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strongswan/src/pluto/pkcs1.c

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/* Support of PKCS#1 private key data structures
* Copyright (C) 2005 Jan Hutter, Martin Willi
* Copyright (C) 2002-2005 Andreas Steffen
* Hochschule fuer Technik Rapperswil, Switzerland
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* RCSID $Id: pkcs1.c,v 1.17 2006/01/04 21:00:43 as Exp $
*/
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <freeswan.h>
#include "constants.h"
#include "defs.h"
#include "mp_defs.h"
#include "asn1.h"
#include "oid.h"
#include "log.h"
#include "pkcs1.h"
#include "md2.h"
#include "md5.h"
#include "sha1.h"
#include "rnd.h"
const struct fld RSA_private_field[] =
{
{ "Modulus", offsetof(RSA_private_key_t, pub.n) },
{ "PublicExponent", offsetof(RSA_private_key_t, pub.e) },
{ "PrivateExponent", offsetof(RSA_private_key_t, d) },
{ "Prime1", offsetof(RSA_private_key_t, p) },
{ "Prime2", offsetof(RSA_private_key_t, q) },
{ "Exponent1", offsetof(RSA_private_key_t, dP) },
{ "Exponent2", offsetof(RSA_private_key_t, dQ) },
{ "Coefficient", offsetof(RSA_private_key_t, qInv) },
};
/* ASN.1 definition of a PKCS#1 RSA private key */
static const asn1Object_t privkeyObjects[] = {
{ 0, "RSAPrivateKey", ASN1_SEQUENCE, ASN1_NONE }, /* 0 */
{ 1, "version", ASN1_INTEGER, ASN1_BODY }, /* 1 */
{ 1, "modulus", ASN1_INTEGER, ASN1_BODY }, /* 2 */
{ 1, "publicExponent", ASN1_INTEGER, ASN1_BODY }, /* 3 */
{ 1, "privateExponent", ASN1_INTEGER, ASN1_BODY }, /* 4 */
{ 1, "prime1", ASN1_INTEGER, ASN1_BODY }, /* 5 */
{ 1, "prime2", ASN1_INTEGER, ASN1_BODY }, /* 6 */
{ 1, "exponent1", ASN1_INTEGER, ASN1_BODY }, /* 7 */
{ 1, "exponent2", ASN1_INTEGER, ASN1_BODY }, /* 8 */
{ 1, "coefficient", ASN1_INTEGER, ASN1_BODY }, /* 9 */
{ 1, "otherPrimeInfos", ASN1_SEQUENCE, ASN1_OPT |
ASN1_LOOP }, /* 10 */
{ 2, "otherPrimeInfo", ASN1_SEQUENCE, ASN1_NONE }, /* 11 */
{ 3, "prime", ASN1_INTEGER, ASN1_BODY }, /* 12 */
{ 3, "exponent", ASN1_INTEGER, ASN1_BODY }, /* 13 */
{ 3, "coefficient", ASN1_INTEGER, ASN1_BODY }, /* 14 */
{ 1, "end opt or loop", ASN1_EOC, ASN1_END } /* 15 */
};
#define PKCS1_PRIV_KEY_VERSION 1
#define PKCS1_PRIV_KEY_MODULUS 2
#define PKCS1_PRIV_KEY_PUB_EXP 3
#define PKCS1_PRIV_KEY_COEFF 9
#define PKCS1_PRIV_KEY_ROOF 16
/*
* forms the FreeS/WAN keyid from the public exponent e and modulus n
*/
void
form_keyid(chunk_t e, chunk_t n, char* keyid, unsigned *keysize)
{
/* eliminate leading zero bytes in modulus from ASN.1 coding */
while (n.len > 1 && *n.ptr == 0x00)
{
n.ptr++; n.len--;
}
/* form the FreeS/WAN keyid */
keyid[0] = '\0'; /* in case of splitkeytoid failure */
splitkeytoid(e.ptr, e.len, n.ptr, n.len, keyid, KEYID_BUF);
/* return the RSA modulus size in octets */
*keysize = n.len;
}
/*
* initialize an RSA_public_key_t object
*/
void
init_RSA_public_key(RSA_public_key_t *rsa, chunk_t e, chunk_t n)
{
n_to_mpz(&rsa->e, e.ptr, e.len);
n_to_mpz(&rsa->n, n.ptr, n.len);
form_keyid(e, n, rsa->keyid, &rsa->k);
}
#ifdef DEBUG
static void
RSA_show_key_fields(RSA_private_key_t *k, int fieldcnt)
{
const struct fld *p;
DBG_log(" keyid: *%s", k->pub.keyid);
for (p = RSA_private_field; p < &RSA_private_field[fieldcnt]; p++)
{
MP_INT *n = (MP_INT *) ((char *)k + p->offset);
size_t sz = mpz_sizeinbase(n, 16);
char buf[RSA_MAX_OCTETS * 2 + 2]; /* ought to be big enough */
passert(sz <= sizeof(buf));
mpz_get_str(buf, 16, n);
DBG_log(" %s: 0x%s", p->name, buf);
}
}
/* debugging info that compromises security! */
void
RSA_show_private_key(RSA_private_key_t *k)
{
RSA_show_key_fields(k, elemsof(RSA_private_field));
}
void
RSA_show_public_key(RSA_public_key_t *k)
{
/* Kludge: pretend that it is a private key, but only display the
* first two fields (which are the public key).
