# asn1.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/openssl-0.10.33/src/asn1.rs`.
Keywords: rust, rustlang, rust-lang

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    #![deny(missing_docs)]

    //! Defines the format of certificiates
    //!
    //! This module is used by [`x509`] and other certificate building functions
    //! to describe time, strings, and objects.
    //!
    //! Abstract Syntax Notation One is an interface description language.
    //! The specification comes from [X.208] by OSI, and rewritten in X.680.
    //! ASN.1 describes properties of an object with a type set.  Those types
    //! can be atomic, structured, choice, and other (CHOICE and ANY).  These
    //! types are expressed as a number and the assignment operator ::=  gives
    //! the type a name.
    //!
    //! The implementation here provides a subset of the ASN.1 types that OpenSSL
    //! uses, especially in the properties of a certificate used in HTTPS.
    //!
    //! [X.208]: https://www.itu.int/rec/T-REC-X.208-198811-W/en
    //! [`x509`]: ../x509/struct.X509Builder.html
    //!
    //! ## Examples
    //!
    //! ```
    //! use openssl::asn1::Asn1Time;
    //! let tomorrow = Asn1Time::days_from_now(1);
    //! ```
    use cfg_if::cfg_if;
    use foreign_types::{ForeignType, ForeignTypeRef};
    use libc::{c_char, c_int, c_long, time_t};
    #[cfg(ossl102)]
    use std::cmp::Ordering;
    use std::ffi::CString;
    use std::fmt;
    use std::ptr;
    use std::slice;
    use std::str;

    use crate::bio::MemBio;
    use crate::bn::{BigNum, BigNumRef};
    use crate::error::ErrorStack;
    use crate::nid::Nid;
    use crate::string::OpensslString;
    use crate::{cvt, cvt_p};

    foreign_type_and_impl_send_sync! {
        type CType = ffi::ASN1_GENERALIZEDTIME;
        fn drop = ffi::ASN1_GENERALIZEDTIME_free;

        /// Non-UTC representation of time
        ///
        /// If a time can be represented by UTCTime, UTCTime is used
        /// otherwise, ASN1_GENERALIZEDTIME is used.  This would be, for
        /// example outside the year range of 1950-2049.
        ///
        /// [ASN1_GENERALIZEDTIME_set] documentation from OpenSSL provides
        /// further details of implmentation.  Note: these docs are from the master
        /// branch as documentation on the 1.1.0 branch did not include this page.
        ///
        /// [ASN1_GENERALIZEDTIME_set]: https://www.openssl.org/docs/manmaster/man3/ASN1_GENERALIZEDTIME_set.html
        pub struct Asn1GeneralizedTime;
        /// Reference to a [`Asn1GeneralizedTime`]
        ///
        /// [`Asn1GeneralizedTime`]: struct.Asn1GeneralizedTime.html
        pub struct Asn1GeneralizedTimeRef;
    }

    impl fmt::Display for Asn1GeneralizedTimeRef {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            unsafe {
                let mem_bio = match MemBio::new() {
                    Err(_) => return f.write_str("error"),
                    Ok(m) => m,
                };
                let print_result = cvt(ffi::ASN1_GENERALIZEDTIME_print(
                    mem_bio.as_ptr(),
                    self.as_ptr(),
                ));
                match print_result {
                    Err(_) => f.write_str("error"),
                    Ok(_) => f.write_str(str::from_utf8_unchecked(mem_bio.get_buf())),
                }
            }
        }
    }

    /// The type of an ASN.1 value.
    #[derive(Debug, Copy, Clone, PartialEq, Eq)]
    pub struct Asn1Type(c_int);

