add print cert info method in support of status action a la yubico-piv-tool

Cargo.toml

@@ -34,6 +34,7 @@ sha-1 = "0.8"
 subtle = "2"
 x509-parser = "0.6"
 zeroize = "1"
+sha2 = "0.8"
 
 [dev-dependencies]
 env_logger = "0.7"
@@ -43,3 +44,4 @@ untested = []
 
 [package.metadata.docs.rs]
 all-features = true
+

src/certificate.rs

@@ -48,6 +48,7 @@ use rsa::{PublicKey, RSAPublicKey};
 use std::fmt;
 use x509_parser::{parse_x509_der, x509::SubjectPublicKeyInfo};
 use zeroize::Zeroizing;
+use sha2::{Sha256, Digest};
 
 // TODO: Make these der_parser::oid::Oid constants when it has const fn support.
 const OID_RSA_ENCRYPTION: &str = "1.2.840.113549.1.1.1";
@@ -400,3 +401,40 @@ mod read_pki {
         }
     }
 }
+
+///Write information about certificate found in slot a la yubico-piv-tool output.
+pub fn print_cert_info(yubikey: &mut YubiKey, slot: SlotId) -> Result<(), Error> {
+    let txn = yubikey.begin_transaction()?;
+    let buf = match read_certificate(&txn, slot) {
+        Ok(b) => b,
+        Err(e) => {
+            println!("error reading certificate in slot {:?}: {}", slot, e);
+            return Err(e);
+        }
+    };
+
+    if !buf.is_empty() {
+        let mut hasher = Sha256::new();
+        hasher.input(buf.clone().to_vec());
+        let fingerprint = hasher.result();
+
+        let slot_id: u8 = slot.into();
+        println!("Slot {:x}: ", slot_id);
+        match parse_x509_der(&buf) {
+            Ok((_rem, cert)) => {
+                println!("\tAlgorithm: {}", cert.tbs_certificate.subject_pki.algorithm.algorithm);
+                println!("\tSubject: {}", cert.tbs_certificate.subject);
+                println!("\tIssuer: {}", cert.tbs_certificate.issuer);
+                println!("\tFingerprint: {:X}", fingerprint);
+                println!("\tNot Before: {}", cert.tbs_certificate.validity.not_before.asctime());
+                println!("\tNot After: {}", cert.tbs_certificate.validity.not_after.asctime());
+            }
+            _ => {
+                println!("Failed to parse certificate");
+                return Err(Error::GenericError);
+            }
+        };
+    }
+
+    Ok(())
+}