*/
passert(offsetof(RSA_private_key_t, pub) == 0);
RSA_show_key_fields((RSA_private_key_t *)k, 2);
}
#endif
err_t
RSA_private_key_sanity(RSA_private_key_t *k)
{
/* note that the *last* error found is reported */
err_t ugh = NULL;
mpz_t t, u, q1;
#ifdef DEBUG /* debugging info that compromises security */
DBG(DBG_PRIVATE, RSA_show_private_key(k));
#endif
/* PKCS#1 1.5 section 6 requires modulus to have at least 12 octets.
* We actually require more (for security).
*/
if (k->pub.k < RSA_MIN_OCTETS)
return RSA_MIN_OCTETS_UGH;
/* we picked a max modulus size to simplify buffer allocation */
if (k->pub.k > RSA_MAX_OCTETS)
return RSA_MAX_OCTETS_UGH;
mpz_init(t);
mpz_init(u);
mpz_init(q1);
/* check that n == p * q */
mpz_mul(u, &k->p, &k->q);
if (mpz_cmp(u, &k->pub.n) != 0)
ugh = "n != p * q";
/* check that e divides neither p-1 nor q-1 */
mpz_sub_ui(t, &k->p, 1);
mpz_mod(t, t, &k->pub.e);
if (mpz_cmp_ui(t, 0) == 0)
ugh = "e divides p-1";
mpz_sub_ui(t, &k->q, 1);
mpz_mod(t, t, &k->pub.e);
if (mpz_cmp_ui(t, 0) == 0)
ugh = "e divides q-1";
/* check that d is e^-1 (mod lcm(p-1, q-1)) */
/* see PKCS#1v2, aka RFC 2437, for the "lcm" */
mpz_sub_ui(q1, &k->q, 1);
mpz_sub_ui(u, &k->p, 1);
mpz_gcd(t, u, q1); /* t := gcd(p-1, q-1) */
mpz_mul(u, u, q1); /* u := (p-1) * (q-1) */
mpz_divexact(u, u, t); /* u := lcm(p-1, q-1) */
mpz_mul(t, &k->d, &k->pub.e);
mpz_mod(t, t, u);
if (mpz_cmp_ui(t, 1) != 0)
ugh = "(d * e) mod (lcm(p-1, q-1)) != 1";
/* check that dP is d mod (p-1) */
mpz_sub_ui(u, &k->p, 1);
mpz_mod(t, &k->d, u);
if (mpz_cmp(t, &k->dP) != 0)
ugh = "dP is not congruent to d mod (p-1)";
/* check that dQ is d mod (q-1) */
mpz_sub_ui(u, &k->q, 1);
mpz_mod(t, &k->d, u);
if (mpz_cmp(t, &k->dQ) != 0)
ugh = "dQ is not congruent to d mod (q-1)";
/* check that qInv is (q^-1) mod p */
mpz_mul(t, &k->qInv, &k->q);
mpz_mod(t, t, &k->p);
if (mpz_cmp_ui(t, 1) != 0)
ugh = "qInv is not conguent ot (q^-1) mod p";
mpz_clear(t);
mpz_clear(u);
mpz_clear(q1);
return ugh;
}
/*
* Check the equality of two RSA public keys
*/
bool
same_RSA_public_key(const RSA_public_key_t *a, const RSA_public_key_t *b)
{
return a == b
|| (a->k == b->k && mpz_cmp(&a->n, &b->n) == 0 && mpz_cmp(&a->e, &b->e) == 0);
}
/*
* Parses a PKCS#1 private key
*/
bool
pkcs1_parse_private_key(chunk_t blob, RSA_private_key_t *key)
{
err_t ugh = NULL;
asn1_ctx_t ctx;
chunk_t object, modulus, exp;
u_int level;
int objectID = 0;
