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// Bitcoin secp256k1 bindings
// Written in 2021 by
// Maxim Orlovsky <orlovsky@pandoracore.com>
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software.
// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
//
//! Helpers for displaying secret values
use ::core::fmt;
use ::{SecretKey, KeyPair, to_hex};
use constants::SECRET_KEY_SIZE;
macro_rules! impl_display_secret {
// Default hasher exists only in standard library and not alloc
($thing:ident) => {
#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
impl ::core::fmt::Debug for $thing {
fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
use ::core::hash::Hasher;
const DEBUG_HASH_TAG: &[u8] = &[
0x66, 0xa6, 0x77, 0x1b, 0x9b, 0x6d, 0xae, 0xa1, 0xb2, 0xee, 0x4e, 0x07, 0x49,
0x4a, 0xac, 0x87, 0xa9, 0xb8, 0x5b, 0x4b, 0x35, 0x02, 0xaa, 0x6d, 0x0f, 0x79,
0xcb, 0x63, 0xe6, 0xf8, 0x66, 0x22
]; // =SHA256(b"rust-secp256k1DEBUG");
let mut hasher = ::std::collections::hash_map::DefaultHasher::new();
hasher.write(DEBUG_HASH_TAG);
hasher.write(DEBUG_HASH_TAG);
hasher.write(&self.serialize_secret());
let hash = hasher.finish();
f.debug_tuple(stringify!($thing))
.field(&format_args!("#{:016x}", hash))
.finish()
}
}
}
}
/// Helper struct for safely printing secrets (like [`SecretKey`] value).
/// Formats the explicit byte value of the secret kept inside the type as a
/// little-endian hexadecimal string using the provided formatter.
///
/// Secrets should not implement neither [`Debug`] and [`Display`] traits directly,
/// and instead provide `fn display_secret<'a>(&'a self) -> DisplaySecret<'a>`
/// function to be used in different display contexts (see "examples" below).
///
/// [`Display`]: fmt::Display
/// [`Debug`]: fmt::Debug
pub struct DisplaySecret {
secret: [u8; SECRET_KEY_SIZE]
}
impl fmt::Debug for DisplaySecret {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut slice = [0u8; 64];
let hex = to_hex(&self.secret, &mut slice).expect("fixed-size hex serializer failed");
f.debug_tuple("DisplaySecret")
.field(&hex)
.finish()
}
}
impl fmt::Display for DisplaySecret {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
for i in &self.secret {
write!(f, "{:02x}", i)?;
}
Ok(())
}
}
impl SecretKey {
/// Formats the explicit byte value of the secret key kept inside the type as a
/// little-endian hexadecimal string using the provided formatter.
///
/// This is the only method that outputs the actual secret key value, and, thus,
/// should be used with extreme precaution.
///
/// # Example
///
/// ```
/// use secp256k1::ONE_KEY;
/// let key = ONE_KEY;
/// // Normal display hides value
/// assert_eq!(
/// "SecretKey(#2518682f7819fb2d)",
/// format!("{:?}", key)
/// );
/// // Here we explicitly display the secret value:
/// assert_eq!(
/// "0000000000000000000000000000000000000000000000000000000000000001",
/// format!("{}", key.display_secret())
/// );
/// assert_eq!(
/// "DisplaySecret(\"0000000000000000000000000000000000000000000000000000000000000001\")",
/// format!("{:?}", key.display_secret())
/// );
/// ```
#[inline]
pub fn display_secret(&self) -> DisplaySecret {
DisplaySecret { secret: self.serialize_secret() }
}
}
impl KeyPair {
/// Formats the explicit byte value of the secret key kept inside the type as a
/// little-endian hexadecimal string using the provided formatter.
///
/// This is the only method that outputs the actual secret key value, and, thus,
/// should be used with extreme precaution.
///
/// # Example
///
/// ```
/// use secp256k1::ONE_KEY;
/// use secp256k1::KeyPair;
/// use secp256k1::Secp256k1;
///
/// let secp = Secp256k1::new();
/// let key = ONE_KEY;
/// let key = KeyPair::from_secret_key(&secp, key);
///
/// // Normal display hides value
/// assert_eq!(
/// "KeyPair(#2518682f7819fb2d)",
/// format!("{:?}", key)
/// );
/// // Here we explicitly display the secret value:
/// assert_eq!(
/// "0000000000000000000000000000000000000000000000000000000000000001",
/// format!("{}", key.display_secret())
/// );
/// assert_eq!(
/// "DisplaySecret(\"0000000000000000000000000000000000000000000000000000000000000001\")",
/// format!("{:?}", key.display_secret())
/// );
#[inline]
pub fn display_secret(&self) -> DisplaySecret {
DisplaySecret { secret: self.serialize_secret() }
}
}