security: fix for vulnerability CVE-2014-0017
When accepting a new connection, a forking server based on libssh forks and the child process handles the request. The RAND_bytes() function of openssl doesn't reset its state after the fork, but simply adds the current process id (getpid) to the PRNG state, which is not guaranteed to be unique. This can cause several children to end up with same PRNG state which is a security issue.
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родитель
c96e862c08
Коммит
e99246246b
@ -70,5 +70,6 @@ int crypt_set_algorithms_server(ssh_session session);
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struct ssh_crypto_struct *crypto_new(void);
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void crypto_free(struct ssh_crypto_struct *crypto);
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void ssh_reseed(void);
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#endif /* WRAPPER_H_ */
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@ -458,6 +458,8 @@ int ssh_bind_accept_fd(ssh_bind sshbind, ssh_session session, socket_t fd){
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return SSH_ERROR;
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}
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}
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/* force PRNG to change state in case we fork after ssh_bind_accept */
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ssh_reseed();
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return SSH_OK;
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}
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@ -23,6 +23,7 @@
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/time.h>
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#include "libssh/priv.h"
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#include "libssh/session.h"
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@ -38,6 +39,8 @@
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#include <openssl/rsa.h>
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#include <openssl/hmac.h>
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#include <openssl/opensslv.h>
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#include <openssl/rand.h>
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#ifdef HAVE_OPENSSL_AES_H
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#define HAS_AES
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#include <openssl/aes.h>
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@ -74,6 +77,12 @@ static int alloc_key(struct ssh_cipher_struct *cipher) {
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return 0;
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}
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void ssh_reseed(void){
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struct timeval tv;
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gettimeofday(&tv, NULL);
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RAND_add(&tv, sizeof(tv), 0.0);
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}
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SHACTX sha1_init(void) {
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SHACTX c = malloc(sizeof(*c));
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if (c == NULL) {
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@ -45,6 +45,9 @@ static int alloc_key(struct ssh_cipher_struct *cipher) {
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return 0;
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}
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void ssh_reseed(void){
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}
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SHACTX sha1_init(void) {
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SHACTX ctx = NULL;
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gcry_md_open(&ctx, GCRY_MD_SHA1, 0);
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