der: initial Writer trait (#605)

Begins moving core encoding functionality into a `Writer` trait. The longer-term goal is to make the `Encode` trait accept a generic type as a backend, which can enable things like 1-pass PEM encoding or computing key fingerprints by impl'ing `Writer` for a hash function.
RustCrypto · Apr 23, 2022 · ad4a4fc · ad4a4fc
1 parent 677bc84
commit ad4a4fc
Show file tree

Hide file tree

Showing 19 changed files with 73 additions and 67 deletions.
diff --git a/der/src/asn1/any.rs b/der/src/asn1/any.rs
@@ -2,7 +2,7 @@
 
 use crate::{
     asn1::*, ByteSlice, Choice, Decode, DecodeValue, Decoder, DerOrd, EncodeValue, Encoder, Error,
-    ErrorKind, FixedTag, Header, Length, Result, Tag, Tagged, ValueOrd,
+    ErrorKind, FixedTag, Header, Length, Result, Tag, Tagged, ValueOrd, Writer,
 };
 use core::cmp::Ordering;
 
@@ -168,7 +168,7 @@ impl EncodeValue for Any<'_> {
     }
 
     fn encode_value(&self, encoder: &mut Encoder<'_>) -> Result<()> {
-        encoder.bytes(self.value())
+        encoder.write(self.value())
     }
 }
 

diff --git a/der/src/asn1/bit_string.rs b/der/src/asn1/bit_string.rs
@@ -2,7 +2,7 @@
 
 use crate::{
     asn1::Any, ByteSlice, DecodeValue, Decoder, DerOrd, EncodeValue, Encoder, Error, ErrorKind,
-    FixedTag, Header, Length, Result, Tag, ValueOrd,
+    FixedTag, Header, Length, Result, Tag, ValueOrd, Writer,
 };
 use core::{cmp::Ordering, iter::FusedIterator};
 
@@ -134,8 +134,8 @@ impl EncodeValue for BitString<'_> {
     }
 
     fn encode_value(&self, encoder: &mut Encoder<'_>) -> Result<()> {
-        encoder.byte(self.unused_bits)?;
-        encoder.bytes(self.raw_bytes())
+        encoder.write_byte(self.unused_bits)?;
+        encoder.write(self.raw_bytes())
     }
 }
 

diff --git a/der/src/asn1/boolean.rs b/der/src/asn1/boolean.rs
@@ -2,7 +2,7 @@
 
 use crate::{
     asn1::Any, ord::OrdIsValueOrd, ByteSlice, DecodeValue, Decoder, EncodeValue, Encoder, Error,
-    ErrorKind, FixedTag, Header, Length, Result, Tag,
+    ErrorKind, FixedTag, Header, Length, Result, Tag, Writer,
 };
 
 /// Byte used to encode `true` in ASN.1 DER. From X.690 Section 11.1:
@@ -34,7 +34,7 @@ impl EncodeValue for bool {
     }
 
     fn encode_value(&self, encoder: &mut Encoder<'_>) -> Result<()> {
-        encoder.byte(if *self { TRUE_OCTET } else { FALSE_OCTET })
+        encoder.write_byte(if *self { TRUE_OCTET } else { FALSE_OCTET })
     }
 }
 

diff --git a/der/src/asn1/generalized_time.rs b/der/src/asn1/generalized_time.rs
@@ -5,7 +5,7 @@ use crate::{
     datetime::{self, DateTime},
     ord::OrdIsValueOrd,
     ByteSlice, DecodeValue, Decoder, EncodeValue, Encoder, Error, ErrorKind, FixedTag, Header,
-    Length, Result, Tag,
+    Length, Result, Tag, Writer,
 };
 use core::time::Duration;
 
@@ -115,7 +115,7 @@ impl EncodeValue for GeneralizedTime {
         datetime::encode_decimal(encoder, Self::TAG, self.0.hour())?;
         datetime::encode_decimal(encoder, Self::TAG, self.0.minutes())?;
         datetime::encode_decimal(encoder, Self::TAG, self.0.seconds())?;
-        encoder.byte(b'Z')
+        encoder.write_byte(b'Z')
     }
 }
 

diff --git a/der/src/asn1/integer/bigint.rs b/der/src/asn1/integer/bigint.rs
@@ -3,7 +3,7 @@
 use super::uint;
 use crate::{
     asn1::Any, ByteSlice, DecodeValue, Decoder, EncodeValue, Encoder, Error, ErrorKind, FixedTag,
-    Header, Length, Result, Tag,
+    Header, Length, Result, Tag, Writer,
 };
 
