Implement get_security_support_template()

openpgp-card-sequoia/src/lib.rs

@@ -35,7 +35,7 @@ use openpgp_card::algorithm::{Algo, AlgoInfo, Curve};
 use openpgp_card::card_do::{
     ApplicationId, ApplicationRelatedData, Cardholder, ExtendedCap,
     ExtendedLengthInfo, Features, Fingerprint, Historical, KeySet, PWStatus,
-    Sex,
+    SecuritySupportTemplate, Sex,
 };
 use openpgp_card::crypto_data::{
     CardUploadableKey, Cryptogram, EccKey, EccType, Hash, PrivateKeyMaterial,
@@ -684,7 +684,9 @@ impl CardBase {
     }
 
     // --- security support template (7a) ---
-    pub fn get_security_support_template(&mut self) -> Result<Vec<u8>> {
+    pub fn get_security_support_template(
+        &mut self,
+    ) -> Result<SecuritySupportTemplate> {
         self.card_app.get_security_support_template()
     }
 

openpgp-card/src/card_app.rs

@@ -10,7 +10,9 @@ use anyhow::{anyhow, Result};
 
 use crate::algorithm::{Algo, AlgoInfo, AlgoSimple, RsaAttrs};
 use crate::apdu::{commands, response::Response};
-use crate::card_do::{ApplicationRelatedData, Cardholder, Sex};
+use crate::card_do::{
+    ApplicationRelatedData, Cardholder, SecuritySupportTemplate, Sex,
+};
 use crate::crypto_data::{
     CardUploadableKey, Cryptogram, EccType, Hash, PublicKeyMaterial,
 };
@@ -159,14 +161,30 @@ impl CardApp {
     }
 
     // --- security support template (7a) ---
-    // FIXME: parse data into a proper data structure
-    pub fn get_security_support_template(&mut self) -> Result<Vec<u8>> {
+    pub fn get_security_support_template(
+        &mut self,
+    ) -> Result<SecuritySupportTemplate> {
         let sst = commands::get_security_support_template();
         let resp = apdu::send_command(&mut self.card_client, sst, true)?;
         resp.check_ok()?;
 
         let tlv = Tlv::try_from(resp.data()?)?;
-        Ok(tlv.serialize())
+        let res = tlv
+            .find(&Tag::from([0x93]))
+            .ok_or(anyhow!("Couldn't get SecuritySupportTemplate DO"))?;
+
+        if let TlvEntry::S(data) = res {
+            let mut data = data.to_vec();
+            assert_eq!(data.len(), 3);
+
+            data.insert(0, 0); // prepend a zero
+            let data: [u8; 4] = data.try_into().unwrap();
+
+            let dsc: u32 = u32::from_be_bytes(data);
+            Ok(SecuritySupportTemplate { dsc })
+        } else {
+            Err(anyhow!("Failed to process SecuritySupportTemplate"))
+        }
     }
 
     // DO "Algorithm Information" (0xFA)

openpgp-card/src/card_do/mod.rs

@@ -168,6 +168,19 @@ impl ApplicationRelatedData {
     }
 }
 
+#[derive(Debug)]
+pub struct SecuritySupportTemplate {
+    // Digital signature counter [3 bytes]
+    // (counts usage of Compute Digital Signature command)
+    pub(crate) dsc: u32,
+}
+
+impl SecuritySupportTemplate {
+    pub fn get_signature_count(&self) -> u32 {
+        self.dsc
+    }
+}
+
 /// An OpenPGP key generation Time
 #[derive(Clone, Eq, PartialEq, Debug)]
 pub struct KeyGeneration(u32);