From a39f25d8a32bd6c747bb79c0333c9d83d4c4d455 Mon Sep 17 00:00:00 2001
From: Heiko Schaefer <heiko@schaefer.name>
Date: Fri, 17 Sep 2021 13:36:20 +0200
Subject: [PATCH] Handle SW_EXACT_LENGTH (0x6c??) in send_command()

---
 openpgp-card/src/apdu.rs         | 21 +++++++++++++++++----
 openpgp-card/src/apdu/command.rs | 24 +++++++++++++++++++-----
 2 files changed, 36 insertions(+), 9 deletions(-)

diff --git a/openpgp-card/src/apdu.rs b/openpgp-card/src/apdu.rs
index 12d4f82..2d0496c 100644
--- a/openpgp-card/src/apdu.rs
+++ b/openpgp-card/src/apdu.rs
@@ -11,6 +11,7 @@ pub mod response;
 use anyhow::Result;
 use std::convert::TryFrom;
 
+use crate::apdu::command::Expect;
 use crate::apdu::{command::Command, response::RawResponse};
 use crate::{CardClientBox, Error, StatusBytes};
 
@@ -28,10 +29,22 @@ pub(crate) fn send_command(
 ) -> Result<RawResponse, Error> {
     let mut resp = RawResponse::try_from(send_command_low_level(
         card_client,
-        cmd,
-        expect_reply,
+        cmd.clone(),
+        if expect_reply {
+            Expect::Some
+        } else {
+            Expect::Empty
+        },
     )?)?;
 
+    if let StatusBytes::UnknownStatus(0x6c, size) = resp.status() {
+        resp = RawResponse::try_from(send_command_low_level(
+            card_client,
+            cmd,
+            Expect::Short(size),
+        )?)?;
+    }
+
     while let StatusBytes::OkBytesAvailable(_) = resp.status() {
         // More data is available for this command from the card
         log::debug!(" chained response, getting more data");
@@ -40,7 +53,7 @@ pub(crate) fn send_command(
         let next = RawResponse::try_from(send_command_low_level(
             card_client,
             commands::get_response(),
-            expect_reply,
+            Expect::Some,
         )?)?;
 
         match next.status() {
@@ -71,7 +84,7 @@ pub(crate) fn send_command(
 fn send_command_low_level(
     card_client: &mut CardClientBox,
     cmd: Command,
-    expect_response: bool,
+    expect_response: Expect,
 ) -> Result<Vec<u8>, Error> {
     let (ext_support, chaining_support, mut max_cmd_bytes, max_rsp_bytes) =
         if let Some(caps) = card_client.get_caps() {
diff --git a/openpgp-card/src/apdu/command.rs b/openpgp-card/src/apdu/command.rs
index d0bdb2e..3c77898 100644
--- a/openpgp-card/src/apdu/command.rs
+++ b/openpgp-card/src/apdu/command.rs
@@ -6,6 +6,13 @@
 
 use anyhow::Result;
 
+#[derive(Clone, Copy)]
+pub enum Expect {
+    Empty,
+    Some,
+    Short(u8),
+}
+
 #[derive(Clone, Debug)]
 pub(crate) struct Command {
     // Class byte (CLA)
@@ -63,7 +70,7 @@ impl Command {
     pub(crate) fn serialize(
         &self,
         ext_len: bool,
-        expect_response: bool,
+        expect_response: Expect,
     ) -> Result<Vec<u8>> {
         // FIXME? (from scd/apdu.c):
         //  T=0 does not allow the use of Lc together with Le;
@@ -101,18 +108,22 @@ impl Command {
 
     /// Encode value for Le field
     /// ("maximum number of bytes expected in the response data field").
-    fn make_le(nc: u16, ext_len: bool, expect_response: bool) -> Vec<u8> {
+    fn make_le(nc: u16, ext_len: bool, expect_response: Expect) -> Vec<u8> {
         match (ext_len, expect_response) {
-            (_, false) => {
+            (_, Expect::Empty) => {
                 // No response data expected.
                 // "If the Le field is absent, then Ne is zero"
                 vec![]
             }
-            (false, true) => {
+            (false, Expect::Some) => {
                 // A short Le field consists of one byte with any value
                 vec![0]
             }
-            (true, true) => {
+            (false, Expect::Short(size)) => {
+                // A short Le field consists of one byte with any value
+                vec![size]
+            }
+            (true, Expect::Some) => {
                 if nc == 0 {
                     // "three bytes (one byte set to '00' followed by two
                     // bytes with any value) if the Lc field is absent"
@@ -123,6 +134,9 @@ impl Command {
                     vec![0, 0]
                 }
             }
+            _ => {
+                unreachable!("This should not happen")
+            }
         }
     }
 }