    #[allow(missing_docs)] // no need to document the constants
    impl Asn1Type {
        pub const EOC: Asn1Type = Asn1Type(ffi::V_ASN1_EOC);

        pub const BOOLEAN: Asn1Type = Asn1Type(ffi::V_ASN1_BOOLEAN);

        pub const INTEGER: Asn1Type = Asn1Type(ffi::V_ASN1_INTEGER);

        pub const BIT_STRING: Asn1Type = Asn1Type(ffi::V_ASN1_BIT_STRING);

        pub const OCTET_STRING: Asn1Type = Asn1Type(ffi::V_ASN1_OCTET_STRING);

        pub const NULL: Asn1Type = Asn1Type(ffi::V_ASN1_NULL);

        pub const OBJECT: Asn1Type = Asn1Type(ffi::V_ASN1_OBJECT);

        pub const OBJECT_DESCRIPTOR: Asn1Type = Asn1Type(ffi::V_ASN1_OBJECT_DESCRIPTOR);

        pub const EXTERNAL: Asn1Type = Asn1Type(ffi::V_ASN1_EXTERNAL);

        pub const REAL: Asn1Type = Asn1Type(ffi::V_ASN1_REAL);

        pub const ENUMERATED: Asn1Type = Asn1Type(ffi::V_ASN1_ENUMERATED);

        pub const UTF8STRING: Asn1Type = Asn1Type(ffi::V_ASN1_UTF8STRING);

        pub const SEQUENCE: Asn1Type = Asn1Type(ffi::V_ASN1_SEQUENCE);

        pub const SET: Asn1Type = Asn1Type(ffi::V_ASN1_SET);

        pub const NUMERICSTRING: Asn1Type = Asn1Type(ffi::V_ASN1_NUMERICSTRING);

        pub const PRINTABLESTRING: Asn1Type = Asn1Type(ffi::V_ASN1_PRINTABLESTRING);

        pub const T61STRING: Asn1Type = Asn1Type(ffi::V_ASN1_T61STRING);

        pub const TELETEXSTRING: Asn1Type = Asn1Type(ffi::V_ASN1_TELETEXSTRING);

        pub const VIDEOTEXSTRING: Asn1Type = Asn1Type(ffi::V_ASN1_VIDEOTEXSTRING);

        pub const IA5STRING: Asn1Type = Asn1Type(ffi::V_ASN1_IA5STRING);

        pub const UTCTIME: Asn1Type = Asn1Type(ffi::V_ASN1_UTCTIME);

        pub const GENERALIZEDTIME: Asn1Type = Asn1Type(ffi::V_ASN1_GENERALIZEDTIME);

        pub const GRAPHICSTRING: Asn1Type = Asn1Type(ffi::V_ASN1_GRAPHICSTRING);

        pub const ISO64STRING: Asn1Type = Asn1Type(ffi::V_ASN1_ISO64STRING);

        pub const VISIBLESTRING: Asn1Type = Asn1Type(ffi::V_ASN1_VISIBLESTRING);

        pub const GENERALSTRING: Asn1Type = Asn1Type(ffi::V_ASN1_GENERALSTRING);

        pub const UNIVERSALSTRING: Asn1Type = Asn1Type(ffi::V_ASN1_UNIVERSALSTRING);

        pub const BMPSTRING: Asn1Type = Asn1Type(ffi::V_ASN1_BMPSTRING);

        /// Constructs an `Asn1Type` from a raw OpenSSL value.
        pub fn from_raw(value: c_int) -> Self {
            Asn1Type(value)
        }

        /// Returns the raw OpenSSL value represented by this type.
        pub fn as_raw(&self) -> c_int {
            self.0
        }
    }

    /// Difference between two ASN1 times.
    ///
    /// This `struct` is created by the [`diff`] method on [`Asn1TimeRef`]. See its
    /// documentation for more.
    ///
    /// [`diff`]: struct.Asn1TimeRef.html#method.diff
    /// [`Asn1TimeRef`]: struct.Asn1TimeRef.html
    #[derive(Debug, Clone, PartialEq, Eq, Hash)]
    #[cfg(ossl102)]
    pub struct TimeDiff {
        /// Difference in days
        pub days: c_int,
        /// Difference in seconds.
        ///
        /// This is always less than the number of seconds in a day.
        pub secs: c_int,
    }