asn1_init(&ctx, blob, 0, FALSE, DBG_PRIVATE);
while (objectID < PKCS1_PRIV_KEY_ROOF) {
if (!extract_object(privkeyObjects, &objectID, &object, &level, &ctx))
return FALSE;
if (objectID == PKCS1_PRIV_KEY_VERSION)
{
if (object.len > 0 && *object.ptr != 0)
{
plog(" wrong PKCS#1 private key version");
return FALSE;
}
}
else if (objectID >= PKCS1_PRIV_KEY_MODULUS &&
objectID <= PKCS1_PRIV_KEY_COEFF)
{
MP_INT *u = (MP_INT *) ((char *)key
+ RSA_private_field[objectID - PKCS1_PRIV_KEY_MODULUS].offset);
n_to_mpz(u, object.ptr, object.len);
if (objectID == PKCS1_PRIV_KEY_MODULUS)
modulus = object;
else if (objectID == PKCS1_PRIV_KEY_PUB_EXP)
exp = object;
}
objectID++;
}
form_keyid(exp, modulus, key->pub.keyid, &key->pub.k);
ugh = RSA_private_key_sanity(key);
return (ugh == NULL);
}
/*
* compute a digest over a binary blob
*/
bool
compute_digest(chunk_t tbs, int alg, chunk_t *digest)
{
switch (alg)
{
case OID_MD2:
case OID_MD2_WITH_RSA:
{
MD2_CTX context;
MD2Init(&context);
MD2Update(&context, tbs.ptr, tbs.len);
MD2Final(digest->ptr, &context);
digest->len = MD2_DIGEST_SIZE;
return TRUE;
}
case OID_MD5:
case OID_MD5_WITH_RSA:
{
MD5_CTX context;
MD5Init(&context);
MD5Update(&context, tbs.ptr, tbs.len);
MD5Final(digest->ptr, &context);
digest->len = MD5_DIGEST_SIZE;
return TRUE;
}
case OID_SHA1:
case OID_SHA1_WITH_RSA:
case OID_SHA1_WITH_RSA_OIW:
{
SHA1_CTX context;
SHA1Init(&context);
SHA1Update(&context, tbs.ptr, tbs.len);
SHA1Final(digest->ptr, &context);
digest->len = SHA1_DIGEST_SIZE;
return TRUE;
}
default:
digest->len = 0;
return FALSE;
}
}
/*
* compute an RSA signature with PKCS#1 padding
*/
void
sign_hash(const RSA_private_key_t *k, const u_char *hash_val, size_t hash_len
, u_char *sig_val, size_t sig_len)
{
chunk_t ch;
mpz_t t1, t2;
size_t padlen;
u_char *p = sig_val;
DBG(DBG_CONTROL | DBG_CRYPT,
DBG_log("signing hash with RSA Key *%s", k->pub.keyid)
)
/* PKCS#1 v1.5 8.1 encryption-block formatting */
*p++ = 0x00;
*p++ = 0x01; /* BT (block type) 01 */
padlen = sig_len - 3 - hash_len;
memset(p, 0xFF, padlen);
p += padlen;
*p++ = 0x00;
memcpy(p, hash_val, hash_len);
passert(p + hash_len - sig_val == (ptrdiff_t)sig_len);
/* PKCS#1 v1.5 8.2 octet-string-to-integer conversion */
n_to_mpz(t1, sig_val, sig_len); /* (could skip leading 0x00) */
/* PKCS#1 v1.5 8.3 RSA computation y = x^c mod n
* Better described in PKCS#1 v2.0 5.1 RSADP.
* There are two methods, depending on the form of the private key.
