ring/ec/suite_b/ecdsa/verification.rs
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335
// Copyright 2015-2016 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//! ECDSA Signatures using the P-256 and P-384 curves.
use super::digest_scalar::digest_scalar;
use crate::{
arithmetic::montgomery::*,
digest,
ec::suite_b::{ops::*, public_key::*, verify_jacobian_point_is_on_the_curve},
error,
io::der,
limb, sealed, signature,
};
/// An ECDSA verification algorithm.
pub struct EcdsaVerificationAlgorithm {
ops: &'static PublicScalarOps,
digest_alg: &'static digest::Algorithm,
split_rs:
for<'a> fn(
ops: &'static ScalarOps,
input: &mut untrusted::Reader<'a>,
)
-> Result<(untrusted::Input<'a>, untrusted::Input<'a>), error::Unspecified>,
id: AlgorithmID,
}
#[derive(Debug)]
enum AlgorithmID {
ECDSA_P256_SHA256_ASN1,
ECDSA_P256_SHA256_FIXED,
ECDSA_P256_SHA384_ASN1,
ECDSA_P384_SHA256_ASN1,
ECDSA_P384_SHA384_ASN1,
ECDSA_P384_SHA384_FIXED,
}
derive_debug_via_id!(EcdsaVerificationAlgorithm);
impl signature::VerificationAlgorithm for EcdsaVerificationAlgorithm {
fn verify(
&self,
public_key: untrusted::Input,
msg: untrusted::Input,
signature: untrusted::Input,
) -> Result<(), error::Unspecified> {
let e = {
// NSA Guide Step 2: "Use the selected hash function to compute H =
// Hash(M)."
let h = digest::digest(self.digest_alg, msg.as_slice_less_safe());
// NSA Guide Step 3: "Convert the bit string H to an integer e as
// described in Appendix B.2."
digest_scalar(self.ops.scalar_ops, h)
};
self.verify_digest(public_key, e, signature)
}
}
impl EcdsaVerificationAlgorithm {
/// This is intentionally not public.
fn verify_digest(
&self,
public_key: untrusted::Input,
e: Scalar,
signature: untrusted::Input,
) -> Result<(), error::Unspecified> {
// NSA Suite B Implementer's Guide to ECDSA Section 3.4.2.
let public_key_ops = self.ops.public_key_ops;
let scalar_ops = self.ops.scalar_ops;
// NSA Guide Prerequisites:
//
// Prior to accepting a verified digital signature as valid the
// verifier shall have:
//
// 1. assurance of the signatory’s claimed identity,
// 2. an authentic copy of the domain parameters, (q, FR, a, b, SEED,
// G, n, h),
// 3. assurance of the validity of the public key, and
// 4. assurance that the claimed signatory actually possessed the
// private key that was used to generate the digital signature at
// the time that the signature was generated.
//
// Prerequisites #1 and #4 are outside the scope of what this function
// can do. Prerequisite #2 is handled implicitly as the domain
// parameters are hard-coded into the source. Prerequisite #3 is
// handled by `parse_uncompressed_point`.
let peer_pub_key = parse_uncompressed_point(public_key_ops, public_key)?;
let (r, s) = signature.read_all(error::Unspecified, |input| {
(self.split_rs)(scalar_ops, input)
})?;
// NSA Guide Step 1: "If r and s are not both integers in the interval
// [1, n − 1], output INVALID."
let r = scalar_parse_big_endian_variable(public_key_ops.common, limb::AllowZero::No, r)?;
let s = scalar_parse_big_endian_variable(public_key_ops.common, limb::AllowZero::No, s)?;
// NSA Guide Step 4: "Compute w = s**−1 mod n, using the routine in
// Appendix B.1."
let w = scalar_ops.scalar_inv_to_mont(&s);
// NSA Guide Step 5: "Compute u1 = (e * w) mod n, and compute
// u2 = (r * w) mod n."
let u1 = scalar_ops.scalar_product(&e, &w);
let u2 = scalar_ops.scalar_product(&r, &w);
// NSA Guide Step 6: "Compute the elliptic curve point
// R = (xR, yR) = u1*G + u2*Q, using EC scalar multiplication and EC
// addition. If R is equal to the point at infinity, output INVALID."
let product = (self.ops.twin_mul)(&u1, &u2, &peer_pub_key);
// Verify that the point we computed is on the curve; see
// `verify_affine_point_is_on_the_curve_scaled` for details on why. It
// would be more secure to do the check on the affine coordinates if we
// were going to convert to affine form (again, see
// `verify_affine_point_is_on_the_curve_scaled` for details on why).
