109 lines
4.3 KiB
Rust
109 lines
4.3 KiB
Rust
// Copyright 2016 Brian Smith.
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice appear in all copies.
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//
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// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
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// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
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// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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//! Functionality shared by operations on public keys (ECDSA verification and
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//! ECDH agreement).
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use super::{ops::*, verify_affine_point_is_on_the_curve};
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use crate::{arithmetic::montgomery::*, error};
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use untrusted;
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/// Parses a public key encoded in uncompressed form. The key is validated
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/// using the ECC Partial Public-Key Validation Routine from
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/// [NIST SP 800-56A, revision 2] Section 5.6.2.3.3, the NSA's
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/// "Suite B Implementer's Guide to NIST SP 800-56A," Appendix B.3, and the
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/// NSA's "Suite B Implementer's Guide to FIPS 186-3 (ECDSA)," Appendix A.3.
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///
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/// [NIST SP 800-56A, revision 2]:
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/// http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-56Ar2.pdf
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pub fn parse_uncompressed_point(
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ops: &PublicKeyOps, input: untrusted::Input,
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) -> Result<(Elem<R>, Elem<R>), error::Unspecified> {
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// NIST SP 800-56A Step 1: "Verify that Q is not the point at infinity.
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// This can be done by inspection if the point is entered in the standard
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// affine representation." (We do it by inspection since we only accept
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// the affine representation.)
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let (x, y) = input.read_all(error::Unspecified, |input| {
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// The encoding must be 4, which is the encoding for "uncompressed".
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let encoding = input.read_byte()?;
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if encoding != 4 {
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return Err(error::Unspecified);
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}
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// NIST SP 800-56A Step 2: "Verify that xQ and yQ are integers in the
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// interval [0, p-1] in the case that q is an odd prime p[.]"
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let x = ops.elem_parse(input)?;
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let y = ops.elem_parse(input)?;
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Ok((x, y))
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})?;
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// NIST SP 800-56A Step 3: "If q is an odd prime p, verify that
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// yQ**2 = xQ**3 + axQ + b in GF(p), where the arithmetic is performed
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// modulo p."
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verify_affine_point_is_on_the_curve(ops.common, (&x, &y))?;
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// NIST SP 800-56A Note: "Since its order is not verified, there is no
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// check that the public key is in the correct EC subgroup."
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//
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// NSA Suite B Implementer's Guide Note: "ECC Full Public-Key Validation
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// includes an additional check to ensure that the point has the correct
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// order. This check is not necessary for curves having prime order (and
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// cofactor h = 1), such as P-256 and P-384."
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Ok((x, y))
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}
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#[cfg(test)]
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mod tests {
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use super::{super::ops, *};
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use crate::test;
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use untrusted;
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#[test]
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fn parse_uncompressed_point_test() {
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test::from_file(
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"src/ec/suite_b/suite_b_public_key_tests.txt",
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|section, test_case| {
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assert_eq!(section, "");
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let curve_name = test_case.consume_string("Curve");
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let public_key = test_case.consume_bytes("Q");
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let public_key = untrusted::Input::from(&public_key);
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let valid = test_case.consume_string("Result") == "P";
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let curve_ops = public_key_ops_from_curve_name(&curve_name);
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let result = parse_uncompressed_point(curve_ops, public_key);
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assert_eq!(valid, result.is_ok());
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// TODO: Verify that we when we re-serialize the parsed (x, y), the
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// output is equal to the input.
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Ok(())
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},
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);
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}
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fn public_key_ops_from_curve_name(curve_name: &str) -> &'static PublicKeyOps {
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if curve_name == "P-256" {
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&ops::p256::PUBLIC_KEY_OPS
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} else if curve_name == "P-384" {
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&ops::p384::PUBLIC_KEY_OPS
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} else {
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panic!("Unsupported curve: {}", curve_name);
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}
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}
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}
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