boring_imp/
derive.rs

1//! Shared secret derivation.
2use crate::ffi;
3use foreign_types::ForeignTypeRef;
4use std::marker::PhantomData;
5use std::ptr;
6
7use crate::error::ErrorStack;
8use crate::pkey::{HasPrivate, HasPublic, PKeyRef};
9use crate::{cvt, cvt_p};
10
11/// A type used to derive a shared secret between two keys.
12pub struct Deriver<'a>(*mut ffi::EVP_PKEY_CTX, PhantomData<&'a ()>);
13
14unsafe impl<'a> Sync for Deriver<'a> {}
15unsafe impl<'a> Send for Deriver<'a> {}
16
17impl<'a> Drop for Deriver<'a> {
18    fn drop(&mut self) {
19        unsafe {
20            ffi::EVP_PKEY_CTX_free(self.0);
21        }
22    }
23}
24
25#[allow(clippy::len_without_is_empty)]
26impl<'a> Deriver<'a> {
27    /// Creates a new `Deriver` using the provided private key.
28    ///
29    /// This corresponds to [`EVP_PKEY_derive_init`].
30    ///
31    /// [`EVP_PKEY_derive_init`]: https://www.openssl.org/docs/man1.0.2/crypto/EVP_PKEY_derive_init.html
32    pub fn new<T>(key: &'a PKeyRef<T>) -> Result<Deriver<'a>, ErrorStack>
33    where
34        T: HasPrivate,
35    {
36        unsafe {
37            cvt_p(ffi::EVP_PKEY_CTX_new(key.as_ptr(), ptr::null_mut()))
38                .map(|p| Deriver(p, PhantomData))
39                .and_then(|ctx| cvt(ffi::EVP_PKEY_derive_init(ctx.0)).map(|_| ctx))
40        }
41    }
42
43    /// Sets the peer key used for secret derivation.
44    ///
45    /// This corresponds to [`EVP_PKEY_derive_set_peer`]:
46    ///
47    /// [`EVP_PKEY_derive_set_peer`]: https://www.openssl.org/docs/man1.0.2/crypto/EVP_PKEY_derive_init.html
48    pub fn set_peer<T>(&mut self, key: &'a PKeyRef<T>) -> Result<(), ErrorStack>
49    where
50        T: HasPublic,
51    {
52        unsafe { cvt(ffi::EVP_PKEY_derive_set_peer(self.0, key.as_ptr())).map(|_| ()) }
53    }
54
55    /// Returns the size of the shared secret.
56    ///
57    /// It can be used to size the buffer passed to [`Deriver::derive`].
58    ///
59    /// This corresponds to [`EVP_PKEY_derive`].
60    ///
61    /// [`Deriver::derive`]: #method.derive
62    /// [`EVP_PKEY_derive`]: https://www.openssl.org/docs/man1.0.2/crypto/EVP_PKEY_derive_init.html
63    pub fn len(&mut self) -> Result<usize, ErrorStack> {
64        unsafe {
65            let mut len = 0;
66            cvt(ffi::EVP_PKEY_derive(self.0, ptr::null_mut(), &mut len)).map(|_| len)
67        }
68    }
69
70    /// Derives a shared secret between the two keys, writing it into the buffer.
71    ///
72    /// Returns the number of bytes written.
73    ///
74    /// This corresponds to [`EVP_PKEY_derive`].
75    ///
76    /// [`EVP_PKEY_derive`]: https://www.openssl.org/docs/man1.0.2/crypto/EVP_PKEY_derive_init.html
77    pub fn derive(&mut self, buf: &mut [u8]) -> Result<usize, ErrorStack> {
78        let mut len = buf.len();
79        unsafe {
80            cvt(ffi::EVP_PKEY_derive(
81                self.0,
82                buf.as_mut_ptr() as *mut _,
83                &mut len,
84            ))
85            .map(|_| len)
86        }
87    }
88
89    /// A convenience function which derives a shared secret and returns it in a new buffer.
90    ///
91    /// This simply wraps [`Deriver::len`] and [`Deriver::derive`].
92    ///
93    /// [`Deriver::len`]: #method.len
94    /// [`Deriver::derive`]: #method.derive
95    pub fn derive_to_vec(&mut self) -> Result<Vec<u8>, ErrorStack> {
96        let len = self.len()?;
97        let mut buf = vec![0; len];
98        let len = self.derive(&mut buf)?;
99        buf.truncate(len);
100        Ok(buf)
101    }
102}
103
104#[cfg(test)]
105mod test {
106    use super::*;
107
108    use crate::ec::{EcGroup, EcKey};
109    use crate::nid::Nid;
110    use crate::pkey::PKey;
111
112    #[test]
113    fn derive_without_peer() {
114        let group = EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap();
115        let ec_key = EcKey::generate(&group).unwrap();
116        let pkey = PKey::from_ec_key(ec_key).unwrap();
117        let mut deriver = Deriver::new(&pkey).unwrap();
118        deriver.derive_to_vec().unwrap_err();
119    }
120
121    #[test]
122    fn test_ec_key_derive() {
123        let group = EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap();
124        let ec_key = EcKey::generate(&group).unwrap();
125        let ec_key2 = EcKey::generate(&group).unwrap();
126        let pkey = PKey::from_ec_key(ec_key).unwrap();
127        let pkey2 = PKey::from_ec_key(ec_key2).unwrap();
128        let mut deriver = Deriver::new(&pkey).unwrap();
129        deriver.set_peer(&pkey2).unwrap();
130        let shared = deriver.derive_to_vec().unwrap();
131        assert!(!shared.is_empty());
132    }
133}
boring_imp/derive.rs

boring_imp/
derive.rs
