//! The asymmetric encryption context.
//!
//! # Examples
//!
//! Encrypt data with RSA
//!
//! ```
//! use openssl::rsa::Rsa;
//! use openssl::pkey::PKey;
//! use openssl::pkey_ctx::PkeyCtx;
//!
//! let key = Rsa::generate(4096).unwrap();
//! let key = PKey::from_rsa(key).unwrap();
//!
//! let mut ctx = PkeyCtx::new(&key).unwrap();
//! ctx.encrypt_init().unwrap();
//!
//! let data = b"Some Crypto Text";
//! let mut ciphertext = vec![];
//! ctx.encrypt_to_vec(data, &mut ciphertext).unwrap();
//! ```

#![cfg_attr(
    not(boringssl),
    doc = r#"\
Generate a CMAC key

```
use openssl::pkey_ctx::PkeyCtx;
use openssl::pkey::Id;
use openssl::cipher::Cipher;

let mut ctx = PkeyCtx::new_id(Id::CMAC).unwrap();
ctx.keygen_init().unwrap();
ctx.set_keygen_cipher(Cipher::aes_128_cbc()).unwrap();
ctx.set_keygen_mac_key(b"0123456789abcdef").unwrap();
let cmac_key = ctx.keygen().unwrap();
```"#
)]

//!
//! Sign and verify data with RSA
//!
//! ```
//! use openssl::pkey_ctx::PkeyCtx;
//! use openssl::pkey::PKey;
//! use openssl::rsa::Rsa;
//!
//! // Generate a random RSA key.
//! let key = Rsa::generate(4096).unwrap();
//! let key = PKey::from_rsa(key).unwrap();
//!
//! let text = b"Some Crypto Text";
//!
//! // Create the signature.
//! let mut ctx = PkeyCtx::new(&key).unwrap();
//! ctx.sign_init().unwrap();
//! let mut signature = vec![];
//! ctx.sign_to_vec(text, &mut signature).unwrap();
//!
//! // Verify the signature.
//! let mut ctx = PkeyCtx::new(&key).unwrap();
//! ctx.verify_init().unwrap();
//! let valid = ctx.verify(text, &signature).unwrap();
//! assert!(valid);
//! ```
#[cfg(not(boringssl))]
use crate::cipher::CipherRef;
use crate::error::ErrorStack;
use crate::md::MdRef;
use crate::pkey::{HasPrivate, HasPublic, Id, PKey, PKeyRef, Private};
use crate::rsa::Padding;
use crate::sign::RsaPssSaltlen;
use crate::{cvt, cvt_p};
use foreign_types::{ForeignType, ForeignTypeRef};
#[cfg(not(boringssl))]
use libc::c_int;
#[cfg(ossl320)]
use libc::c_uint;
use openssl_macros::corresponds;
use std::convert::TryFrom;
#[cfg(ossl320)]
use std::ffi::CStr;
use std::ptr;

/// HKDF modes of operation.
#[cfg(any(ossl111, libressl360))]
pub struct HkdfMode(c_int);

#[cfg(any(ossl111, libressl360))]
impl HkdfMode {
    /// This is the default mode. Calling [`derive`][PkeyCtxRef::derive] on a [`PkeyCtxRef`] set up
    /// for HKDF will perform an extract followed by an expand operation in one go. The derived key
    /// returned will be the result after the expand operation. The intermediate fixed-length
    /// pseudorandom key K is not returned.
    pub const EXTRACT_THEN_EXPAND: Self = HkdfMode(ffi::EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND);

    /// In this mode calling [`derive`][PkeyCtxRef::derive] will just perform the extract operation.
    /// The value returned will be the intermediate fixed-length pseudorandom key K.
    ///
    /// The digest, key and salt values must be set before a key is derived or an error occurs.
    pub const EXTRACT_ONLY: Self = HkdfMode(ffi::EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY);

    /// In this mode calling [`derive`][PkeyCtxRef::derive] will just perform the expand operation.
    /// The input key should be set to the intermediate fixed-length pseudorandom key K returned
    /// from a previous extract operation.
    ///
    /// The digest, key and info values must be set before a key is derived or an error occurs.
    pub const EXPAND_ONLY: Self = HkdfMode(ffi::EVP_PKEY_HKDEF_MODE_EXPAND_ONLY);
}

/// Nonce type for ECDSA and DSA.
#[cfg(ossl320)]
#[derive(Debug, PartialEq)]
pub struct NonceType(c_uint);

#[cfg(ossl320)]
impl NonceType {
    /// This is the default mode. It uses a random value for the nonce k as defined in FIPS 186-4 Section 6.3
    /// “Secret Number Generation”.
    pub const RANDOM_K: Self = NonceType(0);

    /// Uses a deterministic value for the nonce k as defined in RFC #6979 (See Section 3.2 “Generation of k”).
    pub const DETERMINISTIC_K: Self = NonceType(1);
}

generic_foreign_type_and_impl_send_sync! {
    type CType = ffi::EVP_PKEY_CTX;
    fn drop = ffi::EVP_PKEY_CTX_free;

