126 lines
4.1 KiB
Rust
126 lines
4.1 KiB
Rust
//! Shared secret derivation.
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use ffi;
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use foreign_types::ForeignTypeRef;
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use std::marker::PhantomData;
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use std::ptr;
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use error::ErrorStack;
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use pkey::{HasPrivate, HasPublic, PKeyRef};
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use {cvt, cvt_p};
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/// A type used to derive a shared secret between two keys.
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pub struct Deriver<'a>(*mut ffi::EVP_PKEY_CTX, PhantomData<&'a ()>);
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unsafe impl<'a> Sync for Deriver<'a> {}
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unsafe impl<'a> Send for Deriver<'a> {}
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#[allow(clippy::len_without_is_empty)]
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impl<'a> Deriver<'a> {
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/// Creates a new `Deriver` using the provided private key.
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///
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/// This corresponds to [`EVP_PKEY_derive_init`].
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///
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/// [`EVP_PKEY_derive_init`]: https://www.openssl.org/docs/man1.0.2/crypto/EVP_PKEY_derive_init.html
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pub fn new<T>(key: &'a PKeyRef<T>) -> Result<Deriver<'a>, ErrorStack>
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where
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T: HasPrivate,
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{
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unsafe {
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cvt_p(ffi::EVP_PKEY_CTX_new(key.as_ptr(), ptr::null_mut()))
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.map(|p| Deriver(p, PhantomData))
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.and_then(|ctx| cvt(ffi::EVP_PKEY_derive_init(ctx.0)).map(|_| ctx))
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}
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}
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/// Sets the peer key used for secret derivation.
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///
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/// This corresponds to [`EVP_PKEY_derive_set_peer`]:
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///
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/// [`EVP_PKEY_derive_set_peer`]: https://www.openssl.org/docs/man1.0.2/crypto/EVP_PKEY_derive_init.html
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pub fn set_peer<T>(&mut self, key: &'a PKeyRef<T>) -> Result<(), ErrorStack>
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where
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T: HasPublic,
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{
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unsafe { cvt(ffi::EVP_PKEY_derive_set_peer(self.0, key.as_ptr())).map(|_| ()) }
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}
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/// Returns the size of the shared secret.
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///
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/// It can be used to size the buffer passed to [`Deriver::derive`].
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///
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/// This corresponds to [`EVP_PKEY_derive`].
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///
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/// [`Deriver::derive`]: #method.derive
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/// [`EVP_PKEY_derive`]: https://www.openssl.org/docs/man1.0.2/crypto/EVP_PKEY_derive_init.html
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pub fn len(&mut self) -> Result<usize, ErrorStack> {
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unsafe {
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let mut len = 0;
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cvt(ffi::EVP_PKEY_derive(self.0, ptr::null_mut(), &mut len)).map(|_| len)
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}
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}
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/// Derives a shared secret between the two keys, writing it into the buffer.
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///
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/// Returns the number of bytes written.
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///
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/// This corresponds to [`EVP_PKEY_derive`].
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///
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/// [`EVP_PKEY_derive`]: https://www.openssl.org/docs/man1.0.2/crypto/EVP_PKEY_derive_init.html
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pub fn derive(&mut self, buf: &mut [u8]) -> Result<usize, ErrorStack> {
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let mut len = buf.len();
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unsafe {
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cvt(ffi::EVP_PKEY_derive(
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self.0,
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buf.as_mut_ptr() as *mut _,
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&mut len,
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))
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.map(|_| len)
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}
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}
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/// A convenience function which derives a shared secret and returns it in a new buffer.
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///
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/// This simply wraps [`Deriver::len`] and [`Deriver::derive`].
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///
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/// [`Deriver::len`]: #method.len
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/// [`Deriver::derive`]: #method.derive
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pub fn derive_to_vec(&mut self) -> Result<Vec<u8>, ErrorStack> {
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let len = self.len()?;
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let mut buf = vec![0; len];
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let len = self.derive(&mut buf)?;
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buf.truncate(len);
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Ok(buf)
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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use ec::{EcGroup, EcKey};
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use nid::Nid;
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use pkey::PKey;
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#[test]
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fn derive_without_peer() {
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let group = EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap();
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let ec_key = EcKey::generate(&group).unwrap();
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let pkey = PKey::from_ec_key(ec_key).unwrap();
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let mut deriver = Deriver::new(&pkey).unwrap();
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deriver.derive_to_vec().unwrap_err();
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}
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#[test]
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fn test_ec_key_derive() {
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let group = EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap();
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let ec_key = EcKey::generate(&group).unwrap();
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let ec_key2 = EcKey::generate(&group).unwrap();
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let pkey = PKey::from_ec_key(ec_key).unwrap();
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let pkey2 = PKey::from_ec_key(ec_key2).unwrap();
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let mut deriver = Deriver::new(&pkey).unwrap();
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deriver.set_peer(&pkey2).unwrap();
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let shared = deriver.derive_to_vec().unwrap();
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assert!(!shared.is_empty());
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}
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}
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