* We use the one based on the Chinese Remainder Theorem.
*/
mpz_init(t2);
mpz_powm(t2, t1, &k->dP, &k->p); /* m1 = c^dP mod p */
mpz_powm(t1, t1, &k->dQ, &k->q); /* m2 = c^dQ mod Q */
mpz_sub(t2, t2, t1); /* h = qInv (m1 - m2) mod p */
mpz_mod(t2, t2, &k->p);
mpz_mul(t2, t2, &k->qInv);
mpz_mod(t2, t2, &k->p);
mpz_mul(t2, t2, &k->q); /* m = m2 + h q */
mpz_add(t1, t1, t2);
/* PKCS#1 v1.5 8.4 integer-to-octet-string conversion */
ch = mpz_to_n(t1, sig_len);
memcpy(sig_val, ch.ptr, sig_len);
pfree(ch.ptr);
mpz_clear(t1);
mpz_clear(t2);
}
/*
* encrypt data with an RSA public key after padding
*/
chunk_t
RSA_encrypt(const RSA_public_key_t *key, chunk_t in)
{
u_char padded[RSA_MAX_OCTETS];
u_char *pos = padded;
int padding = key->k - in.len - 3;
int i;
if (padding < 8 || key->k > RSA_MAX_OCTETS)
return empty_chunk;
/* add padding according to PKCS#1 7.2.1 1.+2. */
*pos++ = 0x00;
*pos++ = 0x02;
/* pad with pseudo random bytes unequal to zero */
get_rnd_bytes(pos, padding);
for (i = 0; i < padding; i++)
{
while (!*pos)
get_rnd_bytes(pos, 1);
pos++;
}
/* append the padding terminator */
*pos++ = 0x00;
/* now add the data */
memcpy(pos, in.ptr, in.len);
DBG(DBG_RAW,
DBG_dump_chunk("data for rsa encryption:\n", in);
DBG_dump("padded data for rsa encryption:\n", padded, key->k)
)
/* convert chunk to integer (PKCS#1 7.2.1 3.a) */
{
chunk_t out;
mpz_t m, c;
mpz_init(c);
n_to_mpz(m, padded, key->k);
/* encrypt(PKCS#1 7.2.1 3.b) */
mpz_powm(c, m, &key->e, &key->n);
/* convert integer back to a chunk (PKCS#1 7.2.1 3.c) */
out = mpz_to_n(c, key->k);
mpz_clear(c);
mpz_clear(m);
DBG(DBG_RAW,
DBG_dump_chunk("rsa encrypted data:\n", out)
)
return out;
}
}
/*
* decrypt data with an RSA private key and remove padding
*/
bool
RSA_decrypt(const RSA_private_key_t *key, chunk_t in, chunk_t *out)
{
chunk_t padded;
u_char *pos;
mpz_t t1, t2;
n_to_mpz(t1, in.ptr,in.len);
/* PKCS#1 v1.5 8.3 RSA computation y = x^c mod n
* Better described in PKCS#1 v2.0 5.1 RSADP.
* There are two methods, depending on the form of the private key.
* We use the one based on the Chinese Remainder Theorem.