    /// A context object which can perform asymmetric cryptography operations.
    pub struct PkeyCtx<T>;
    /// A reference to a [`PkeyCtx`].
    pub struct PkeyCtxRef<T>;
}

impl<T> PkeyCtx<T> {
    /// Creates a new pkey context using the provided key.
    #[corresponds(EVP_PKEY_CTX_new)]
    #[inline]
    pub fn new(pkey: &PKeyRef<T>) -> Result<Self, ErrorStack> {
        unsafe {
            let ptr = cvt_p(ffi::EVP_PKEY_CTX_new(pkey.as_ptr(), ptr::null_mut()))?;
            Ok(PkeyCtx::from_ptr(ptr))
        }
    }
}

impl PkeyCtx<()> {
    /// Creates a new pkey context for the specified algorithm ID.
    #[corresponds(EVP_PKEY_new_id)]
    #[inline]
    pub fn new_id(id: Id) -> Result<Self, ErrorStack> {
        unsafe {
            let ptr = cvt_p(ffi::EVP_PKEY_CTX_new_id(id.as_raw(), ptr::null_mut()))?;
            Ok(PkeyCtx::from_ptr(ptr))
        }
    }
}

impl<T> PkeyCtxRef<T>
where
    T: HasPublic,
{
    /// Prepares the context for encryption using the public key.
    #[corresponds(EVP_PKEY_encrypt_init)]
    #[inline]
    pub fn encrypt_init(&mut self) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_encrypt_init(self.as_ptr()))?;
        }

        Ok(())
    }

    /// Prepares the context for signature verification using the public key.
    #[corresponds(EVP_PKEY_verify_init)]
    #[inline]
    pub fn verify_init(&mut self) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_verify_init(self.as_ptr()))?;
        }

        Ok(())
    }

    /// Prepares the context for signature recovery using the public key.
    #[corresponds(EVP_PKEY_verify_recover_init)]
    #[inline]
    pub fn verify_recover_init(&mut self) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_verify_recover_init(self.as_ptr()))?;
        }

        Ok(())
    }

    /// Encrypts data using the public key.
    ///
    /// If `to` is set to `None`, an upper bound on the number of bytes required for the output buffer will be
    /// returned.
    #[corresponds(EVP_PKEY_encrypt)]
    #[inline]
    pub fn encrypt(&mut self, from: &[u8], to: Option<&mut [u8]>) -> Result<usize, ErrorStack> {
        let mut written = to.as_ref().map_or(0, |b| b.len());
        unsafe {
            cvt(ffi::EVP_PKEY_encrypt(
                self.as_ptr(),
                to.map_or(ptr::null_mut(), |b| b.as_mut_ptr()),
                &mut written,
                from.as_ptr(),
                from.len(),
            ))?;
        }

        Ok(written)
    }

    /// Like [`Self::encrypt`] but appends ciphertext to a [`Vec`].
    pub fn encrypt_to_vec(&mut self, from: &[u8], out: &mut Vec<u8>) -> Result<usize, ErrorStack> {
        let base = out.len();
        let len = self.encrypt(from, None)?;
        out.resize(base + len, 0);
        let len = self.encrypt(from, Some(&mut out[base..]))?;
        out.truncate(base + len);
        Ok(len)
    }

    /// Verifies the signature of data using the public key.
    ///
    /// Returns `Ok(true)` if the signature is valid, `Ok(false)` if the signature is invalid, and `Err` if an error
    /// occurred.
    ///
    /// # Note
    ///
    /// This verifies the signature of the *raw* data. It is more common to compute and verify the signature of the
    /// cryptographic hash of an arbitrary amount of data. The [`MdCtx`](crate::md_ctx::MdCtx) type can be used to do
    /// that.
    #[corresponds(EVP_PKEY_verify)]
    #[inline]
    pub fn verify(&mut self, data: &[u8], sig: &[u8]) -> Result<bool, ErrorStack> {
        unsafe {
            let r = ffi::EVP_PKEY_verify(
                self.as_ptr(),
                sig.as_ptr(),
                sig.len(),
                data.as_ptr(),
                data.len(),
            );
            // `EVP_PKEY_verify` is not terribly consistent about how it,
            // reports errors. It does not clearly distinguish between 0 and
            // -1, and may put errors on the stack in both cases. If there's
            // errors on the stack, we return `Err()`, else we return
            // `Ok(false)`.
            if r <= 0 {
                let errors = ErrorStack::get();
                if !errors.errors().is_empty() {
                    return Err(errors);
                }
            }

            Ok(r == 1)
        }
    }

    /// Recovers the original data signed by the private key. You almost
    /// always want `verify` instead.
    ///
    /// Returns the number of bytes written to `to`, or the number of bytes
    /// that would be written, if `to` is `None.
    #[corresponds(EVP_PKEY_verify_recover)]
    #[inline]
    pub fn verify_recover(
        &mut self,
        sig: &[u8],
        to: Option<&mut [u8]>,
    ) -> Result<usize, ErrorStack> {
        let mut written = to.as_ref().map_or(0, |b| b.len());
        unsafe {
            cvt(ffi::EVP_PKEY_verify_recover(
                self.as_ptr(),
                to.map_or(ptr::null_mut(), |b| b.as_mut_ptr()),
                &mut written,
                sig.as_ptr(),
                sig.len(),
            ))?;
        }

