ring/arithmetic/bigint/
boxed_limbs.rs

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1// Copyright 2015-2023 Brian Smith.
2//
3// Permission to use, copy, modify, and/or distribute this software for any
4// purpose with or without fee is hereby granted, provided that the above
5// copyright notice and this permission notice appear in all copies.
6//
7// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
8// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
10// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14
15use super::Modulus;
16use crate::{
17    error,
18    limb::{self, Limb, LimbMask, LIMB_BYTES},
19};
20use alloc::{boxed::Box, vec};
21use core::{
22    marker::PhantomData,
23    ops::{Deref, DerefMut},
24};
25
26/// All `BoxedLimbs<M>` are stored in the same number of limbs.
27pub(super) struct BoxedLimbs<M> {
28    limbs: Box<[Limb]>,
29
30    /// The modulus *m* that determines the size of `limbx`.
31    m: PhantomData<M>,
32}
33
34impl<M> Deref for BoxedLimbs<M> {
35    type Target = [Limb];
36    #[inline]
37    fn deref(&self) -> &Self::Target {
38        &self.limbs
39    }
40}
41
42impl<M> DerefMut for BoxedLimbs<M> {
43    #[inline]
44    fn deref_mut(&mut self) -> &mut Self::Target {
45        &mut self.limbs
46    }
47}
48
49// TODO: `derive(Clone)` after https://github.com/rust-lang/rust/issues/26925
50// is resolved or restrict `M: Clone`.
51impl<M> Clone for BoxedLimbs<M> {
52    fn clone(&self) -> Self {
53        Self {
54            limbs: self.limbs.clone(),
55            m: self.m,
56        }
57    }
58}
59
60impl<M> BoxedLimbs<M> {
61    // The caller must ensure that `limbs.len()` is the same width as the
62    // modulus.
63    pub(super) fn new_unchecked(limbs: Box<[Limb]>) -> Self {
64        Self {
65            limbs,
66            m: PhantomData,
67        }
68    }
69
70    pub(super) fn positive_minimal_width_from_be_bytes(
71        input: untrusted::Input,
72    ) -> Result<Self, error::KeyRejected> {
73        // Reject leading zeros. Also reject the value zero ([0]) because zero
74        // isn't positive.
75        if untrusted::Reader::new(input).peek(0) {
76            return Err(error::KeyRejected::invalid_encoding());
77        }
78        let num_limbs = (input.len() + LIMB_BYTES - 1) / LIMB_BYTES;
79        let mut r = Self::zero(num_limbs);
80        limb::parse_big_endian_and_pad_consttime(input, &mut r)
81            .map_err(|error::Unspecified| error::KeyRejected::unexpected_error())?;
82        Ok(r)
83    }
84
85    pub(super) fn from_be_bytes_padded_less_than(
86        input: untrusted::Input,
87        m: &Modulus<M>,
88    ) -> Result<Self, error::Unspecified> {
89        let mut r = Self::zero(m.limbs().len());
90        limb::parse_big_endian_and_pad_consttime(input, &mut r)?;
91        if limb::limbs_less_than_limbs_consttime(&r, m.limbs()) != LimbMask::True {
92            return Err(error::Unspecified);
93        }
94        Ok(r)
95    }
96
97    #[inline]
98    pub(super) fn is_zero(&self) -> bool {
99        limb::limbs_are_zero_constant_time(&self.limbs) == LimbMask::True
100    }
101
102    pub(super) fn zero(len: usize) -> Self {
103        Self {
104            limbs: vec![0; len].into_boxed_slice(),
105            m: PhantomData,
106        }
107    }
108
109    pub(super) fn into_limbs(self) -> Box<[Limb]> {
110        self.limbs
111    }
112}
ring/arithmetic/bigint/boxed_limbs.rs

ring/arithmetic/bigint/
boxed_limbs.rs
