argon2: more const-ness (#450)

argon2/src/algorithm.rs

@@ -58,7 +58,7 @@ impl Algorithm {
     }
 
     /// Get the identifier string for this PBKDF2 [`Algorithm`].
-    pub fn as_str(&self) -> &'static str {
+    pub const fn as_str(&self) -> &'static str {
         match self {
             Algorithm::Argon2d => "argon2d",
             Algorithm::Argon2i => "argon2i",
@@ -69,7 +69,7 @@ impl Algorithm {
     /// Get the [`Ident`] that corresponds to this Argon2 [`Algorithm`].
     #[cfg(feature = "password-hash")]
     #[cfg_attr(docsrs, doc(cfg(feature = "password-hash")))]
-    pub fn ident(&self) -> Ident<'static> {
+    pub const fn ident(&self) -> Ident<'static> {
         match self {
             Algorithm::Argon2d => ARGON2D_IDENT,
             Algorithm::Argon2i => ARGON2I_IDENT,
@@ -78,7 +78,7 @@ impl Algorithm {
     }
 
     /// Serialize primitive type as little endian bytes
-    pub(crate) fn to_le_bytes(self) -> [u8; 4] {
+    pub(crate) const fn to_le_bytes(self) -> [u8; 4] {
         (self as u32).to_le_bytes()
     }
 }

argon2/src/lib.rs

@@ -470,7 +470,7 @@ impl<'key> Argon2<'key> {
     }
 
     /// Get default configured [`Params`].
-    pub fn params(&self) -> &Params {
+    pub const fn params(&self) -> &Params {
         &self.params
     }
 
@@ -531,7 +531,7 @@ impl<'key> Argon2<'key> {
         digest.finalize()
     }
 
-    fn verify_inputs(pwd: &[u8], salt: &[u8]) -> Result<()> {
+    const fn verify_inputs(pwd: &[u8], salt: &[u8]) -> Result<()> {
         if pwd.len() > MAX_PWD_LEN {
             return Err(Error::PwdTooLong);
         }

argon2/src/params.rs

@@ -104,36 +104,74 @@ impl Params {
     /// - `t_cost`: number of iterations. Between 1 and (2^32)-1.
     /// - `p_cost`: degree of parallelism. Between 1 and 255.
     /// - `output_len`: size of the KDF output in bytes. Default 32.
-    pub fn new(m_cost: u32, t_cost: u32, p_cost: u32, output_len: Option<usize>) -> Result<Self> {
-        let mut builder = ParamsBuilder::new();
+    pub const fn new(
+        m_cost: u32,
+        t_cost: u32,
+        p_cost: u32,
+        output_len: Option<usize>,
+    ) -> Result<Self> {
+        if m_cost < Params::MIN_M_COST {
+            return Err(Error::MemoryTooLittle);
+        }
 
-        builder.m_cost(m_cost).t_cost(t_cost).p_cost(p_cost);
+        // Note: we don't need to check `MAX_M_COST`, since it's `u32::MAX`
+
+        if m_cost < p_cost * 8 {
+            return Err(Error::MemoryTooLittle);
+        }
+
+        if t_cost < Params::MIN_T_COST {
+            return Err(Error::TimeTooSmall);
+        }
+
+        // Note: we don't need to check `MAX_T_COST`, since it's `u32::MAX`
+
+        if p_cost < Params::MIN_P_COST {
+            return Err(Error::ThreadsTooFew);
+        }
+
+        if p_cost > Params::MAX_P_COST {
+            return Err(Error::ThreadsTooMany);
+        }
 
         if let Some(len) = output_len {
-            builder.output_len(len);
+            if len < Params::MIN_OUTPUT_LEN {
+                return Err(Error::OutputTooShort);
+            }
+
+            if len > Params::MAX_OUTPUT_LEN {
+                return Err(Error::OutputTooLong);
+            }
         }
 
-        builder.build()
+        Ok(Params {
+            m_cost,
+            t_cost,
+            p_cost,
+            keyid: KeyId::EMPTY,
+            data: AssociatedData::EMPTY,
+            output_len,
+        })
     }
 
     /// Memory size, expressed in kibibytes. Between 1 and (2^32)-1.
     ///
     /// Value is an integer in decimal (1 to 10 digits).
-    pub fn m_cost(&self) -> u32 {
+    pub const fn m_cost(&self) -> u32 {
         self.m_cost
     }
 
     /// Number of iterations. Between 1 and (2^32)-1.
     ///
     /// Value is an integer in decimal (1 to 10 digits).
-    pub fn t_cost(&self) -> u32 {
+    pub const fn t_cost(&self) -> u32 {
         self.t_cost
     }
 
     /// Degree of parallelism. Between 1 and 255.
     ///
     /// Value is an integer in decimal (1 to 3 digits).
-    pub fn p_cost(&self) -> u32 {
+    pub const fn p_cost(&self) -> u32 {
         self.p_cost
     }
 
@@ -164,25 +202,25 @@ impl Params {
     }
 
     /// Length of the output (in bytes).
-    pub fn output_len(&self) -> Option<usize> {
+    pub const fn output_len(&self) -> Option<usize> {
         self.output_len
     }
 
     /// Get the number of lanes.
     #[allow(clippy::cast_possible_truncation)]
-    pub(crate) fn lanes(&self) -> usize {
+    pub(crate) const fn lanes(&self) -> usize {
         self.p_cost as usize
     }
 
     /// Get the number of blocks in a lane.
-    pub(crate) fn lane_length(&self) -> usize {
+    pub(crate) const fn lane_length(&self) -> usize {
         self.segment_length() * SYNC_POINTS
     }
 
