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libssh/libssh-0.8.6-fix-rsa-sha2-ext.patch
Anderson Toshiyuki Sasaki 129c4e7d94 Fix rsa-sha2 extension handling 
Resolves: #1666342
2019-01-15 16:40:16 +01:00

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From d028b2495d0bb2b7ae9b0af42b4377af4a964b00 Mon Sep 17 00:00:00 2001
From: Jakub Jelen <jjelen@redhat.com>
Date: Tue, 8 Jan 2019 11:32:10 +0100
Subject: [PATCH 1/3] dh: Make sure we do not access uninitialized memory
Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
(cherry picked from commit ca62632170c311923026f978c57d2e0a0be3e0e1)
---
src/dh.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/src/dh.c b/src/dh.c
index 90c1813c..cc12fd46 100644
--- a/src/dh.c
+++ b/src/dh.c
@@ -1274,6 +1274,10 @@ int ssh_get_server_publickey(ssh_session session, ssh_key *key)
ssh_key ssh_dh_get_current_server_publickey(ssh_session session)
{
+ if (session->current_crypto == NULL) {
+ return NULL;
+ }
+
return session->current_crypto->server_pubkey;
}
--
2.20.1
From 0acfd81f85f8c41547ac700782fa96a000abdc79 Mon Sep 17 00:00:00 2001
From: Jakub Jelen <jjelen@redhat.com>
Date: Mon, 7 Jan 2019 18:49:58 +0100
Subject: [PATCH 2/3] server: Correctly handle extensions
If the server had an RSA host key, it provided unconditionally SHA2
signatures without consulting the client proposed list of supported host
keys.
This commit implements more fine-grained detection of the extension
to provide the client with valid signatures according to RFC 8332
Section 3.1.
Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
(cherry picked from commit 27fe60954c29e548c30af239d92ab4faaf8cf788)
---
include/libssh/session.h | 7 ++++---
src/kex.c | 24 ++++++++++++++++++++----
src/server.c | 2 +-
3 files changed, 25 insertions(+), 8 deletions(-)
diff --git a/include/libssh/session.h b/include/libssh/session.h
index 8b963066..23633cc2 100644
--- a/include/libssh/session.h
+++ b/include/libssh/session.h
@@ -87,10 +87,11 @@ enum ssh_pending_call_e {
#define SSH_OPT_FLAG_GSSAPI_AUTH 0x8
/* extensions flags */
+/* negotiation enabled */
+#define SSH_EXT_NEGOTIATION 0x01
/* server-sig-algs extension */
-#define SSH_EXT_SIG_RSA_SHA256 0x01
-#define SSH_EXT_SIG_RSA_SHA512 0x02
-#define SSH_EXT_ALL SSH_EXT_SIG_RSA_SHA256 | SSH_EXT_SIG_RSA_SHA512
+#define SSH_EXT_SIG_RSA_SHA256 0x02
+#define SSH_EXT_SIG_RSA_SHA512 0x04
/* members that are common to ssh_session and ssh_bind */
struct ssh_common_struct {
diff --git a/src/kex.c b/src/kex.c
index 35a5a602..d9d0c7e5 100644
--- a/src/kex.c
+++ b/src/kex.c
@@ -526,13 +526,29 @@ SSH_PACKET_CALLBACK(ssh_packet_kexinit){
ok = ssh_match_group(session->next_crypto->client_kex.methods[SSH_KEX],
KEX_EXTENSION_CLIENT);
if (ok) {
+ const char *hostkeys = NULL;
+
+ /* The client supports extension negotiation */
+ session->extensions |= SSH_EXT_NEGOTIATION;
/*
- * Enable all the supported extensions and when the time comes
- * (after NEWKEYS) send them to the client.
+ * RFC 8332 Section 3.1: Use for Server Authentication
+ * Check what algorithms were provided in the SSH_HOSTKEYS list
+ * by the client and enable the respective extensions to provide
+ * correct signature in the next packet if RSA is negotiated
*/
+ hostkeys = session->next_crypto->client_kex.methods[SSH_HOSTKEYS];
+ ok = ssh_match_group(hostkeys, "rsa-sha2-512");
+ if (ok) {
+ session->extensions |= SSH_EXT_SIG_RSA_SHA512;
+ }
+ ok = ssh_match_group(hostkeys, "rsa-sha2-256");
+ if (ok) {
+ session->extensions |= SSH_EXT_SIG_RSA_SHA256;
+ }
SSH_LOG(SSH_LOG_DEBUG, "The client supports extension "
- "negotiation: enabling all extensions");
- session->extensions = SSH_EXT_ALL;
+ "negotiation. Enabled signature algorithms: %s%s",
+ session->extensions & SSH_EXT_SIG_RSA_SHA256 ? "SHA256" : "",
+ session->extensions & SSH_EXT_SIG_RSA_SHA512 ? " SHA512" : "");
}
/*
diff --git a/src/server.c b/src/server.c
index 8197fd86..02471e91 100644
--- a/src/server.c
+++ b/src/server.c
@@ -523,7 +523,7 @@ static void ssh_server_connection_callback(ssh_session session){
* our supported extensions now. This is the first message after
* sending NEWKEYS message and after turning on crypto.
