Refactor X.509 encoding library to use the der crate

The der crate-based implementation is significantly less code and follows a
more consistent pattern. Since this allows defining types with encoding
rules, this will make it much simpler to add structures for ML-DSA
structures for Caliptra 2.0.

The der crate is part of RustCrypto and is intended to be
embedded/no_std friendly.

crypto/src/signer.rs

@@ -10,6 +10,22 @@ pub struct EcdsaSig {
     pub s: CryptoBuf,
 }
 
+pub const MAX_ENCODED_ECDSA_PUB: usize = 1 + (2 * CryptoBuf::MAX_SIZE);
+
+#[derive(ZeroizeOnDrop)]
+pub struct EncodedEcdsaPub(pub ArrayVec<u8, MAX_ENCODED_ECDSA_PUB>);
+
+impl From<&EcdsaPub> for EncodedEcdsaPub {
+    fn from(value: &EcdsaPub) -> Self {
+        // PANIC FREE: Size of data is same is 1 + x_max + y_max
+        let mut encoded = EncodedEcdsaPub(ArrayVec::<u8, MAX_ENCODED_ECDSA_PUB>::new());
+        encoded.0.push(0x4);
+        encoded.0.try_extend_from_slice(value.x.bytes()).unwrap();
+        encoded.0.try_extend_from_slice(value.y.bytes()).unwrap();
+        encoded
+    }
+}
+
 /// An ECDSA public key
 #[derive(ZeroizeOnDrop)]
 pub struct EcdsaPub {

dpe/Cargo.toml

@@ -30,14 +30,15 @@ caliptra-cfi-lib-git = { workspace = true, default-features = false, features =
 caliptra-cfi-derive-git.workspace = true
 constant_time_eq = "0.3.0"
 crypto = {path = "../crypto", default-features = false}
+der = { version = "0.7.9", default-features = false, features = ["oid", "derive"] }
 platform = {path = "../platform", default-features = false}
 ufmt = { git = "https://github.com/korran/ufmt.git", rev = "1d0743c1ffffc68bc05ca8eeb81c166192863f33", features = ["inline"] }
 zerocopy.workspace = true
 zeroize = { version = "1.6.0", default-features = false, features = ["zeroize_derive"] }
 cfg-if = "1.0.0"
 
 [dev-dependencies]
-asn1 = "0.13.0"
+asn1 = { version = "0.13.0", default-features = false}
 caliptra-cfi-lib-git = { workspace = true, features = ["cfi-test"] }
 openssl.workspace = true
 x509-parser = "0.15.1"

dpe/src/commands/certify_key.rs

@@ -5,7 +5,7 @@ use crate::{
     dpe_instance::{DpeEnv, DpeInstance, DpeTypes},
     response::{CertifyKeyResp, DpeErrorCode, Response, ResponseHdr},
     tci::TciNodeData,
-    x509::{CertWriter, DirectoryString, MeasurementData, Name},
+    x509::{CertWriter, MeasurementData, Name},
     DPE_PROFILE, MAX_CERT_SIZE, MAX_HANDLES,
 };
 use bitflags::bitflags;
@@ -116,8 +116,8 @@ impl CommandExecution for CertifyKeyCmd {
         let truncated_subj_serial = &subj_serial[..64];
 
         let subject_name = Name {
-            cn: DirectoryString::PrintableString(b"DPE Leaf"),
-            serial: DirectoryString::PrintableString(truncated_subj_serial),
+            cn: b"DPE Leaf",
+            serial: truncated_subj_serial,
         };
 
         // Get TCI Nodes
@@ -178,7 +178,7 @@ impl CommandExecution for CertifyKeyCmd {
                         let cert_validity = env.platform.get_cert_validity()?;
                         let mut bytes_written = tbs_writer.encode_ecdsa_tbs(
                             /*serial=*/
-                            &subject_name.serial.bytes()[..20], // Serial number must be truncated to 20 bytes
+                            &subject_name.serial[..20], // Serial number must be truncated to 20 bytes
                             &issuer_name[..issuer_len],
                             &subject_name,
                             &pub_key,
@@ -671,13 +671,13 @@ mod tests {
             .unwrap();
         let truncated_subj_serial = &subj_serial[..64];
         let subject_name = Name {
-            cn: DirectoryString::PrintableString(b"DPE Leaf"),
-            serial: DirectoryString::PrintableString(truncated_subj_serial),
+            cn: b"DPE Leaf",
+            serial: truncated_subj_serial,
         };
         let expected_subject_name = format!(
             "CN={}, serialNumber={}",
-            str::from_utf8(subject_name.cn.bytes()).unwrap(),
-            str::from_utf8(&subject_name.serial.bytes()).unwrap()
+            str::from_utf8(subject_name.cn).unwrap(),
+            str::from_utf8(&subject_name.serial).unwrap()
         );
         let actual_subject_name = cri.subject.to_string_with_registry(oid_registry()).unwrap();
         assert_eq!(expected_subject_name, actual_subject_name);

dpe/src/response.rs

@@ -5,8 +5,9 @@ Abstract:
     DPE reponses and serialization.
 --*/
 use crate::{
-    context::ContextHandle, validation::ValidationError, CURRENT_PROFILE_MAJOR_VERSION,
-    CURRENT_PROFILE_MINOR_VERSION, DPE_PROFILE, MAX_CERT_SIZE, MAX_HANDLES,
+    context::ContextHandle, validation::ValidationError, x509::X509Error,
+    CURRENT_PROFILE_MAJOR_VERSION, CURRENT_PROFILE_MINOR_VERSION, DPE_PROFILE, MAX_CERT_SIZE,
+    MAX_HANDLES,
 };
 use crypto::CryptoError;
 use platform::PlatformError;
@@ -151,6 +152,7 @@ pub enum DpeErrorCode {
     Platform(PlatformError) = 0x01000000,
     Crypto(CryptoError) = 0x02000000,
     Validation(ValidationError) = 0x03000000,
+    X509(X509Error) = 0x04000000,
 }
 
 impl From<PlatformError> for DpeErrorCode {
@@ -165,6 +167,12 @@ impl From<CryptoError> for DpeErrorCode {
     }
 }
 
+impl From<X509Error> for DpeErrorCode {
+    fn from(e: X509Error) -> Self {
+        DpeErrorCode::X509(e)
+    }
+}
+
 impl DpeErrorCode {
     /// Get the spec-defined numeric error code. This does not include the
     /// extended error information returned from the Platform and Crypto
@@ -181,6 +189,7 @@ impl DpeErrorCode {
             DpeErrorCode::Platform(e) => self.discriminant() | e.discriminant() as u32,
             DpeErrorCode::Crypto(e) => self.discriminant() | e.discriminant() as u32,
             DpeErrorCode::Validation(e) => self.discriminant() | e.discriminant() as u32,
+            DpeErrorCode::X509(e) => self.discriminant() | e.discriminant() as u32,
             _ => self.discriminant(),
         }
     }
@@ -194,6 +203,7 @@ impl DpeErrorCode {
         match self {
             DpeErrorCode::Platform(e) => e.get_error_detail(),
             DpeErrorCode::Crypto(e) => e.get_error_detail(),
+            DpeErrorCode::X509(e) => e.get_error_detail(),
             _ => None,
         }
     }