apple_security/

key.rs

//! Encryption key support

use crate::cvt;
use core_foundation::{
    base::TCFType, string::{CFStringRef, CFString},
    dictionary::CFMutableDictionary,
};
use core_foundation::base::ToVoid;
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use core_foundation::boolean::CFBoolean;
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use core_foundation::data::CFData;
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use core_foundation::dictionary::CFDictionary;
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use core_foundation::number::CFNumber;
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use core_foundation::error::{CFError, CFErrorRef};

use apple_security_sys::{
    item::{kSecAttrKeyTypeRSA, kSecValueRef}, 
    keychain_item::SecItemDelete
};
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use apple_security_sys::{item::{
    kSecAttrIsPermanent, kSecAttrLabel, kSecAttrKeyType,
    kSecAttrKeySizeInBits, kSecPrivateKeyAttrs
}};
#[cfg(target_os="macos")]
use apple_security_sys::item::{
    kSecAttrKeyType3DES, kSecAttrKeyTypeDSA, kSecAttrKeyTypeAES,
    kSecAttrKeyTypeDES, kSecAttrKeyTypeRC4, kSecAttrKeyTypeCAST,
};

use apple_security_sys::key::SecKeyGetTypeID;
use apple_security_sys::base::SecKeyRef;

#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
pub use apple_security_sys::key::Algorithm;

#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use apple_security_sys::key::{
    SecKeyCopyAttributes, SecKeyCopyExternalRepresentation,
    SecKeyCreateSignature, SecKeyCreateRandomKey,
    SecKeyCopyPublicKey,
};
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use apple_security_sys::item::kSecAttrApplicationLabel;
use std::fmt;

use crate::base::Error;
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
use crate::item::Location;

/// Types of `SecKey`s.
#[derive(Debug, Copy, Clone)]
pub struct KeyType(CFStringRef);

#[allow(missing_docs)]
impl KeyType {
    #[inline(always)]
    #[must_use]
    pub fn rsa() -> Self {
        unsafe { Self(kSecAttrKeyTypeRSA) }
    }

    #[cfg(target_os = "macos")]
    #[inline(always)]
    #[must_use]
    pub fn dsa() -> Self {
        unsafe { Self(kSecAttrKeyTypeDSA) }
    }

    #[cfg(target_os = "macos")]
    #[inline(always)]
    #[must_use]
    pub fn aes() -> Self {
        unsafe { Self(kSecAttrKeyTypeAES) }
    }

    #[cfg(target_os = "macos")]
    #[inline(always)]
    #[must_use]
    pub fn des() -> Self {
        unsafe { Self(kSecAttrKeyTypeDES) }
    }

    #[cfg(target_os = "macos")]
    #[inline(always)]
    #[must_use]
    pub fn triple_des() -> Self {
        unsafe { Self(kSecAttrKeyType3DES) }
    }

    #[cfg(target_os = "macos")]
    #[inline(always)]
    #[must_use]
    pub fn rc4() -> Self {
        unsafe { Self(kSecAttrKeyTypeRC4) }
    }

    #[cfg(target_os = "macos")]
    #[inline(always)]
    #[must_use]
    pub fn cast() -> Self {
        unsafe { Self(kSecAttrKeyTypeCAST) }
    }

    #[cfg(any(feature = "OSX_10_9", target_os = "ios"))]
    #[inline(always)]
    #[must_use]
    pub fn ec() -> Self {
        use apple_security_sys::item::kSecAttrKeyTypeEC;

        unsafe { Self(kSecAttrKeyTypeEC) }
    }

    pub(crate) fn to_str(self) -> CFString {
        unsafe { CFString::wrap_under_get_rule(self.0) }
    }
}

declare_TCFType! {
    /// A type representing an encryption key.
    SecKey, SecKeyRef
}
impl_TCFType!(SecKey, SecKeyRef, SecKeyGetTypeID);

unsafe impl Sync for SecKey {}
unsafe impl Send for SecKey {}

impl SecKey {
    #[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
    /// Translates to `SecKeyCreateRandomKey`
    /// `GenerateKeyOptions` provides a helper to create an attribute
    /// `CFDictionary`.
    pub fn generate(attributes: CFDictionary) -> Result<Self, CFError> {
        let mut error: CFErrorRef = ::std::ptr::null_mut();
        let sec_key = unsafe { SecKeyCreateRandomKey(attributes.as_concrete_TypeRef(), &mut error)};
        if !error.is_null() {
            Err(unsafe { CFError::wrap_under_create_rule(error) })
        } else {
            Ok(unsafe { SecKey::wrap_under_create_rule(sec_key) })
        }
    }

