From c921cfcf9738a9a0335631ad683d550a9d3cecf7 Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@z.cash>
Date: Fri, 10 Jul 2020 22:15:23 +1200
Subject: [PATCH] zcash_proofs: Add LocalProver::bundled

Requires the bundled-prover feature, which enables the
wagyu-zcash-parameters crate and adds around 50 MiB to the overall
binary size. That crate bundles the same Sapling parameter files we
normally obtain from disk, so we constrain them to match the same
hard-coded hashes.
---
 zcash_proofs/Cargo.toml    |  2 ++
 zcash_proofs/src/lib.rs    | 30 ++++++++++++++++++++++++------
 zcash_proofs/src/prover.rs | 33 ++++++++++++++++++++++++++++-----
 3 files changed, 54 insertions(+), 11 deletions(-)

diff --git a/zcash_proofs/Cargo.toml b/zcash_proofs/Cargo.toml
index 4a58e9dfb..1f0ded25f 100644
--- a/zcash_proofs/Cargo.toml
+++ b/zcash_proofs/Cargo.toml
@@ -20,6 +20,7 @@ ff = { version = "0.6", path = "../ff" }
 minreq = { version = "2", features = ["https"], optional = true }
 pairing = { version = "0.16", path = "../pairing" }
 rand_core = "0.5.1"
+wagyu-zcash-parameters = { version = "0.2", optional = true }
 zcash_primitives = { version = "0.2", path = "../zcash_primitives" }
 
 [dev-dependencies]
@@ -27,6 +28,7 @@ rand_xorshift = "0.2"
 
 [features]
 default = ["local-prover", "multicore"]
+bundled-prover = ["wagyu-zcash-parameters"]
 download-params = ["minreq"]
 local-prover = ["directories"]
 multicore = ["bellman/multicore"]
diff --git a/zcash_proofs/src/lib.rs b/zcash_proofs/src/lib.rs
index e14a26953..7c574c295 100644
--- a/zcash_proofs/src/lib.rs
+++ b/zcash_proofs/src/lib.rs
@@ -22,11 +22,13 @@ mod hashreader;
 pub mod sapling;
 pub mod sprout;
 
-#[cfg(feature = "local-prover")]
+#[cfg(any(feature = "local-prover", feature = "bundled-prover"))]
 pub mod prover;
 
 // Circuit names
+#[cfg(feature = "local-prover")]
 const SAPLING_SPEND_NAME: &str = "sapling-spend.params";
+#[cfg(feature = "local-prover")]
 const SAPLING_OUTPUT_NAME: &str = "sapling-output.params";
 
 // Circuit hashes
@@ -118,11 +120,27 @@ pub fn load_parameters(
     let sprout_fs =
         sprout_path.map(|p| File::open(p).expect("couldn't load Sprout groth16 parameters file"));
 
-    let mut spend_fs = hashreader::HashReader::new(BufReader::with_capacity(1024 * 1024, spend_fs));
-    let mut output_fs =
-        hashreader::HashReader::new(BufReader::with_capacity(1024 * 1024, output_fs));
-    let mut sprout_fs =
-        sprout_fs.map(|fs| hashreader::HashReader::new(BufReader::with_capacity(1024 * 1024, fs)));
+    parse_parameters(
+        BufReader::with_capacity(1024 * 1024, spend_fs),
+        BufReader::with_capacity(1024 * 1024, output_fs),
+        sprout_fs.map(|fs| BufReader::with_capacity(1024 * 1024, fs)),
+    )
+}
+
+fn parse_parameters<R: io::Read>(
+    spend_fs: R,
+    output_fs: R,
+    sprout_fs: Option<R>,
+) -> (
+    Parameters<Bls12>,
+    PreparedVerifyingKey<Bls12>,
+    Parameters<Bls12>,
+    PreparedVerifyingKey<Bls12>,
+    Option<PreparedVerifyingKey<Bls12>>,
+) {
+    let mut spend_fs = hashreader::HashReader::new(spend_fs);
+    let mut output_fs = hashreader::HashReader::new(output_fs);
+    let mut sprout_fs = sprout_fs.map(|fs| hashreader::HashReader::new(fs));
 
     // Deserialize params
     let spend_params = Parameters::<Bls12>::read(&mut spend_fs, false)
diff --git a/zcash_proofs/src/prover.rs b/zcash_proofs/src/prover.rs
index d1c23aac7..5201a7e07 100644
--- a/zcash_proofs/src/prover.rs
+++ b/zcash_proofs/src/prover.rs
@@ -2,7 +2,6 @@
 
 use bellman::groth16::{Parameters, PreparedVerifyingKey};
 use pairing::bls12_381::{Bls12, Fr};
-use std::path::Path;
 use zcash_primitives::{
     jubjub::{edwards, fs::Fs, Unknown},
     primitives::{Diversifier, PaymentAddress, ProofGenerationKey},
@@ -16,10 +15,15 @@ use zcash_primitives::{
     JUBJUB,
 };
 
-use crate::{
-    default_params_folder, load_parameters, sapling::SaplingProvingContext, SAPLING_OUTPUT_NAME,
-    SAPLING_SPEND_NAME,
-};
+use crate::sapling::SaplingProvingContext;
+
+#[cfg(feature = "local-prover")]
+use crate::{default_params_folder, load_parameters, SAPLING_OUTPUT_NAME, SAPLING_SPEND_NAME};
+#[cfg(feature = "local-prover")]
+use std::path::Path;
+
+#[cfg(feature = "bundled-prover")]
+use crate::parse_parameters;
 
 /// An implementation of [`TxProver`] using Sapling Spend and Output parameters from
 /// locally-accessible paths.
@@ -48,6 +52,7 @@ impl LocalTxProver {
     ///
     /// This function will panic if the paths do not point to valid parameter files with
     /// the expected hashes.
+    #[cfg(feature = "local-prover")]
     pub fn new(spend_path: &Path, output_path: &Path) -> Self {
         let (spend_params, spend_vk, output_params, _, _) =
             load_parameters(spend_path, output_path, None);
@@ -79,6 +84,7 @@ impl LocalTxProver {
     ///
     /// This function will panic if the parameters in the default local location do not
     /// have the expected hashes.
+    #[cfg(feature = "local-prover")]
     pub fn with_default_location() -> Option<Self> {
         let params_dir = default_params_folder()?;
         let (spend_path, output_path) = if params_dir.exists() {
@@ -95,6 +101,23 @@ impl LocalTxProver {
 
         Some(LocalTxProver::new(&spend_path, &output_path))
     }
+
+    /// Creates a `LocalTxProver` using Sapling parameters bundled inside the binary.
+    ///
+    /// This requires the `bundled-prover` feature, which will increase the binary size by
+    /// around 50 MiB.
+    #[cfg(feature = "bundled-prover")]
+    pub fn bundled() -> Self {
+        let (spend_buf, output_buf) = wagyu_zcash_parameters::load_sapling_parameters();
+        let (spend_params, spend_vk, output_params, _, _) =
+            parse_parameters(&spend_buf[..], &output_buf[..], None);
+
+        LocalTxProver {
+            spend_params,
+            spend_vk,
+            output_params,
+        }
+    }
 }
 
 impl TxProver for LocalTxProver {