     /// Get the segment length given the configured `m_cost` and `p_cost`.
     ///
     /// Minimum memory_blocks = 8*`L` blocks, where `L` is the number of lanes.
-    pub(crate) fn segment_length(&self) -> usize {
+    pub(crate) const fn segment_length(&self) -> usize {
         let m_cost = self.m_cost as usize;
 
         let memory_blocks = if m_cost < 2 * SYNC_POINTS * self.lanes() {
@@ -195,7 +233,7 @@ impl Params {
     }
 
     /// Get the number of blocks required given the configured `m_cost` and `p_cost`.
-    pub fn block_count(&self) -> usize {
+    pub const fn block_count(&self) -> usize {
         self.segment_length() * self.lanes() * SYNC_POINTS
     }
 }
@@ -233,6 +271,12 @@ macro_rules! param_buf {
                 Ok(Self { bytes, len })
             }
 
+            /// Empty value.
+            pub const EMPTY: Self = Self {
+                bytes: [0u8; Self::MAX_LEN],
+                len: 0,
+            };
+
             #[doc = "Decode"]
             #[doc = $name]
             #[doc = " from a B64 string"]
@@ -249,12 +293,12 @@ macro_rules! param_buf {
             }
 
             /// Get the length in bytes.
-            pub fn len(&self) -> usize {
+            pub const fn len(&self) -> usize {
                 self.len
             }
 
             /// Is this value empty?
-            pub fn is_empty(&self) -> bool {
+            pub const fn is_empty(&self) -> bool {
                 self.len() == 0
             }
         }
@@ -384,8 +428,8 @@ pub struct ParamsBuilder {
 
 impl ParamsBuilder {
     /// Create a new builder with the default parameters.
-    pub fn new() -> Self {
-        Self::default()
+    pub const fn new() -> Self {
+        Self::DEFAULT
     }
 
     /// Set memory size, expressed in kibibytes, between 1 and (2^32)-1.
@@ -428,52 +472,18 @@ impl ParamsBuilder {
     ///
     /// This performs validations to ensure that the given parameters are valid
     /// and compatible with each other, and will return an error if they are not.
-    pub fn build(&self) -> Result<Params> {
-        if self.m_cost < Params::MIN_M_COST {
-            return Err(Error::MemoryTooLittle);
-        }
-
-        // Note: we don't need to check `MAX_M_COST`, since it's `u32::MAX`
-
-        if self.m_cost < self.p_cost * 8 {
-            return Err(Error::MemoryTooLittle);
-        }
-
-        if self.t_cost < Params::MIN_T_COST {
-            return Err(Error::TimeTooSmall);
-        }
-
-        // Note: we don't need to check `MAX_T_COST`, since it's `u32::MAX`
-
-        if self.p_cost < Params::MIN_P_COST {
-            return Err(Error::ThreadsTooFew);
-        }
-
-        if self.p_cost > Params::MAX_P_COST {
-            return Err(Error::ThreadsTooMany);
-        }
-
-        if let Some(len) = self.output_len {
-            if len < Params::MIN_OUTPUT_LEN {
-                return Err(Error::OutputTooShort);
-            }
+    pub const fn build(&self) -> Result<Params> {
+        let mut params = match Params::new(self.m_cost, self.t_cost, self.p_cost, self.output_len) {
+            Ok(params) => params,
+            Err(err) => return Err(err),
+        };
 
-            if len > Params::MAX_OUTPUT_LEN {
-                return Err(Error::OutputTooLong);
-            }
+        if let Some(keyid) = self.keyid {
+            params.keyid = keyid;
         }
 
-        let keyid = self.keyid.unwrap_or_default();
-
-        let data = self.data.unwrap_or_default();
-
-        let params = Params {
-            m_cost: self.m_cost,
-            t_cost: self.t_cost,
-            p_cost: self.p_cost,
-            keyid,
-            data,
-            output_len: self.output_len,
+        if let Some(data) = self.data {
+            params.data = data;
         };
 
         Ok(params)
@@ -483,11 +493,9 @@ impl ParamsBuilder {
     pub fn context(&self, algorithm: Algorithm, version: Version) -> Result<Argon2<'_>> {
         Ok(Argon2::new(algorithm, version, self.build()?))
     }
-}
-
-impl Default for ParamsBuilder {
-    fn default() -> Self {
-        let params = Params::default();
+    /// Default parameters (recommended).
+    pub const DEFAULT: ParamsBuilder = {
+        let params = Params::DEFAULT;
         Self {
             m_cost: params.m_cost,
             t_cost: params.t_cost,
@@ -496,6 +504,12 @@ impl Default for ParamsBuilder {
             data: None,
             output_len: params.output_len,
         }
+    };
+}
+
+impl Default for ParamsBuilder {
+    fn default() -> Self {
+        Self::DEFAULT
     }
 }
 

argon2/src/version.rs

@@ -3,7 +3,7 @@
 use crate::{Error, Result};
 
 /// Version of the algorithm.
-#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[derive(Copy, Clone, Debug, Default, Eq, PartialEq, PartialOrd, Ord)]
 #[repr(u32)]
 pub enum Version {
     /// Version 16 (0x10 in hex)
@@ -14,22 +14,17 @@ pub enum Version {
     /// Version 19 (0x13 in hex, default)
     ///
     /// Performs XOR internally
+    #[default]
     V0x13 = 0x13,
 }
 
 impl Version {
     /// Serialize version as little endian bytes
-    pub(crate) fn to_le_bytes(self) -> [u8; 4] {
+    pub(crate) const fn to_le_bytes(self) -> [u8; 4] {
         (self as u32).to_le_bytes()
     }
 }
 
-impl Default for Version {
-    fn default() -> Self {
-        Self::V0x13
-    }
-}
-
 impl From<Version> for u32 {
     fn from(version: Version) -> u32 {
         version as u32