 /// "Big" unsigned ASN.1 `INTEGER` type.
@@ -67,10 +67,10 @@ impl<'a> EncodeValue for UIntBytes<'a> {
     fn encode_value(&self, encoder: &mut Encoder<'_>) -> Result<()> {
         // Add leading `0x00` byte if required
         if self.value_len()? > self.len() {
-            encoder.byte(0)?;
+            encoder.write_byte(0)?;
         }
 
-        encoder.bytes(self.as_bytes())
+        encoder.write(self.as_bytes())
     }
 }
 

diff --git a/der/src/asn1/integer/int.rs b/der/src/asn1/integer/int.rs
@@ -1,7 +1,7 @@
 //! Support for encoding negative integers
 
 use super::is_highest_bit_set;
-use crate::{Encoder, ErrorKind, Length, Result};
+use crate::{Encoder, ErrorKind, Length, Result, Writer};
 
 /// Decode an unsigned integer of the specified size.
 ///
@@ -28,7 +28,7 @@ pub(super) fn decode_to_array<const N: usize>(bytes: &[u8]) -> Result<[u8; N]> {
 
 /// Encode the given big endian bytes representing an integer as ASN.1 DER.
 pub(super) fn encode_bytes(encoder: &mut Encoder<'_>, bytes: &[u8]) -> Result<()> {
-    encoder.bytes(strip_leading_ones(bytes))
+    encoder.write(strip_leading_ones(bytes))
 }
 
 /// Get the encoded length for the given unsigned integer serialized as bytes.

diff --git a/der/src/asn1/integer/uint.rs b/der/src/asn1/integer/uint.rs
@@ -1,6 +1,6 @@
 //! Unsigned integer decoders/encoders.
 
-use crate::{Encoder, Length, Result, Tag};
+use crate::{Encoder, Length, Result, Tag, Writer};
 
 /// Decode an unsigned integer into a big endian byte slice with all leading
 /// zeroes removed.
@@ -44,10 +44,10 @@ pub(crate) fn encode_bytes(encoder: &mut Encoder<'_>, bytes: &[u8]) -> Result<()
     let bytes = strip_leading_zeroes(bytes);
 
     if needs_leading_zero(bytes) {
-        encoder.byte(0)?;
+        encoder.write_byte(0)?;
     }
 
-    encoder.bytes(bytes)
+    encoder.write(bytes)
 }
 
 /// Get the encoded length for the given unsigned integer serialized as bytes.

diff --git a/der/src/asn1/oid.rs b/der/src/asn1/oid.rs
@@ -2,7 +2,7 @@
 
 use crate::{
     asn1::Any, ord::OrdIsValueOrd, ByteSlice, DecodeValue, Decoder, EncodeValue, Encoder, Error,
-    FixedTag, Header, Length, Result, Tag, Tagged,
+    FixedTag, Header, Length, Result, Tag, Tagged, Writer,
 };
 use const_oid::ObjectIdentifier;
 
@@ -19,7 +19,7 @@ impl EncodeValue for ObjectIdentifier {
     }
 
     fn encode_value(&self, encoder: &mut Encoder<'_>) -> Result<()> {
-        encoder.bytes(self.as_bytes())
+        encoder.write(self.as_bytes())
     }
 }
 

diff --git a/der/src/asn1/real.rs b/der/src/asn1/real.rs
@@ -9,7 +9,7 @@
 
 use crate::{
     str_slice::StrSlice, ByteSlice, DecodeValue, Decoder, EncodeValue, Encoder, FixedTag, Header,
-    Length, Result, Tag,
+    Length, Result, Tag, Writer,
 };
 
 use super::integer::uint::strip_leading_zeroes;
@@ -136,18 +136,18 @@ impl EncodeValue for f64 {
                 return Ok(());
             } else if self.is_nan() {
                 // Not a number
-                encoder.bytes(&[0b0100_0010])?;
+                encoder.write_byte(0b0100_0010)?;
             } else if self.is_infinite() {
                 if self.is_sign_negative() {
                     // Negative infinity
-                    encoder.bytes(&[0b0100_0001])?;
+                    encoder.write_byte(0b0100_0001)?;
                 } else {
                     // Plus infinity
-                    encoder.bytes(&[0b0100_0000])?;
+                    encoder.write_byte(0b0100_0000)?;
                 }
             } else {
                 // Minus zero
-                encoder.bytes(&[0b0100_0011])?;
+                encoder.write_byte(0b0100_0011)?;
             }
         } else {
             // Always use binary encoding, set bit 8 to 1
@@ -178,16 +178,16 @@ impl EncodeValue for f64 {
                 }
             }
 