// But, we're going to avoid converting to affine for performance
// reasons, so we do the verification using the Jacobian coordinates.
let z2 = verify_jacobian_point_is_on_the_curve(public_key_ops.common, &product)?;
// NSA Guide Step 7: "Compute v = xR mod n."
// NSA Guide Step 8: "Compare v and r0. If v = r0, output VALID;
// otherwise, output INVALID."
//
// Instead, we use Greg Maxwell's trick to avoid the inversion mod `q`
// that would be necessary to compute the affine X coordinate.
let x = public_key_ops.common.point_x(&product);
fn sig_r_equals_x(
ops: &PublicScalarOps,
r: &Elem<Unencoded>,
x: &Elem<R>,
z2: &Elem<R>,
) -> bool {
let cops = ops.public_key_ops.common;
let r_jacobian = cops.elem_product(z2, r);
let x = cops.elem_unencoded(x);
ops.elem_equals_vartime(&r_jacobian, &x)
}
let mut r = self.ops.scalar_as_elem(&r);
if sig_r_equals_x(self.ops, &r, &x, &z2) {
return Ok(());
}
if self.ops.elem_less_than(&r, &self.ops.q_minus_n) {
self.ops
.scalar_ops
.common
.elem_add(&mut r, &public_key_ops.common.n);
if sig_r_equals_x(self.ops, &r, &x, &z2) {
return Ok(());
}
}
Err(error::Unspecified)
}
}
impl sealed::Sealed for EcdsaVerificationAlgorithm {}
fn split_rs_fixed<'a>(
ops: &'static ScalarOps,
input: &mut untrusted::Reader<'a>,
) -> Result<(untrusted::Input<'a>, untrusted::Input<'a>), error::Unspecified> {
let scalar_len = ops.scalar_bytes_len();
let r = input.read_bytes(scalar_len)?;
let s = input.read_bytes(scalar_len)?;
Ok((r, s))
}
fn split_rs_asn1<'a>(
_ops: &'static ScalarOps,
input: &mut untrusted::Reader<'a>,
) -> Result<(untrusted::Input<'a>, untrusted::Input<'a>), error::Unspecified> {
der::nested(input, der::Tag::Sequence, error::Unspecified, |input| {
let r = der::positive_integer(input)?.big_endian_without_leading_zero_as_input();
let s = der::positive_integer(input)?.big_endian_without_leading_zero_as_input();
Ok((r, s))
})
}
/// Verification of fixed-length (PKCS#11 style) ECDSA signatures using the
/// P-256 curve and SHA-256.
///
/// See "`ECDSA_*_FIXED` Details" in `ring::signature`'s module-level
/// documentation for more details.
pub static ECDSA_P256_SHA256_FIXED: EcdsaVerificationAlgorithm = EcdsaVerificationAlgorithm {
ops: &p256::PUBLIC_SCALAR_OPS,
digest_alg: &digest::SHA256,
split_rs: split_rs_fixed,
id: AlgorithmID::ECDSA_P256_SHA256_FIXED,
};
/// Verification of fixed-length (PKCS#11 style) ECDSA signatures using the
/// P-384 curve and SHA-384.
///
/// See "`ECDSA_*_FIXED` Details" in `ring::signature`'s module-level
/// documentation for more details.
pub static ECDSA_P384_SHA384_FIXED: EcdsaVerificationAlgorithm = EcdsaVerificationAlgorithm {
ops: &p384::PUBLIC_SCALAR_OPS,
digest_alg: &digest::SHA384,
split_rs: split_rs_fixed,
id: AlgorithmID::ECDSA_P384_SHA384_FIXED,
};
/// Verification of ASN.1 DER-encoded ECDSA signatures using the P-256 curve
/// and SHA-256.
