Preliminary x.509 support. This is some of the ugliest code I've ever written, but it works. Ish.

src/x509/validity.rs

@@ -0,0 +1,118 @@
+use chrono::{DateTime,Utc};
+use simple_asn1::{ASN1Block,ASN1Class,ASN1EncodeErr,FromASN1,ToASN1};
+use x509::error::X509ParseError;
+
+#[derive(Clone,Debug,PartialEq)]
+pub struct Validity {
+    not_before: DateTime<Utc>,
+    not_after:  DateTime<Utc>
+}
+
+fn decode_validity_data(bs: &ASN1Block) -> Result<Validity,X509ParseError> {
+    // Validity ::= SEQUENCE {
+    //      notBefore      Time,
+    //      notAfter       Time  }
+    match bs {
+        &ASN1Block::Sequence(_, _, ref valxs) => {
+            if valxs.len() != 2 {
+                return Err(X509ParseError::IllFormedValidity);
+            }
+            let nb = get_time(&valxs[0])?;
+            let na = get_time(&valxs[1])?;
+            Ok(Validity{ not_before: nb, not_after: na })
+        }
+        _ =>
+            Err(X509ParseError::IllFormedValidity)
+    }
+}
+
+impl FromASN1 for Validity {
+    type Error = X509ParseError;
+
+    fn from_asn1(v: &[ASN1Block])
+        -> Result<(Validity,&[ASN1Block]),X509ParseError>
+    {
+        match v.split_first() {
+            None =>
+                Err(X509ParseError::NotEnoughData),
+            Some((x, rest)) => {
+                let v = decode_validity_data(&x)?;
+                Ok((v, rest))
+            }
+        }
+    }
+}
+
+fn encode_validity_data(c: ASN1Class, v: &Validity) -> ASN1Block {
+    let mut vs = Vec::with_capacity(2);
+    vs.push(ASN1Block::GeneralizedTime(c, 0, v.not_before));
+    vs.push(ASN1Block::GeneralizedTime(c, 0, v.not_after));
+    ASN1Block::Sequence(c, 0, vs)
+}
+
+impl ToASN1 for Validity {
+    type Error = ASN1EncodeErr;
+
+    fn to_asn1_class(&self, c: ASN1Class)
+        -> Result<Vec<ASN1Block>,ASN1EncodeErr>
+    {
+        let block = encode_validity_data(c, self);
+        Ok(vec![block])
+    }
+}
+
+fn get_time(b: &ASN1Block) -> Result<DateTime<Utc>, X509ParseError> {
+    match b {
+        &ASN1Block::UTCTime(_, _, v)         => Ok(v.clone()),
+        &ASN1Block::GeneralizedTime(_, _, v) => Ok(v.clone()),
+        _                                 =>
+            Err(X509ParseError::IllFormedValidity)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use chrono::TimeZone;
+    use chrono::offset::LocalResult;
+    use quickcheck::{Arbitrary,Gen};
+    use rand::Rng;
+    use super::*;
+
+    fn arbitrary_date<G: Gen>(g: &mut G) -> DateTime<Utc> {
+        loop {
+            let y  = g.gen_range(1900,3000);
+            let mo = g.gen_range(0,12);
+            let d  = g.gen_range(0,31);
+            let h  = g.gen_range(0,24);
+            let mi = g.gen_range(0,60);
+            let s  = g.gen_range(0,60);
+            match Utc.ymd_opt(y,mo,d).and_hms_opt(h,mi,s) {
+                LocalResult::None =>
+                    continue,
+                LocalResult::Single(x) =>
+                    return x,
+                LocalResult::Ambiguous(x,_) =>
+                    return x
+            }
+        }
+    }
+
+    impl Arbitrary for Validity {
+        fn arbitrary<G: Gen>(g: &mut G) -> Validity {
+            Validity {
+                not_before: arbitrary_date(g),
+                not_after:  arbitrary_date(g)
+            }
+        }
+    }
+
+    quickcheck! {
+        fn validity_roundtrips(v: Validity) -> bool {
+            let bstr = encode_validity_data(ASN1Class::Universal, &v);
+            match decode_validity_data(&bstr) {
+                Err(_) => false,
+                Ok(v2) => v == v2
+            }
+        }
+    }
+}