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tor/src/common/crypto_s2k.c

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/* Copyright (c) 2001, Matej Pfajfar.
* Copyright (c) 2001-2004, Roger Dingledine.
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2015, The Tor Project, Inc. */
/* See LICENSE for licensing information */
#define CRYPTO_S2K_PRIVATE
#include "crypto.h"
#include "util.h"
#include "compat.h"
#include "crypto_s2k.h"
#include <openssl/evp.h>
#ifdef HAVE_LIBSCRYPT_H
#define HAVE_SCRYPT
#include <libscrypt.h>
#endif
/* Encoded secrets take the form:
u8 type;
u8 salt_and_parameters[depends on type];
u8 key[depends on type];
As a special case, if the encoded secret is exactly 29 bytes long,
type 0 is understood.
Recognized types are:
00 -- RFC2440. salt_and_parameters is 9 bytes. key is 20 bytes.
salt_and_parameters is 8 bytes random salt,
1 byte iteration info.
01 -- PKBDF2_SHA1. salt_and_parameters is 17 bytes. key is 20 bytes.
salt_and_parameters is 16 bytes random salt,
1 byte iteration info.
02 -- SCRYPT_SALSA208_SHA256. salt_and_parameters is 18 bytes. key is
32 bytes.
salt_and_parameters is 18 bytes random salt, 2 bytes iteration
info.
*/
#define S2K_TYPE_RFC2440 0
#define S2K_TYPE_PBKDF2 1
#define S2K_TYPE_SCRYPT 2
#define PBKDF2_SPEC_LEN 17
#define PBKDF2_KEY_LEN 20
#define SCRYPT_SPEC_LEN 18
#define SCRYPT_KEY_LEN 32
/** Given an algorithm ID (one of S2K_TYPE_*), return the length of the
* specifier part of it, without the prefix type byte. */
static int
secret_to_key_spec_len(uint8_t type)
{
switch (type) {
case S2K_TYPE_RFC2440:
return S2K_RFC2440_SPECIFIER_LEN;
case S2K_TYPE_PBKDF2:
return PBKDF2_SPEC_LEN;
case S2K_TYPE_SCRYPT:
return SCRYPT_SPEC_LEN;
default:
return -1;
}
}
/** Given an algorithm ID (one of S2K_TYPE_*), return the length of the
* its preferred output. */
static int
secret_to_key_key_len(uint8_t type)
{
switch (type) {
case S2K_TYPE_RFC2440:
return DIGEST_LEN;
case S2K_TYPE_PBKDF2:
return DIGEST_LEN;
case S2K_TYPE_SCRYPT:
return DIGEST256_LEN;
default:
return -1;
}
}
/** Given a specifier in <b>spec_and_key</b> of length
* <b>spec_and_key_len</b>, along with its prefix algorithm ID byte, and along
* with a key if <b>key_included</b> is true, check whether the whole
* specifier-and-key is of valid length, and return the algorithm type if it
* is. Set *<b>legacy_out</b> to 1 iff this is a legacy password hash or
* legacy specifier. Return an error code on failure.
*/
static int
secret_to_key_get_type(const uint8_t *spec_and_key, size_t spec_and_key_len,
int key_included, int *legacy_out)
{
size_t legacy_len = S2K_RFC2440_SPECIFIER_LEN;
uint8_t type;
int total_len;
if (key_included)
legacy_len += DIGEST_LEN;
if (spec_and_key_len == legacy_len) {
*legacy_out = 1;
return S2K_TYPE_RFC2440;
}
*legacy_out = 0;
if (spec_and_key_len == 0)
return S2K_BAD_LEN;
type = spec_and_key[0];
total_len = secret_to_key_spec_len(type);
if (total_len < 0)
return S2K_BAD_ALGORITHM;
if (key_included) {
int keylen = secret_to_key_key_len(type);
if (keylen < 0)
return S2K_BAD_ALGORITHM;
total_len += keylen;
}
if ((size_t)total_len + 1 == spec_and_key_len)
return type;
else
return S2K_BAD_LEN;
}
/**
* Write a new random s2k specifier of type <b>type</b>, without prefixing
* type byte, to <b>spec_out</b>, which must have enough room. May adjust
* parameter choice based on <b>flags</b>.
