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