-            encoder.bytes(&[first_byte])?;
+            encoder.write_byte(first_byte)?;
 
             // Encode both bytes or just the last one, handled by encode_bytes directly
             // Rust already encodes the data as two's complement, so no further processing is needed
-            encoder.bytes(ebytes)?;
+            encoder.write(ebytes)?;
 
             // Now, encode the mantissa as unsigned binary number
             let mantissa_bytes = mantissa.to_be_bytes();
             let mbytes = strip_leading_zeroes(&mantissa_bytes);
-            encoder.bytes(mbytes)?;
+            encoder.write(mbytes)?;
         }
         Ok(())
     }

diff --git a/der/src/asn1/utc_time.rs b/der/src/asn1/utc_time.rs
@@ -5,7 +5,7 @@ use crate::{
     datetime::{self, DateTime},
     ord::OrdIsValueOrd,
     ByteSlice, DecodeValue, Decoder, EncodeValue, Encoder, Error, ErrorKind, FixedTag, Header,
-    Length, Result, Tag,
+    Length, Result, Tag, Writer,
 };
 use core::time::Duration;
 
@@ -128,7 +128,7 @@ impl EncodeValue for UtcTime {
         datetime::encode_decimal(encoder, Self::TAG, self.0.hour())?;
         datetime::encode_decimal(encoder, Self::TAG, self.0.minutes())?;
         datetime::encode_decimal(encoder, Self::TAG, self.0.seconds())?;
-        encoder.byte(b'Z')
+        encoder.write_byte(b'Z')
     }
 }
 

diff --git a/der/src/byte_slice.rs b/der/src/byte_slice.rs
@@ -3,7 +3,7 @@
 
 use crate::{
     str_slice::StrSlice, DecodeValue, Decoder, DerOrd, EncodeValue, Encoder, Error, Header, Length,
-    Result,
+    Result, Writer,
 };
 use core::cmp::Ordering;
 
@@ -67,7 +67,7 @@ impl EncodeValue for ByteSlice<'_> {
     }
 
     fn encode_value(&self, encoder: &mut Encoder<'_>) -> Result<()> {
-        encoder.bytes(self.as_ref())
+        encoder.write(self.as_ref())
     }
 }
 

diff --git a/der/src/datetime.rs b/der/src/datetime.rs
@@ -5,7 +5,7 @@
 // Copyright (c) 2016 The humantime Developers
 // Released under the MIT OR Apache 2.0 licenses
 
-use crate::{Encoder, Error, ErrorKind, Result, Tag};
+use crate::{Encoder, Error, ErrorKind, Result, Tag, Writer};
 use core::{fmt, str::FromStr, time::Duration};
 
 #[cfg(feature = "std")]
@@ -372,17 +372,15 @@ pub(crate) fn decode_decimal(tag: Tag, hi: u8, lo: u8) -> Result<u8> {
 }
 
 /// Encode 2-digit decimal value
-// TODO(tarcieri): checked arithmetic
-#[allow(clippy::integer_arithmetic)]
 pub(crate) fn encode_decimal(encoder: &mut Encoder<'_>, tag: Tag, value: u8) -> Result<()> {
     let hi_val = value / 10;
 
     if hi_val >= 10 {
         return Err(tag.value_error());
     }
 
-    encoder.byte(hi_val + b'0')?;
-    encoder.byte((value % 10) + b'0')
+    encoder.write_byte(b'0'.checked_add(hi_val).ok_or(ErrorKind::Overflow)?)?;
+    encoder.write_byte(b'0'.checked_add(value % 10).ok_or(ErrorKind::Overflow)?)
 }
 
 #[cfg(test)]

diff --git a/der/src/document.rs b/der/src/document.rs
@@ -1,6 +1,6 @@
 //! ASN.1 DER-encoded documents stored on the heap.
 
