fix(zseri/store-ref-scanner): no_std support and runtime panics r/3385

This also changes the fuzzing infrastructure from proptest to cargo-fuzz,
and this lead to the discovery of two mishandlings of edge-cases:

* when a "path_to_store" is at the end of the input, it tried to access
  the input slice out-of-bounds (the `just_store` test covers that now)
* non-ASCII characters lead to an out-of-bounds access in HalfBytesMask
  (the `non_ascii` test covers that now)

Change-Id: Icaa2518dcd93e1789a2c0da4cf0fec46016d3bad
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4604
Tested-by: BuildkiteCI
Reviewed-by: zseri <zseri.devel@ytrizja.de>

1 files changed, 16 insertions, 22 deletions

diff --git a/users/zseri/store-ref-scanner/src/spec.rs b/users/zseri/store-ref-scanner/src/spec.rs
index 034779e8e8..79da0842c5 100644
--- a/users/zseri/store-ref-scanner/src/spec.rs
+++ b/users/zseri/store-ref-scanner/src/spec.rs
@@ -1,10 +1,8 @@
 use crate::hbm::HalfBytesMask;
-use camino::Utf8PathBuf;
-use once_cell::sync::Lazy;
 
-pub struct StoreSpec {
+pub struct StoreSpec<'path> {
     /// path to store without trailing slash
-    pub path_to_store: Utf8PathBuf,
+    pub path_to_store: &'path str,
 
     /// compressed map of allowed ASCII characters in hash part
     pub valid_hashbytes: HalfBytesMask,
@@ -16,7 +14,7 @@ pub struct StoreSpec {
     pub hashbytes_len: u8,
 }
 
-impl StoreSpec {
+impl StoreSpec<'_> {
     pub(crate) fn check_rest(&self, rest: &[u8]) -> bool {
         let hbl = self.hashbytes_len.into();
         rest.iter()
@@ -25,22 +23,18 @@ impl StoreSpec {
             .count()
             == hbl
     }
-}
 
-pub static SPEC_DFL_NIX2: Lazy<StoreSpec> = Lazy::new(|| StoreSpec {
-    path_to_store: "/nix/store".into(),
-    valid_hashbytes: HalfBytesMask::B32_REVSHA256,
-    valid_restbytes: HalfBytesMask::from_bytes(
-        b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-._?=",
-    ),
-    hashbytes_len: 32,
-});
+    pub const DFL_NIX2: StoreSpec<'static> = StoreSpec {
+        path_to_store: "/nix/store",
+        valid_hashbytes: HalfBytesMask::B32_REVSHA256,
+        valid_restbytes: HalfBytesMask::DFL_REST,
+        hashbytes_len: 32,
+    };
 
-pub static SPEC_DFL_YZIX1: Lazy<StoreSpec> = Lazy::new(|| StoreSpec {
-    path_to_store: "/yzixs".into(),
-    valid_hashbytes: HalfBytesMask::B64_BLAKE2B256,
-    valid_restbytes: HalfBytesMask::from_bytes(
-        b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-._?=",
-    ),
-    hashbytes_len: 43,
-});
+    pub const DFL_YZIX1: StoreSpec<'static> = StoreSpec {
+        path_to_store: "/yzixs",
+        valid_hashbytes: HalfBytesMask::B64_BLAKE2B256,
+        valid_restbytes: HalfBytesMask::DFL_REST,
+        hashbytes_len: 43,
+    };
+}