Download Sapling parameters using zcash_proofs, rather than fetch-par…

…ams.sh
ZcashFoundation · Nov 17, 2021 · 2fdc50a · 2fdc50a
1 parent 0770f03
commit 2fdc50a
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Showing 3 changed files with 19 additions and 127 deletions.
diff --git a/zebra-consensus/src/primitives/groth16.rs b/zebra-consensus/src/primitives/groth16.rs
@@ -18,16 +18,16 @@ use once_cell::sync::Lazy;
 use rand::thread_rng;
 use tokio::sync::broadcast::{channel, error::RecvError, Sender};
 use tower::{util::ServiceFn, Service};
+
 use tower_batch::{Batch, BatchControl};
 use tower_fallback::Fallback;
+
 use zebra_chain::sapling::{Output, PerSpendAnchor, Spend};
 
-mod hash_reader;
 mod params;
 #[cfg(test)]
 mod tests;
 
-use self::hash_reader::HashReader;
 use params::PARAMS;
 
 /// Global batch verification context for Groth16 proofs of Spend statements.

diff --git a/zebra-consensus/src/primitives/groth16/hash_reader.rs b/zebra-consensus/src/primitives/groth16/hash_reader.rs
diff --git a/zebra-consensus/src/primitives/groth16/params.rs b/zebra-consensus/src/primitives/groth16/params.rs
@@ -1,16 +1,6 @@
-use std::{
-    fs,
-    io::{self, BufReader},
-};
-
 use bellman::groth16;
 use bls12_381::Bls12;
 
-use super::HashReader;
-
-const SAPLING_SPEND_HASH: &str = "8270785a1a0d0bc77196f000ee6d221c9c9894f55307bd9357c3f0105d31ca63991ab91324160d8f53e2bbd3c2633a6eb8bdf5205d822e7f3f73edac51b2b70c";
-const SAPLING_OUTPUT_HASH: &str = "657e3d38dbb5cb5e7dd2970e8b03d69b4787dd907285b5a7f0790dcc8072f60bf593b32cc2d1c030e00ff5ae64bf84c5c3beb84ddc841d48264b4a171744d028";
-
 lazy_static::lazy_static! {
     pub static ref PARAMS: Groth16Params = Groth16Params::new();
 }
@@ -38,87 +28,32 @@ pub struct SaplingParams {
 }
 
 impl SaplingParams {
-    fn new() -> Self {
-        // Use exactly the same paths as fetch-params.sh.
-        let mut params_dir = dirs::home_dir().unwrap_or_else(|| "/".into());
+    fn new() -> SaplingParams {
+        let params_dir =
+            zcash_proofs::default_params_folder().expect("unable to find user home directory");
 
-        // TODO: Is this path correct for Windows?
-        #[cfg(not(any(target_os = "macos", target_os = "ios")))]
-        params_dir.push(".zcash-params");
-
-        #[cfg(any(target_os = "macos", target_os = "ios"))]
-        params_dir.push("Library/Application Support/ZcashParams");
-
-        // Now the directory is correct, make sure we don't accidentally modify it.
-        let params_dir = params_dir;
-
-        // TODO: Make into a constant or re-implement in Rust.
-        let fetch_params_url =
-            "https://raw.githubusercontent.com/zcash/zcash/master/zcutil/fetch-params.sh";
-        let params_hint = format!(
-            "Hint: download parameters to {:?} using {:?}.",
-            params_dir, fetch_params_url,
-        );
+        // TODO: Sprout
 
         let mut spend_path = params_dir.clone();
         spend_path.push("sapling-spend.params");
-        let spend = fs::File::open(spend_path).unwrap_or_else(|_| {
-            panic!(
-                "unexpected missing or unreadable Sapling spend parameters file. {}",
-                params_hint
-            )
-        });
 
         let mut output_path = params_dir;
         output_path.push("sapling-output.params");
-        let output = fs::File::open(output_path).unwrap_or_else(|_| {
-            panic!(
-                "unexpected missing or unreadable Sapling output parameters file. {}",
-                params_hint
-            )
-        });
-
-        let spend_fs = BufReader::with_capacity(1024 * 1024, spend);
-        let output_fs = BufReader::with_capacity(1024 * 1024, output);
 
-        Self::read(spend_fs, output_fs)
-            .unwrap_or_else(|_| panic!("unexpected error reading parameter files. {}", params_hint))
-    }
-
-    fn read<R: io::Read>(spend_fs: R, output_fs: R) -> Result<Self, io::Error> {
-        let mut spend_fs = HashReader::new(spend_fs);
-        let mut output_fs = HashReader::new(output_fs);
-
-        // Deserialize params
-        let spend = groth16::Parameters::<Bls12>::read(&mut spend_fs, false)?;
-        let output = groth16::Parameters::<Bls12>::read(&mut output_fs, false)?;
-
-        // There is extra stuff (the transcript) at the end of the parameter file which is
-        // used to verify the parameter validity, but we're not interested in that. We do
-        // want to read it, though, so that the BLAKE2b computed afterward is consistent
-        // with `b2sum` on the files.
-        let mut sink = io::sink();
-        io::copy(&mut spend_fs, &mut sink)?;
-        io::copy(&mut output_fs, &mut sink)?;
-
-        assert!(
-            spend_fs.into_hash() == SAPLING_SPEND_HASH,
-            "Sapling spend parameter is not correct."
-        );
-        assert!(
-            output_fs.into_hash() == SAPLING_OUTPUT_HASH,
-            "Sapling output parameter is not correct."
-        );
+        // Download parameters if needed.
+        //
+        // TODO: use try_exists when it stabilises, to exit early on permissions errors (#83186)
+        if !spend_path.exists() || !output_path.exists() {
+            zcash_proofs::download_parameters().expect("error downloading parameter files");
+        }
 
-        // Prepare verifying keys
-        let spend_prepared_verifying_key = groth16::prepare_verifying_key(&spend.vk);
-        let output_prepared_verifying_key = groth16::prepare_verifying_key(&output.vk);
+        let parameters = zcash_proofs::load_parameters(&spend_path, &output_path, None);
 
-        Ok(Self {
-            spend,
-            spend_prepared_verifying_key,
-            output,
-            output_prepared_verifying_key,
-        })
+        SaplingParams {
+            spend: parameters.spend_params,
+            spend_prepared_verifying_key: parameters.spend_vk,
+            output: parameters.output_params,
+            output_prepared_verifying_key: parameters.output_vk,
+        }
     }
 }