fix: resolve clippy lints and update dependencies (#65)

* fix(deps): update aes dependency from 0.7 to 0.8

Migrate to use separate ctr crate following RustCrypto best practices.
The aes 0.8 release removed the ctr feature, requiring use of the
standalone ctr crate for AES-CTR mode operations.

Changes:
- Update aes dependency to 0.8 (remove ctr feature)
- Add ctr 0.9 dependency
- Update v1_local and v3_local cipher implementations to use new API
- Add ctr feature to v1_local and v3_local feature flags

All feature combinations tested and passing.

Closes #54

* feat: add compile-time checks for incompatible feature combinations

Prevents cryptic trait conflict errors by detecting incompatible feature
combinations at compile time with clear error messages.

Changes:
- Add compile_error! macros for conflicting public features
- Configure docs.rs to avoid --all-features (use default features)
- Document architectural design decisions in Cargo.toml

The PASETO specification recommends using a single version per application.
Multiple public features cause conflicting From<ed25519_dalek::ed25519::Error>
implementations. These checks enforce this design at compile time.

Error messages guide users to:
- Choose only one public feature
- Reference issue #48 for context
- Understand this is intentional design

Docs.rs configuration prevents build failures by using default features
(batteries_included + v4_local + v4_public) instead of --all-features.

Addresses #48

* chore(deps): update rand_core from 0.6 to 0.9

Update rand_core dependency to latest compatible version.

All 8 feature combinations tested and passing:
- v1_local: 12 tests passed
- v2_local: 14 tests passed
- v3_local: 16 tests passed
- v4_local: 13 tests passed
- v1_public: 8 tests passed
- v2_public: 10 tests passed
- v3_public: 7 tests passed
- v4_public: 10 tests passed

* chore(deps): update thiserror to 2.0

Update thiserror dependency from 1.0.69 to 2.0.17. All tests pass
across the entire feature matrix (v1-v4, local and public).

Changes include automatic clippy fixes for code style issues.

* chore(deps): update primes dev dependency to 0.4

Update primes from 0.3 to 0.4 in dev dependencies.

* docs: fix doc comment indentation for list items

Resolve clippy::doc-lazy-continuation warnings by properly indenting
continuation lines in documentation comments.

* refactor: remove unnecessary parentheses around impl types

Remove redundant parentheses from impl trait parameter types in
function signatures for all PASETO version implementations.

* refactor: replace deprecated ring constant-time comparison with subtle

Replace ring::constant_time::verify_slices_are_equal with subtle crate's
ConstantTimeEq trait for constant-time byte comparison. The subtle crate
is already present as a transitive dependency and provides the same
security guarantees.

* build: add subtle crate as direct dependency

Add subtle 2.6 as a direct dependency for constant-time operations.
While already present as a transitive dependency, explicit declaration
is required to import and use its ConstantTimeEq trait.

* fix: use correct PasetoError variant for MAC verification failures

Use PasetoError::Cryption for MAC tag comparison failures instead of
non-existent InvalidToken variant. This maintains security by providing
a general unspecified cryptographic error.

* fix: add explicit type annotation for subtle::Choice conversion

Use bool::from() for explicit type conversion of subtle::Choice to bool
to satisfy type inference requirements.

Author: rrrodzilla

Cargo.toml

@@ -71,6 +71,7 @@ aes = { version = "0.8", optional = true }
 ctr = { version = "0.9", optional = true }
 hmac = { version = "0.12", optional = true }
 sha2 = { version = "0.10", optional = true }
+subtle = "2.6"
 zeroize = { version = "1.4", features = ["zeroize_derive"] }
 time = { version = "0.3", features = ["parsing", "formatting"] }
 rand_core = "0.9"

src/core/common/pre_authentication_encoding.rs

@@ -7,8 +7,8 @@ pub struct PreAuthenticationEncoding(Vec<u8>);
 ///
 impl PreAuthenticationEncoding {
     /// * `pieces` - The Pieces to concatenate, and encode together.
-    /// Refactored from original code found at
-    /// <https://github.com/instructure/paseto/blob/trunk/src/pae.rs>
+    ///   Refactored from original code found at
+    ///   <https://github.com/instructure/paseto/blob/trunk/src/pae.rs>
     pub fn parse<'a>(pieces: &'a [&'a [u8]]) -> Self {
         let the_vec = PreAuthenticationEncoding::le64(pieces.len() as u64);
 