    foreign_type_and_impl_send_sync! {
        type CType = ffi::ASN1_TIME;
        fn drop = ffi::ASN1_TIME_free;
        /// Time storage and comparison
        ///
        /// Asn1Time should be used to store and share time information
        /// using certificates.  If Asn1Time is set using a string, it must
        /// be in either YYMMDDHHMMSSZ, YYYYMMDDHHMMSSZ, or another ASN.1 format.
        ///
        /// [ASN_TIME_set] documentation at OpenSSL explains the ASN.1 implementation
        /// used by OpenSSL.
        ///
        /// [ASN_TIME_set]: https://www.openssl.org/docs/man1.1.0/crypto/ASN1_TIME_set.html
        pub struct Asn1Time;
        /// Reference to an [`Asn1Time`]
        ///
        /// [`Asn1Time`]: struct.Asn1Time.html
        pub struct Asn1TimeRef;
    }

    impl Asn1TimeRef {
        /// Find difference between two times
        ///
        /// This corresponds to [`ASN1_TIME_diff`].
        ///
        /// [`ASN1_TIME_diff`]: https://www.openssl.org/docs/man1.1.0/crypto/ASN1_TIME_diff.html
        #[cfg(ossl102)]
        pub fn diff(&self, compare: &Self) -> Result<TimeDiff, ErrorStack> {
            let mut days = 0;
            let mut secs = 0;
            let other = compare.as_ptr();

            let err = unsafe { ffi::ASN1_TIME_diff(&mut days, &mut secs, self.as_ptr(), other) };

            match err {
                0 => Err(ErrorStack::get()),
                _ => Ok(TimeDiff { days, secs }),
            }
        }

        /// Compare two times
        ///
        /// This corresponds to [`ASN1_TIME_compare`] but is implemented using [`diff`] so that it is
        /// also supported on older versions of OpenSSL.
        ///
        /// [`ASN1_TIME_compare`]: https://www.openssl.org/docs/man1.1.1/man3/ASN1_TIME_compare.html
        /// [`diff`]: struct.Asn1TimeRef.html#method.diff
        #[cfg(ossl102)]
        pub fn compare(&self, other: &Self) -> Result<Ordering, ErrorStack> {
            let d = self.diff(other)?;
            if d.days > 0 || d.secs > 0 {
                return Ok(Ordering::Less);
            }
            if d.days < 0 || d.secs < 0 {
                return Ok(Ordering::Greater);
            }

            Ok(Ordering::Equal)
        }
    }

    #[cfg(ossl102)]
    impl PartialEq for Asn1TimeRef {
        fn eq(&self, other: &Asn1TimeRef) -> bool {
            self.diff(other)
                .map(|t| t.days == 0 && t.secs == 0)
                .unwrap_or(false)
        }
    }

    #[cfg(ossl102)]
    impl PartialEq<Asn1Time> for Asn1TimeRef {
        fn eq(&self, other: &Asn1Time) -> bool {
            self.diff(other)
                .map(|t| t.days == 0 && t.secs == 0)
                .unwrap_or(false)
        }
    }

    #[cfg(ossl102)]
    impl<'a> PartialEq<Asn1Time> for &'a Asn1TimeRef {
        fn eq(&self, other: &Asn1Time) -> bool {
            self.diff(other)
                .map(|t| t.days == 0 && t.secs == 0)
                .unwrap_or(false)
        }
    }

    #[cfg(ossl102)]
    impl PartialOrd for Asn1TimeRef {
        fn partial_cmp(&self, other: &Asn1TimeRef) -> Option<Ordering> {
            self.compare(other).ok()
        }
    }

    #[cfg(ossl102)]
    impl PartialOrd<Asn1Time> for Asn1TimeRef {
        fn partial_cmp(&self, other: &Asn1Time) -> Option<Ordering> {
            self.compare(other).ok()
        }
    }