        Ok(written)
    }
}

impl<T> PkeyCtxRef<T>
where
    T: HasPrivate,
{
    /// Prepares the context for decryption using the private key.
    #[corresponds(EVP_PKEY_decrypt_init)]
    #[inline]
    pub fn decrypt_init(&mut self) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_decrypt_init(self.as_ptr()))?;
        }

        Ok(())
    }

    /// Prepares the context for signing using the private key.
    #[corresponds(EVP_PKEY_sign_init)]
    #[inline]
    pub fn sign_init(&mut self) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_sign_init(self.as_ptr()))?;
        }

        Ok(())
    }

    /// Sets the peer key used for secret derivation.
    #[corresponds(EVP_PKEY_derive_set_peer)]
    pub fn derive_set_peer<U>(&mut self, key: &PKeyRef<U>) -> Result<(), ErrorStack>
    where
        U: HasPublic,
    {
        unsafe {
            cvt(ffi::EVP_PKEY_derive_set_peer(self.as_ptr(), key.as_ptr()))?;
        }

        Ok(())
    }

    /// Decrypts data using the private key.
    ///
    /// If `to` is set to `None`, an upper bound on the number of bytes required for the output buffer will be
    /// returned.
    #[corresponds(EVP_PKEY_decrypt)]
    #[inline]
    pub fn decrypt(&mut self, from: &[u8], to: Option<&mut [u8]>) -> Result<usize, ErrorStack> {
        let mut written = to.as_ref().map_or(0, |b| b.len());
        unsafe {
            cvt(ffi::EVP_PKEY_decrypt(
                self.as_ptr(),
                to.map_or(ptr::null_mut(), |b| b.as_mut_ptr()),
                &mut written,
                from.as_ptr(),
                from.len(),
            ))?;
        }

        Ok(written)
    }

    /// Like [`Self::decrypt`] but appends plaintext to a [`Vec`].
    pub fn decrypt_to_vec(&mut self, from: &[u8], out: &mut Vec<u8>) -> Result<usize, ErrorStack> {
        let base = out.len();
        let len = self.decrypt(from, None)?;
        out.resize(base + len, 0);
        let len = self.decrypt(from, Some(&mut out[base..]))?;
        out.truncate(base + len);
        Ok(len)
    }

    /// Signs the contents of `data`.
    ///
    /// If `sig` is set to `None`, an upper bound on the number of bytes required for the output buffer will be
    /// returned.
    ///
    /// # Note
    ///
    /// This computes the signature of the *raw* bytes of `data`. It is more common to sign the cryptographic hash of
    /// an arbitrary amount of data. The [`MdCtx`](crate::md_ctx::MdCtx) type can be used to do that.
    #[corresponds(EVP_PKEY_sign)]
    #[inline]
    pub fn sign(&mut self, data: &[u8], sig: Option<&mut [u8]>) -> Result<usize, ErrorStack> {
        let mut written = sig.as_ref().map_or(0, |b| b.len());
        unsafe {
            cvt(ffi::EVP_PKEY_sign(
                self.as_ptr(),
                sig.map_or(ptr::null_mut(), |b| b.as_mut_ptr()),
                &mut written,
                data.as_ptr(),
                data.len(),
            ))?;
        }

        Ok(written)
    }

    /// Like [`Self::sign`] but appends the signature to a [`Vec`].
    pub fn sign_to_vec(&mut self, data: &[u8], sig: &mut Vec<u8>) -> Result<usize, ErrorStack> {
        let base = sig.len();
        let len = self.sign(data, None)?;
        sig.resize(base + len, 0);
        let len = self.sign(data, Some(&mut sig[base..]))?;
        sig.truncate(base + len);
        Ok(len)
    }
}

impl<T> PkeyCtxRef<T> {
    /// Prepares the context for shared secret derivation.
    #[corresponds(EVP_PKEY_derive_init)]
    #[inline]
    pub fn derive_init(&mut self) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_derive_init(self.as_ptr()))?;
        }

        Ok(())
    }

    /// Prepares the context for key generation.
    #[corresponds(EVP_PKEY_keygen_init)]
    #[inline]
    pub fn keygen_init(&mut self) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_keygen_init(self.as_ptr()))?;
        }

        Ok(())
    }

    /// Sets which algorithm was used to compute the digest used in a
    /// signature. With RSA signatures this causes the signature to be wrapped
    /// in a `DigestInfo` structure. This is almost always what you want with
    /// RSA signatures.
    #[corresponds(EVP_PKEY_CTX_set_signature_md)]
    #[inline]
    pub fn set_signature_md(&self, md: &MdRef) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set_signature_md(
                self.as_ptr(),
                md.as_ptr(),
            ))?;
        }
        Ok(())
    }

