off one a and it will not lead to file name too long. That ends
up being 212 a’s. An even smaller max could be picked if we want to
support more file systems.

Working backwards, this is why:

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-${name}.drv.chroot

> 255 - 32 - 1 - 4 - 7 = 211
Diffstat (limited to 'src')
-rw-r--r--src/libstore/store-api.cc4
1 files changed, 4 insertions, 0 deletions
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index f5608d3849f1..3bb9db0b723b 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -97,6 +97,10 @@ void checkStoreName(const string & name)
        reasons (e.g., "." and ".."). */
     if (string(name, 0, 1) == ".")
         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') ||