    /// Returns the programmatic identifier for the key. For keys of class
    /// kSecAttrKeyClassPublic and kSecAttrKeyClassPrivate, the value is the
    /// hash of the public key.
    #[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
    pub fn application_label(&self) -> Option<Vec<u8>> {
        self.attributes()
            .find(unsafe { kSecAttrApplicationLabel.to_void() })
            .map(|v| unsafe { CFData::wrap_under_get_rule(v.cast()) }.to_vec())
    }

    #[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
    /// Translates to `SecKeyCopyAttributes`
    #[must_use]
    pub fn attributes(&self) -> CFDictionary {
        let pka = unsafe { SecKeyCopyAttributes(self.to_void() as _) };
        unsafe { CFDictionary::wrap_under_create_rule(pka) }
    }

    #[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
    /// Translates to `SecKeyCopyExternalRepresentation`
    #[must_use]
    pub fn external_representation(&self) -> Option<CFData> {
        let mut error: CFErrorRef = ::std::ptr::null_mut();
        let data = unsafe { SecKeyCopyExternalRepresentation(self.to_void() as _, &mut error) };
        if data.is_null() {
            return None;
        }
        Some(unsafe { CFData::wrap_under_create_rule(data) })
    }

    #[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
    /// Translates to `SecKeyCopyPublicKey`
    #[must_use]
    pub fn public_key(&self) -> Option<Self> {
        let pub_seckey = unsafe { SecKeyCopyPublicKey(self.0.cast()) };
        if pub_seckey.is_null() {
            return None;
        }

        Some(unsafe { SecKey::wrap_under_create_rule(pub_seckey) })
    }

    #[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
    /// Creates the cryptographic signature for a block of data using a private
    /// key and specified algorithm.
    pub fn create_signature(&self, algorithm: Algorithm, input: &[u8]) -> Result<Vec<u8>, CFError> {
        let mut error: CFErrorRef = std::ptr::null_mut();

        let output = unsafe {
            SecKeyCreateSignature(
                self.as_concrete_TypeRef(),
                algorithm.into(),
                CFData::from_buffer(input).as_concrete_TypeRef(),
                &mut error,
            )
        };

        if !error.is_null() {
            Err(unsafe { CFError::wrap_under_create_rule(error) })
        } else {
            let output = unsafe { CFData::wrap_under_create_rule(output) };
            Ok(output.to_vec())
        }
    }

    /// Verifies the cryptographic signature for a block of data using a public
    /// key and specified algorithm.
    #[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
    pub fn verify_signature(&self, algorithm: Algorithm, signed_data: &[u8], signature: &[u8]) -> Result<bool, CFError> {
        use apple_security_sys::key::SecKeyVerifySignature;
        let mut error: CFErrorRef = std::ptr::null_mut();

        let valid = unsafe {
            SecKeyVerifySignature(
                self.as_concrete_TypeRef(),
                algorithm.into(),
                CFData::from_buffer(signed_data).as_concrete_TypeRef(),
                CFData::from_buffer(signature).as_concrete_TypeRef(),
                &mut error,
            )
        };

        if !error.is_null() {
            return Err(unsafe { CFError::wrap_under_create_rule(error) })?;
        }
        Ok(valid != 0)
    }

    /// Translates to `SecItemDelete`, passing in the `SecKeyRef`
    pub fn delete(&self) -> Result<(), Error> {
        let query = CFMutableDictionary::from_CFType_pairs(&[(
            unsafe { kSecValueRef }.to_void(),
            self.to_void(),
        )]);

        cvt(unsafe { SecItemDelete(query.as_concrete_TypeRef()) })
    }
}

/// Where to generate the key.
pub enum Token {
    /// Generate the key in software, compatible with all `KeyType`s.
    Software,
    /// Generate the key in the Secure Enclave such that the private key is not
    /// extractable. Only compatible with `KeyType::ec()`.
    SecureEnclave,
}

