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Merge pull request #8273 from jedisct1/pbkdf2-check

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crypto/pbkdf2: simplify the check for the max number of iterations
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Andrew Kelley 2021-03-17 11:25:19 -07:00 committed by GitHub
commit 587243c7a5
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1 changed files with 67 additions and 70 deletions
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137
lib/std/crypto/pbkdf2.zig
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@ -20,20 +20,20 @@ const Error = std.crypto.Error;
// pseudorandom function. See Appendix B.1 for further discussion.)
// PBKDF2 is recommended for new applications.
//
// PBKDF2 (P, S, c, dkLen)
// PBKDF2 (P, S, c, dk_len)
//
// Options: PRF underlying pseudorandom function (hLen
// Options: PRF underlying pseudorandom function (h_len
// 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
// dk_len intended length in octets of the derived
// key, a positive integer, at most
// (2^32 - 1) * hLen
// (2^32 - 1) * h_len
//
// Output: DK derived key, a dkLen-octet string
// Output: DK derived key, a dk_len-octet string
// Based on Apple's CommonKeyDerivation, based originally on code by Damien Bergamini.
@ -41,7 +41,7 @@ const Error = std.crypto.Error;
///
/// 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.
/// dk: 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.
@ -52,43 +52,38 @@ const Error = std.crypto.Error;
///
/// 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.
/// the dk. 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) Error!void {
pub fn pbkdf2(dk: []u8, password: []const u8, salt: []const u8, rounds: u32, comptime Prf: type) Error!void {
if (rounds < 1) return error.WeakParameters;
const dkLen = derivedKey.len;
const hLen = Prf.mac_length;
comptime std.debug.assert(hLen >= 1);
const dk_len = dk.len;
const h_len = Prf.mac_length;
comptime std.debug.assert(h_len >= 1);
// FromSpec:
//
// 1. If dkLen > maxInt(u32) * hLen, output "derived key too long" and
// 1. If dk_len > maxInt(u32) * h_len, 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
if (dk_len / h_len >= maxInt(u32)) {
// Counter starts at 1 and is 32 bit, so if we have to return more blocks, we would overflow
return error.OutputTooLong;
}
// FromSpec:
//
// 2. Let l be the number of hLen-long blocks of bytes in the derived key,
// 2. Let l be the number of h_len-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_;
const blocks_count = @intCast(u32, std.math.divCeil(usize, dk_len, h_len) catch unreachable);
var r = dk_len % h_len;
if (r == 0) {
r = h_len;
}
// FromSpec:
//
@ -118,37 +113,38 @@ pub fn pbkdf2(derivedKey: []u8, password: []const u8, salt: []const u8, rounds:
// 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
// 4. Concatenate the blocks and extract the first dk_len 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;
var block: u32 = 0;
while (block < blocks_count) : (block += 1) {
var prev_block: [h_len]u8 = undefined;
var new_block: [h_len]u8 = undefined;
// U_1 = PRF (P, S || INT (i))
const blockIndex = mem.toBytes(mem.nativeToBig(u32, block + 1)); // Block index starts at 0001
const block_index = 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..]);
ctx.update(block_index[0..]);
ctx.final(prev_block[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]);
const offset = block * h_len;
const block_len = if (block != blocks_count - 1) h_len else r;
const dk_block: []u8 = dk[offset..][0..block_len];
