HMAC sign example

//!

//! let text = b"Some Crypto Text";

//!

//! // Create the signature

//! // Create the signature.

//! let mut ctx = MdCtx::new().unwrap();

//! ctx.digest_sign_init(Some(Md::sha256()), &key).unwrap();

//! ctx.digest_sign_update(text).unwrap();

//! let mut signature = vec![];

//! ctx.digest_sign_final_to_vec(&mut signature).unwrap();

//!

//! // Verify the signature

//! // Verify the signature.

//! let mut ctx = MdCtx::new().unwrap();

//! ctx.digest_verify_init(Some(Md::sha256()), &key).unwrap();

//! ctx.digest_verify_update(text).unwrap();

//! let valid = ctx.digest_verify_final(&signature).unwrap();

//! assert!(valid);

//! ```

//!

//! Compute and verify an HMAC-SHA256

//!

//! ```

//! use openssl::md::Md;

//! use openssl::md_ctx::MdCtx;

//! use openssl::memcmp;

//! use openssl::pkey::PKey;

//!

//! // Create a key with the HMAC secret.

//! let key = PKey::hmac(b"my secret").unwrap();

//!

//! let text = b"Some Crypto Text";

//!

//! // Compute the HMAC.

//! let mut ctx = MdCtx::new().unwrap();

//! ctx.digest_sign_init(Some(Md::sha256()), &key).unwrap();

//! ctx.digest_sign_update(text).unwrap();

//! let mut hmac = vec![];

//! ctx.digest_sign_final_to_vec(&mut hmac).unwrap();

//!

//! // Verify the HMAC. You can't use MdCtx to do this; instead use a constant time equality check.

//! # let target = hmac.clone();

//! let valid = memcmp::eq(&hmac, &target);

//! assert!(valid);

//! ```

use crate::error::ErrorStack;

use crate::md::MdRef;

use crate::pkey::{HasPrivate, PKeyRef};