*/
static int
make_specifier(uint8_t *spec_out, uint8_t type, unsigned flags)
{
int speclen = secret_to_key_spec_len(type);
if (speclen < 0)
return S2K_BAD_ALGORITHM;
crypto_rand((char*)spec_out, speclen);
switch (type) {
case S2K_TYPE_RFC2440:
/* Hash 64 k of data. */
spec_out[S2K_RFC2440_SPECIFIER_LEN-1] = 96;
break;
case S2K_TYPE_PBKDF2:
/* 131 K iterations */
spec_out[PBKDF2_SPEC_LEN-1] = 17;
break;
case S2K_TYPE_SCRYPT:
if (flags & S2K_FLAG_LOW_MEM) {
/* N = 1<<12 */
spec_out[SCRYPT_SPEC_LEN-2] = 12;
} else {
/* N = 1<<15 */
spec_out[SCRYPT_SPEC_LEN-2] = 15;
}
/* r = 8; p = 2. */
spec_out[SCRYPT_SPEC_LEN-1] = (3u << 4) | (1u << 0);
break;
default:
tor_fragile_assert();
return S2K_BAD_ALGORITHM;
}
return speclen;
}
/** Implement RFC2440-style iterated-salted S2K conversion: convert the
* <b>secret_len</b>-byte <b>secret</b> into a <b>key_out_len</b> byte
* <b>key_out</b>. As in RFC2440, the first 8 bytes of s2k_specifier
* are a salt; the 9th byte describes how much iteration to do.
* If <b>key_out_len</b> &gt; DIGEST_LEN, use HDKF to expand the result.
*/
void
secret_to_key_rfc2440(char *key_out, size_t key_out_len, const char *secret,
size_t secret_len, const char *s2k_specifier)
{
crypto_digest_t *d;
uint8_t c;
size_t count, tmplen;
char *tmp;
uint8_t buf[DIGEST_LEN];
tor_assert(key_out_len < SIZE_T_CEILING);
#define EXPBIAS 6
c = s2k_specifier[8];
count = ((uint32_t)16 + (c & 15)) << ((c >> 4) + EXPBIAS);
#undef EXPBIAS
d = crypto_digest_new();
tmplen = 8+secret_len;
tmp = tor_malloc(tmplen);
memcpy(tmp,s2k_specifier,8);
memcpy(tmp+8,secret,secret_len);
secret_len += 8;
while (count) {
if (count >= secret_len) {
crypto_digest_add_bytes(d, tmp, secret_len);
count -= secret_len;
} else {
crypto_digest_add_bytes(d, tmp, count);
count = 0;
}
}
crypto_digest_get_digest(d, (char*)buf, sizeof(buf));
if (key_out_len <= sizeof(buf)) {
memcpy(key_out, buf, key_out_len);
} else {
crypto_expand_key_material_rfc5869_sha256(buf, DIGEST_LEN,
(const uint8_t*)s2k_specifier, 8,
(const uint8_t*)"EXPAND", 6,
(uint8_t*)key_out, key_out_len);
}
memwipe(tmp, 0, tmplen);
memwipe(buf, 0, sizeof(buf));
tor_free(tmp);
crypto_digest_free(d);
}
/**
* Helper: given a valid specifier without prefix type byte in <b>spec</b>,
* whose length must be correct, and given a secret passphrase <b>secret</b>
* of length <b>secret_len</b>, compute the key and store it into
* <b>key_out</b>, which must have enough room for secret_to_key_key_len(type)
* bytes. Return the number of bytes written on success and an error code
* on failure.
*/
STATIC int
secret_to_key_compute_key(uint8_t *key_out, size_t key_out_len,
const uint8_t *spec, size_t spec_len,
const char *secret, size_t secret_len,
int type)
{
int rv;
if (key_out_len > INT_MAX)
return S2K_BAD_LEN;
switch (type) {
case S2K_TYPE_RFC2440:
secret_to_key_rfc2440((char*)key_out, key_out_len, secret, secret_len,
(const char*)spec);
return (int)key_out_len;
case S2K_TYPE_PBKDF2: {
uint8_t log_iters;
if (spec_len < 1 || secret_len > INT_MAX || spec_len > INT_MAX)
return S2K_BAD_LEN;
log_iters = spec[spec_len-1];
if (log_iters > 31)
return S2K_BAD_PARAMS;
rv = PKCS5_PBKDF2_HMAC_SHA1(secret, (int)secret_len,
spec, (int)spec_len-1,
(1<<log_iters),
(int)key_out_len, key_out);
if (rv < 0)
return S2K_FAILED;
return (int)key_out_len;
}
case S2K_TYPE_SCRYPT: {
#ifdef HAVE_SCRYPT
uint8_t log_N, log_r, log_p;
uint64_t N;
uint32_t r, p;
if (spec_len < 2)
return S2K_BAD_LEN;
log_N = spec[spec_len-2];
log_r = (spec[spec_len-1]) >> 4;
log_p = (spec[spec_len-1]) & 15;
if (log_N > 63)
return S2K_BAD_PARAMS;
N = ((uint64_t)1) << log_N;
r = 1u << log_r;
p = 1u << log_p;
rv = libscrypt_scrypt((const uint8_t*)secret, secret_len,
spec, spec_len-2, N, r, p, key_out, key_out_len);
if (rv != 0)
return S2K_FAILED;
return (int)key_out_len;
#else
return S2K_NO_SCRYPT_SUPPORT;
#endif
}
default:
return S2K_BAD_ALGORITHM;
}
}
/**
* Given a specifier previously constructed with secret_to_key_make_specifier
* in <b>spec</b> of length <b>spec_len</b>, and a secret password in
* <b>secret</b> of length <b>secret_len</b>, generate <b>key_out_len</b>
* bytes of cryptographic material in <b>key_out</b>. The native output of
* the secret-to-key function will be truncated if key_out_len is short, and
* expanded with HKDF if key_out_len is long. Returns S2K_OKAY on success,
* and an error code on failure.