///
/// See "`ECDSA_*_ASN1` Details" in `ring::signature`'s module-level
/// documentation for more details.
pub static ECDSA_P256_SHA256_ASN1: EcdsaVerificationAlgorithm = EcdsaVerificationAlgorithm {
ops: &p256::PUBLIC_SCALAR_OPS,
digest_alg: &digest::SHA256,
split_rs: split_rs_asn1,
id: AlgorithmID::ECDSA_P256_SHA256_ASN1,
};
/// *Not recommended*. Verification of ASN.1 DER-encoded ECDSA signatures using
/// the P-256 curve and SHA-384.
///
/// In most situations, P-256 should be used only with SHA-256 and P-384
/// should be used only with SHA-384. However, in some cases, particularly TLS
/// on the web, it is necessary to support P-256 with SHA-384 for compatibility
/// with widely-deployed implementations that do not follow these guidelines.
///
/// See "`ECDSA_*_ASN1` Details" in `ring::signature`'s module-level
/// documentation for more details.
pub static ECDSA_P256_SHA384_ASN1: EcdsaVerificationAlgorithm = EcdsaVerificationAlgorithm {
ops: &p256::PUBLIC_SCALAR_OPS,
digest_alg: &digest::SHA384,
split_rs: split_rs_asn1,
id: AlgorithmID::ECDSA_P256_SHA384_ASN1,
};
/// *Not recommended*. Verification of ASN.1 DER-encoded ECDSA signatures using
/// the P-384 curve and SHA-256.
///
/// In most situations, P-256 should be used only with SHA-256 and P-384
/// should be used only with SHA-384. However, in some cases, particularly TLS
/// on the web, it is necessary to support P-256 with SHA-384 for compatibility
/// with widely-deployed implementations that do not follow these guidelines.
///
/// See "`ECDSA_*_ASN1` Details" in `ring::signature`'s module-level
/// documentation for more details.
pub static ECDSA_P384_SHA256_ASN1: EcdsaVerificationAlgorithm = EcdsaVerificationAlgorithm {
ops: &p384::PUBLIC_SCALAR_OPS,
digest_alg: &digest::SHA256,
split_rs: split_rs_asn1,
id: AlgorithmID::ECDSA_P384_SHA256_ASN1,
};
/// Verification of ASN.1 DER-encoded ECDSA signatures using the P-384 curve
/// and SHA-384.
///
/// See "`ECDSA_*_ASN1` Details" in `ring::signature`'s module-level
/// documentation for more details.
pub static ECDSA_P384_SHA384_ASN1: EcdsaVerificationAlgorithm = EcdsaVerificationAlgorithm {
ops: &p384::PUBLIC_SCALAR_OPS,
digest_alg: &digest::SHA384,
split_rs: split_rs_asn1,
id: AlgorithmID::ECDSA_P384_SHA384_ASN1,
};
#[cfg(test)]
mod tests {
extern crate alloc;
use super::*;
use crate::test;
use alloc::{vec, vec::Vec};
#[test]
fn test_digest_based_test_vectors() {
test::run(
test_file!("../../../../crypto/fipsmodule/ecdsa/ecdsa_verify_tests.txt"),
|section, test_case| {
assert_eq!(section, "");
let curve_name = test_case.consume_string("Curve");
let public_key = {
let mut public_key = vec![0x04];
public_key.extend(&test_case.consume_bytes("X"));
public_key.extend(&test_case.consume_bytes("Y"));
public_key
};
let digest = test_case.consume_bytes("Digest");
let sig = {
let mut sig = Vec::new();
sig.extend(&test_case.consume_bytes("R"));
sig.extend(&test_case.consume_bytes("S"));
sig
};
let invalid = test_case.consume_optional_string("Invalid");
let alg = match curve_name.as_str() {
"P-256" => &ECDSA_P256_SHA256_FIXED,
"P-384" => &ECDSA_P384_SHA384_FIXED,
_ => {
panic!("Unsupported curve: {}", curve_name);
}
};
let digest = super::super::digest_scalar::digest_bytes_scalar(
alg.ops.scalar_ops,
&digest[..],
);
let actual_result = alg.verify_digest(
untrusted::Input::from(&public_key[..]),
digest,
untrusted::Input::from(&sig[..]),
);
assert_eq!(actual_result.is_ok(), invalid.is_none());
Ok(())
},
);
}
}