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Merge pull request #6336 from Rocknest/pbkdf2

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Some changes to #6326 (pbkdf2)
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Andrew Kelley 2020-09-17 17:31:58 -04:00 committed by GitHub
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24
lib/std/crypto.zig
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@ -35,6 +35,15 @@ pub const onetimeauth = struct {
pub const Poly1305 = @import("crypto/poly1305.zig").Poly1305;
};
/// A Key Derivation Function (KDF) is intended to turn a weak, human generated password into a
/// strong key, suitable for cryptographic uses. It does this by salting and stretching the
/// password. Salting injects non-secret random data, so that identical passwords will be converted
/// into unique keys. Stretching applies a deliberately slow hashing function to frustrate
/// brute-force guessing.
pub const kdf = struct {
pub const pbkdf2 = @import("crypto/pbkdf2.zig").pbkdf2;
};
/// Core functions, that should rarely be used directly by applications.
pub const core = struct {
pub const aes = @import("crypto/aes.zig");
@ -70,6 +79,20 @@ const std = @import("std.zig");
pub const randomBytes = std.os.getrandom;
test "crypto" {
inline for (std.meta.declarations(@This())) |decl| {
switch (decl.data) {
.Type => |t| {
std.meta.refAllDecls(t);
},
.Var => |v| {
_ = v;
},
.Fn => |f| {
_ = f;
},
}
}
_ = @import("crypto/aes.zig");
_ = @import("crypto/blake2.zig");
_ = @import("crypto/blake3.zig");
@ -77,6 +100,7 @@ test "crypto" {
_ = @import("crypto/gimli.zig");
_ = @import("crypto/hmac.zig");
_ = @import("crypto/md5.zig");
_ = @import("crypto/pbkdf2.zig");
_ = @import("crypto/poly1305.zig");
_ = @import("crypto/sha1.zig");
_ = @import("crypto/sha2.zig");

280
lib/std/crypto/pbkdf2.zig Normal file
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@ -0,0 +1,280 @@
// SPDX-License-Identifier: MIT
// Copyright (c) 2015-2020 Zig Contributors
// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
// The MIT license requires this copyright notice to be included in all copies
// and substantial portions of the software.
const std = @import("std");
const mem = std.mem;
const maxInt = std.math.maxInt;
// RFC 2898 Section 5.2
//
// FromSpec:
//
// PBKDF2 applies a pseudorandom function (see Appendix B.1 for an
// example) to derive keys. The length of the derived key is essentially
// unbounded. (However, the maximum effective search space for the
// derived key may be limited by the structure of the underlying
// pseudorandom function. See Appendix B.1 for further discussion.)
// PBKDF2 is recommended for new applications.
//
// PBKDF2 (P, S, c, dkLen)
//
// Options: PRF underlying pseudorandom function (hLen
// denotes the length in octets of the
// pseudorandom function output)
//
// Input: P password, an octet string
// S salt, an octet string
// c iteration count, a positive integer
// dkLen intended length in octets of the derived
// key, a positive integer, at most
// (2^32 - 1) * hLen
//
// Output: DK derived key, a dkLen-octet string
// Based on Apple's CommonKeyDerivation, based originally on code by Damien Bergamini.
pub const Pbkdf2Error = error{
/// At least one round is required
TooFewRounds,
/// Maximum length of the derived key is `maxInt(u32) * Prf.mac_length`
DerivedKeyTooLong,
};
/// Apply PBKDF2 to generate a key from a password.
///
/// PBKDF2 is defined in RFC 2898, and is a recommendation of NIST SP 800-132.
///
/// derivedKey: Slice of appropriate size for generated key. Generally 16 or 32 bytes in length.
/// May be uninitialized. All bytes will be overwritten.
/// Maximum size is `maxInt(u32) * Hash.digest_length`
/// It is a programming error to pass buffer longer than the maximum size.
///
/// password: Arbitrary sequence of bytes of any length, including empty.
///
/// salt: Arbitrary sequence of bytes of any length, including empty. A common length is 8 bytes.
///
/// rounds: Iteration count. Must be greater than 0. Common values range from 1,000 to 100,000.
/// Larger iteration counts improve security by increasing the time required to compute
/// the derivedKey. It is common to tune this parameter to achieve approximately 100ms.
///
/// Prf: Pseudo-random function to use. A common choice is `std.crypto.auth.hmac.HmacSha256`.
pub fn pbkdf2(derivedKey: []u8, password: []const u8, salt: []const u8, rounds: u32, comptime Prf: type) Pbkdf2Error!void {
if (rounds < 1) return error.TooFewRounds;
const dkLen = derivedKey.len;
const hLen = Prf.mac_length;
comptime std.debug.assert(hLen >= 1);
// FromSpec:
//
// 1. If dkLen > maxInt(u32) * hLen, output "derived key too long" and
// stop.