    /// Returns the RSA padding mode in use.
    ///
    /// This is only useful for RSA keys.
    #[corresponds(EVP_PKEY_CTX_get_rsa_padding)]
    #[inline]
    pub fn rsa_padding(&self) -> Result<Padding, ErrorStack> {
        let mut pad = 0;
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_get_rsa_padding(self.as_ptr(), &mut pad))?;
        }

        Ok(Padding::from_raw(pad))
    }

    /// Sets the RSA padding mode.
    ///
    /// This is only useful for RSA keys.
    #[corresponds(EVP_PKEY_CTX_set_rsa_padding)]
    #[inline]
    pub fn set_rsa_padding(&mut self, padding: Padding) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set_rsa_padding(
                self.as_ptr(),
                padding.as_raw(),
            ))?;
        }

        Ok(())
    }

    /// Sets the RSA PSS salt length.
    ///
    /// This is only useful for RSA keys.
    #[corresponds(EVP_PKEY_CTX_set_rsa_pss_saltlen)]
    #[inline]
    pub fn set_rsa_pss_saltlen(&mut self, len: RsaPssSaltlen) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set_rsa_pss_saltlen(
                self.as_ptr(),
                len.as_raw(),
            ))
            .map(|_| ())
        }
    }

    /// Sets the RSA MGF1 algorithm.
    ///
    /// This is only useful for RSA keys.
    #[corresponds(EVP_PKEY_CTX_set_rsa_mgf1_md)]
    #[inline]
    pub fn set_rsa_mgf1_md(&mut self, md: &MdRef) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set_rsa_mgf1_md(
                self.as_ptr(),
                md.as_ptr(),
            ))?;
        }

        Ok(())
    }

    /// Sets the RSA OAEP algorithm.
    ///
    /// This is only useful for RSA keys.
    #[corresponds(EVP_PKEY_CTX_set_rsa_oaep_md)]
    #[cfg(any(ossl102, libressl310, boringssl))]
    #[inline]
    pub fn set_rsa_oaep_md(&mut self, md: &MdRef) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set_rsa_oaep_md(
                self.as_ptr(),
                md.as_ptr() as *mut _,
            ))?;
        }

        Ok(())
    }

    /// Sets the RSA OAEP label.
    ///
    /// This is only useful for RSA keys.
    #[corresponds(EVP_PKEY_CTX_set0_rsa_oaep_label)]
    #[cfg(any(ossl102, libressl310, boringssl))]
    pub fn set_rsa_oaep_label(&mut self, label: &[u8]) -> Result<(), ErrorStack> {
        use crate::LenType;
        let len = LenType::try_from(label.len()).unwrap();

        unsafe {
            let p = ffi::OPENSSL_malloc(label.len() as _);
            ptr::copy_nonoverlapping(label.as_ptr(), p as *mut _, label.len());

            let r = cvt(ffi::EVP_PKEY_CTX_set0_rsa_oaep_label(
                self.as_ptr(),
                p as *mut _,
                len,
            ));
            if r.is_err() {
                ffi::OPENSSL_free(p);
            }
            r?;
        }

        Ok(())
    }

    /// Sets the cipher used during key generation.
    #[cfg(not(boringssl))]
    #[corresponds(EVP_PKEY_CTX_ctrl)]
    #[inline]
    pub fn set_keygen_cipher(&mut self, cipher: &CipherRef) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_ctrl(
                self.as_ptr(),
                -1,
                ffi::EVP_PKEY_OP_KEYGEN,
                ffi::EVP_PKEY_CTRL_CIPHER,
                0,
                cipher.as_ptr() as *mut _,
            ))?;
        }

        Ok(())
    }

    /// Sets the key MAC key used during key generation.
    #[cfg(not(boringssl))]
    #[corresponds(EVP_PKEY_CTX_ctrl)]
    #[inline]
    pub fn set_keygen_mac_key(&mut self, key: &[u8]) -> Result<(), ErrorStack> {
        let len = c_int::try_from(key.len()).unwrap();

        unsafe {
            cvt(ffi::EVP_PKEY_CTX_ctrl(
                self.as_ptr(),
                -1,
                ffi::EVP_PKEY_OP_KEYGEN,
                ffi::EVP_PKEY_CTRL_SET_MAC_KEY,
                len,
                key.as_ptr() as *mut _,
            ))?;
        }

        Ok(())
    }

    /// Sets the digest used for HKDF derivation.
    ///
    /// Requires OpenSSL 1.1.0 or newer.
    #[corresponds(EVP_PKEY_CTX_set_hkdf_md)]
    #[cfg(any(ossl110, boringssl, libressl360))]
    #[inline]
    pub fn set_hkdf_md(&mut self, digest: &MdRef) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set_hkdf_md(
                self.as_ptr(),
                digest.as_ptr(),
            ))?;
        }

        Ok(())
    }

    /// Sets the HKDF mode of operation.
    ///
    /// Defaults to [`HkdfMode::EXTRACT_THEN_EXPAND`].
    ///
    /// WARNING: Although this API calls it a "mode", HKDF-Extract and HKDF-Expand are distinct
    /// operations with distinct inputs and distinct kinds of keys. Callers should not pass input
    /// secrets for one operation into the other.
    ///
    /// Requires OpenSSL 1.1.1 or newer.
    #[corresponds(EVP_PKEY_CTX_set_hkdf_mode)]
    #[cfg(any(ossl111, libressl360))]
    #[inline]
    pub fn set_hkdf_mode(&mut self, mode: HkdfMode) -> Result<(), ErrorStack> {
        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set_hkdf_mode(self.as_ptr(), mode.0))?;
        }