@@ -21,7 +21,7 @@ impl PreAuthenticationEncoding {
     /// Encodes a u64-bit unsigned integer into a little-endian binary string.
     ///
     /// * `to_encode` - The u8 to encode.
-    /// Copied and gently refactored from <https://github.com/instructure/paseto/blob/trunk/src/pae.rs>
+    ///   Copied and gently refactored from <https://github.com/instructure/paseto/blob/trunk/src/pae.rs>
     pub(crate) fn le64(mut to_encode: u64) -> Vec<u8> {
         let mut the_vec = Vec::with_capacity(8);
 

src/core/paseto_impl/v1_local.rs

@@ -1,9 +1,9 @@
 #![cfg(feature = "v1_local")]
 use std::str;
 use hmac::{Hmac, Mac};
+use subtle::ConstantTimeEq;
 use crate::core::{Footer, Header, Key, Local, Paseto, PasetoError, PasetoNonce, PasetoSymmetricKey, V1};
 use crate::core::common::{AuthenticationKey, AuthenticationKeySeparator, CipherText, EncryptionKey, EncryptionKeySeparator, PreAuthenticationEncoding, RawPayload, Tag};
-use ring::constant_time::verify_slices_are_equal as ConstantTimeEquals;
 use sha2::Sha384;
 
 impl<'a> Paseto<'a, V1, Local> {
@@ -26,7 +26,7 @@ impl<'a> Paseto<'a, V1, Local> {
     pub fn try_decrypt(
         token: &'a str,
         key: &PasetoSymmetricKey<V1, Local>,
-        footer: (impl Into<Option<Footer<'a>>> + Copy),
+        footer: impl Into<Option<Footer<'a>>> + Copy,
     ) -> Result<String, PasetoError> {
         let decoded_payload = Self::parse_raw_token(token, footer, &V1::default(), &Local::default())?;
         let nonce = Key::from(&decoded_payload[..32]);
@@ -51,7 +51,9 @@ impl<'a> Paseto<'a, V1, Local> {
         let tag = &decoded_payload[(nonce.len() + ciphertext.len())..];
         let tag2 = &Tag::<V1, Local>::from(authentication_key, &pae);
         //compare tags
-        ConstantTimeEquals(tag, tag2)?;
+        if !bool::from(tag.ct_eq(tag2.as_ref())) {
+            return Err(PasetoError::Cryption);
+        }
 
         //decrypt payload
         let ciphertext = CipherText::<V1, Local>::from(ciphertext, &encryption_key);

src/core/paseto_impl/v1_public.rs

@@ -9,7 +9,7 @@ impl<'a> Paseto<'a, V1, Public> {
     pub fn try_verify(
         signature: &'a str,
         public_key: &PasetoAsymmetricPublicKey<V1, Public>,
-        footer: (impl Into<Option<Footer<'a>>> + Copy),
+        footer: impl Into<Option<Footer<'a>>> + Copy,
     ) -> Result<String, PasetoError> {
         let decoded_payload = Self::parse_raw_token(signature, footer, &V1::default(), &Public::default())?;
 

src/core/paseto_impl/v2_local.rs

@@ -25,7 +25,7 @@ impl<'a> Paseto<'a, V2, Local> {
     pub fn try_decrypt(
         token: &'a str,
         key: &PasetoSymmetricKey<V2, Local>,
-        footer: (impl Into<Option<Footer<'a>>> + Copy),
+        footer: impl Into<Option<Footer<'a>>> + Copy,
     ) -> Result<String, PasetoError> {
         //get footer
 

src/core/paseto_impl/v2_public.rs

@@ -10,7 +10,7 @@ impl<'a> Paseto<'a, V2, Public> {
     pub fn try_verify(
         signature: &'a str,
         public_key: &PasetoAsymmetricPublicKey<V2, Public>,
-        footer: (impl Into<Option<Footer<'a>>> + Copy),
+        footer: impl Into<Option<Footer<'a>>> + Copy,
     ) -> Result<String, PasetoError> {
         let decoded_payload = Self::parse_raw_token(signature, footer, &V2::default(), &Public::default())?;
 

src/core/paseto_impl/v3_local.rs

@@ -2,7 +2,7 @@
 
 use std::str;
 