/// Helper for creating `CFDictionary` attributes for `SecKey::generate`
/// Recommended reading:
/// <https://developer.apple.com/documentation/technotes/tn3137-on-mac-keychains>
#[derive(Default)]
#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
pub struct GenerateKeyOptions {
    /// kSecAttrKeyType
    pub key_type: Option<KeyType>,
    /// kSecAttrKeySizeInBits
    pub size_in_bits: Option<u32>,
    /// kSecAttrLabel
    pub label: Option<String>,
    /// kSecAttrTokenID
    pub token: Option<Token>,
    /// Which keychain to store the key in, if any.
    pub location: Option<Location>,
}

#[cfg(any(feature = "OSX_10_12", target_os = "ios"))]
impl GenerateKeyOptions {
    /// Set `key_type`
    pub fn set_key_type(&mut self, key_type: KeyType) -> &mut Self {
        self.key_type = Some(key_type);
        self
    }
    /// Set `size_in_bits`
    pub fn set_size_in_bits(&mut self, size_in_bits: u32) -> &mut Self {
        self.size_in_bits = Some(size_in_bits);
        self
    }
    /// Set `label`
    pub fn set_label(&mut self, label: impl Into<String>) -> &mut Self {
        self.label = Some(label.into());
        self
    }
    /// Set `token`
    pub fn set_token(&mut self, token: Token) -> &mut Self {
        self.token = Some(token);
        self
    }
    /// Set `location`
    pub fn set_location(&mut self, location: Location) -> &mut Self {
        self.location = Some(location);
        self
    }

    /// Collect options into a `CFDictioanry`
    pub fn to_dictionary(&self) -> CFDictionary {
        #[cfg(target_os = "macos")]
        use apple_security_sys::item::kSecUseKeychain;
        use apple_security_sys::item::{
            kSecAttrTokenID, kSecAttrTokenIDSecureEnclave, kSecPublicKeyAttrs,
        };

        let is_permanent = CFBoolean::from(self.location.is_some());
        let private_attributes = CFMutableDictionary::from_CFType_pairs(&[(
            unsafe { kSecAttrIsPermanent }.to_void(),
            is_permanent.to_void(),
        )]);

        let public_attributes = CFMutableDictionary::from_CFType_pairs(&[(
            unsafe { kSecAttrIsPermanent }.to_void(),
            is_permanent.to_void(),
        )]);

        let key_type = self.key_type.unwrap_or_else(KeyType::rsa).to_str();

        let size_in_bits = self.size_in_bits.unwrap_or(match () {
            _ if key_type == KeyType::rsa().to_str() => 2048,
            _ if key_type == KeyType::ec().to_str() => 256,
            _ => 256,
        });
        let size_in_bits = CFNumber::from(size_in_bits as i32);

        let mut attribute_key_values = vec![
            (unsafe { kSecAttrKeyType }.to_void(), key_type.to_void()),
            (
                unsafe { kSecAttrKeySizeInBits }.to_void(),
                size_in_bits.to_void(),
            ),
            (
                unsafe { kSecPrivateKeyAttrs }.to_void(),
                private_attributes.to_void(),
            ),
            (
                unsafe { kSecPublicKeyAttrs }.to_void(),
                public_attributes.to_void(),
            ),
        ];
        let label = self.label.as_deref().map(CFString::new);
        if let Some(label) = &label {
            attribute_key_values.push((unsafe { kSecAttrLabel }.to_void(), label.to_void()));
        }

        #[cfg(target_os = "macos")]
        match &self.location {
            #[cfg(feature = "OSX_10_15")]
            Some(Location::DataProtectionKeychain) => {
                use apple_security_sys::item::kSecUseDataProtectionKeychain;
                attribute_key_values.push((
                    unsafe { kSecUseDataProtectionKeychain }.to_void(),
                    CFBoolean::true_value().to_void(),
                ));
            }
            Some(Location::FileKeychain(keychain)) => {
                attribute_key_values.push((
                    unsafe { kSecUseKeychain }.to_void(),
                    keychain.as_concrete_TypeRef().to_void(),
                ));
            }
            _ => {}
        }

        match self.token.as_ref().unwrap_or(&Token::Software) {
            Token::Software => {},
            Token::SecureEnclave => {
                attribute_key_values.push((
                    unsafe { kSecAttrTokenID }.to_void(),
                    unsafe { kSecAttrTokenIDSecureEnclave }.to_void(),
                ));
            }
        }

        CFMutableDictionary::from_CFType_pairs(&attribute_key_values).to_immutable()
    }
}

impl fmt::Debug for SecKey {
    #[cold]
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_struct("SecKey").finish_non_exhaustive()
    }
}