        Ok(())
    }

    /// Sets the input material for HKDF generation as the "key".
    ///
    /// Which input is the key depends on the "mode" (see [`set_hkdf_mode`][Self::set_hkdf_mode]).
    /// If [`HkdfMode::EXTRACT_THEN_EXPAND`] or [`HkdfMode::EXTRACT_ONLY`], this function specifies
    /// the input keying material (IKM) for HKDF-Extract. If [`HkdfMode::EXPAND_ONLY`], it instead
    /// specifies the pseudorandom key (PRK) for HKDF-Expand.
    ///
    /// Requires OpenSSL 1.1.0 or newer.
    #[corresponds(EVP_PKEY_CTX_set1_hkdf_key)]
    #[cfg(any(ossl110, boringssl, libressl360))]
    #[inline]
    pub fn set_hkdf_key(&mut self, key: &[u8]) -> Result<(), ErrorStack> {
        #[cfg(not(boringssl))]
        let len = c_int::try_from(key.len()).unwrap();
        #[cfg(boringssl)]
        let len = key.len();

        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set1_hkdf_key(
                self.as_ptr(),
                key.as_ptr(),
                len,
            ))?;
        }

        Ok(())
    }

    /// Sets the salt value for HKDF generation.
    ///
    /// If performing HKDF-Expand only, this parameter is ignored.
    ///
    /// Requires OpenSSL 1.1.0 or newer.
    #[corresponds(EVP_PKEY_CTX_set1_hkdf_salt)]
    #[cfg(any(ossl110, boringssl, libressl360))]
    #[inline]
    pub fn set_hkdf_salt(&mut self, salt: &[u8]) -> Result<(), ErrorStack> {
        #[cfg(not(boringssl))]
        let len = c_int::try_from(salt.len()).unwrap();
        #[cfg(boringssl)]
        let len = salt.len();

        unsafe {
            cvt(ffi::EVP_PKEY_CTX_set1_hkdf_salt(
                self.as_ptr(),
                salt.as_ptr(),
                len,
            ))?;
        }

        Ok(())
    }

    /// Appends info bytes for HKDF generation.
    ///
    /// If performing HKDF-Extract only, this parameter is ignored.
    ///
    /// Requires OpenSSL 1.1.0 or newer.
    #[corresponds(EVP_PKEY_CTX_add1_hkdf_info)]
    #[cfg(any(ossl110, boringssl, libressl360))]
    #[inline]
    pub fn add_hkdf_info(&mut self, info: &[u8]) -> Result<(), ErrorStack> {
        #[cfg(not(boringssl))]
        let len = c_int::try_from(info.len()).unwrap();
        #[cfg(boringssl)]
        let len = info.len();

        unsafe {
            cvt(ffi::EVP_PKEY_CTX_add1_hkdf_info(
                self.as_ptr(),
                info.as_ptr(),
                len,
            ))?;
        }

        Ok(())
    }

    /// Derives a shared secret between two keys.
    ///
    /// If `buf` is set to `None`, an upper bound on the number of bytes required for the buffer will be returned.
    #[corresponds(EVP_PKEY_derive)]
    pub fn derive(&mut self, buf: Option<&mut [u8]>) -> Result<usize, ErrorStack> {
        let mut len = buf.as_ref().map_or(0, |b| b.len());
        unsafe {
            cvt(ffi::EVP_PKEY_derive(
                self.as_ptr(),
                buf.map_or(ptr::null_mut(), |b| b.as_mut_ptr()),
                &mut len,
            ))?;
        }

        Ok(len)
    }

    /// Like [`Self::derive`] but appends the secret to a [`Vec`].
    pub fn derive_to_vec(&mut self, buf: &mut Vec<u8>) -> Result<usize, ErrorStack> {
        let base = buf.len();
        let len = self.derive(None)?;
        buf.resize(base + len, 0);
        let len = self.derive(Some(&mut buf[base..]))?;
        buf.truncate(base + len);
        Ok(len)
    }

    /// Generates a new public/private keypair.
    #[corresponds(EVP_PKEY_keygen)]
    #[inline]
    pub fn keygen(&mut self) -> Result<PKey<Private>, ErrorStack> {
        unsafe {
            let mut key = ptr::null_mut();
            cvt(ffi::EVP_PKEY_keygen(self.as_ptr(), &mut key))?;
            Ok(PKey::from_ptr(key))
        }
    }