*/
mpz_init(t2);
mpz_powm(t2, t1, &key->dP, &key->p); /* m1 = c^dP mod p */
mpz_powm(t1, t1, &key->dQ, &key->q); /* m2 = c^dQ mod Q */
mpz_sub(t2, t2, t1); /* h = qInv (m1 - m2) mod p */
mpz_mod(t2, t2, &key->p);
mpz_mul(t2, t2, &key->qInv);
mpz_mod(t2, t2, &key->p);
mpz_mul(t2, t2, &key->q); /* m = m2 + h q */
mpz_add(t1, t1, t2);
padded = mpz_to_n(t1, key->pub.k);
mpz_clear(t1);
mpz_clear(t2);
DBG(DBG_PRIVATE,
DBG_dump_chunk("rsa decrypted data with padding:\n", padded)
)
pos = padded.ptr;
/* PKCS#1 v1.5 8.1 encryption-block formatting (EB = 00 || 02 || PS || 00 || D) */
/* check for hex pattern 00 02 in decrypted message */
if ((*pos++ != 0x00) || (*(pos++) != 0x02))
{
plog("incorrect padding - probably wrong RSA key");
freeanychunk(padded);
return FALSE;
}
padded.len -= 2;
/* the plaintext data starts after first 0x00 byte */
while (padded.len-- > 0 && *pos++ != 0x00)
if (padded.len == 0)
{
plog("no plaintext data");
freeanychunk(padded);
return FALSE;
}
clonetochunk(*out, pos, padded.len, "decrypted data");
freeanychunk(padded);
return TRUE;
}
/*
* build signatureValue
*/
chunk_t
pkcs1_build_signature(chunk_t tbs, int hash_alg, const RSA_private_key_t *key
, bool bit_string)
{
size_t siglen = key->pub.k;
u_char digest_buf[MAX_DIGEST_LEN];
chunk_t digest = { digest_buf, MAX_DIGEST_LEN };
chunk_t digestInfo, alg_id, signatureValue;
u_char *pos;
switch (hash_alg)
{
case OID_MD5:
case OID_MD5_WITH_RSA:
alg_id = ASN1_md5_id;
break;
case OID_SHA1:
case OID_SHA1_WITH_RSA:
alg_id = ASN1_sha1_id;
break;
default:
return empty_chunk;
}
compute_digest(tbs, hash_alg, &digest);
/* according to PKCS#1 v2.1 digest must be packaged into
* an ASN.1 structure for encryption
*/
digestInfo = asn1_wrap(ASN1_SEQUENCE, "cm"
, alg_id
, asn1_simple_object(ASN1_OCTET_STRING, digest));
/* generate the RSA signature */
if (bit_string)
{
pos = build_asn1_object(&signatureValue, ASN1_BIT_STRING, 1 + siglen);
*pos++ = 0x00;
}
else
{
pos = build_asn1_object(&signatureValue, ASN1_OCTET_STRING, siglen);
}
sign_hash(key, digestInfo.ptr, digestInfo.len, pos, siglen);
pfree(digestInfo.ptr);
return signatureValue;
}
/*
* build a DER-encoded PKCS#1 private key object
*/
chunk_t
pkcs1_build_private_key(const RSA_private_key_t *key)
{
chunk_t pkcs1 = asn1_wrap(ASN1_SEQUENCE, "cmmmmmmmm"
, ASN1_INTEGER_0
, asn1_integer_from_mpz(&key->pub.n)
, asn1_integer_from_mpz(&key->pub.e)
, asn1_integer_from_mpz(&key->d)
, asn1_integer_from_mpz(&key->p)
, asn1_integer_from_mpz(&key->q)
, asn1_integer_from_mpz(&key->dP)
, asn1_integer_from_mpz(&key->dQ)
, asn1_integer_from_mpz(&key->qInv));
DBG(DBG_PRIVATE,
DBG_dump_chunk("PKCS#1 encoded private key:", pkcs1)
)
return pkcs1;
}
/*
* build a DER-encoded PKCS#1 public key object
*/
chunk_t
pkcs1_build_public_key(const RSA_public_key_t *rsa)
{
return asn1_wrap(ASN1_SEQUENCE, "mm"
, asn1_integer_from_mpz(&rsa->n)
, asn1_integer_from_mpz(&rsa->e));
}
/*
* build a DER-encoded publicKeyInfo object
*/
chunk_t
pkcs1_build_publicKeyInfo(const RSA_public_key_t *rsa)
{
chunk_t publicKey;
chunk_t rawKey = pkcs1_build_public_key(rsa);
u_char *pos = build_asn1_object(&publicKey, ASN1_BIT_STRING
, 1 + rawKey.len);
*pos++ = 0x00;
mv_chunk(&pos, rawKey);
return asn1_wrap(ASN1_SEQUENCE, "cm"
, ASN1_rsaEncryption_id
, publicKey);
}
void
free_RSA_public_content(RSA_public_key_t *rsa)
{
mpz_clear(&rsa->n);
mpz_clear(&rsa->e);
}
void
free_RSA_private_content(RSA_private_key_t *rsak)
{
free_RSA_public_content(&rsak->pub);
mpz_clear(&rsak->d);
mpz_clear(&rsak->p);
mpz_clear(&rsak->q);
mpz_clear(&rsak->dP);
mpz_clear(&rsak->dQ);
mpz_clear(&rsak->qInv);
}
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