upstream: add support for ECDSA keys in PKCS#11 tokens

Work by markus@ and Pedro Martelletto, feedback and ok me@

OpenBSD-Commit-ID: a37d651e221341376636056512bddfc16efb4424

1 files changed, 92 insertions, 11 deletions

diff --git a/ssh-pkcs11-client.c b/ssh-pkcs11-client.c
index d1241ce67..6e16b2f9a 100644
--- a/ssh-pkcs11-client.c
+++ b/ssh-pkcs11-client.c
@@ -1,6 +1,7 @@
-/* $OpenBSD: ssh-pkcs11-client.c,v 1.10 2018/07/09 21:59:10 markus Exp $ */
+/* $OpenBSD: ssh-pkcs11-client.c,v 1.12 2019/01/20 22:51:37 djm Exp $ */
 /*
  * Copyright (c) 2010 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2014 Pedro Martelletto. All rights reserved.
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -30,6 +31,7 @@
 #include <unistd.h>
 #include <errno.h>
 
+#include <openssl/ecdsa.h>
 #include <openssl/rsa.h>
 
 #include "openbsd-compat/openssl-compat.h"
@@ -113,8 +115,7 @@ pkcs11_terminate(void)
 }
 
 static int
-pkcs11_rsa_private_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa,
-    int padding)
+rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding)
 {
         struct sshkey key;      /* XXX */
         u_char *blob, *signature = NULL;
@@ -154,18 +155,89 @@ pkcs11_rsa_private_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa,
         return (ret);
 }
 
-/* redirect the private key encrypt operation to the ssh-pkcs11-helper */
+static ECDSA_SIG *
+ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
+    const BIGNUM *rp, EC_KEY *ec)
+{
+        struct sshkey key; /* XXX */
+        u_char *blob, *signature = NULL;
+        const u_char *cp;
+        size_t blen, slen = 0;
+        ECDSA_SIG *ret = NULL;
+        struct sshbuf *msg;
+        int r;
+
+        key.type = KEY_ECDSA;
+        key.ecdsa = ec;
+        key.ecdsa_nid = sshkey_ecdsa_key_to_nid(ec);
+        if (key.ecdsa_nid < 0) {
+                error("%s: couldn't get curve nid", __func__);
+                return (NULL);
+        }
+        if ((r = sshkey_to_blob(&key, &blob, &blen)) != 0) {
+                error("%s: sshkey_to_blob: %s", __func__, ssh_err(r));
+                return (NULL);
+        }
+        if ((msg = sshbuf_new()) == NULL)
+                fatal("%s: sshbuf_new failed", __func__);
+        if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
+            (r = sshbuf_put_string(msg, blob, blen)) != 0 ||
+            (r = sshbuf_put_string(msg, dgst, dgst_len)) != 0 ||
+            (r = sshbuf_put_u32(msg, 0)) != 0)
+                fatal("%s: buffer error: %s", __func__, ssh_err(r));
+        free(blob);
+        send_msg(msg);
+        sshbuf_reset(msg);
+
+        if (recv_msg(msg) == SSH2_AGENT_SIGN_RESPONSE) {
+                if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
+                        fatal("%s: buffer error: %s", __func__, ssh_err(r));
+                cp = signature;
+                ret = d2i_ECDSA_SIG(NULL, &cp, slen);
+                free(signature);
+        }
+
+        sshbuf_free(msg);
+        return (ret);
+}
+
+static RSA_METHOD       *helper_rsa;
+static EC_KEY_METHOD    *helper_ecdsa;
+
+/* redirect private key crypto operations to the ssh-pkcs11-helper */
+static void
+wrap_key(struct sshkey *k)
+{
+        if (k->type == KEY_RSA)
+                RSA_set_method(k->rsa, helper_rsa);
+        else if (k->type == KEY_ECDSA)
+                EC_KEY_set_method(k->ecdsa, helper_ecdsa);
+        else
+                fatal("%s: unknown key type", __func__);
+}
+
 static int
-wrap_key(RSA *rsa)
+pkcs11_start_helper_methods(void)
 {
-        static RSA_METHOD *helper_rsa;
+        if (helper_ecdsa != NULL)
+                return (0);
+
+        int (*orig_sign)(int, const unsigned char *, int, unsigned char *,
+            unsigned int *, const BIGNUM *, const BIGNUM *, EC_KEY *) = NULL;
+        if (helper_ecdsa != NULL)
+                return (0);
+        helper_ecdsa = EC_KEY_METHOD_new(EC_KEY_OpenSSL());
+        if (helper_ecdsa == NULL)
+                return (-1);
+        EC_KEY_METHOD_get_sign(helper_ecdsa, &orig_sign, NULL, NULL);
+        EC_KEY_METHOD_set_sign(helper_ecdsa, orig_sign, NULL, ecdsa_do_sign);
 
         if ((helper_rsa = RSA_meth_dup(RSA_get_default_method())) == NULL)
                 fatal("%s: RSA_meth_dup failed", __func__);
         if (!RSA_meth_set1_name(helper_rsa, "ssh-pkcs11-helper") ||
-            !RSA_meth_set_priv_enc(helper_rsa, pkcs11_rsa_private_encrypt))
+            !RSA_meth_set_priv_enc(helper_rsa, rsa_encrypt))
                 fatal("%s: failed to prepare method", __func__);
-        RSA_set_method(rsa, helper_rsa);
+
         return (0);
 }
 
@@ -174,6 +246,11 @@ pkcs11_start_helper(void)
 {
         int pair[2];
 
+        if (pkcs11_start_helper_methods() == -1) {
+                error("pkcs11_start_helper_methods failed");
+                return (-1);
+        }
+
         if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {
                 error("socketpair: %s", strerror(errno));
                 return (-1);
@@ -204,7 +281,7 @@ int
 pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp)
 {
         struct sshkey *k;
-        int r;
+        int r, type;
         u_char *blob;
         size_t blen;
         u_int nkeys, i;
@@ -222,7 +299,8 @@ pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp)
         send_msg(msg);
         sshbuf_reset(msg);
 
-        if (recv_msg(msg) == SSH2_AGENT_IDENTITIES_ANSWER) {
+        type = recv_msg(msg);
+        if (type == SSH2_AGENT_IDENTITIES_ANSWER) {
                 if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
                 *keysp = xcalloc(nkeys, sizeof(struct sshkey *));
@@ -234,10 +312,13 @@ pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp)
                                     __func__, ssh_err(r));
                         if ((r = sshkey_from_blob(blob, blen, &k)) != 0)
                                 fatal("%s: bad key: %s", __func__, ssh_err(r));
-                        wrap_key(k->rsa);
+                        wrap_key(k);
                         (*keysp)[i] = k;
                         free(blob);
                 }
+        } else if (type == SSH2_AGENT_FAILURE) {
+                if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
+                        nkeys = -1;
         } else {
                 nkeys = -1;
         }