    /// Sets the nonce type for a private key context.
    ///
    /// The nonce for DSA and ECDSA can be either random (the default) or deterministic (as defined by RFC 6979).
    ///
    /// This is only useful for DSA and ECDSA.
    /// Requires OpenSSL 3.2.0 or newer.
    #[cfg(ossl320)]
    #[corresponds(EVP_PKEY_CTX_set_params)]
    pub fn set_nonce_type(&mut self, nonce_type: NonceType) -> Result<(), ErrorStack> {
        let nonce_field_name = CStr::from_bytes_with_nul(b"nonce-type\0").unwrap();
        let mut nonce_type = nonce_type.0;
        unsafe {
            let param_nonce =
                ffi::OSSL_PARAM_construct_uint(nonce_field_name.as_ptr(), &mut nonce_type);
            let param_end = ffi::OSSL_PARAM_construct_end();

            let params = [param_nonce, param_end];
            cvt(ffi::EVP_PKEY_CTX_set_params(self.as_ptr(), params.as_ptr()))?;
        }
        Ok(())
    }

    /// Gets the nonce type for a private key context.
    ///
    /// The nonce for DSA and ECDSA can be either random (the default) or deterministic (as defined by RFC 6979).
    ///
    /// This is only useful for DSA and ECDSA.
    /// Requires OpenSSL 3.2.0 or newer.
    #[cfg(ossl320)]
    #[corresponds(EVP_PKEY_CTX_get_params)]
    pub fn nonce_type(&mut self) -> Result<NonceType, ErrorStack> {
        let nonce_field_name = CStr::from_bytes_with_nul(b"nonce-type\0").unwrap();
        let mut nonce_type: c_uint = 0;
        unsafe {
            let param_nonce =
                ffi::OSSL_PARAM_construct_uint(nonce_field_name.as_ptr(), &mut nonce_type);
            let param_end = ffi::OSSL_PARAM_construct_end();

            let mut params = [param_nonce, param_end];
            cvt(ffi::EVP_PKEY_CTX_get_params(
                self.as_ptr(),
                params.as_mut_ptr(),
            ))?;
        }
        Ok(NonceType(nonce_type))
    }
}

#[cfg(test)]
mod test {
    use super::*;
    #[cfg(not(boringssl))]
    use crate::cipher::Cipher;
    use crate::ec::{EcGroup, EcKey};
    use crate::hash::{hash, MessageDigest};
    use crate::md::Md;
    use crate::nid::Nid;
    use crate::pkey::PKey;
    use crate::rsa::Rsa;
    use crate::sign::Verifier;

    #[test]
    fn rsa() {
        let key = include_bytes!("../test/rsa.pem");
        let rsa = Rsa::private_key_from_pem(key).unwrap();
        let pkey = PKey::from_rsa(rsa).unwrap();

        let mut ctx = PkeyCtx::new(&pkey).unwrap();
        ctx.encrypt_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1).unwrap();

        let pt = "hello world".as_bytes();
        let mut ct = vec![];
        ctx.encrypt_to_vec(pt, &mut ct).unwrap();

        ctx.decrypt_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1).unwrap();

        let mut out = vec![];
        ctx.decrypt_to_vec(&ct, &mut out).unwrap();

        assert_eq!(pt, out);
    }

    #[test]
    #[cfg(any(ossl102, libressl310, boringssl))]
    fn rsa_oaep() {
        let key = include_bytes!("../test/rsa.pem");
        let rsa = Rsa::private_key_from_pem(key).unwrap();
        let pkey = PKey::from_rsa(rsa).unwrap();

        let mut ctx = PkeyCtx::new(&pkey).unwrap();
        ctx.encrypt_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1_OAEP).unwrap();
        ctx.set_rsa_oaep_md(Md::sha256()).unwrap();
        ctx.set_rsa_mgf1_md(Md::sha256()).unwrap();

        let pt = "hello world".as_bytes();
        let mut ct = vec![];
        ctx.encrypt_to_vec(pt, &mut ct).unwrap();

        ctx.decrypt_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1_OAEP).unwrap();
        ctx.set_rsa_oaep_md(Md::sha256()).unwrap();
        ctx.set_rsa_mgf1_md(Md::sha256()).unwrap();

        let mut out = vec![];
        ctx.decrypt_to_vec(&ct, &mut out).unwrap();

        assert_eq!(pt, out);
    }

    #[test]
    fn rsa_sign() {
        let key = include_bytes!("../test/rsa.pem");
        let rsa = Rsa::private_key_from_pem(key).unwrap();
        let pkey = PKey::from_rsa(rsa).unwrap();

        let mut ctx = PkeyCtx::new(&pkey).unwrap();
        ctx.sign_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1).unwrap();
        ctx.set_signature_md(Md::sha384()).unwrap();

        let msg = b"hello world";
        let digest = hash(MessageDigest::sha384(), msg).unwrap();
        let mut signature = vec![];
        ctx.sign_to_vec(&digest, &mut signature).unwrap();

        let mut verifier = Verifier::new(MessageDigest::sha384(), &pkey).unwrap();
        verifier.update(msg).unwrap();
        assert!(matches!(verifier.verify(&signature), Ok(true)));
    }