-use crate::{Decode, Decoder, Encode, Encoder, Error, FixedTag, Length, Result, Tag};
+use crate::{Decode, Decoder, Encode, Encoder, Error, FixedTag, Length, Result, Tag, Writer};
 use alloc::vec::Vec;
 use core::fmt::{self, Debug};
 
@@ -166,7 +166,7 @@ impl Encode for Document {
     }
 
     fn encode(&self, encoder: &mut Encoder<'_>) -> Result<()> {
-        encoder.bytes(self.as_bytes())
+        encoder.write(self.as_bytes())
     }
 }
 

diff --git a/der/src/encoder.rs b/der/src/encoder.rs
@@ -2,7 +2,7 @@
 
 use crate::{
     asn1::*, Encode, EncodeRef, EncodeValue, Error, ErrorKind, Header, Length, Result, Tag,
-    TagMode, TagNumber, Tagged,
+    TagMode, TagNumber, Tagged, Writer,
 };
 
 /// DER encoder.
@@ -213,23 +213,6 @@ impl<'a> Encoder<'a> {
         Ok(slice)
     }
 
-    /// Encode a single byte into the backing buffer.
-    pub(crate) fn byte(&mut self, byte: u8) -> Result<()> {
-        match self.reserve(1u8)?.first_mut() {
-            Some(b) => {
-                *b = byte;
-                Ok(())
-            }
-            None => self.error(ErrorKind::Overlength),
-        }
-    }
-
-    /// Encode the provided byte slice into the backing buffer.
-    pub(crate) fn bytes(&mut self, slice: &[u8]) -> Result<()> {
-        self.reserve(slice.len())?.copy_from_slice(slice);
-        Ok(())
-    }
-
     /// Get the size of the buffer in bytes.
     fn buffer_len(&self) -> Result<Length> {
         self.bytes
@@ -250,6 +233,13 @@ impl<'a> Encoder<'a> {
     }
 }
 
+impl<'a> Writer for Encoder<'a> {
+    fn write(&mut self, slice: &[u8]) -> Result<()> {
+        self.reserve(slice.len())?.copy_from_slice(slice);
+        Ok(())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use hex_literal::hex;

diff --git a/der/src/length.rs b/der/src/length.rs
@@ -1,6 +1,6 @@
 //! Length calculations for encoded ASN.1 DER values
 
-use crate::{Decode, Decoder, DerOrd, Encode, Encoder, Error, ErrorKind, Result};
+use crate::{Decode, Decoder, DerOrd, Encode, Encoder, Error, ErrorKind, Result, Writer};
 use core::{
     cmp::Ordering,
     fmt,
@@ -241,17 +241,17 @@ impl Encode for Length {
     #[allow(clippy::cast_possible_truncation)]
     fn encode(&self, encoder: &mut Encoder<'_>) -> Result<()> {
         if let Some(tag_byte) = self.initial_octet() {
-            encoder.byte(tag_byte)?;
+            encoder.write_byte(tag_byte)?;
 
             // Strip leading zeroes
             match self.0.to_be_bytes() {
-                [0, 0, 0, byte] => encoder.byte(byte),
-                [0, 0, bytes @ ..] => encoder.bytes(&bytes),
-                [0, bytes @ ..] => encoder.bytes(&bytes),
-                bytes => encoder.bytes(&bytes),
+                [0, 0, 0, byte] => encoder.write_byte(byte),
+                [0, 0, bytes @ ..] => encoder.write(&bytes),
+                [0, bytes @ ..] => encoder.write(&bytes),
+                bytes => encoder.write(&bytes),
             }
         } else {
-            encoder.byte(self.0 as u8)
+            encoder.write_byte(self.0 as u8)
         }
     }
 }

diff --git a/der/src/lib.rs b/der/src/lib.rs
@@ -359,6 +359,7 @@ mod length;
 mod ord;
 mod str_slice;
 mod tag;
+mod writer;
 
 #[cfg(feature = "alloc")]
 mod document;
@@ -376,6 +377,7 @@ pub use crate::{
     length::Length,
     ord::{DerOrd, ValueOrd},
     tag::{Class, FixedTag, Tag, TagMode, TagNumber, Tagged},
+    writer::Writer,
 };
 
 #[cfg(feature = "alloc")]