openpgp: Improve performance of detached signature verification.

  - Previously, we transformed data and detached signatures into
    signed messages on the fly, then used the streaming Verifier to
    verify the message.  However, this introduces a nontrivial
    overhead, even if unnecessary copies are carefully avoided.

  - Instead, specialize the streaming Decryptor to handle detached
    signatures.  use crypto::hash_buffered_reader to compute the
    hashes over the data, then attach the computed signatures to the
    signature packets, and use Decryptor's verification machinery.

  - While this is arguably less elegant, it is much simpler, and a lot
    faster.  Notably, if we operate on files and can mmap them into
    memory, we can compute the hash in one call to the compression
    function.  Verification of detached signatures is an important use
    case, so this speedup outweighs the loss of elegance.

  - Fixes #457.

1 files changed, 2 insertions, 5 deletions

diff --git a/sqv/src/sqv.rs b/sqv/src/sqv.rs
index cb458797..74e2d078 100644
--- a/sqv/src/sqv.rs
+++ b/sqv/src/sqv.rs
@@ -4,7 +4,6 @@
 /// the motivation.
 
 use std::process::exit;
-use std::io;
 
 use chrono::{DateTime, offset::Utc};
 extern crate clap;
@@ -276,10 +275,8 @@ fn main() -> Result<()> {
 
     let h = VHelper::new(good_threshold, not_before, not_after, keyrings);
 
-    let mut v = DetachedVerifier::from_file(
-        p, sig_file, file, h, None)?;
-
-    io::copy(&mut v, &mut io::sink())?;
+    let mut v = DetachedVerifier::from_file(p, sig_file, h, None)?;
+    v.verify_file(file)?;
 
     let h = v.into_helper();