Enable library users to detect if a smart card doesn't support PIV (#476)

* Enable library users to detect if a smart card doesn't support PIV

Closes iqlusioninc/yubikey.rs#456.

* Avoid resetting the card if we fail to select PIV or fetch version/serial

src/error.rs

@@ -45,6 +45,12 @@ pub enum Error {
     /// Applet error
     AppletError,
 
+    /// We tried to select an applet that could not be found.
+    AppletNotFound {
+        /// Human-readable name of the applet.
+        applet_name: &'static str,
+    },
+
     /// Argument error
     ArgumentError,
 
@@ -125,6 +131,9 @@ impl Error {
         match self {
             Error::AlgorithmError => f.write_str("algorithm error"),
             Error::AppletError => f.write_str("applet error"),
+            Error::AppletNotFound { applet_name } => {
+                f.write_str(&format!("{} applet not found", applet_name))
+            }
             Error::ArgumentError => f.write_str("argument error"),
             Error::AuthenticationError => f.write_str("authentication error"),
             Error::GenericError => f.write_str("generic error"),

src/lib.rs

@@ -49,6 +49,7 @@ mod mgm;
 mod mscmap;
 #[cfg(feature = "untested")]
 mod msroots;
+mod otp;
 pub mod piv;
 mod policy;
 pub mod reader;

src/mgm.rs

@@ -48,6 +48,16 @@ use des::{
 #[cfg(feature = "untested")]
 use {hmac::Hmac, pbkdf2::pbkdf2, sha1::Sha1};
 
+/// YubiKey MGMT Applet Name
+#[cfg(feature = "untested")]
+pub(crate) const APPLET_NAME: &str = "YubiKey MGMT";
+
+/// MGMT Applet ID.
+///
+/// <https://developers.yubico.com/PIV/Introduction/Admin_access.html>
+#[cfg(feature = "untested")]
+pub(crate) const APPLET_ID: &[u8] = &[0xa0, 0x00, 0x00, 0x05, 0x27, 0x47, 0x11, 0x17];
+
 pub(crate) const ADMIN_FLAGS_1_PROTECTED_MGM: u8 = 0x02;
 
 #[cfg(feature = "untested")]

src/otp.rs

@@ -0,0 +1,5 @@
+/// YubiKey OTP Applet Name
+pub(crate) const APPLET_NAME: &str = "YubiKey OTP";
+
+/// YubiKey OTP Applet ID. Needed to query serial on YK4.
+pub(crate) const APPLET_ID: &[u8] = &[0xa0, 0x00, 0x00, 0x05, 0x27, 0x20, 0x01, 0x01];

src/piv.rs

@@ -73,6 +73,12 @@ use {
 #[cfg(feature = "untested")]
 use zeroize::Zeroizing;
 
+/// PIV Applet Name
+pub(crate) const APPLET_NAME: &str = "PIV";
+
+/// PIV Applet ID
+pub(crate) const APPLET_ID: &[u8] = &[0xa0, 0x00, 0x00, 0x03, 0x08];
+
 const CB_ECC_POINTP256: usize = 65;
 const CB_ECC_POINTP384: usize = 97;
 

src/transaction.rs

@@ -5,7 +5,8 @@ use crate::{
     apdu::{Apdu, Ins, StatusWords},
     consts::{CB_BUF_MAX, CB_OBJ_MAX},
     error::{Error, Result},
-    piv::{AlgorithmId, SlotId},
+    otp,
+    piv::{self, AlgorithmId, SlotId},
     serialization::*,
     yubikey::*,
     Buffer, ObjectId,
@@ -16,12 +17,6 @@ use zeroize::Zeroizing;
 #[cfg(feature = "untested")]
 use crate::mgm::{MgmKey, DES_LEN_3DES};
 
-/// PIV Applet ID
-const PIV_AID: [u8; 5] = [0xa0, 0x00, 0x00, 0x03, 0x08];
-
-/// YubiKey OTP Applet ID. Needed to query serial on YK4.
-const YK_AID: [u8; 8] = [0xa0, 0x00, 0x00, 0x05, 0x27, 0x20, 0x01, 0x01];
-
 const CB_PIN_MAX: usize = 8;
 
 #[cfg(feature = "untested")]
@@ -69,7 +64,7 @@ impl<'tx> Transaction<'tx> {
     pub fn select_application(&self) -> Result<()> {
         let response = Apdu::new(Ins::SelectApplication)
             .p1(0x04)
-            .data(PIV_AID)
+            .data(piv::APPLET_ID)
             .transmit(self, 0xFF)
             .map_err(|e| {
                 error!("failed communicating with card: '{}'", e);
@@ -81,7 +76,12 @@ impl<'tx> Transaction<'tx> {
                 "failed selecting application: {:04x}",
                 response.status_words().code()
             );
-            return Err(Error::GenericError);
+            return Err(match response.status_words() {
+                StatusWords::NotFoundError => Error::AppletNotFound {
+                    applet_name: piv::APPLET_NAME,
+                },
+                _ => Error::GenericError,
+            });
         }
 
