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std.crypto.tls.Client: avoid hard-coded bytes in key_share

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This commit is contained in:
Andrew Kelley 2022-12-18 18:27:53 -07:00
parent 7a23778384
commit f460c21705
1 changed files with 18 additions and 16 deletions
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34
lib/std/crypto/tls/Client.zig
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@ -31,16 +31,22 @@ eof: bool,
pub fn init(stream: net.Stream, host: []const u8) !Client {
const host_len = @intCast(u16, host.len);
const kp = crypto.dh.X25519.KeyPair.create(null) catch |err| switch (err) {
// Only possible to happen if the private key is all zeroes.
error.IdentityElement => return error.InsufficientEntropy,
};
// This is used both for the random bytes and for the legacy session id.
var random_buffer: [64]u8 = undefined;
var random_buffer: [128]u8 = undefined;
crypto.random.bytes(&random_buffer);
const hello_rand = random_buffer[0..32].*;
const legacy_session_id = random_buffer[32..64].*;
const x25519_kp_seed = random_buffer[64..96].*;
const secp256r1_kp_seed = random_buffer[96..128].*;
const x25519_kp = crypto.dh.X25519.KeyPair.create(x25519_kp_seed) catch |err| switch (err) {
// Only possible to happen if the private key is all zeroes.
error.IdentityElement => return error.InsufficientEntropy,
};
const secp256r1_kp = crypto.sign.ecdsa.EcdsaP256Sha256.KeyPair.create(secp256r1_kp_seed) catch |err| switch (err) {
// Only possible to happen if the private key is all zeroes.
error.IdentityElement => return error.InsufficientEntropy,
};
_ = secp256r1_kp;
const extensions_payload =
tls.extension(.supported_versions, [_]u8{
@ -66,14 +72,10 @@ pub fn init(stream: net.Stream, host: []const u8) !Client {
})) ++ tls.extension(.supported_groups, enum_array(tls.NamedGroup, &.{
//.secp256r1,
.x25519,
})) ++ [_]u8{
// Extension: key_share
0, 51, // ExtensionType.key_share
0, 38, // byte length of this extension payload
0, 36, // byte length of client_shares
0x00, 0x1D, // NamedGroup.x25519
0, 32, // byte length of key_exchange
} ++ kp.public_key ++
})) ++ tls.extension(
.key_share,
array(1, int2(@enumToInt(tls.NamedGroup.x25519)) ++ array(1, x25519_kp.public_key)),
) ++
int2(@enumToInt(tls.ExtensionType.server_name)) ++
int2(host_len + 5) ++ // byte length of this extension payload
int2(host_len + 3) ++ // server_name_list byte count
@ -230,7 +232,7 @@ pub fn init(stream: net.Stream, host: []const u8) !Client {
}
const shared_key = crypto.dh.X25519.scalarmult(
kp.secret_key,
x25519_kp.secret_key,
x25519_server_pub_key.*,
) catch return error.TlsDecryptFailure;