degrade semi-gracefully when libfido2 is too old

2 files changed, 29 insertions, 3 deletions

diff --git a/configure.ac b/configure.ac
index 0f15ef2bf..756e26572 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3180,9 +3180,14 @@ if test "x$enable_sk" = "xyes" -a "x$enable_sk_internal" = "xyes" ; then
                 ], [ AC_MSG_ERROR([no usable libfido2 found]) ],
                 [ $OTHERLIBS ]
         )
-        AC_CHECK_LIB([fido2], [fido_cred_set_prot], [],
-                [ AC_MSG_ERROR([libfido2 missing fido_cred_set_prot; please use libfido2 >= 1.4.0]) ],
-        )
+        saved_LIBS="$LIBS"
+        LIBS="$LIBS $LIBFIDO2"
+        AC_CHECK_FUNCS([ \
+                fido_cred_set_prot \
+                fido_dev_get_touch_status \
+                fido_dev_supports_cred_prot \
+        ])
+        LIBS="$saved_LIBS"
         AC_CHECK_HEADER([fido.h], [],
                 AC_MSG_ERROR([missing fido.h from libfido2]))
         AC_CHECK_HEADER([fido/credman.h], [],
diff --git a/sk-usbhid.c b/sk-usbhid.c
index 0305683fe..0b11e40aa 100644
--- a/sk-usbhid.c
+++ b/sk-usbhid.c
@@ -41,6 +41,17 @@
 #include <fido.h>
 #include <fido/credman.h>
 
+/* backwards compat for libfido2 */
+#ifndef HAVE_FIDO_DEV_SUPPORTS_CRED_PROT
+#define fido_dev_supports_cred_prot(x) (0)
+#endif
+#ifndef HAVE_FIDO_DEV_GET_TOUCH_BEGIN
+#define fido_dev_get_touch_begin(x) (FIDO_ERR_UNSUPPORTED_OPTION)
+#endif
+#ifndef HAVE_FIDO_DEV_GET_TOUCH_STATUS
+#define fido_dev_get_touch_status(x, y, z) (FIDO_ERR_UNSUPPORTED_OPTION)
+#endif
+
 #ifndef SK_STANDALONE
 # include "log.h"
 # include "xmalloc.h"
@@ -377,6 +388,11 @@ sk_select_by_touch(const fido_dev_info_t *devlist, size_t ndevs)
         size_t skvcnt, idx;
         int touch, ms_remain;
 
+#ifndef HAVE_FIDO_DEV_GET_TOUCH_STATUS
+        skdebug(__func__, "libfido2 version does not support a feature needed for multiple tokens. Please upgrade to >=1.5.0");
+        return NULL;
+#endif
+
         if ((skv = sk_openv(devlist, ndevs, &skvcnt)) == NULL) {
                 skdebug(__func__, "sk_openv failed");
                 return NULL;
@@ -705,6 +721,11 @@ sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len,
                 goto out;
         }
         if ((flags & (SSH_SK_RESIDENT_KEY|SSH_SK_USER_VERIFICATION_REQD)) != 0) {
+#ifndef HAVE_FIDO_DEV_SUPPORTS_CRED_PROT
+                skdebug(__func__, "libfido2 version does not support a feature required for this operation. Please upgrade to >=1.5.0");
+                ret = SSH_SK_ERR_UNSUPPORTED;
+                goto out;
+#endif
                 if (!fido_dev_supports_cred_prot(sk->dev)) {
                         skdebug(__func__, "%s does not support credprot, "
                             "refusing to create unprotected "