-use ring::constant_time::verify_slices_are_equal as ConstantTimeEquals;
+use subtle::ConstantTimeEq;
 
 use crate::core::{Footer, Header, ImplicitAssertion, Key, Local, Paseto, PasetoError, PasetoNonce, PasetoSymmetricKey, V3};
 use crate::core::common::{AuthenticationKey, AuthenticationKeySeparator, CipherText, EncryptionKey, EncryptionKeySeparator, PreAuthenticationEncoding, RawPayload, Tag};
@@ -27,8 +27,8 @@ impl<'a> Paseto<'a, V3, Local> {
     pub fn try_decrypt(
         token: &'a str,
         key: &PasetoSymmetricKey<V3, Local>,
-        footer: (impl Into<Option<Footer<'a>>> + Copy),
-        implicit_assertion: (impl Into<Option<ImplicitAssertion<'a>>> + Copy),
+        footer: impl Into<Option<Footer<'a>>> + Copy,
+        implicit_assertion: impl Into<Option<ImplicitAssertion<'a>>> + Copy,
     ) -> Result<String, PasetoError> {
         //get footer
 
@@ -55,7 +55,9 @@ impl<'a> Paseto<'a, V3, Local> {
         let tag = &decoded_payload[(nonce.len() + ciphertext.len())..];
         let tag2 = &Tag::<V3, Local>::from(authentication_key, &pae);
         //compare tags
-        ConstantTimeEquals(tag, tag2)?;
+        if !bool::from(tag.ct_eq(tag2.as_ref())) {
+            return Err(PasetoError::Cryption);
+        }
 
         //decrypt payload
         let ciphertext = CipherText::<V3, Local>::from(ciphertext, &encryption_key);

src/core/paseto_impl/v3_public.rs

@@ -14,8 +14,8 @@ impl<'a> Paseto<'a, V3, Public> {
     pub fn try_verify(
         signature: &'a str,
         public_key: &PasetoAsymmetricPublicKey<V3, Public>,
-        footer: (impl Into<Option<Footer<'a>>> + Copy),
-        implicit_assertion: (impl Into<Option<ImplicitAssertion<'a>>> + Copy),
+        footer: impl Into<Option<Footer<'a>>> + Copy,
+        implicit_assertion: impl Into<Option<ImplicitAssertion<'a>>> + Copy,
     ) -> Result<String, PasetoError> {
         let decoded_payload = Self::parse_raw_token(signature, footer, &V3::default(), &Public::default())?;
 

src/core/paseto_impl/v4_local.rs

@@ -2,7 +2,7 @@
 
 use std::str;
 
-use ring::constant_time::verify_slices_are_equal as ConstantTimeEquals;
+use subtle::ConstantTimeEq;
 
 use crate::core::{Footer, Header, ImplicitAssertion, Key, Local, Paseto, PasetoError, PasetoNonce, PasetoSymmetricKey, V4};
 use crate::core::common::{AuthenticationKey, AuthenticationKeySeparator, CipherText, EncryptionKey, EncryptionKeySeparator, PreAuthenticationEncoding, RawPayload, Tag};
@@ -55,7 +55,9 @@ impl<'a> Paseto<'a, V4, Local> {
         let tag = &decoded_payload[(nonce.len() + ciphertext.len())..];
         let tag2 = &Tag::<V4, Local>::from(authentication_key, &pae);
         //compare tags
-        ConstantTimeEquals(tag, tag2)?;
+        if !bool::from(tag.ct_eq(tag2.as_ref())) {
+            return Err(PasetoError::Cryption);
+        }
 
         //decrypt payload
         let ciphertext = CipherText::<V4, Local>::from(ciphertext, &encryption_key);

src/core/traits.rs

@@ -1,6 +1,6 @@
 use base64::DecodeError;
 use base64::prelude::*;
-use ring::constant_time::verify_slices_are_equal as ConstantTimeEquals;
+use subtle::ConstantTimeEq;
 use std::fmt::Display;
 
 //marker traits
@@ -27,6 +27,6 @@ pub(crate) trait Base64Encodable<T: ?Sized + AsRef<[u8]>>: Display + AsRef<T> {
   where
     B: AsRef<str>,
   {
-    ConstantTimeEquals(self.encode().as_ref(), other.as_ref().as_bytes()).is_ok()
+    self.encode().as_bytes().ct_eq(other.as_ref().as_bytes()).into()
   }
 }