From 1ca99815afd65ad23bb9f95d2ee5d0de451a3494 Mon Sep 17 00:00:00 2001
From: Pierre Chifflier <chifflier@wzdftpd.net>
Date: Wed, 21 Feb 2024 13:59:32 +0100
Subject: [PATCH] Option: require T::Tagged, and check tag before constraints
 (Closes #27)

---
 src/asn1_types/optional.rs             | 16 +++++-
 tests/issue-27-option-struct-derive.rs | 71 ++++++++++++++++++++++++++
 2 files changed, 85 insertions(+), 2 deletions(-)
 create mode 100644 tests/issue-27-option-struct-derive.rs

diff --git a/src/asn1_types/optional.rs b/src/asn1_types/optional.rs
index a8027ab..4aa31ae 100644
--- a/src/asn1_types/optional.rs
+++ b/src/asn1_types/optional.rs
@@ -8,14 +8,20 @@ use crate::*;
 impl<'a, T> FromBer<'a> for Option<T>
 where
     T: FromBer<'a>,
+    T: Tagged,
 {
     fn from_ber(bytes: &'a [u8]) -> ParseResult<Self> {
         if bytes.is_empty() {
             return Ok((bytes, None));
         }
+        if let Ok((_, header)) = Header::from_ber(bytes) {
+            if T::TAG != header.tag {
+                // not the expected tag, early return
+                return Ok((bytes, None));
+            }
+        }
         match T::from_ber(bytes) {
             Ok((rem, t)) => Ok((rem, Some(t))),
-            Err(nom::Err::Error(Error::UnexpectedTag { .. })) => Ok((bytes, None)),
             Err(e) => Err(e),
         }
     }
@@ -24,14 +30,20 @@ where
 impl<'a, T> FromDer<'a> for Option<T>
 where
     T: FromDer<'a>,
+    T: Tagged,
 {
     fn from_der(bytes: &'a [u8]) -> ParseResult<Self> {
         if bytes.is_empty() {
             return Ok((bytes, None));
         }
+        if let Ok((_, header)) = Header::from_der(bytes) {
+            if T::TAG != header.tag {
+                // not the expected tag, early return
+                return Ok((bytes, None));
+            }
+        }
         match T::from_der(bytes) {
             Ok((rem, t)) => Ok((rem, Some(t))),
-            Err(nom::Err::Error(Error::UnexpectedTag { .. })) => Ok((bytes, None)),
             Err(e) => Err(e),
         }
     }
diff --git a/tests/issue-27-option-struct-derive.rs b/tests/issue-27-option-struct-derive.rs
new file mode 100644
index 0000000..5c6e945
--- /dev/null
+++ b/tests/issue-27-option-struct-derive.rs
@@ -0,0 +1,71 @@
+use asn1_rs::*;
+
+#[derive(DerSequence, Debug, PartialEq)]
+struct TestBool {
+    a: u16,
+    b: Option<bool>,
+    c: u32,
+}
+
+#[test]
+fn issue_27_1() {
+    let x = TestBool {
+        a: 0x1234,
+        b: None,
+        c: 0x5678,
+    };
+
+    let expected = &[48, 8, 2, 2, 18, 52, 2, 2, 86, 120];
+
+    let (_, val) = TestBool::from_der(expected).unwrap();
+    assert_eq!(val, x);
+}
+
+#[test]
+fn issue_27_2() {
+    let x = TestBool {
+        a: 0x1234,
+        b: Some(true),
+        c: 0x5678,
+    };
+
+    let expected = &[48, 11, 2, 2, 18, 52, 1, 1, 255, 2, 2, 86, 120];
+
+    let (_, val) = TestBool::from_der(expected).unwrap();
+    assert_eq!(val, x);
+}
+
+#[derive(DerSequence, Debug, PartialEq)]
+struct TestInt {
+    a: u16,
+    b: Option<u32>,
+    c: bool,
+}
+
+#[test]
+fn issue_27_3() {
+    let x = TestInt {
+        a: 0x1234,
+        b: None,
+        c: true,
+    };
+
+    let expected = &[48, 7, 2, 2, 18, 52, 1, 1, 255];
+
+    let (_, val) = TestInt::from_der(expected).unwrap();
+    assert_eq!(val, x);
+}
+
+#[test]
+fn issue_27_4() {
+    let x = TestInt {
+        a: 0x1234,
+        b: Some(0x5678),
+        c: true,
+    };
+
+    let expected = &[48, 11, 2, 2, 18, 52, 2, 2, 86, 120, 1, 1, 255];
+
+    let (_, val) = TestInt::from_der(expected).unwrap();
+    assert_eq!(val, x);
+}