    #[cfg(ossl102)]
    impl<'a> PartialOrd<Asn1Time> for &'a Asn1TimeRef {
        fn partial_cmp(&self, other: &Asn1Time) -> Option<Ordering> {
            self.compare(other).ok()
        }
    }

    impl fmt::Display for Asn1TimeRef {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            unsafe {
                let mem_bio = match MemBio::new() {
                    Err(_) => return f.write_str("error"),
                    Ok(m) => m,
                };
                let print_result = cvt(ffi::ASN1_TIME_print(mem_bio.as_ptr(), self.as_ptr()));
                match print_result {
                    Err(_) => f.write_str("error"),
                    Ok(_) => f.write_str(str::from_utf8_unchecked(mem_bio.get_buf())),
                }
            }
        }
    }

    impl fmt::Debug for Asn1TimeRef {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.write_str(&self.to_string())
        }
    }

    impl Asn1Time {
        fn new() -> Result<Asn1Time, ErrorStack> {
            ffi::init();

            unsafe {
                let handle = cvt_p(ffi::ASN1_TIME_new())?;
                Ok(Asn1Time::from_ptr(handle))
            }
        }

        fn from_period(period: c_long) -> Result<Asn1Time, ErrorStack> {
            ffi::init();

            unsafe {
                let handle = cvt_p(ffi::X509_gmtime_adj(ptr::null_mut(), period))?;
                Ok(Asn1Time::from_ptr(handle))
            }
        }

        /// Creates a new time on specified interval in days from now
        pub fn days_from_now(days: u32) -> Result<Asn1Time, ErrorStack> {
            Asn1Time::from_period(days as c_long * 60 * 60 * 24)
        }

        /// Creates a new time from the specified `time_t` value
        pub fn from_unix(time: time_t) -> Result<Asn1Time, ErrorStack> {
            ffi::init();

            unsafe {
                let handle = cvt_p(ffi::ASN1_TIME_set(ptr::null_mut(), time))?;
                Ok(Asn1Time::from_ptr(handle))
            }
        }

        /// Creates a new time corresponding to the specified ASN1 time string.
        ///
        /// This corresponds to [`ASN1_TIME_set_string`].
        ///
        /// [`ASN1_TIME_set_string`]: https://www.openssl.org/docs/manmaster/man3/ASN1_TIME_set_string.html
        #[allow(clippy::should_implement_trait)]
        pub fn from_str(s: &str) -> Result<Asn1Time, ErrorStack> {
            unsafe {
                let s = CString::new(s).unwrap();

                let time = Asn1Time::new()?;
                cvt(ffi::ASN1_TIME_set_string(time.as_ptr(), s.as_ptr()))?;

                Ok(time)
            }
        }

        /// Creates a new time corresponding to the specified X509 time string.
        ///
        /// This corresponds to [`ASN1_TIME_set_string_X509`].
        ///
        /// Requires OpenSSL 1.1.1 or newer.
        ///
        /// [`ASN1_TIME_set_string_X509`]: https://www.openssl.org/docs/manmaster/man3/ASN1_TIME_set_string.html
        #[cfg(ossl111)]
        pub fn from_str_x509(s: &str) -> Result<Asn1Time, ErrorStack> {
            unsafe {
                let s = CString::new(s).unwrap();

                let time = Asn1Time::new()?;
                cvt(ffi::ASN1_TIME_set_string_X509(time.as_ptr(), s.as_ptr()))?;

                Ok(time)
            }
        }
    }

    #[cfg(ossl102)]
    impl PartialEq for Asn1Time {
        fn eq(&self, other: &Asn1Time) -> bool {
            self.diff(other)
                .map(|t| t.days == 0 && t.secs == 0)
                .unwrap_or(false)
        }
    }

    #[cfg(ossl102)]
    impl PartialEq<Asn1TimeRef> for Asn1Time {
        fn eq(&self, other: &Asn1TimeRef) -> bool {
            self.diff(other)
                .map(|t| t.days == 0 && t.secs == 0)
                .unwrap_or(false)
        }
    }

    #[cfg(ossl102)]
    impl<'a> PartialEq<&'a Asn1TimeRef> for Asn1Time {
        fn eq(&self, other: &&'a Asn1TimeRef) -> bool {
            self.diff(other)
                .map(|t| t.days == 0 && t.secs == 0)
                .unwrap_or(false)
        }
    }

    #[cfg(ossl102)]
    impl PartialOrd for Asn1Time {
        fn partial_cmp(&self, other: &Asn1Time) -> Option<Ordering> {
            self.compare(other).ok()
        }
    }

