rama_boring/
derive.rs

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

rama_boring/
derive.rs