    #[test]
    fn rsa_sign_pss() {
        let key = include_bytes!("../test/rsa.pem");
        let rsa = Rsa::private_key_from_pem(key).unwrap();
        let pkey = PKey::from_rsa(rsa).unwrap();

        let mut ctx = PkeyCtx::new(&pkey).unwrap();
        ctx.sign_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1_PSS).unwrap();
        ctx.set_signature_md(Md::sha384()).unwrap();
        ctx.set_rsa_pss_saltlen(RsaPssSaltlen::custom(14)).unwrap();

        let msg = b"hello world";
        let digest = hash(MessageDigest::sha384(), msg).unwrap();
        let mut signature = vec![];
        ctx.sign_to_vec(&digest, &mut signature).unwrap();

        let mut verifier = Verifier::new(MessageDigest::sha384(), &pkey).unwrap();
        verifier.set_rsa_padding(Padding::PKCS1_PSS).unwrap();
        verifier
            .set_rsa_pss_saltlen(RsaPssSaltlen::custom(14))
            .unwrap();
        verifier.update(msg).unwrap();
        assert!(matches!(verifier.verify(&signature), Ok(true)));
    }

    #[test]
    fn derive() {
        let group = EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap();
        let key1 = EcKey::generate(&group).unwrap();
        let key1 = PKey::from_ec_key(key1).unwrap();
        let key2 = EcKey::generate(&group).unwrap();
        let key2 = PKey::from_ec_key(key2).unwrap();

        let mut ctx = PkeyCtx::new(&key1).unwrap();
        ctx.derive_init().unwrap();
        ctx.derive_set_peer(&key2).unwrap();

        let mut buf = vec![];
        ctx.derive_to_vec(&mut buf).unwrap();
    }

    #[test]
    #[cfg(not(boringssl))]
    fn cmac_keygen() {
        let mut ctx = PkeyCtx::new_id(Id::CMAC).unwrap();
        ctx.keygen_init().unwrap();
        ctx.set_keygen_cipher(Cipher::aes_128_cbc()).unwrap();
        ctx.set_keygen_mac_key(&hex::decode("9294727a3638bb1c13f48ef8158bfc9d").unwrap())
            .unwrap();
        ctx.keygen().unwrap();
    }

    #[test]
    #[cfg(any(ossl110, boringssl, libressl360))]
    fn hkdf() {
        let mut ctx = PkeyCtx::new_id(Id::HKDF).unwrap();
        ctx.derive_init().unwrap();
        ctx.set_hkdf_md(Md::sha256()).unwrap();
        ctx.set_hkdf_key(&hex::decode("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b").unwrap())
            .unwrap();
        ctx.set_hkdf_salt(&hex::decode("000102030405060708090a0b0c").unwrap())
            .unwrap();
        ctx.add_hkdf_info(&hex::decode("f0f1f2f3f4f5f6f7f8f9").unwrap())
            .unwrap();
        let mut out = [0; 42];
        ctx.derive(Some(&mut out)).unwrap();

        assert_eq!(
            &out[..],
            hex::decode("3cb25f25faacd57a90434f64d0362f2a2d2d0a90cf1a5a4c5db02d56ecc4c5bf34007208d5b887185865")
                .unwrap()
        );
    }

    #[test]
    #[cfg(any(ossl111, libressl360))]
    fn hkdf_expand() {
        let mut ctx = PkeyCtx::new_id(Id::HKDF).unwrap();
        ctx.derive_init().unwrap();
        ctx.set_hkdf_mode(HkdfMode::EXPAND_ONLY).unwrap();
        ctx.set_hkdf_md(Md::sha256()).unwrap();
        ctx.set_hkdf_key(
            &hex::decode("077709362c2e32df0ddc3f0dc47bba6390b6c73bb50f9c3122ec844ad7c2b3e5")
                .unwrap(),
        )
        .unwrap();
        ctx.add_hkdf_info(&hex::decode("f0f1f2f3f4f5f6f7f8f9").unwrap())
            .unwrap();
        let mut out = [0; 42];
        ctx.derive(Some(&mut out)).unwrap();

        assert_eq!(
            &out[..],
            hex::decode("3cb25f25faacd57a90434f64d0362f2a2d2d0a90cf1a5a4c5db02d56ecc4c5bf34007208d5b887185865")
                .unwrap()
        );
    }

    #[test]
    #[cfg(any(ossl111, libressl360))]
    fn hkdf_extract() {
        let mut ctx = PkeyCtx::new_id(Id::HKDF).unwrap();
        ctx.derive_init().unwrap();
        ctx.set_hkdf_mode(HkdfMode::EXTRACT_ONLY).unwrap();
        ctx.set_hkdf_md(Md::sha256()).unwrap();
        ctx.set_hkdf_key(&hex::decode("0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b").unwrap())
            .unwrap();
        ctx.set_hkdf_salt(&hex::decode("000102030405060708090a0b0c").unwrap())
            .unwrap();
        let mut out = vec![];
        ctx.derive_to_vec(&mut out).unwrap();

        assert_eq!(
            &out[..],
            hex::decode("077709362c2e32df0ddc3f0dc47bba6390b6c73bb50f9c3122ec844ad7c2b3e5")
                .unwrap()
        );
    }