    #[cfg(ossl102)]
    impl PartialOrd<Asn1TimeRef> for Asn1Time {
        fn partial_cmp(&self, other: &Asn1TimeRef) -> Option<Ordering> {
            self.compare(other).ok()
        }
    }

    #[cfg(ossl102)]
    impl<'a> PartialOrd<&'a Asn1TimeRef> for Asn1Time {
        fn partial_cmp(&self, other: &&'a Asn1TimeRef) -> Option<Ordering> {
            self.compare(other).ok()
        }
    }

    foreign_type_and_impl_send_sync! {
        type CType = ffi::ASN1_STRING;
        fn drop = ffi::ASN1_STRING_free;
        /// Primary ASN.1 type used by OpenSSL
        ///
        /// Almost all ASN.1 types in OpenSSL are represented by ASN1_STRING
        /// structures.  This implementation uses [ASN1_STRING-to_UTF8] to preserve
        /// compatibility with Rust's String.
        ///
        /// [ASN1_STRING-to_UTF8]: https://www.openssl.org/docs/man1.1.0/crypto/ASN1_STRING_to_UTF8.html
        pub struct Asn1String;
        /// Reference to [`Asn1String`]
        ///
        /// [`Asn1String`]: struct.Asn1String.html
        pub struct Asn1StringRef;
    }

    impl Asn1StringRef {
        /// Converts the ASN.1 underlying format to UTF8
        ///
        /// ASN.1 strings may utilize UTF-16, ASCII, BMP, or UTF8.  This is important to
        /// consume the string in a meaningful way without knowing the underlying
        /// format.
        pub fn as_utf8(&self) -> Result<OpensslString, ErrorStack> {
            unsafe {
                let mut ptr = ptr::null_mut();
                let len = ffi::ASN1_STRING_to_UTF8(&mut ptr, self.as_ptr());
                if len < 0 {
                    return Err(ErrorStack::get());
                }

                Ok(OpensslString::from_ptr(ptr as *mut c_char))
            }
        }

        /// Return the string as an array of bytes.
        ///
        /// The bytes do not directly correspond to UTF-8 encoding.  To interact with
        /// strings in rust, it is preferable to use [`as_utf8`]
        ///
        /// [`as_utf8`]: struct.Asn1String.html#method.as_utf8
        pub fn as_slice(&self) -> &[u8] {
            unsafe { slice::from_raw_parts(ASN1_STRING_get0_data(self.as_ptr()), self.len()) }
        }

        /// Returns the number of bytes in the string.
        pub fn len(&self) -> usize {
            unsafe { ffi::ASN1_STRING_length(self.as_ptr()) as usize }
        }

        /// Determines if the string is empty.
        pub fn is_empty(&self) -> bool {
            self.len() == 0
        }
    }

    impl fmt::Debug for Asn1StringRef {
        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
            match self.as_utf8() {
                Ok(openssl_string) => openssl_string.fmt(fmt),
                Err(_) => fmt.write_str("error"),
            }
        }
    }

    foreign_type_and_impl_send_sync! {
        type CType = ffi::ASN1_INTEGER;
        fn drop = ffi::ASN1_INTEGER_free;

        /// Numeric representation
        ///
        /// Integers in ASN.1 may include BigNum, int64 or uint64.  BigNum implementation
        /// can be found within [`bn`] module.
        ///
        /// OpenSSL documentation includes [`ASN1_INTEGER_set`].
        ///
        /// [`bn`]: ../bn/index.html
        /// [`ASN1_INTEGER_set`]: https://www.openssl.org/docs/man1.1.0/crypto/ASN1_INTEGER_set.html
        pub struct Asn1Integer;
        /// Reference to [`Asn1Integer`]
        ///
        /// [`Asn1Integer`]: struct.Asn1Integer.html
        pub struct Asn1IntegerRef;
    }