//
if (comptime (maxInt(usize) > maxInt(u32) * hLen) and (dkLen > @as(usize, maxInt(u32) * hLen))) {
// If maxInt(usize) is less than `maxInt(u32) * hLen` then dkLen is always inbounds
return error.DerivedKeyTooLong;
}
// FromSpec:
//
// 2. Let l be the number of hLen-long blocks of bytes in the derived key,
// rounding up, and let r be the number of bytes in the last
// block
//
// l will not overflow, proof:
// let `L(dkLen, hLen) = (dkLen + hLen - 1) / hLen`
// then `L^-1(l, hLen) = l*hLen - hLen + 1`
// 1) L^-1(maxInt(u32), hLen) <= maxInt(u32)*hLen
// 2) maxInt(u32)*hLen - hLen + 1 <= maxInt(u32)*hLen // subtract maxInt(u32)*hLen + 1
// 3) -hLen <= -1 // multiply by -1
// 4) hLen >= 1
const r_ = dkLen % hLen;
const l = @intCast(u32, (dkLen / hLen) + @as(u1, if (r_ == 0) 0 else 1)); // original: (dkLen + hLen - 1) / hLen
const r = if (r_ == 0) hLen else r_;
// FromSpec:
//
// 3. For each block of the derived key apply the function F defined
// below to the password P, the salt S, the iteration count c, and
// the block index to compute the block:
//
// T_1 = F (P, S, c, 1) ,
// T_2 = F (P, S, c, 2) ,
// ...
// T_l = F (P, S, c, l) ,
//
// where the function F is defined as the exclusive-or sum of the
// first c iterates of the underlying pseudorandom function PRF
// applied to the password P and the concatenation of the salt S
// and the block index i:
//
// F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
//
// where
//
// U_1 = PRF (P, S || INT (i)) ,
// U_2 = PRF (P, U_1) ,
// ...
// U_c = PRF (P, U_{c-1}) .
//
// Here, INT (i) is a four-octet encoding of the integer i, most
// significant octet first.
//
// 4. Concatenate the blocks and extract the first dkLen octets to
// produce a derived key DK:
//
// DK = T_1 || T_2 || ... || T_l<0..r-1>
var block: u32 = 0; // Spec limits to u32
while (block < l) : (block += 1) {
var prevBlock: [hLen]u8 = undefined;
var newBlock: [hLen]u8 = undefined;
// U_1 = PRF (P, S || INT (i))
const blockIndex = mem.toBytes(mem.nativeToBig(u32, block + 1)); // Block index starts at 0001
var ctx = Prf.init(password);
ctx.update(salt);
ctx.update(blockIndex[0..]);
ctx.final(prevBlock[0..]);
// Choose portion of DK to write into (T_n) and initialize
const offset = block * hLen;
const blockLen = if (block != l - 1) hLen else r;
const dkBlock: []u8 = derivedKey[offset..][0..blockLen];
mem.copy(u8, dkBlock, prevBlock[0..dkBlock.len]);
var i: u32 = 1;
while (i < rounds) : (i += 1) {
// U_c = PRF (P, U_{c-1})
Prf.create(&newBlock, prevBlock[0..], password);
mem.copy(u8, prevBlock[0..], newBlock[0..]);
// F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
for (dkBlock) |_, j| {
dkBlock[j] ^= newBlock[j];
}
}
}
}
const htest = @import("test.zig");
const HmacSha1 = std.crypto.auth.hmac.HmacSha1;
// RFC 6070 PBKDF2 HMAC-SHA1 Test Vectors
test "RFC 6070 one iteration" {
const p = "password";
const s = "salt";
const c = 1;
const dkLen = 20;
var derivedKey: [dkLen]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
const expected = "0c60c80f961f0e71f3a9b524af6012062fe037a6";
htest.assertEqual(expected, derivedKey[0..]);
}
test "RFC 6070 two iterations" {
const p = "password";
const s = "salt";
const c = 2;
const dkLen = 20;
var derivedKey: [dkLen]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
const expected = "ea6c014dc72d6f8ccd1ed92ace1d41f0d8de8957";
htest.assertEqual(expected, derivedKey[0..]);
}
test "RFC 6070 4096 iterations" {
const p = "password";
const s = "salt";
const c = 4096;
const dkLen = 20;
var derivedKey: [dkLen]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
const expected = "4b007901b765489abead49d926f721d065a429c1";
htest.assertEqual(expected, derivedKey[0..]);
}
test "RFC 6070 16,777,216 iterations" {
// These iteration tests are slow so we always skip them. Results have been verified.
if (true) {
return error.SkipZigTest;
}
const p = "password";
const s = "salt";
const c = 16777216;
const dkLen = 20;
var derivedKey = [_]u8{0} ** dkLen;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
const expected = "eefe3d61cd4da4e4e9945b3d6ba2158c2634e984";
htest.assertEqual(expected, derivedKey[0..]);
}
test "RFC 6070 multi-block salt and password" {
const p = "passwordPASSWORDpassword";
const s = "saltSALTsaltSALTsaltSALTsaltSALTsalt";
const c = 4096;
const dkLen = 25;
var derivedKey: [dkLen]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
const expected = "3d2eec4fe41c849b80c8d83662c0e44a8b291a964cf2f07038";
htest.assertEqual(expected, derivedKey[0..]);
}
test "RFC 6070 embedded NUL" {
const p = "pass\x00word";
const s = "sa\x00lt";
const c = 4096;
const dkLen = 16;
var derivedKey: [dkLen]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
const expected = "56fa6aa75548099dcc37d7f03425e0c3";
htest.assertEqual(expected, derivedKey[0..]);
}
test "Very large dkLen" {
// This test allocates 8GB of memory and is expected to take several hours to run.
if (true) {
return error.SkipZigTest;
}
const p = "password";
const s = "salt";
const c = 1;
const dkLen = 1 << 33;
var derivedKey = try std.testing.allocator.alloc(u8, dkLen);
defer {
std.testing.allocator.free(derivedKey);
}
try pbkdf2(derivedKey, p, s, c, HmacSha1);
// Just verify this doesn't crash with an overflow
}