Add constructor for creating Asn1Object from a textual OID representation

This is effectively a wrapper for OBJ_txt2obj.

openssl-sys/src/object.rs

@@ -16,4 +16,5 @@ extern "C" {
     pub fn OBJ_find_sigid_algs(signid: c_int, pdig_nid: *mut c_int, ppkey_nid: *mut c_int)
         -> c_int;
     pub fn OBJ_sn2nid(sn: *const libc::c_char) -> libc::c_int;
+    pub fn OBJ_txt2obj(s: *const libc::c_char, no_name: libc::c_int) -> *mut ASN1_OBJECT;
 }

openssl/src/asn1.rs

@@ -537,6 +537,24 @@ foreign_type_and_impl_send_sync! {
     pub struct Asn1ObjectRef;
 }
 
+impl Asn1Object {
+    /// Constructs an ASN.1 Object Identifier from a string representation of
+    /// the OID.
+    ///
+    /// This corresponds to [`OBJ_txt2obj`].
+    ///
+    /// [`OBJ_txt2obj`]: https://www.openssl.org/docs/man1.1.0/man3/OBJ_txt2obj.html
+    #[allow(clippy::should_implement_trait)]
+    pub fn from_str(txt: &str) -> Result<Asn1Object, ErrorStack> {
+        unsafe {
+            ffi::init();
+            let txt = CString::new(txt).unwrap();
+            let obj: *mut ffi::ASN1_OBJECT = cvt_p(ffi::OBJ_txt2obj(txt.as_ptr() as *const _, 0))?;
+            Ok(Asn1Object::from_ptr(obj))
+        }
+    }
+}
+
 impl Asn1ObjectRef {
     /// Returns the NID associated with this OID.
     pub fn nid(&self) -> Nid {
@@ -584,6 +602,7 @@ mod tests {
     use super::*;
 
     use bn::BigNum;
+    use nid::Nid;
 
     /// Tests conversion between BigNum and Asn1Integer.
     #[test]
@@ -660,4 +679,17 @@ mod tests {
         assert!(b_ref <= a_ref);
         assert!(c_ref < a_ref);
     }
+
+    #[test]
+    fn object_from_str() {
+        let object = Asn1Object::from_str("2.16.840.1.101.3.4.2.1").unwrap();
+        assert_eq!(object.nid(), Nid::SHA256);
+    }
+
+    #[test]
+    fn object_from_str_with_invalid_input() {
+        Asn1Object::from_str("NOT AN OID")
+            .map(|object| object.to_string())
+            .expect_err("parsing invalid OID should fail");
+    }
 }