    impl Asn1Integer {
        /// Converts a bignum to an `Asn1Integer`.
        ///
        /// Corresponds to [`BN_to_ASN1_INTEGER`]. Also see
        /// [`BigNumRef::to_asn1_integer`].
        ///
        /// [`BN_to_ASN1_INTEGER`]: https://www.openssl.org/docs/man1.1.0/crypto/BN_to_ASN1_INTEGER.html
        /// [`BigNumRef::to_asn1_integer`]: ../bn/struct.BigNumRef.html#method.to_asn1_integer
        pub fn from_bn(bn: &BigNumRef) -> Result<Self, ErrorStack> {
            bn.to_asn1_integer()
        }
    }

    impl Asn1IntegerRef {
        #[allow(missing_docs)]
        #[deprecated(since = "0.10.6", note = "use to_bn instead")]
        pub fn get(&self) -> i64 {
            unsafe { ffi::ASN1_INTEGER_get(self.as_ptr()) as i64 }
        }

        /// Converts the integer to a `BigNum`.
        ///
        /// This corresponds to [`ASN1_INTEGER_to_BN`].
        ///
        /// [`ASN1_INTEGER_to_BN`]: https://www.openssl.org/docs/man1.1.0/crypto/ASN1_INTEGER_get.html
        pub fn to_bn(&self) -> Result<BigNum, ErrorStack> {
            unsafe {
                cvt_p(ffi::ASN1_INTEGER_to_BN(self.as_ptr(), ptr::null_mut()))
                    .map(|p| BigNum::from_ptr(p))
            }
        }

        /// Sets the ASN.1 value to the value of a signed 32-bit integer, for larger numbers
        /// see [`bn`].
        ///
        /// OpenSSL documentation at [`ASN1_INTEGER_set`]
        ///
        /// [`bn`]: ../bn/struct.BigNumRef.html#method.to_asn1_integer
        /// [`ASN1_INTEGER_set`]: https://www.openssl.org/docs/man1.1.0/crypto/ASN1_INTEGER_set.html
        pub fn set(&mut self, value: i32) -> Result<(), ErrorStack> {
            unsafe { cvt(ffi::ASN1_INTEGER_set(self.as_ptr(), value as c_long)).map(|_| ()) }
        }
    }

    foreign_type_and_impl_send_sync! {
        type CType = ffi::ASN1_BIT_STRING;
        fn drop = ffi::ASN1_BIT_STRING_free;
        /// Sequence of bytes
        ///
        /// Asn1BitString is used in [`x509`] certificates for the signature.
        /// The bit string acts as a collection of bytes.
        ///
        /// [`x509`]: ../x509/struct.X509.html#method.signature
        pub struct Asn1BitString;
        /// Reference to [`Asn1BitString`]
        ///
        /// [`Asn1BitString`]: struct.Asn1BitString.html
        pub struct Asn1BitStringRef;
    }

    impl Asn1BitStringRef {
        /// Returns the Asn1BitString as a slice.
        pub fn as_slice(&self) -> &[u8] {
            unsafe { slice::from_raw_parts(ASN1_STRING_get0_data(self.as_ptr() as *mut _), self.len()) }
        }

        /// Returns the number of bytes in the string.
        pub fn len(&self) -> usize {
            unsafe { ffi::ASN1_STRING_length(self.as_ptr() as *const _) as usize }
        }

        /// Determines if the string is empty.
        pub fn is_empty(&self) -> bool {
            self.len() == 0
        }
    }

    foreign_type_and_impl_send_sync! {
        type CType = ffi::ASN1_OBJECT;
        fn drop = ffi::ASN1_OBJECT_free;

        /// Object Identifier
        ///
        /// Represents an ASN.1 Object.  Typically, NIDs, or numeric identifiers
        /// are stored as a table within the [`Nid`] module.  These constants are
        /// used to determine attributes of a certificate, such as mapping the
        /// attribute "CommonName" to "CN" which is represented as the OID of 13.
        /// This attribute is a constant in the [`nid::COMMONNAME`].
        ///
        /// OpenSSL documentation at [`OBJ_nid2obj`]
        ///
        /// [`Nid`]: ../nid/index.html
        /// [`nid::COMMONNAME`]: ../nid/constant.COMMONNAME.html
        /// [`OBJ_nid2obj`]: https://www.openssl.org/docs/man1.1.0/crypto/OBJ_obj2nid.html
        pub struct Asn1Object;
        /// Reference to [`Asn1Object`]
        ///
        /// [`Asn1Object`]: struct.Asn1Object.html
        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 {
            unsafe { Nid::from_raw(ffi::OBJ_obj2nid(self.as_ptr())) }
        }
    }