    #[test]
    fn verify_fail() {
        let key1 = Rsa::generate(4096).unwrap();
        let key1 = PKey::from_rsa(key1).unwrap();

        let data = b"Some Crypto Text";

        let mut ctx = PkeyCtx::new(&key1).unwrap();
        ctx.sign_init().unwrap();
        let mut signature = vec![];
        ctx.sign_to_vec(data, &mut signature).unwrap();

        let bad_data = b"Some Crypto text";

        ctx.verify_init().unwrap();
        let valid = ctx.verify(bad_data, &signature);
        assert!(matches!(valid, Ok(false) | Err(_)));
        assert!(ErrorStack::get().errors().is_empty());
    }

    #[test]
    fn verify_fail_ec() {
        let key1 =
            EcKey::generate(&EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap()).unwrap();
        let key1 = PKey::from_ec_key(key1).unwrap();

        let data = b"Some Crypto Text";
        let mut ctx = PkeyCtx::new(&key1).unwrap();
        ctx.verify_init().unwrap();
        assert!(matches!(ctx.verify(data, &[0; 64]), Ok(false) | Err(_)));
        assert!(ErrorStack::get().errors().is_empty());
    }

    #[test]
    fn test_verify_recover() {
        let key = Rsa::generate(2048).unwrap();
        let key = PKey::from_rsa(key).unwrap();

        let digest = [
            0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
            24, 25, 26, 27, 28, 29, 30, 31,
        ];

        let mut ctx = PkeyCtx::new(&key).unwrap();
        ctx.sign_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1).unwrap();
        ctx.set_signature_md(Md::sha256()).unwrap();
        let mut signature = vec![];
        ctx.sign_to_vec(&digest, &mut signature).unwrap();

        // Attempt recovery of just the digest.
        let mut ctx = PkeyCtx::new(&key).unwrap();
        ctx.verify_recover_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1).unwrap();
        ctx.set_signature_md(Md::sha256()).unwrap();
        let length = ctx.verify_recover(&signature, None).unwrap();
        let mut result_buf = vec![0; length];
        let length = ctx
            .verify_recover(&signature, Some(&mut result_buf))
            .unwrap();
        assert_eq!(length, digest.len());
        // result_buf contains the digest
        assert_eq!(result_buf[..length], digest);

        // Attempt recovery of teh entire DigestInfo
        let mut ctx = PkeyCtx::new(&key).unwrap();
        ctx.verify_recover_init().unwrap();
        ctx.set_rsa_padding(Padding::PKCS1).unwrap();
        let length = ctx.verify_recover(&signature, None).unwrap();
        let mut result_buf = vec![0; length];
        let length = ctx
            .verify_recover(&signature, Some(&mut result_buf))
            .unwrap();
        // 32-bytes of SHA256 digest + the ASN.1 DigestInfo structure == 51 bytes
        assert_eq!(length, 51);
        // The digest is the end of the DigestInfo structure.
        assert_eq!(result_buf[length - digest.len()..length], digest);
    }

    #[test]
    #[cfg(ossl320)]
    fn set_nonce_type() {
        let key1 =
            EcKey::generate(&EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap()).unwrap();
        let key1 = PKey::from_ec_key(key1).unwrap();

        let mut ctx = PkeyCtx::new(&key1).unwrap();
        ctx.sign_init().unwrap();
        ctx.set_nonce_type(NonceType::DETERMINISTIC_K).unwrap();
        let nonce_type = ctx.nonce_type().unwrap();
        assert_eq!(nonce_type, NonceType::DETERMINISTIC_K);
        assert!(ErrorStack::get().errors().is_empty());
    }

    // Test vector from
    // https://github.com/openssl/openssl/blob/openssl-3.2.0/test/recipes/30-test_evp_data/evppkey_ecdsa_rfc6979.txt
    #[test]
    #[cfg(ossl320)]
    fn ecdsa_deterministic_signature() {
        let private_key_pem = "-----BEGIN PRIVATE KEY-----
MDkCAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQEEHzAdAgEBBBhvqwNJNOTA/Jrmf1tWWanX0f79GH7g
n9Q=
-----END PRIVATE KEY-----";

        let key1 = EcKey::private_key_from_pem(private_key_pem.as_bytes()).unwrap();
        let key1 = PKey::from_ec_key(key1).unwrap();
        let input = "sample";
        let expected_output = hex::decode("303502190098C6BD12B23EAF5E2A2045132086BE3EB8EBD62ABF6698FF021857A22B07DEA9530F8DE9471B1DC6624472E8E2844BC25B64").unwrap();

        let hashed_input = hash(MessageDigest::sha1(), input.as_bytes()).unwrap();
        let mut ctx = PkeyCtx::new(&key1).unwrap();
        ctx.sign_init().unwrap();
        ctx.set_signature_md(Md::sha1()).unwrap();
        ctx.set_nonce_type(NonceType::DETERMINISTIC_K).unwrap();

        let mut output = vec![];
        ctx.sign_to_vec(&hashed_input, &mut output).unwrap();
        assert_eq!(output, expected_output);
        assert!(ErrorStack::get().errors().is_empty());
    }
}