*/
- if (session->extensions &&
+ if (session->extensions & SSH_EXT_NEGOTIATION &&
session->session_state != SSH_SESSION_STATE_AUTHENTICATED) {
ssh_server_send_extensions(session);
}
--
2.20.1
From bfc39d578db2412d2ae379a105c3cb658f48748c Mon Sep 17 00:00:00 2001
From: Jakub Jelen <jjelen@redhat.com>
Date: Tue, 8 Jan 2019 14:27:39 +0100
Subject: [PATCH 3/3] kex: List also the SHA2 extension when ordering hostkey
algorithms
By default, the list of already stored known host types is preferred,
but this selection so far ignored the SHA2 extension and excluded these
keys in the KEXINIT list leading to not using this extension if not
explicitly enabled from configuration.
This commit extends the default list with the SHA2 signatures algoritms
and compares only base types so they can be listed in the KEXINIT list.
This adjust the tests to expect the full list of algorithms to pass.
Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
(cherry picked from commit 531b80a60bcb89c0ea09e85e36e240755407febf)
---
src/kex.c | 36 +++++++++++---------
tests/unittests/torture_knownhosts_parsing.c | 10 +++---
2 files changed, 26 insertions(+), 20 deletions(-)
diff --git a/src/kex.c b/src/kex.c
index d9d0c7e5..44d60f59 100644
--- a/src/kex.c
+++ b/src/kex.c
@@ -38,6 +38,7 @@
#include "libssh/curve25519.h"
#include "libssh/knownhosts.h"
#include "libssh/misc.h"
+#include "libssh/pki.h"
#ifdef HAVE_LIBGCRYPT
# define BLOWFISH "blowfish-cbc,"
@@ -619,6 +620,8 @@ char *ssh_client_select_hostkeys(ssh_session session)
"ecdsa-sha2-nistp521",
"ecdsa-sha2-nistp384",
"ecdsa-sha2-nistp256",
+ "rsa-sha2-512",
+ "rsa-sha2-256",
"ssh-rsa",
#ifdef HAVE_DSA
"ssh-dss",
@@ -644,29 +647,30 @@ char *ssh_client_select_hostkeys(ssh_session session)
for (i = 0; preferred_hostkeys[i] != NULL; ++i) {
bool found = false;
+ /* This is a signature type: We list also the SHA2 extensions */
+ enum ssh_keytypes_e base_preferred =
+ ssh_key_type_from_signature_name(preferred_hostkeys[i]);
for (it = ssh_list_get_iterator(algo_list);
it != NULL;
it = it->next) {
const char *algo = ssh_iterator_value(const char *, it);
- int cmp;
- int ok;
+ /* This is always key type so we do not have to care for the
+ * SHA2 extension */
+ enum ssh_keytypes_e base_algo = ssh_key_type_from_name(algo);
- cmp = strcmp(preferred_hostkeys[i], algo);
- if (cmp == 0) {
- ok = ssh_verify_existing_algo(SSH_HOSTKEYS, algo);
- if (ok) {
- if (needcomma) {
- strncat(methods_buffer,
- ",",
- sizeof(methods_buffer) - strlen(methods_buffer) - 1);
- }
+ if (base_preferred == base_algo) {
+ /* Matching the keys already verified it is a known type */
+ if (needcomma) {
strncat(methods_buffer,
- algo,
+ ",",
sizeof(methods_buffer) - strlen(methods_buffer) - 1);
- needcomma = 1;
- found = true;
}
+ strncat(methods_buffer,
+ preferred_hostkeys[i],
+ sizeof(methods_buffer) - strlen(methods_buffer) - 1);
+ needcomma = 1;
+ found = true;
}
}
/* Collect the rest of the algorithms in other buffer, that will
@@ -728,10 +732,10 @@ int ssh_set_client_kex(ssh_session session)
memset(client->methods, 0, KEX_METHODS_SIZE * sizeof(char **));
/* first check if we have specific host key methods */
- if(session->opts.wanted_methods[SSH_HOSTKEYS] == NULL){
+ if (session->opts.wanted_methods[SSH_HOSTKEYS] == NULL) {
/* Only if no override */
session->opts.wanted_methods[SSH_HOSTKEYS] =
- ssh_client_select_hostkeys(session);
+ ssh_client_select_hostkeys(session);
}
for (i = 0; i < KEX_METHODS_SIZE; i++) {
diff --git a/tests/unittests/torture_knownhosts_parsing.c b/tests/unittests/torture_knownhosts_parsing.c
index 148c5da8..a7a0d99d 100644
--- a/tests/unittests/torture_knownhosts_parsing.c
+++ b/tests/unittests/torture_knownhosts_parsing.c
@@ -310,8 +310,9 @@ torture_knownhosts_algorithms(void **state)
const char *knownhosts_file = *state;
char *algo_list = NULL;
ssh_session session;
- const char *expect = "ssh-ed25519,ssh-rsa,ecdsa-sha2-nistp521,"
- "ecdsa-sha2-nistp384,ecdsa-sha2-nistp256"
+ const char *expect = "ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa,"
+ "ecdsa-sha2-nistp521,ecdsa-sha2-nistp384,"
+ "ecdsa-sha2-nistp256"
#ifdef HAVE_DSA
",ssh-dss"
#endif
@@ -339,8 +340,9 @@ torture_knownhosts_algorithms_global(void **state)
const char *knownhosts_file = *state;
char *algo_list = NULL;
ssh_session session;
- const char *expect = "ssh-ed25519,ssh-rsa,ecdsa-sha2-nistp521,"
- "ecdsa-sha2-nistp384,ecdsa-sha2-nistp256"
+ const char *expect = "ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa,"
+ "ecdsa-sha2-nistp521,ecdsa-sha2-nistp384,"
+ "ecdsa-sha2-nistp256"
#ifdef HAVE_DSA
",ssh-dss"
#endif
--
2.20.1
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