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// Copyright 2021 Contributors to the Parsec project.
// SPDX-License-Identifier: Apache-2.0
//! # PsaCipherDecrypt operation
//!
//! Decrypt a short message with a symmetric cipher
use super::psa_key_attributes::Attributes;
use crate::operations::psa_algorithm::Cipher;
use crate::requests::ResponseStatus;
use derivative::Derivative;
/// Native object for cipher decryption operations.
#[derive(Derivative)]
#[derivative(Debug)]
pub struct Operation {
/// Defines which key should be used for the decryption operation.
pub key_name: String,
/// An cipher encryption algorithm to be used for decryption, that is compatible with the type of key.
pub alg: Cipher,
/// The short encrypted message to be decrypted.
#[derivative(Debug = "ignore")]
pub ciphertext: zeroize::Zeroizing<Vec<u8>>,
}
impl Operation {
/// Validate the contents of the operation against the attributes of the key it targets
///
/// This method checks that:
/// * the key policy allows decrypting messages
/// * the key policy allows the decryption algorithm requested in the operation
/// * the key type is compatible with the requested algorithm
/// * the message to decrypt is valid (not length 0)
pub fn validate(&self, key_attributes: Attributes) -> crate::requests::Result<()> {
key_attributes.can_decrypt_message()?;
key_attributes.permits_alg(self.alg.into())?;
key_attributes.compatible_with_alg(self.alg.into())?;
if self.ciphertext.is_empty() {
return Err(ResponseStatus::PsaErrorInvalidArgument);
}
Ok(())
}
}
/// Native object for cipher decrypt result.
// Debug derived as NativeResult enum requires it, even though nothing inside this Result is debuggable
// as `plaintext` is sensitive.
#[derive(Derivative)]
#[derivative(Debug)]
pub struct Result {
/// Decrypted message
#[derivative(Debug = "ignore")]
pub plaintext: zeroize::Zeroizing<Vec<u8>>,
}
#[cfg(test)]
mod tests {
use super::*;
use crate::operations::psa_algorithm::Cipher;
use crate::operations::psa_key_attributes::{Lifetime, Policy, Type, UsageFlags};
fn get_attrs() -> Attributes {
let mut usage_flags = UsageFlags::default();
let _ = usage_flags.set_decrypt();
Attributes {
lifetime: Lifetime::Persistent,
key_type: Type::Arc4,
bits: 256,
policy: Policy {
usage_flags,
permitted_algorithms: Cipher::StreamCipher.into(),
},
}
}
#[test]
fn validate_success() {
(Operation {
key_name: String::from("some key"),
alg: Cipher::StreamCipher,
ciphertext: vec![0xff, 32].into(),
})
.validate(get_attrs())
.unwrap();
}
#[test]
fn cannot_decrypt() {
let mut attrs = get_attrs();
attrs.policy.usage_flags = UsageFlags::default();
assert_eq!(
(Operation {
key_name: String::from("some key"),
alg: Cipher::StreamCipher,
ciphertext: vec![0xff, 32].into(),
})
.validate(attrs)
.unwrap_err(),
ResponseStatus::PsaErrorNotPermitted
);
}
#[test]
fn wrong_algorithm() {
assert_eq!(
(Operation {
key_name: String::from("some key"),
alg: Cipher::Cfb,
ciphertext: vec![0xff, 32].into(),
})
.validate(get_attrs())
.unwrap_err(),
ResponseStatus::PsaErrorNotPermitted
);
}
#[test]
fn invalid_ciphertext() {
assert_eq!(
(Operation {
key_name: String::from("some key"),
alg: Cipher::StreamCipher,
ciphertext: vec![].into(),
})
.validate(get_attrs())
.unwrap_err(),
ResponseStatus::PsaErrorInvalidArgument
);
}
}