X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=crypt.c;h=99804470783c04e3758e8800f87f083c4e54f623;hp=ba2e7df0c4c8cd2b88200f198c5dff8ae0db1155;hb=e4db7671a91a7552c642acc979f0eb278f8d467f;hpb=a7a37b282c4e936b2fb34c2bd7423f9f800dfd44 diff --git a/crypt.c b/crypt.c index ba2e7df0..99804470 100644 --- a/crypt.c +++ b/crypt.c @@ -1,33 +1,99 @@ /* - * Copyright (C) 2005-2007 Andre Noll + * Copyright (C) 2005-2011 Andre Noll * - * 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. - * - * 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. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA. + * Licensed under the GPL v2. For licencing details see COPYING. */ -/** \file crypt.c openssl-based RSA encryption/decryption routines */ +/** \file crypt.c Openssl-based encryption/decryption routines. */ + +#include +#include +#include +#include +#include +#include +#include +#include #include "para.h" #include "error.h" #include "string.h" #include "crypt.h" +#include "fd.h" + +struct asymmetric_key { + RSA *rsa; +}; + +/** + * Fill a buffer with random content. + * + * \param buf The buffer to fill. + * \param num The size of \a buf in bytes. + * + * This function puts \a num cryptographically strong pseudo-random bytes into + * buf. If libssl can not guarantee an unpredictable byte sequence (for example + * because the PRNG has not been seeded with enough randomness) the function + * logs an error message and calls exit(). + */ +void get_random_bytes_or_die(unsigned char *buf, int num) +{ + unsigned long err; + + /* RAND_bytes() returns 1 on success, 0 otherwise. */ + if (RAND_bytes(buf, num) == 1) + return; + err = ERR_get_error(); + PARA_EMERG_LOG("%s\n", ERR_reason_error_string(err)); + exit(EXIT_FAILURE); +} + +/** + * Seed pseudo random number generators. + * + * This function reads 64 bytes from /dev/urandom and adds them to the SSL + * PRNG. It also seeds the PRNG used by random() with a random seed obtained + * from SSL. If /dev/random could not be read, an error message is logged and + * the function calls exit(). + * + * \sa RAND_load_file(3), \ref get_random_bytes_or_die(), srandom(3), + * random(3), \ref para_random(). + */ +void init_random_seed_or_die(void) +{ + int seed, ret = RAND_load_file("/dev/urandom", 64); + + if (ret != 64) { + PARA_EMERG_LOG("could not seed PRNG (ret = %d)\n", ret); + exit(EXIT_FAILURE); + } + get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed)); + srandom(seed); +} + +static int check_key_file(const char *file, int private) +{ + struct stat st; + + if (stat(file, &st) != 0) + return -ERRNO_TO_PARA_ERROR(errno); + if (private != LOAD_PRIVATE_KEY) + return 0; + if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) + return -E_KEY_PERM; + return 1; +} static EVP_PKEY *load_key(const char *file, int private) { BIO *key; EVP_PKEY *pkey = NULL; + int ret = check_key_file(file, private); + if (ret < 0) { + PARA_ERROR_LOG("%s\n", para_strerror(-ret)); + return NULL; + } key = BIO_new(BIO_s_file()); if (!key) return NULL; @@ -42,50 +108,58 @@ static EVP_PKEY *load_key(const char *file, int private) } /** - * read an RSA key from a file + * Read an asymmetric key from a file. * - * \param key_file the file containing the key - * \param rsa RSA structure is returned here - * \param private if non-zero, read the private key, otherwise the public key + * \param key_file The file containing the key. + * \param private if non-zero, read the private key, otherwise the public key. + * \param result The key structure is returned here. * - * \return The size of the RSA key on success, negative on errors. + * \return The size of the key on success, negative on errors. * * \sa openssl(1), rsa(1). */ -int get_rsa_key(char *key_file, RSA **rsa, int private) +int get_asymmetric_key(const char *key_file, int private, + struct asymmetric_key **result) { - EVP_PKEY *key = load_key(key_file, private); + struct asymmetric_key *key; + RSA *rsa; + EVP_PKEY *pkey = load_key(key_file, private); - if (!key) + if (!pkey) return (private == LOAD_PRIVATE_KEY)? -E_PRIVATE_KEY : -E_PUBLIC_KEY; - *rsa = EVP_PKEY_get1_RSA(key); - EVP_PKEY_free(key); - if (!