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authorAris Adamantiadis <aris@0xbadc0de.be>2014-02-05 20:24:12 (GMT)
committer Aris Adamantiadis <aris@0xbadc0de.be>2014-03-04 08:54:25 (GMT)
commit48f0bfc70363ca31c8889ca68759e587bc6d7cbd (patch)
tree57bc7d4da024be3bfce56749daccb1dd1faabf33
parent87549f7bb6a570481f377e628001a04175f7d3a5 (diff)
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security: fix for vulnerability CVE-2014-0017v0-5
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. Conflicts: src/bind.c
-rw-r--r--include/libssh/wrapper.h1
-rw-r--r--src/bind.c3
-rw-r--r--src/libcrypto.c9
-rw-r--r--src/libgcrypt.c3
4 files changed, 15 insertions, 1 deletions
diff --git a/include/libssh/wrapper.h b/include/libssh/wrapper.h
index 8c03497..b8cd4d2 100644
--- a/include/libssh/wrapper.h
+++ b/include/libssh/wrapper.h
@@ -44,5 +44,6 @@ int crypt_set_algorithms_server(ssh_session session);
struct ssh_crypto_struct *crypto_new(void);
void crypto_free(struct ssh_crypto_struct *crypto);
+void ssh_reseed(void);
#endif /* WRAPPER_H_ */
diff --git a/src/bind.c b/src/bind.c
index cc79f8e..cdcdabe 100644
--- a/src/bind.c
+++ b/src/bind.c
@@ -374,7 +374,8 @@ int ssh_bind_accept(ssh_bind sshbind, ssh_session session) {
ssh_socket_get_poll_handle_out(session->socket);
session->dsa_key = dsa;
session->rsa_key = rsa;
-
+ /* force PRNG to change state in case we fork after ssh_bind_accept */
+ ssh_reseed();
return SSH_OK;
}
diff --git a/src/libcrypto.c b/src/libcrypto.c
index f43a91e..0932cbe 100644
--- a/src/libcrypto.c
+++ b/src/libcrypto.c
@@ -23,6 +23,7 @@
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
+#include <sys/time.h>
#include "libssh/priv.h"
#include "libssh/session.h"
@@ -38,6 +39,8 @@
#include <openssl/rsa.h>
#include <openssl/hmac.h>
#include <openssl/opensslv.h>
+#include <openssl/rand.h>
+
#ifdef HAVE_OPENSSL_AES_H
#define HAS_AES
#include <openssl/aes.h>
@@ -66,6 +69,12 @@ static int alloc_key(struct crypto_struct *cipher) {
return 0;
}
+void ssh_reseed(void){
+ struct timeval tv;
+ gettimeofday(&tv, NULL);
+ RAND_add(&tv, sizeof(tv), 0.0);
+}
+
SHACTX sha1_init(void) {
SHACTX c = malloc(sizeof(*c));
if (c == NULL) {
diff --git a/src/libgcrypt.c b/src/libgcrypt.c
index f8fe96f..9a7ea43 100644
--- a/src/libgcrypt.c
+++ b/src/libgcrypt.c
@@ -41,6 +41,9 @@ static int alloc_key(struct crypto_struct *cipher) {
return 0;
}
+void ssh_reseed(void){
+ }
+
SHACTX sha1_init(void) {
SHACTX ctx = NULL;
gcry_md_open(&ctx, GCRY_MD_SHA1, 0);