From 7bcd8664a4eb085c91f701041751977e4565ef8f Mon Sep 17 00:00:00 2001
From: Jack Grigg <thestr4d@gmail.com>
Date: Sun, 1 Dec 2019 21:37:06 +0000
Subject: [PATCH] AlgorithmId::write helper to match policy helpers

---
 src/consts.rs |  1 -
 src/key.rs    | 27 ++++++++++++++-------------
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/src/consts.rs b/src/consts.rs
index 65242c0..95576e6 100644
--- a/src/consts.rs
+++ b/src/consts.rs
@@ -122,7 +122,6 @@ pub const TAG_RSA_MODULUS: u8 = 0x81;
 pub const TAG_RSA_EXP: u8 = 0x82;
 pub const TAG_ECC_POINT: u8 = 0x86;
 
-pub const YKPIV_ALGO_TAG: u8 = 0x80;
 pub const YKPIV_ALGO_3DES: u8 = 0x03;
 
 pub const YKPIV_ATR_NEO_R3: &[u8] = b";\xFC\x13\0\0\x811\xFE\x15YubikeyNEOr3\xE1\0";
diff --git a/src/key.rs b/src/key.rs
index f14aa81..50152ea 100644
--- a/src/key.rs
+++ b/src/key.rs
@@ -312,6 +312,16 @@ impl From<AlgorithmId> for u8 {
     }
 }
 
+impl AlgorithmId {
+    /// Writes the `AlgorithmId` in the format the YubiKey expects during key generation.
+    pub(crate) fn write(self, buf: &mut [u8]) -> usize {
+        buf[0] = 0x80;
+        buf[1] = 0x01;
+        buf[2] = self.into();
+        3
+    }
+}
+
 /// PIV cryptographic keys stored in a YubiKey
 #[derive(Clone, Debug)]
 pub struct Key {
@@ -412,7 +422,6 @@ pub fn generate(
     pin_policy: PinPolicy,
     touch_policy: TouchPolicy,
 ) -> Result<GeneratedKey, Error> {
-    let mut in_data = [0u8; 11];
     let mut templ = [0, Ins::GenerateAsymmetric.code(), 0, 0];
     let setting_roca: settings::BoolValue;
 
@@ -463,19 +472,11 @@ pub fn generate(
 
     templ[3] = slot.into();
 
+    let mut in_data = [0u8; 11];
+    in_data[0] = 0xac;
+    in_data[1] = 3; // length sans this 2-byte header
+    assert_eq!(algorithm.write(&mut in_data[2..]), 3);
     let mut offset = 5;
-    in_data[..offset].copy_from_slice(&[
-        0xac,
-        3, // length sans this 2-byte header
-        YKPIV_ALGO_TAG,
-        1,
-        algorithm.into(),
-    ]);
-
-    if in_data[4] == 0 {
-        error!("unexpected algorithm");
-        return Err(Error::AlgorithmError);
-    }
 
     let pin_len = pin_policy.write(&mut in_data[offset..]);
     in_data[1] += pin_len as u8;