*rsa) + rsa = EVP_PKEY_get1_RSA(pkey); + EVP_PKEY_free(pkey); + if (!rsa) return -E_RSA; - return RSA_size(*rsa); + key = para_malloc(sizeof(*key)); + key->rsa = rsa; + *result = key; + return RSA_size(rsa); } /** - * free an RSA structure + * Deallocate an asymmetric key structure. * - * \param rsa pointer to the RSA struct to free + * \param key Pointer to the key structure to free. * - * This must be called for any key obtained by get_rsa_key(). + * This must be called for any key obtained by get_asymmetric_key(). */ -void rsa_free(RSA *rsa) +void free_asymmetric_key(struct asymmetric_key *key) { - if (rsa) - RSA_free(rsa); + if (!key) + return; + RSA_free(key->rsa); + free(key); } /** - * decrypt a buffer using an RSA key + * Decrypt a buffer using a private key. * - * \param key_file full path of the rsa key - * \param outbuf the output buffer - * \param inbuf the encrypted input buffer - * \param rsa_inlen the length of \a inbuf + * \param key_file Full path of the key. + * \param outbuf The output buffer. + * \param inbuf The encrypted input buffer. + * \param inlen The length of \a inbuf in bytes. * * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes. * @@ -93,92 +167,200 @@ void rsa_free(RSA *rsa) * * \sa RSA_private_decrypt(3) **/ -int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf, - unsigned rsa_inlen) +int priv_decrypt(const char *key_file, unsigned char *outbuf, + unsigned char *inbuf, int inlen) { - RSA *rsa; - int ret, inlen = rsa_inlen; + struct asymmetric_key *priv; + int ret; if (inlen < 0) return -E_RSA; - ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY); + ret = get_asymmetric_key(key_file, LOAD_PRIVATE_KEY, &priv); if (ret < 0) return ret; - ret = RSA_private_decrypt(inlen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING); - rsa_free(rsa); - return (ret > 0)? ret : -E_DECRYPT; + /* + * RSA is vulnerable to timing attacks. Generate a random blinding + * factor to protect against this kind of attack. + */ + ret = -E_BLINDING; + if (RSA_blinding_on(priv->rsa, NULL) == 0) + goto out; + ret = RSA_private_decrypt(inlen, inbuf, outbuf, priv->rsa, + RSA_PKCS1_OAEP_PADDING); + RSA_blinding_off(priv->rsa); + if (ret <= 0) + ret = -E_DECRYPT; +out: + free_asymmetric_key(priv); + return ret; } /** - * decrypt the challenge number sent by para_server + * Encrypt a buffer using an RSA key * - * \param key_file full path of the rsa key - * \param challenge_nr result is stored here - * \param inbuf the input buffer - * \param rsa_inlen the length of \a inbuf + * \param pub: The public key. + * \param inbuf The input buffer. + * \param len The length of \a inbuf. + * \param outbuf The output buffer. * - * \return positive on success, negative on errors + * \return The size of the encrypted data on success, negative on errors. * - * \sa para_decrypt_buffer() + * \sa RSA_public_encrypt(3) */ -int para_decrypt_challenge(char *key_file, long unsigned *challenge_nr, - unsigned char *inbuf, unsigned rsa_inlen) +int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf, + unsigned len, unsigned char *outbuf) { - unsigned char *rsa_out = OPENSSL_malloc(rsa_inlen + 1); - int ret = para_decrypt_buffer(key_file, rsa_out, inbuf, rsa_inlen); + int ret, flen = len; /* RSA_public_encrypt expects a signed int */ - if (ret >= 0) { - rsa_out[ret] = '\0'; - ret = sscanf((char *)rsa_out, "%lu", challenge_nr) == 1? - 1 : -E_CHALLENGE; - } - OPENSSL_free(rsa_out); - return ret; + if (flen < 0) + return -E_ENCRYPT; + ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa, + RSA_PKCS1_OAEP_PADDING); + return ret < 0? -E_ENCRYPT : ret; +} + +#define RC4_ALIGN 8 +struct stream_cipher { + RC4_KEY key; +}; + +/** + * Allocate and initialize a stream cipher structure. + * + * \param data The key. + * \param len The size of the key. + * + * \return A new stream cipher structure. + */ +struct stream_cipher *sc_new(const unsigned char *data, int len) +{ + struct stream_cipher *sc = para_malloc(sizeof(*sc)); + RC4_set_key(&sc->key, len, data); + return sc; } /** - * encrypt a buffer using an RSA key + * Deallocate a stream cipher structure. * - * \param rsa: public rsa key - * \param inbuf the input buffer - * \param len the length of \a inbuf - * \param outbuf the output buffer + * \param sc A stream cipher previously obtained by sc_new(). + */ +void sc_free(struct stream_cipher *sc) +{ + free(sc); +} + +/** + * Encrypt and send a buffer. * - * \return The size of the encrypted data on success, negative on errors + * \param scc The context. + * \param buf The buffer to send. + * \param len The size of \a buf in bytes. * - * \sa RSA_public_encrypt(3) + * \return The return value of the underyling call to write_all(). + * + * \sa \ref write_all(), RC4(3). */ -int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf, - unsigned len, unsigned char *outbuf) +int sc_send_bin_buffer(struct stream_cipher_context *scc, const char *buf, + size_t len) { - int ret, flen = len; /* RSA_public_encrypt expects a signed int */ + int ret; + unsigned char *tmp; + static unsigned char remainder[RC4_ALIGN]; + size_t l1 = ROUND_DOWN(len, RC4_ALIGN), l2 = ROUND_UP(len, RC4_ALIGN); - if (flen < 0) - return -E_ENCRYPT; - ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING); - return ret < 0? -E_ENCRYPT : ret; + assert(len); + tmp = para_malloc(l2); + RC4(&scc->send->key, l1, (const unsigned char *)buf, tmp); + if (len > l1) { + memcpy(remainder, buf + l1, len - l1); + RC4(&scc->send->key, len - l1, remainder, tmp + l1); + } + ret = write_all(scc->fd, (char *)tmp, &len); + free(tmp); + return ret; +} + +/** + * Encrypt and send a \p NULL-terminated buffer. + * + * \param scc The context. + * \param buf The buffer to send. + * + * \return The return value of the underyling call to sc_send_bin_buffer(). + */ +int sc_send_buffer(struct stream_cipher_context *scc, const char *buf) +{ + return sc_send_bin_buffer(scc, buf, strlen(buf)); } /** - * encrypt the given challenge number + * Format, encrypt and send a buffer. * - * \param rsa: public rsa key - * \param challenge_nr the number to be encrypted - * \param outbuf the output buffer + * \param scc The context. + * \param fmt A format string. * - * \a outbuf must be at least 64 bytes long + * \return The return value of the underyling call to sc_send_buffer(). + */ +__printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc, + const char *fmt, ...) +{ + char *msg; + int ret; + + PARA_VSPRINTF(fmt, msg); + ret = sc_send_buffer(scc, msg); + free(msg); + return ret; +} + +/** + * Receive a buffer and decrypt it. * - * \return The size of the encrypted data on success, negative on errors + * \param scc The context. + * \param buf The buffer to write the decrypted data to. + * \param size The size of \a buf. * - * \sa para_encrypt_buffer() + * \return The number of bytes received on success, negative on errors, zero if + * the peer has performed an orderly shutdown. * + * \sa recv(2), RC4(3). */ -int para_encrypt_challenge(RSA* rsa, long unsigned challenge_nr, - unsigned char *outbuf) +int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf, + size_t size) { - unsigned char *inbuf = (unsigned char*) make_message("%lu", challenge_nr); - int ret = para_encrypt_buffer(rsa, inbuf, strlen((char *)inbuf), outbuf); - free(inbuf); + unsigned char *tmp = para_malloc(size); + ssize_t ret = recv(scc->fd, tmp, size, 0); + + if (ret > 0) + RC4(&scc->recv->key, ret, tmp, (unsigned char *)buf); + else if (ret < 0) + ret = -ERRNO_TO_PARA_ERROR(errno); + free(tmp); return ret; } +/** + * Receive a buffer, decrypt it and write terminating NULL byte. + * + * \param scc The context. + * \param buf The buffer to write the decrypted data to. + * \param size The size of \a buf. + * + * Read at most \a size - 1 bytes from file descriptor given by \a scc, decrypt + * the received data and write a NULL byte at the end of the decrypted data. + * + * \return The return value of the underlying call to \ref + * sc_recv_bin_buffer(). + */ +int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size) +{ + int n; + + assert(size); + n = sc_recv_bin_buffer(scc, buf, size - 1); + if (n >= 0) + buf[n] = '\0'; + else + *buf = '\0'; + return n; +}