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())) }
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    #[corresponds(EVP_PKEY_derive)]
54    pub fn len(&mut self) -> Result<usize, ErrorStack> {
55        unsafe {
56            let mut len = 0;
57            cvt(ffi::EVP_PKEY_derive(self.0, ptr::null_mut(), &mut len)).map(|_| len)
58        }
59    }
60
61    /// Derives a shared secret between the two keys, writing it into the buffer.
62    ///
63    /// Returns the number of bytes written.
64    #[corresponds(EVP_PKEY_derive)]
65    pub fn derive(&mut self, buf: &mut [u8]) -> Result<usize, ErrorStack> {
66        let mut len = buf.len();
67        unsafe { cvt(ffi::EVP_PKEY_derive(self.0, buf.as_mut_ptr(), &mut len)).map(|_| len) }
68    }
69
70    /// A convenience function which derives a shared secret and returns it in a new buffer.
71    ///
72    /// This simply wraps [`Deriver::len`] and [`Deriver::derive`].
73    ///
74    /// [`Deriver::len`]: #method.len
75    /// [`Deriver::derive`]: #method.derive
76    pub fn derive_to_vec(&mut self) -> Result<Vec<u8>, ErrorStack> {
77        let len = self.len()?;
78        let mut buf = vec![0; len];
79        let len = self.derive(&mut buf)?;
80        buf.truncate(len);
81        Ok(buf)
82    }
83}
84
85#[cfg(test)]
86mod test {
87    use super::*;
88
89    use crate::ec::{EcGroup, EcKey};
90    use crate::nid::Nid;
91    use crate::pkey::PKey;
92
93    #[test]
94    fn derive_without_peer() {
95        let group = EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap();
96        let ec_key = EcKey::generate(&group).unwrap();
97        let pkey = PKey::from_ec_key(ec_key).unwrap();
98        let mut deriver = Deriver::new(&pkey).unwrap();
99        deriver.derive_to_vec().unwrap_err();
100    }
101
102    #[test]
103    fn test_ec_key_derive() {
104        let group = EcGroup::from_curve_name(Nid::X9_62_PRIME256V1).unwrap();
105        let ec_key = EcKey::generate(&group).unwrap();
106        let ec_key2 = EcKey::generate(&group).unwrap();
107        let pkey = PKey::from_ec_key(ec_key).unwrap();
108        let pkey2 = PKey::from_ec_key(ec_key2).unwrap();
109        let mut deriver = Deriver::new(&pkey).unwrap();
110        deriver.set_peer(&pkey2).unwrap();
111        let shared = deriver.derive_to_vec().unwrap();
112        assert!(!shared.is_empty());
113    }
114}
boring/derive.rs

boring/
derive.rs