         Ok(())
@@ -110,13 +110,18 @@ impl<'tx> Transaction<'tx> {
             4 => {
                 let sw = Apdu::new(Ins::SelectApplication)
                     .p1(0x04)
-                    .data(YK_AID)
+                    .data(otp::APPLET_ID)
                     .transmit(self, 0xFF)?
                     .status_words();
 
                 if !sw.is_success() {
                     error!("failed selecting yk application: {:04x}", sw.code());
-                    return Err(Error::GenericError);
+                    return Err(match sw {
+                        StatusWords::NotFoundError => Error::AppletNotFound {
+                            applet_name: otp::APPLET_NAME,
+                        },
+                        _ => Error::GenericError,
+                    });
                 }
 
                 let response = Apdu::new(0x01).p1(0x10).transmit(self, 0xFF)?;
@@ -133,13 +138,18 @@ impl<'tx> Transaction<'tx> {
                 // reselect the PIV applet
                 let sw = Apdu::new(Ins::SelectApplication)
                     .p1(0x04)
-                    .data(PIV_AID)
+                    .data(piv::APPLET_ID)
                     .transmit(self, 0xFF)?
                     .status_words();
 
                 if !sw.is_success() {
                     error!("failed selecting application: {:04x}", sw.code());
-                    return Err(Error::GenericError);
+                    return Err(match sw {
+                        StatusWords::NotFoundError => Error::AppletNotFound {
+                            applet_name: piv::APPLET_NAME,
+                        },
+                        _ => Error::GenericError,
+                    });
                 }
 
                 response.data().try_into()

src/yubikey.rs

@@ -55,6 +55,7 @@ use {
         apdu::StatusWords,
         consts::{TAG_ADMIN_FLAGS_1, TAG_ADMIN_TIMESTAMP},
         metadata::AdminData,
+        mgm,
         transaction::ChangeRefAction,
         Buffer, ObjectId,
     },
@@ -71,12 +72,6 @@ pub(crate) const ALGO_3DES: u8 = 0x03;
 /// Card management key
 pub(crate) const KEY_CARDMGM: u8 = 0x9b;
 
-/// MGMT Applet ID.
-///
-/// <https://developers.yubico.com/PIV/Introduction/Admin_access.html>
-#[cfg(feature = "untested")]
-const MGMT_AID: [u8; 8] = [0xa0, 0x00, 0x00, 0x05, 0x27, 0x47, 0x11, 0x17];
-
 const TAG_DYN_AUTH: u8 = 0x7c;
 
 /// Cached YubiKey PIN.
@@ -387,7 +382,7 @@ impl YubiKey {
 
         let status_words = Apdu::new(Ins::SelectApplication)
             .p1(0x04)
-            .data(MGMT_AID)
+            .data(mgm::APPLET_ID)
             .transmit(&txn, 255)?
             .status_words();
 
@@ -396,7 +391,12 @@ impl YubiKey {
                 "Failed selecting mgmt application: {:04x}",
                 status_words.code()
             );
-            return Err(Error::GenericError);
+            return Err(match status_words {
+                StatusWords::NotFoundError => Error::AppletNotFound {
+                    applet_name: mgm::APPLET_NAME,
+                },
+                _ => Error::GenericError,
+            });
         }
 
         Ok(())
@@ -682,23 +682,40 @@ impl<'a> TryFrom<&'a Reader<'_>> for YubiKey {
 
         info!("connected to reader: {}", reader.name());
 
-        let (version, serial) = {
+        let mut app_version_serial = || -> Result<(Version, Serial)> {
             let txn = Transaction::new(&mut card)?;
             txn.select_application()?;
 
             let v = txn.get_version()?;
             let s = txn.get_serial(v)?;
-            (v, s)
+            Ok((v, s))
         };
 
-        let yubikey = YubiKey {
-            card,
-            name: String::from(reader.name()),
-            pin: None,
-            version,
-            serial,
-        };
+        match app_version_serial() {
+            Err(e) => {
+                error!("Could not use reader: {}", e);
 
-        Ok(yubikey)
+                // We were unable to use the card, so we've effectively only connected as
+                // a side-effect of determining this. Avoid disrupting its internal state
+                // any further (e.g. preserve the PIN cache of whatever applet is selected
+                // currently).
+                if let Err((_, e)) = card.disconnect(pcsc::Disposition::LeaveCard) {
+                    error!("Failed to disconnect gracefully from card: {}", e);
+                }
+
+                Err(e)
+            }
+            Ok((version, serial)) => {
+                let yubikey = YubiKey {
+                    card,
+                    name: String::from(reader.name()),
+                    pin: None,
+                    version,
+                    serial,
+                };
+
+                Ok(yubikey)
+            }
+        }
     }
 }