mem.copy(u8, dk_block, prev_block[0..dk_block.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..]);
Prf.create(&new_block, prev_block[0..], password);
mem.copy(u8, prev_block[0..], new_block[0..]);
// F (P, S, c, i) = U_1 \xor U_2 \xor ... \xor U_c
for (dkBlock) |_, j| {
dkBlock[j] ^= newBlock[j];
for (dk_block) |_, j| {
dk_block[j] ^= new_block[j];
}
}
}
@ -158,49 +154,50 @@ 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;
const dk_len = 20;
var derivedKey: [dkLen]u8 = undefined;
var dk: [dk_len]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
try pbkdf2(&dk, p, s, c, HmacSha1);
const expected = "0c60c80f961f0e71f3a9b524af6012062fe037a6";
htest.assertEqual(expected, derivedKey[0..]);
htest.assertEqual(expected, dk[0..]);
}
test "RFC 6070 two iterations" {
const p = "password";
const s = "salt";
const c = 2;
const dkLen = 20;
const dk_len = 20;
var derivedKey: [dkLen]u8 = undefined;
var dk: [dk_len]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
try pbkdf2(&dk, p, s, c, HmacSha1);
const expected = "ea6c014dc72d6f8ccd1ed92ace1d41f0d8de8957";
htest.assertEqual(expected, derivedKey[0..]);
htest.assertEqual(expected, dk[0..]);
}
test "RFC 6070 4096 iterations" {
const p = "password";
const s = "salt";
const c = 4096;
const dkLen = 20;
const dk_len = 20;
var derivedKey: [dkLen]u8 = undefined;
var dk: [dk_len]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
try pbkdf2(&dk, p, s, c, HmacSha1);
const expected = "4b007901b765489abead49d926f721d065a429c1";
htest.assertEqual(expected, derivedKey[0..]);
htest.assertEqual(expected, dk[0..]);
}
test "RFC 6070 16,777,216 iterations" {
@ -212,48 +209,48 @@ test "RFC 6070 16,777,216 iterations" {
const p = "password";
const s = "salt";
const c = 16777216;
const dkLen = 20;
const dk_len = 20;
var derivedKey = [_]u8{0} ** dkLen;
var dk = [_]u8{0} ** dk_len;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
try pbkdf2(&dk, p, s, c, HmacSha1);
const expected = "eefe3d61cd4da4e4e9945b3d6ba2158c2634e984";
htest.assertEqual(expected, derivedKey[0..]);
htest.assertEqual(expected, dk[0..]);
}
test "RFC 6070 multi-block salt and password" {
const p = "passwordPASSWORDpassword";
const s = "saltSALTsaltSALTsaltSALTsaltSALTsalt";
const c = 4096;
const dkLen = 25;
const dk_len = 25;
var derivedKey: [dkLen]u8 = undefined;
var dk: [dk_len]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
try pbkdf2(&dk, p, s, c, HmacSha1);
const expected = "3d2eec4fe41c849b80c8d83662c0e44a8b291a964cf2f07038";
htest.assertEqual(expected, derivedKey[0..]);
htest.assertEqual(expected, dk[0..]);
}
test "RFC 6070 embedded NUL" {
const p = "pass\x00word";
const s = "sa\x00lt";
const c = 4096;
const dkLen = 16;
const dk_len = 16;
var derivedKey: [dkLen]u8 = undefined;
var dk: [dk_len]u8 = undefined;
try pbkdf2(&derivedKey, p, s, c, HmacSha1);
try pbkdf2(&dk, p, s, c, HmacSha1);
const expected = "56fa6aa75548099dcc37d7f03425e0c3";
htest.assertEqual(expected, derivedKey[0..]);
htest.assertEqual(expected, dk[0..]);
}
test "Very large dkLen" {
test "Very large dk_len" {
// This test allocates 8GB of memory and is expected to take several hours to run.
if (true) {
return error.SkipZigTest;
@ -261,13 +258,13 @@ test "Very large dkLen" {
const p = "password";
const s = "salt";
const c = 1;
const dkLen = 1 << 33;
const dk_len = 1 << 33;
var derivedKey = try std.testing.allocator.alloc(u8, dkLen);
var dk = try std.testing.allocator.alloc(u8, dk_len);
defer {
std.testing.allocator.free(derivedKey);
std.testing.allocator.free(dk);
}
try pbkdf2(derivedKey, p, s, c, HmacSha1);
// Just verify this doesn't crash with an overflow
try pbkdf2(dk, p, s, c, HmacSha1);
}