1 files changed, 156 insertions, 0 deletions

diff --git a/gss-genr.c b/gss-genr.c
index c2b4f2dd8..2a905f5e9 100644
--- a/gss-genr.c
+++ b/gss-genr.c
@@ -32,12 +32,137 @@
 #include "bufaux.h"
 #include "log.h"
 #include "ssh2.h"
+#include <openssl/evp.h>
 
 #include "ssh-gss.h"
 
 extern u_char *session_id2;
 extern u_int session_id2_len;
 
+typedef struct {
+        char *encoded;
+        gss_OID oid;
+} ssh_gss_kex_mapping;
+
+/*
+ * XXX - It would be nice to find a more elegant way of handling the
+ * XXX   passing of the key exchange context to the userauth routines
+ */
+
+Gssctxt *gss_kex_context = NULL;
+
+static ssh_gss_kex_mapping *gss_enc2oid = NULL;
+
+/*
+ * Return a list of the gss-group1-sha1 mechanisms supported by this program
+ *
+ * We test mechanisms to ensure that we can use them, to avoid starting
+ * a key exchange with a bad mechanism
+ */
+
+
+char *
+ssh_gssapi_client_mechanisms(char *host) {
+        gss_OID_set gss_supported;
+        OM_uint32 min_status;
+
+        gss_indicate_mechs(&min_status, &gss_supported);
+
+        return(ssh_gssapi_kex_mechs(gss_supported, ssh_gssapi_check_mechanism,
+            (void *)host));
+}
+
+char *
+ssh_gssapi_kex_mechs(gss_OID_set gss_supported, ssh_gssapi_check_fn *check,
+    void *data) {
+        Buffer buf;
+        int i, oidpos, enclen;
+        char *mechs, *encoded;
+        char digest[EVP_MAX_MD_SIZE];
+        char deroid[2];
+        const EVP_MD *evp_md = EVP_md5();
+        EVP_MD_CTX md;
+
+        evp_md = EVP_md5();
+
+        if (gss_enc2oid != NULL) {
+                for (i=0;gss_enc2oid[i].encoded!=NULL;i++)
+                        xfree(gss_enc2oid[i].encoded);
+                xfree(gss_enc2oid);
+        }
+
+        gss_enc2oid = xmalloc(sizeof(ssh_gss_kex_mapping)*
+            (gss_supported->count+1));
+
+        buffer_init(&buf);
+
+        oidpos = 0;
+        for (i=0;i<gss_supported->count;i++) {
+                if (gss_supported->elements[i].length<128 &&
+                    (*check)(&(gss_supported->elements[i]), data)) {
+
+                        deroid[0] = SSH_GSS_OIDTYPE;
+                        deroid[1] = gss_supported->elements[i].length;
+                        EVP_DigestInit(&md, evp_md);
+                        EVP_DigestUpdate(&md, deroid, 2);
+                        EVP_DigestUpdate(&md,
+                            gss_supported->elements[i].elements,
+                            gss_supported->elements[i].length);
+                        EVP_DigestFinal(&md, digest, NULL);
+
+                        encoded = xmalloc(EVP_MD_size(evp_md)*2);
+                        enclen = __b64_ntop(digest, EVP_MD_size(evp_md),
+                            encoded, EVP_MD_size(evp_md)*2);
+
+                        if (oidpos != 0)
+                            buffer_put_char(&buf,',');
+
+                        buffer_append(&buf, KEX_GSS_SHA1, 
+                            sizeof(KEX_GSS_SHA1)-1);
+                        buffer_append(&buf, encoded, enclen);
+
+                        gss_enc2oid[oidpos].oid = &(gss_supported->elements[i]);
+                        gss_enc2oid[oidpos].encoded = encoded;
+                        oidpos++;
+                }
+        }
+        gss_enc2oid[oidpos].oid = NULL;
+        gss_enc2oid[oidpos].encoded = NULL;
+
+        buffer_put_char(&buf,'\0');
+
+        mechs = xmalloc(buffer_len(&buf));
+        buffer_get(&buf, mechs, buffer_len(&buf));
+        buffer_free(&buf);
+
+        if (strlen(mechs) == 0) {
+                xfree(mechs);
+                mechs = NULL;
+        }
+        
+        return (mechs);
+}
+
+gss_OID
+ssh_gssapi_id_kex(Gssctxt *ctx, char *name) {
+        int i = 0;
+
+        if (strncmp(name, KEX_GSS_SHA1, sizeof(KEX_GSS_SHA1)-1) != 0) 
+                return NULL;
+
+        name+=sizeof(KEX_GSS_SHA1)-1; /* Skip ID string */
+
+        while (gss_enc2oid[i].encoded != NULL &&
+            strcmp(name,gss_enc2oid[i].encoded)!=0) {
+                i++;
+        }
+
+        if (gss_enc2oid[i].oid != NULL && ctx != NULL)
+                ssh_gssapi_set_oid(ctx,gss_enc2oid[i].oid);
+
+        return gss_enc2oid[i].oid;
+}
+
 /* Check that the OID in a data stream matches that in the context */
 int
 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
@@ -248,6 +373,9 @@ ssh_gssapi_acquire_cred(Gssctxt *ctx)
 OM_uint32
 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
 {
+        if (ctx == NULL) 
+                return -1;
+
         if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
             GSS_C_QOP_DEFAULT, buffer, hash)))
                 ssh_gssapi_error(ctx);
@@ -255,6 +383,19 @@ ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
         return (ctx->major);
 }
 
+/* Priviledged when used by server */
+OM_uint32
+ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
+{
+        if (ctx == NULL)
+                return -1;
+
+        ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
+            gssbuf, gssmic, NULL);
+
+        return (ctx->major);
+}
+
 void
 ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
     const char *context)
@@ -277,4 +418,19 @@ ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
         return (ssh_gssapi_acquire_cred(*ctx));
 }
 
+int
+ssh_gssapi_check_mechanism(gss_OID oid, void *host) {
+        Gssctxt * ctx = NULL;
+        gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
+        OM_uint32 major, minor;
+        
+        ssh_gssapi_build_ctx(&ctx);
+        ssh_gssapi_set_oid(ctx, oid);
+        ssh_gssapi_import_name(ctx, host);
+        major = ssh_gssapi_init_ctx(ctx, 0, GSS_C_NO_BUFFER, &token, NULL);
+        gss_release_buffer(&minor, &token);
+        ssh_gssapi_delete_ctx(&ctx);
+        return (!GSS_ERROR(major));
+}
+
 #endif /* GSSAPI */