X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=crypt.c;h=f064fb3a535d9df3306818d7e9c27ca85193bd50;hp=73eebe180dbe2c32718b5dc7fd271f7ca4b329b1;hb=e9ac00becb2aba5bbbf51b4803b81b10ed4d6788;hpb=002731cd3938f3be6b71651e56c062af1adcdec0

diff --git a/crypt.c b/crypt.c
index 73eebe18..f064fb3a 100644
--- a/crypt.c
+++ b/crypt.c
@@ -1,21 +1,75 @@
 /*
- * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2005-2011 Andre Noll <maan@systemlinux.org>
  *
  * 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 <regex.h>
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <openssl/rand.h>
+#include <openssl/err.h>
+#include <openssl/rc4.h>
+#include <openssl/pem.h>
+#include <openssl/sha.h>
+#include <openssl/bn.h>
 
 #include "para.h"
 #include "error.h"
 #include "string.h"
 #include "crypt.h"
+#include "fd.h"
+#include "crypt_backend.h"
+
+struct asymmetric_key {
+	RSA *rsa;
+};
+
+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);
+}
+
+/*
+ * Read 64 bytes from /dev/urandom and adds them to the SSL PRNG. Seed the PRNG
+ * used by random() with a random seed obtained from SSL. If /dev/random is not
+ * readable 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 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;
@@ -29,18 +83,7 @@ static EVP_PKEY *load_key(const char *file, int private)
 	return pkey;
 }
 
-/**
- * read an RSA 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
- *
- * \return The size of the RSA key on success, negative on errors.
- *
- * \sa openssl(1), rsa(1).
- */
-int get_rsa_key(char *key_file, RSA **rsa, int private)
+static int get_openssl_key(const char *key_file, RSA **rsa, int private)
 {
 	EVP_PKEY *key = load_key(key_file, private);
 
@@ -54,119 +97,230 @@ int get_rsa_key(char *key_file, RSA **rsa, int private)
 	return RSA_size(*rsa);
 }
 
-/**
- * free an RSA structure
- *
- * \param rsa pointer to the RSA struct to free
- *
- * This must be called for any key obtained by get_rsa_key().
+/*
+ * The public key loading functions below were inspired by corresponding code
+ * of openssh-5.2p1, Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo,
+ * Finland. However, not much of the original code remains.
  */
-void rsa_free(RSA *rsa)
+
+static int read_bignum(const unsigned char *buf, size_t len, BIGNUM **result)
 {
-	if (rsa)
-		RSA_free(rsa);
+	const unsigned char *p = buf, *end = buf + len;
+	uint32_t bnsize;
+	BIGNUM *bn;
+
+	if (p + 4 < p)
+		return -E_BIGNUM;
+	if (p + 4 > end)
+		return -E_BIGNUM;
+	bnsize = read_ssh_u32(p);
+	PARA_DEBUG_LOG("bnsize: %u\n", bnsize);
+	p += 4;
+	if (p + bnsize < p)
+		return -E_BIGNUM;
+	if (p + bnsize > end)
+		return -E_BIGNUM;
+	if (bnsize > 8192)
+		return -E_BIGNUM;
+	bn = BN_bin2bn(p, bnsize, NULL);
+	if (!bn)
+		return -E_BIGNUM;
+	*result = bn;
+	return bnsize + 4;
 }
 
-/**
- * decrypt a buffer using an RSA 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
- *
- * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
- *
- * \return The size of the recovered plaintext on success, negative on errors.
- *
- * \sa RSA_private_decrypt(3)
- **/
-int para_decrypt_buffer(char *key_file, unsigned char *outbuf, unsigned char *inbuf,
-			unsigned rsa_inlen)
+static int read_rsa_bignums(const unsigned char *blob, int blen, RSA **result)
 {
+	int ret;
 	RSA *rsa;
-	int ret, inlen = rsa_inlen;
+	const unsigned char *p = blob, *end = blob + blen;
 
-	if (inlen < 0)
-		return -E_RSA;
-	ret = get_rsa_key(key_file, &rsa, LOAD_PRIVATE_KEY);
+	rsa = RSA_new();
+	if (!rsa)
+		return -E_BIGNUM;
+	ret = read_bignum(p, end - p, &rsa->e);
 	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;
+		goto fail;
+	p += ret;
+	ret = read_bignum(p, end - p, &rsa->n);
+	if (ret < 0)
+		goto fail;
+	*result = rsa;
+	return 1;
+fail:
+	if (rsa)
+		RSA_free(rsa);
+	return ret;
 }
 
-/**
- * decrypt the challenge number sent by para_server
- *
- * \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
- *
- * \return positive on success, negative on errors
- *
- * \sa para_decrypt_buffer()
- */
-int para_decrypt_challenge(char *key_file, long unsigned *challenge_nr,
-		unsigned char *inbuf, unsigned rsa_inlen)
+int get_asymmetric_key(const char *key_file, int private,
+		struct asymmetric_key **result)
 {
-	unsigned char *rsa_out = OPENSSL_malloc(rsa_inlen + 1);
-	int ret = para_decrypt_buffer(key_file, rsa_out, inbuf, rsa_inlen);
+	struct asymmetric_key *key = NULL;
+	void *map = NULL;
+	unsigned char *blob = NULL;
+	size_t map_size, blob_size, decoded_size;
+	int ret, ret2;
+	char *cp;
 
