/*
* RSA
* Copyright (c) 2006, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "asn1.h"
#include "bignum.h"
#include "rsa.h"
struct crypto_rsa_key {
int private_key; /* whether private key is set */
struct bignum *n; /* modulus (p * q) */
struct bignum *e; /* public exponent */
/* The following parameters are available only if private_key is set */
struct bignum *d; /* private exponent */
struct bignum *p; /* prime p (factor of n) */
struct bignum *q; /* prime q (factor of n) */
struct bignum *dmp1; /* d mod (p - 1); CRT exponent */
struct bignum *dmq1; /* d mod (q - 1); CRT exponent */
struct bignum *iqmp; /* 1 / q mod p; CRT coefficient */
};
static const u8 * crypto_rsa_parse_integer(const u8 *pos, const u8 *end,
struct bignum *num)
{
struct asn1_hdr hdr;
if (pos == NULL)
return NULL;
if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_INTEGER) {
wpa_printf(MSG_DEBUG, "RSA: Expected INTEGER - found class %d "
"tag 0x%x", hdr.class, hdr.tag);
return NULL;
}
if (bignum_set_unsigned_bin(num, hdr.payload, hdr.length) < 0) {
wpa_printf(MSG_DEBUG, "RSA: Failed to parse INTEGER");
return NULL;
}
return hdr.payload + hdr.length;
}
/**
* crypto_rsa_import_public_key - Import an RSA public key
* @buf: Key buffer (DER encoded RSA public key)
* @len: Key buffer length in bytes
* Returns: Pointer to the public key or %NULL on failure
*/
struct crypto_rsa_key *
crypto_rsa_import_public_key(const u8 *buf, size_t len)
{
struct crypto_rsa_key *key;
struct asn1_hdr hdr;
const u8 *pos, *end;
key = os_zalloc(sizeof(*key));
if (key == NULL)
return NULL;
key->n = bignum_init();
key->e = bignum_init();
if (key->n == NULL || key->e == NULL) {
crypto_rsa_free(key);
return NULL;
}
/*
* PKCS #1, 7.1:
* RSAPublicKey ::= SEQUENCE {
* modulus INTEGER, -- n
* publicExponent INTEGER -- e
* }
*/
if (asn1_get_next(buf, len, &hdr) < 0 ||
hdr.class != ASN1_CLASS_UNIVERSAL ||
hdr.tag != ASN1_TAG_SEQUENCE) {
wpa_printf(MSG_DEBUG, "RSA: Expected SEQUENCE "
"(public key) - found class %d tag 0x%x",
hdr.class, hdr.tag);
goto error;
}
pos = hdr.payload;
end = pos + hdr.length;
pos = crypto_rsa_parse_integer(pos, end, key->n);
pos = crypto_rsa_parse_integer(pos, end, key->e);
if (pos == NULL)
goto error;
if (pos != end) {
wpa_hexdump(MSG_DEBUG,
"RSA: Extra data in public key SEQUENCE",
pos, end - pos);
goto error;
}
return key;
error:
crypto_rsa_free(key);
return NULL;
}
/**
* crypto_rsa_import_private_key - Import an RSA private key
* @buf: Key buffer (DER encoded RSA private key)
* @len: Key buffer length in bytes
* Returns: Pointer to the private key or %NULL on failure
*/
struct crypto_rsa_key *
crypto_rsa_import_private_key(const u8 *buf, size_t len)
{
struct crypto_rsa_key *key;
struct bignum *zero;
struct asn1_hdr hdr;
const u8 *pos, *end;
key = os_zalloc(sizeof(*key));
if (key == NULL)
return NULL;
key->private_key = 1;
key->n = bignum_init();
key->e = bignum_init();
key->d = bignum_init();
key->p = bignum_init();
key->q = bignum_init();
key->dmp1 = bignum_init();
key->dmq1 = bignum_init();
key->iqmp = bignum_init();
if (key->n == NULL || key->e == NULL || key->d == NULL ||
key->p == NULL || key->q == NULL || key->dmp1 == NULL ||
key->dmq1 == NULL || key->iqmp == NULL) {
crypto_rsa_free(key);
return NULL;
}
/*
* PKCS #1, 7.2:
* RSAPrivateKey ::= SEQUENCE {
* version Version,
* modulus INTEGER, -- n
* publicExponent INTEGER, -- e
* privateExponent INTEGER, -- d
* prime1 INTEGER, -- p
* prime2 INTEGER, -- q
* exponent1 INTEGER, -- d mod (p-1)
* exponent2 INTEGER, -- d mod (q-1)
* coefficient INTEGER -- (inverse of q) mod p
* }
*
* Version ::= INTEGER -- shall be 0 for this version of the standard
*/
if (asn1_get_next(buf, len, &hdr) < 0 ||
hdr.class != ASN1_CLASS_UNIVERSAL ||
hdr.tag != ASN1_TAG_SEQUENCE) {
wpa_printf(MSG_DEBUG, "RSA: Expected SEQUENCE "
"(public key) - found class %d tag 0x%x",
hdr.class, hdr.tag);
