- djm@cvs.openbsd.org 2013/04/19 01:06:50

     [authfile.c cipher.c cipher.h kex.c kex.h kexecdh.c kexecdhc.c kexecdhs.c]
     [key.c key.h mac.c mac.h packet.c ssh.1 ssh.c]
     add the ability to query supported ciphers, MACs, key type and KEX
     algorithms to ssh. Includes some refactoring of KEX and key type handling
     to be table-driven; ok markus@

1 files changed, 58 insertions, 28 deletions

diff --git a/kex.c b/kex.c
index 57a79dd9e..65a227bc1 100644
--- a/kex.c
+++ b/kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.c,v 1.88 2013/01/08 18:49:04 markus Exp $ */
+/* $OpenBSD: kex.c,v 1.89 2013/04/19 01:06:50 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  *
@@ -62,6 +62,55 @@ extern const EVP_MD *evp_ssh_sha256(void);
 static void kex_kexinit_finish(Kex *);
 static void kex_choose_conf(Kex *);
 
+struct kexalg {
+        char *name;
+        int type;
+        int ec_nid;
+        const EVP_MD *(*mdfunc)(void);
+};
+static const struct kexalg kexalgs[] = {
+        { KEX_DH1, KEX_DH_GRP1_SHA1, 0, EVP_sha1 },
+        { KEX_DH14, KEX_DH_GRP14_SHA1, 0, EVP_sha1 },
+        { KEX_DHGEX_SHA1, KEX_DH_GEX_SHA1, 0, EVP_sha1 },
+#if OPENSSL_VERSION_NUMBER >= 0x00907000L
+        { KEX_DHGEX_SHA256, KEX_DH_GEX_SHA256, 0, EVP_sha256 },
+        { KEX_ECDH_SHA2_NISTP256, KEX_ECDH_SHA2, NID_X9_62_prime256v1, EVP_sha256 },
+        { KEX_ECDH_SHA2_NISTP384, KEX_ECDH_SHA2, NID_secp384r1, EVP_sha384 },
+        { KEX_ECDH_SHA2_NISTP521, KEX_ECDH_SHA2, NID_secp521r1, EVP_sha512 },
+#endif
+        { NULL, -1, -1, NULL},
+};
+
+char *
+kex_alg_list(void)
+{
+        char *ret = NULL;
+        size_t nlen, rlen = 0;
+        const struct kexalg *k;
+
+        for (k = kexalgs; k->name != NULL; k++) {
+                if (ret != NULL)
+                        ret[rlen++] = '\n';
+                nlen = strlen(k->name);
+                ret = xrealloc(ret, 1, rlen + nlen + 2);
+                memcpy(ret + rlen, k->name, nlen + 1);
+                rlen += nlen;
+        }
+        return ret;
+}
+
+static const struct kexalg *
+kex_alg_by_name(const char *name)
+{
+        const struct kexalg *k;
+
+        for (k = kexalgs; k->name != NULL; k++) {
+                if (strcmp(k->name, name) == 0)
+                        return k;
+        }
+        return NULL;
+}
+
 /* Validate KEX method name list */
 int
 kex_names_valid(const char *names)
@@ -73,13 +122,7 @@ kex_names_valid(const char *names)
         s = cp = xstrdup(names);
         for ((p = strsep(&cp, ",")); p && *p != '\0';
             (p = strsep(&cp, ","))) {
-                if (strcmp(p, KEX_DHGEX_SHA256) != 0 &&
-                    strcmp(p, KEX_DHGEX_SHA1) != 0 &&
-                    strcmp(p, KEX_DH14) != 0 &&
-                    strcmp(p, KEX_DH1) != 0 &&
-                    (strncmp(p, KEX_ECDH_SHA2_STEM,
-                    sizeof(KEX_ECDH_SHA2_STEM) - 1) != 0 ||
-                    kex_ecdh_name_to_nid(p) == -1)) {
+                if (kex_alg_by_name(p) == NULL) {
                         error("Unsupported KEX algorithm \"%.100s\"", p);
                         xfree(s);
                         return 0;
@@ -348,29 +391,16 @@ choose_comp(Comp *comp, char *client, char *server)
 static void
 choose_kex(Kex *k, char *client, char *server)
 {
+        const struct kexalg *kexalg;
+
         k->name = match_list(client, server, NULL);
         if (k->name == NULL)
                 fatal("Unable to negotiate a key exchange method");
-        if (strcmp(k->name, KEX_DH1) == 0) {
-                k->kex_type = KEX_DH_GRP1_SHA1;
-                k->evp_md = EVP_sha1();
-        } else if (strcmp(k->name, KEX_DH14) == 0) {
-                k->kex_type = KEX_DH_GRP14_SHA1;
-                k->evp_md = EVP_sha1();
-        } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
-                k->kex_type = KEX_DH_GEX_SHA1;
-                k->evp_md = EVP_sha1();
-#if OPENSSL_VERSION_NUMBER >= 0x00907000L
-        } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
-                k->kex_type = KEX_DH_GEX_SHA256;
-                k->evp_md = evp_ssh_sha256();
-        } else if (strncmp(k->name, KEX_ECDH_SHA2_STEM,
-            sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) {
-                k->kex_type = KEX_ECDH_SHA2;
-                k->evp_md = kex_ecdh_name_to_evpmd(k->name);
-#endif
-        } else
-                fatal("bad kex alg %s", k->name);
+        if ((kexalg = kex_alg_by_name(k->name)) == NULL)
+                fatal("unsupported kex alg %s", k->name);
+        k->kex_type = kexalg->type;
+        k->evp_md = kexalg->mdfunc();
+        k->ec_nid = kexalg->ec_nid;
 }
 
 static void