-	if (ret >= 0) {
-		rsa_out[ret] = '\0';
-		ret = sscanf((char *)rsa_out, "%lu", challenge_nr) == 1?
-			1 : -E_CHALLENGE;
+	key = para_malloc(sizeof(*key));
+	if (private) {
+		ret = get_openssl_key(key_file, &key->rsa, LOAD_PRIVATE_KEY);
+		goto out;
+	}
+	ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
+	if (ret < 0)
+		goto out;
+	ret = is_ssh_rsa_key(map, map_size);
+	if (!ret) {
+		ret = para_munmap(map, map_size);
+		map = NULL;
+		if (ret < 0)
+			goto out;
+		ret = get_openssl_key(key_file, &key->rsa, LOAD_PUBLIC_KEY);
+		goto out;
 	}
-	OPENSSL_free(rsa_out);
+	cp = map + ret;
+	PARA_INFO_LOG("decoding public rsa-ssh key %s\n", key_file);
+	ret = -ERRNO_TO_PARA_ERROR(EOVERFLOW);
+	if (map_size > INT_MAX / 4)
+		goto out;
+	blob_size = 2 * map_size;
+	blob = para_malloc(blob_size);
+	ret = uudecode(cp, blob, blob_size);
+	if (ret < 0)
+		goto out;
+	decoded_size = ret;
+	ret = check_ssh_key_header(blob, decoded_size);
+	if (ret < 0)
+		goto out;
+	ret = read_rsa_bignums(blob + ret, decoded_size - ret, &key->rsa);
+	if (ret < 0)
+		goto out;
+	ret = RSA_size(key->rsa);
+out:
+	ret2 = para_munmap(map, map_size);
+	if (ret >= 0 && ret2 < 0)
+		ret = ret2;
+	if (ret < 0) {
+		free(key);
+		result = NULL;
+		PARA_ERROR_LOG("key %s: %s\n", key_file, para_strerror(-ret));
+	} else
+		*result = key;
+	free(blob);
 	return ret;
 }
 
-/**
- * encrypt a buffer using an RSA key
- *
- * \param rsa: public rsa key
- * \param inbuf the input buffer
- * \param len the length of \a inbuf
- * \param outbuf the output buffer
- *
- * \return The size of the encrypted data on success, negative on errors
- *
- * \sa RSA_public_encrypt(3)
- */
-int para_encrypt_buffer(RSA *rsa, unsigned char *inbuf,
+void free_asymmetric_key(struct asymmetric_key *key)
+{
+	if (!key)
+		return;
+	RSA_free(key->rsa);
+	free(key);
+}
+
+int priv_decrypt(const char *key_file, unsigned char *outbuf,
+		unsigned char *inbuf, int inlen)
+{
+	struct asymmetric_key *priv;
+	int ret;
+
+	if (inlen < 0)
+		return -E_RSA;
+	ret = get_asymmetric_key(key_file, LOAD_PRIVATE_KEY, &priv);
+	if (ret < 0)
+		return ret;
+	/*
+	 * 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;
+}
+
+int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
 		unsigned len, unsigned char *outbuf)
 {
 	int ret, flen = len; /* RSA_public_encrypt expects a signed int */
 
 	if (flen < 0)
 		return -E_ENCRYPT;
-	ret = RSA_public_encrypt(flen, inbuf, outbuf, rsa, RSA_PKCS1_PADDING);
-	return ret < 0?  -E_ENCRYPT : ret;
+	ret = RSA_public_encrypt(flen, inbuf, outbuf, pub->rsa,
+		RSA_PKCS1_OAEP_PADDING);
+	return ret < 0? -E_ENCRYPT : ret;
+}
+
+struct stream_cipher {
+	RC4_KEY key;
+};
+
+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;
+}
+
+void sc_free(struct stream_cipher *sc)
+{
+	free(sc);
 }
 
 /**
- * encrypt the given challenge number
- *
- * \param rsa: public rsa key
- * \param challenge_nr the number to be encrypted
- * \param outbuf the output buffer
- *
- * \a outbuf must be at least 64 bytes long
- *
- * \return The size of the encrypted data on success, negative on errors
- *
- * \sa para_encrypt_buffer()
- *
+ * The RC4() implementation of openssl apparently reads and writes data in
+ * blocks of 8 bytes. So we have to make sure our buffer sizes are a multiple
+ * of this.
  */
-int para_encrypt_challenge(RSA* rsa, long unsigned challenge_nr,
-	unsigned char *outbuf)
+#define RC4_ALIGN 8
+
+int sc_send_bin_buffer(struct stream_cipher_context *scc, char *buf,
+		size_t len)
 {
-	unsigned char *inbuf = (unsigned char*) make_message("%lu", challenge_nr);
-	int ret = para_encrypt_buffer(rsa, inbuf, strlen((char *)inbuf), outbuf);
-	free(inbuf);
+	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);
+
+	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;
 }
 
+int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
+		size_t size)
+{
+	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;
+}
+
+void hash_function(const char *data, unsigned long len, unsigned char *hash)
+{
+	SHA_CTX c;
+	SHA1_Init(&c);
+	SHA1_Update(&c, data, len);
+	SHA1_Final(hash, &c);
+}