    impl fmt::Display for Asn1ObjectRef {
        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
            unsafe {
                let mut buf = [0; 80];
                let len = ffi::OBJ_obj2txt(
                    buf.as_mut_ptr() as *mut _,
                    buf.len() as c_int,
                    self.as_ptr(),
                    0,
                );
                match str::from_utf8(&buf[..len as usize]) {
                    Err(_) => fmt.write_str("error"),
                    Ok(s) => fmt.write_str(s),
                }
            }
        }
    }

    impl fmt::Debug for Asn1ObjectRef {
        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
            fmt.write_str(self.to_string().as_str())
        }
    }

    cfg_if! {
        if #[cfg(any(ossl110, libressl273))] {
            use ffi::ASN1_STRING_get0_data;
        } else {
            #[allow(bad_style)]
            unsafe fn ASN1_STRING_get0_data(s: *mut ffi::ASN1_STRING) -> *const ::libc::c_uchar {
                ffi::ASN1_STRING_data(s)
            }
        }
    }

    #[cfg(test)]
    mod tests {
        use super::*;

        use crate::bn::BigNum;
        use crate::nid::Nid;

        /// Tests conversion between BigNum and Asn1Integer.
        #[test]
        fn bn_cvt() {
            fn roundtrip(bn: BigNum) {
                let large = Asn1Integer::from_bn(&bn).unwrap();
                assert_eq!(large.to_bn().unwrap(), bn);
            }

            roundtrip(BigNum::from_dec_str("1000000000000000000000000000000000").unwrap());
            roundtrip(-BigNum::from_dec_str("1000000000000000000000000000000000").unwrap());
            roundtrip(BigNum::from_u32(1234).unwrap());
            roundtrip(-BigNum::from_u32(1234).unwrap());
        }

        #[test]
        fn time_from_str() {
            Asn1Time::from_str("99991231235959Z").unwrap();
            #[cfg(ossl111)]
            Asn1Time::from_str_x509("99991231235959Z").unwrap();
        }

        #[test]
        fn time_from_unix() {
            let t = Asn1Time::from_unix(0).unwrap();
            assert_eq!("Jan  1 00:00:00 1970 GMT", t.to_string());
        }

        #[test]
        #[cfg(ossl102)]
        fn time_eq() {
            let a = Asn1Time::from_str("99991231235959Z").unwrap();
            let b = Asn1Time::from_str("99991231235959Z").unwrap();
            let c = Asn1Time::from_str("99991231235958Z").unwrap();
            let a_ref = a.as_ref();
            let b_ref = b.as_ref();
            let c_ref = c.as_ref();
            assert!(a == b);
            assert!(a != c);
            assert!(a == b_ref);
            assert!(a != c_ref);
            assert!(b_ref == a);
            assert!(c_ref != a);
            assert!(a_ref == b_ref);
            assert!(a_ref != c_ref);
        }

        #[test]
        #[cfg(ossl102)]
        fn time_ord() {
            let a = Asn1Time::from_str("99991231235959Z").unwrap();
            let b = Asn1Time::from_str("99991231235959Z").unwrap();
            let c = Asn1Time::from_str("99991231235958Z").unwrap();
            let a_ref = a.as_ref();
            let b_ref = b.as_ref();
            let c_ref = c.as_ref();
            assert!(a >= b);
            assert!(a > c);
            assert!(b <= a);
            assert!(c < a);

            assert!(a_ref >= b);
            assert!(a_ref > c);
            assert!(b_ref <= a);
            assert!(c_ref < a);

            assert!(a >= b_ref);
            assert!(a > c_ref);
            assert!(b <= a_ref);
            assert!(c < a_ref);

            assert!(a_ref >= b_ref);
            assert!(a_ref > c_ref);
            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");
        }
    }