libtpmtss: Initialize library from all users

Previously, only the tpm plugin initialized the library, so in order
to use a TPM 2.0 (a required TCTI library is loaded via init), it was
necessary to load it even if none of its actual features were used.

src/libtpmtss/tpm_tss.c

@@ -24,12 +24,22 @@
 #include "plugin_constructors.c"
 #endif
 
+/**
+ * Reference counter for library initialization
+ */
+static refcount_t libtpmtss_ref = 0;
+
 /**
  * Described in header.
  */
 bool libtpmtss_init(void)
 {
-	return tpm_tss_tss2_init();
+	if (ref_cur(&libtpmtss_ref) || tpm_tss_tss2_init())
+	{
+		ref_get(&libtpmtss_ref);
+		return TRUE;
+	}
+	return FALSE;
 }
 
 /**
@@ -37,7 +47,10 @@ bool libtpmtss_init(void)
  */
 void libtpmtss_deinit(void)
 {
-	tpm_tss_tss2_deinit();
+	if (ref_cur(&libtpmtss_ref) && ref_put(&libtpmtss_ref))
+	{
+		tpm_tss_tss2_deinit();
+	}
 }
 
 typedef tpm_tss_t*(*tpm_tss_create)(void);

src/libtpmtss/tpm_tss.h

@@ -192,22 +192,22 @@ struct tpm_tss_t {
 };
 
 /**
- * Create a tpm_tss instance.
- *
- * @param version	TPM version that must be supported by TSS
- */
-tpm_tss_t *tpm_tss_probe(tpm_version_t version);
-
-/**
- * libtpmtss initialization function
+ * Initialize libtpmtss
  *
  * @return					TRUE if initialization was successful
  */
 bool libtpmtss_init(void);
 
 /**
- * libtpmtss de-initialization function
+ * Deinitialize libtpmtss
  */
 void libtpmtss_deinit(void);
 
+/**
+ * Create a tpm_tss instance.
+ *
+ * @param version			TPM version that must be supported by TSS
+ */
+tpm_tss_t *tpm_tss_probe(tpm_version_t version);
+
 #endif /** TPM_TSS_H_ @}*/