GSSAPI key exchange support

This patch has been rejected upstream: "None of the OpenSSH developers are
in favour of adding this, and this situation has not changed for several
years.  This is not a slight on Simon's patch, which is of fine quality, but
just that a) we don't trust GSSAPI implementations that much and b) we don't
like adding new KEX since they are pre-auth attack surface.  This one is
particularly scary, since it requires hooks out to typically root-owned
system resources."

However, quite a lot of people rely on this in Debian, and it's better to
have it merged into the main openssh package rather than having separate
-krb5 packages (as we used to have).  It seems to have a generally good
security history.

Origin: other, https://github.com/openssh-gsskex/openssh-gsskex/commits/debian/master
Bug: https://bugzilla.mindrot.org/show_bug.cgi?id=1242
Last-Updated: 2019-10-09

Patch-Name: gssapi.patch

1 files changed, 29 insertions, 0 deletions

diff --git a/kex.h b/kex.h
index a5ae6ac05..fe7141414 100644
--- a/kex.h
+++ b/kex.h
@@ -102,6 +102,15 @@ enum kex_exchange {
         KEX_ECDH_SHA2,
         KEX_C25519_SHA256,
         KEX_KEM_SNTRUP4591761X25519_SHA512,
+#ifdef GSSAPI
+        KEX_GSS_GRP1_SHA1,
+        KEX_GSS_GRP14_SHA1,
+        KEX_GSS_GRP14_SHA256,
+        KEX_GSS_GRP16_SHA512,
+        KEX_GSS_GEX_SHA1,
+        KEX_GSS_NISTP256_SHA256,
+        KEX_GSS_C25519_SHA256,
+#endif
         KEX_MAX
 };
 
@@ -153,6 +162,12 @@ struct kex {
         u_int   flags;
         int     hash_alg;
         int     ec_nid;
+#ifdef GSSAPI
+        int     gss_deleg_creds;
+        int     gss_trust_dns;
+        char    *gss_host;
+        char    *gss_client;
+#endif
         char    *failed_choice;
         int     (*verify_host_key)(struct sshkey *, struct ssh *);
         struct sshkey *(*load_host_public_key)(int, int, struct ssh *);
@@ -174,8 +189,10 @@ struct kex {
 
 int      kex_names_valid(const char *);
 char    *kex_alg_list(char);
+char    *kex_gss_alg_list(char);
 char    *kex_names_cat(const char *, const char *);
 int      kex_assemble_names(char **, const char *, const char *);
+int      kex_gss_names_valid(const char *);
 
 int      kex_exchange_identification(struct ssh *, int, const char *);
 
@@ -202,6 +219,12 @@ int	 kexgex_client(struct ssh *);
 int      kexgex_server(struct ssh *);
 int      kex_gen_client(struct ssh *);
 int      kex_gen_server(struct ssh *);
+#if defined(GSSAPI) && defined(WITH_OPENSSL)
+int      kexgssgex_client(struct ssh *);
+int      kexgssgex_server(struct ssh *);
+int      kexgss_client(struct ssh *);
+int      kexgss_server(struct ssh *);
+#endif
 
 int      kex_dh_keypair(struct kex *);
 int      kex_dh_enc(struct kex *, const struct sshbuf *, struct sshbuf **,
@@ -234,6 +257,12 @@ int	 kexgex_hash(int, const struct sshbuf *, const struct sshbuf *,
     const BIGNUM *, const u_char *, size_t,
     u_char *, size_t *);
 
+int      kex_gen_hash(int hash_alg, const struct sshbuf *client_version,
+    const struct sshbuf *server_version, const struct sshbuf *client_kexinit,
+    const struct sshbuf *server_kexinit, const struct sshbuf *server_host_key_blob,
+    const struct sshbuf *client_pub, const struct sshbuf *server_pub,
+    const struct sshbuf *shared_secret, u_char *hash, size_t *hashlen);
+
 void    kexc25519_keygen(u_char key[CURVE25519_SIZE], u_char pub[CURVE25519_SIZE])
         __attribute__((__bounded__(__minbytes__, 1, CURVE25519_SIZE)))
         __attribute__((__bounded__(__minbytes__, 2, CURVE25519_SIZE)));