*/
int
secret_to_key_derivekey(uint8_t *key_out, size_t key_out_len,
const uint8_t *spec, size_t spec_len,
const char *secret, size_t secret_len)
{
int legacy_format = 0;
int type = secret_to_key_get_type(spec, spec_len, 0, &legacy_format);
int r;
if (type < 0)
return type;
#ifndef HAVE_SCRYPT
if (type == S2K_TYPE_SCRYPT)
return S2K_NO_SCRYPT_SUPPORT;
#endif
if (! legacy_format) {
++spec;
--spec_len;
}
r = secret_to_key_compute_key(key_out, key_out_len, spec, spec_len,
secret, secret_len, type);
if (r < 0)
return r;
else
return S2K_OKAY;
}
/**
* Construct a new s2k algorithm specifier and salt in <b>buf</b>, according
* to the bitwise-or of some S2K_FLAG_* options in <b>flags</b>. Up to
* <b>buf_len</b> bytes of storage may be used in <b>buf</b>. Return the
* number of bytes used on success and an error code on failure.
*/
int
secret_to_key_make_specifier(uint8_t *buf, size_t buf_len, unsigned flags)
{
int rv;
int spec_len;
#ifdef HAVE_SCRYPT
uint8_t type = S2K_TYPE_SCRYPT;
#else
uint8_t type = S2K_TYPE_RFC2440;
#endif
if (flags & S2K_FLAG_NO_SCRYPT)
type = S2K_TYPE_RFC2440;
if (flags & S2K_FLAG_USE_PBKDF2)
type = S2K_TYPE_PBKDF2;
spec_len = secret_to_key_spec_len(type);
if ((int)buf_len < spec_len + 1)
return S2K_TRUNCATED;
buf[0] = type;
rv = make_specifier(buf+1, type, flags);
if (rv < 0)
return rv;
else
return rv + 1;
}
/**
* Hash a passphrase from <b>secret</b> of length <b>secret_len</b>, according
* to the bitwise-or of some S2K_FLAG_* options in <b>flags</b>, and store the
* hash along with salt and hashing parameters into <b>buf</b>. Up to
* <b>buf_len</b> bytes of storage may be used in <b>buf</b>. Set
* *<b>len_out</b> to the number of bytes used and return S2K_OKAY on success;
* and return an error code on failure.
*/
int
secret_to_key_new(uint8_t *buf,
size_t buf_len,
size_t *len_out,
const char *secret, size_t secret_len,
unsigned flags)
{
int key_len;
int spec_len;
int type;
int rv;
spec_len = secret_to_key_make_specifier(buf, buf_len, flags);
if (spec_len < 0)
return spec_len;
type = buf[0];
key_len = secret_to_key_key_len(type);
if (key_len < 0)
return key_len;
if ((int)buf_len < key_len + spec_len)
return S2K_TRUNCATED;
rv = secret_to_key_compute_key(buf + spec_len, key_len,
buf + 1, spec_len-1,
secret, secret_len, type);
if (rv < 0)
return rv;
*len_out = spec_len + key_len;
return S2K_OKAY;
}
/**
* Given a hashed passphrase in <b>spec_and_key</b> of length
* <b>spec_and_key_len</b> as generated by secret_to_key_new(), verify whether
* it is a hash of the passphrase <b>secret</b> of length <b>secret_len</b>.
* Return S2K_OKAY on a match, S2K_BAD_SECRET on a well-formed hash that
* doesn't match this secret, and another error code on other errors.
*/
int
secret_to_key_check(const uint8_t *spec_and_key, size_t spec_and_key_len,
const char *secret, size_t secret_len)
{
int is_legacy = 0;
int type = secret_to_key_get_type(spec_and_key, spec_and_key_len,
1, &is_legacy);
uint8_t buf[32];
int spec_len;
int key_len;
int rv;
if (type < 0)
return type;
if (! is_legacy) {
spec_and_key++;
spec_and_key_len--;
}
spec_len = secret_to_key_spec_len(type);
key_len = secret_to_key_key_len(type);
tor_assert(spec_len > 0);
tor_assert(key_len > 0);
tor_assert(key_len <= (int) sizeof(buf));
tor_assert((int)spec_and_key_len == spec_len + key_len);
rv = secret_to_key_compute_key(buf, key_len,
spec_and_key, spec_len,
secret, secret_len, type);
if (rv < 0)
goto done;
if (tor_memeq(buf, spec_and_key + spec_len, key_len))
rv = S2K_OKAY;
else
rv = S2K_BAD_SECRET;
done:
memwipe(buf, 0, sizeof(buf));
return rv;
}
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