goto error;
}
pos = hdr.payload;
end = pos + hdr.length;
zero = bignum_init();
if (zero == NULL)
goto error;
pos = crypto_rsa_parse_integer(pos, end, zero);
if (pos == NULL || bignum_cmp_d(zero, 0) != 0) {
wpa_printf(MSG_DEBUG, "RSA: Expected zero INTEGER in the "
"beginning of private key; not found");
bignum_deinit(zero);
goto error;
}
bignum_deinit(zero);
pos = crypto_rsa_parse_integer(pos, end, key->n);
pos = crypto_rsa_parse_integer(pos, end, key->e);
pos = crypto_rsa_parse_integer(pos, end, key->d);
pos = crypto_rsa_parse_integer(pos, end, key->p);
pos = crypto_rsa_parse_integer(pos, end, key->q);
pos = crypto_rsa_parse_integer(pos, end, key->dmp1);
pos = crypto_rsa_parse_integer(pos, end, key->dmq1);
pos = crypto_rsa_parse_integer(pos, end, key->iqmp);
if (pos == NULL)
goto error;
if (pos != end) {
wpa_hexdump(MSG_DEBUG,
"RSA: Extra data in public key SEQUENCE",
pos, end - pos);
goto error;
}
return key;
error:
crypto_rsa_free(key);
return NULL;
}
/**
* crypto_rsa_get_modulus_len - Get the modulus length of the RSA key
* @key: RSA key
* Returns: Modulus length of the key
*/
size_t crypto_rsa_get_modulus_len(struct crypto_rsa_key *key)
{
return bignum_get_unsigned_bin_len(key->n);
}
/**
* crypto_rsa_exptmod - RSA modular exponentiation
* @in: Input data
* @inlen: Input data length
* @out: Buffer for output data
* @outlen: Maximum size of the output buffer and used size on success
* @key: RSA key
* @use_private: 1 = Use RSA private key, 0 = Use RSA public key
* Returns: 0 on success, -1 on failure
*/
int crypto_rsa_exptmod(const u8 *in, size_t inlen, u8 *out, size_t *outlen,
struct crypto_rsa_key *key, int use_private)
{
struct bignum *tmp, *a = NULL, *b = NULL;
int ret = -1;
size_t modlen;
if (use_private && !key->private_key)
return -1;
tmp = bignum_init();
if (tmp == NULL)
return -1;
if (bignum_set_unsigned_bin(tmp, in, inlen) < 0)
goto error;
if (bignum_cmp(key->n, tmp) < 0) {
/* Too large input value for the RSA key modulus */
goto error;
}
if (use_private) {
/*
* Decrypt (or sign) using Chinese remainer theorem to speed
* up calculation. This is equivalent to tmp = tmp^d mod n
* (which would require more CPU to calculate directly).
*
* dmp1 = (1/e) mod (p-1)
* dmq1 = (1/e) mod (q-1)
* iqmp = (1/q) mod p, where p > q
* m1 = c^dmp1 mod p
* m2 = c^dmq1 mod q
* h = q^-1 (m1 - m2) mod p
* m = m2 + hq
*/
a = bignum_init();
b = bignum_init();
if (a == NULL || b == NULL)
goto error;
/* a = tmp^dmp1 mod p */
if (bignum_exptmod(tmp, key->dmp1, key->p, a) < 0)
goto error;
/* b = tmp^dmq1 mod q */
if (bignum_exptmod(tmp, key->dmq1, key->q, b) < 0)
goto error;
/* tmp = (a - b) * (1/q mod p) (mod p) */
if (bignum_sub(a, b, tmp) < 0 ||
bignum_mulmod(tmp, key->iqmp, key->p, tmp) < 0)
goto error;
/* tmp = b + q * tmp */
if (bignum_mul(tmp, key->q, tmp) < 0 ||
bignum_add(tmp, b, tmp) < 0)
goto error;
} else {
/* Encrypt (or verify signature) */
/* tmp = tmp^e mod N */
if (bignum_exptmod(tmp, key->e, key->n, tmp) < 0)
goto error;
}
modlen = crypto_rsa_get_modulus_len(key);
if (modlen > *outlen) {
*outlen = modlen;
goto error;
}
if (bignum_get_unsigned_bin_len(tmp) > modlen)
goto error; /* should never happen */
*outlen = modlen;
os_memset(out, 0, modlen);
if (bignum_get_unsigned_bin(
tmp, out +
(modlen - bignum_get_unsigned_bin_len(tmp)), NULL) < 0)
goto error;
ret = 0;
error:
bignum_deinit(tmp);
bignum_deinit(a);
bignum_deinit(b);
return ret;
}
/**
* crypto_rsa_free - Free RSA key
* @key: RSA key to be freed
*
* This function frees an RSA key imported with either
* crypto_rsa_import_public_key() or crypto_rsa_import_private_key().
*/
void crypto_rsa_free(struct crypto_rsa_key *key)
{
if (key) {
bignum_deinit(key->n);
bignum_deinit(key->e);
bignum_deinit(key->d);
bignum_deinit(key->p);
bignum_deinit(key->q);
bignum_deinit(key->dmp1);
bignum_deinit(key->dmq1);
bignum_deinit(key->iqmp);
os_free(key);
}
}