Added memory locking for secrets (#1491)

When caching a PIN in memory or using an OpenSSL private key this data should not be swapped to disk.

src/libopensc/ctx.c

@@ -38,6 +38,7 @@
 
 #include "common/libscdl.h"
 #include "internal.h"
+#include "sc-ossl-compat.h"
 
 static int ignored_reader(sc_context_t *ctx, sc_reader_t *reader)
 {
@@ -831,6 +832,13 @@ int sc_context_create(sc_context_t **ctx_out, const sc_context_param_t *parm)
 		return r;
 	}
 
+#ifdef ENABLE_OPENSSL
+	if (!CRYPTO_secure_malloc_initialized()) {
+		/* XXX What's a reasonable amount of secure heap? */
+		CRYPTO_secure_malloc_init(4096, 32);
+	}
+#endif
+
 	process_config_file(ctx, &opts);
 	sc_log(ctx, "==================================="); /* first thing in the log */
 	sc_log(ctx, "opensc version: %s", sc_get_version());

src/libopensc/libopensc.exports

@@ -131,6 +131,8 @@ sc_lock
 sc_logout
 sc_make_cache_dir
 sc_mem_clear
+sc_mem_secure_alloc
+sc_mem_secure_free
 sc_mem_reverse
 sc_match_atr_block
 sc_path_print

src/libopensc/opensc.h

@@ -1366,6 +1366,8 @@ int sc_base64_decode(const char *in, u8 *out, size_t outlen);
  * @param  len  length of the memory buffer
  */
 void sc_mem_clear(void *ptr, size_t len);
+void *sc_mem_secure_alloc(size_t len);
+void sc_mem_secure_free(void *ptr, size_t len);
 int sc_mem_reverse(unsigned char *buf, size_t len);
 
 int sc_get_cache_dir(sc_context_t *ctx, char *buf, size_t bufsize);

src/libopensc/pkcs15.c

@@ -2496,8 +2496,15 @@ sc_pkcs15_make_absolute_path(const struct sc_path *parent, struct sc_path *child
 void sc_pkcs15_free_object_content(struct sc_pkcs15_object *obj)
 {
 	if (obj->content.value && obj->content.len)   {
-		sc_mem_clear(obj->content.value, obj->content.len);
-		free(obj->content.value);
+		if (SC_PKCS15_TYPE_AUTH & obj->type
+			|| SC_PKCS15_TYPE_SKEY & obj->type
+			|| SC_PKCS15_TYPE_PRKEY & obj->type) {
+			/* clean everything that potentially contains a secret */
+			sc_mem_clear(obj->content.value, obj->content.len);
+			sc_mem_secure_free(obj->content.value, obj->content.len);
+		} else {
+			free(obj->content.value);
+		}
 	}
 	obj->content.value = NULL;
 	obj->content.len = 0;
@@ -2521,7 +2528,13 @@ sc_pkcs15_allocate_object_content(struct sc_context *ctx, struct sc_pkcs15_objec
 	/* Need to pass by temporary variable,
 	 * because 'value' and 'content.value' pointers can be the sames.
 	 */
-	tmp_buf = calloc(sizeof *tmp_buf, len);
+	if (SC_PKCS15_TYPE_AUTH & obj->type
+			|| SC_PKCS15_TYPE_SKEY & obj->type
+			|| SC_PKCS15_TYPE_PRKEY & obj->type) {
+		tmp_buf = sc_mem_secure_alloc(len);
+	} else {
+		tmp_buf = malloc(len);
+	}
 	if (!tmp_buf)
 		return SC_ERROR_OUT_OF_MEMORY;
 

src/libopensc/sc-ossl-compat.h

@@ -230,6 +230,19 @@ static sc_ossl_inline int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s)
 }
 #endif /* OPENSSL_NO_EC */
 
+static sc_ossl_inline int CRYPTO_secure_malloc_init(size_t size, int minsize)
+{
+    return 0;
+}
+
+static sc_ossl_inline int CRYPTO_secure_malloc_initialized()
+{
+    return 0;
+}
+
+#else
+
+#include <openssl/crypto.h>
 
 #endif /* OPENSSL_VERSION_NUMBER < 0x10100000L */
 

src/libopensc/sc.c

@@ -34,6 +34,7 @@
 #include <openssl/crypto.h>     /* for OPENSSL_cleanse */
 #endif
 
+
 #include "internal.h"
 
 #ifdef PACKAGE_VERSION
@@ -42,6 +43,19 @@ static const char *sc_version = PACKAGE_VERSION;
 static const char *sc_version = "(undef)";
 #endif
 
+#ifdef _WIN32
+#include <windows.h>
+#define PAGESIZE 0
+#else
+#include <sys/mman.h>
+#include <limits.h>
+#include <unistd.h>
+#ifndef PAGESIZE
+#define PAGESIZE 0
+#endif
+#endif
+static size_t page_size = PAGESIZE;
+
 const char *sc_get_version(void)
 {
     return sc_version;
@@ -826,6 +840,52 @@ int _sc_parse_atr(sc_reader_t *reader)
 	return SC_SUCCESS;
 }
 
+static void init_page_size()
+{
+	if (page_size == 0) {
+#ifdef _WIN32
+		SYSTEM_INFO system_info;
+		GetSystemInfo(&system_info);
+		page_size = system_info.dwPageSize;
+#else
+		page_size = sysconf(_SC_PAGESIZE);
+		if ((long) page_size < 0) {
+			page_size = 0;
+		}
+#endif
+	}
+}
+
+void *sc_mem_secure_alloc(size_t len)
+{
+	void *p;
+
+	init_page_size();
+	if (page_size > 0) {
+		size_t pages = (len + page_size - 1) / page_size;
+		len = pages * page_size;
+	}
+
+	p = malloc(len);
+#ifdef _WIN32
+	VirtualLock(p, len);
+#else
+	mlock(p, len);
+#endif
+
+	return p;
+}
+
+void sc_mem_secure_free(void *ptr, size_t len)
+{
+#ifdef _WIN32
+	VirtualUnlock(ptr, len);
+#else
+	munlock(ptr, len);
+#endif
+	free(ptr);
+}
+
 void sc_mem_clear(void *ptr, size_t len)
 {
 	if (len > 0)   {

src/pkcs11/misc.c

@@ -187,7 +187,7 @@ CK_RV push_login_state(struct sc_pkcs11_slot *slot,
 	}
 
 	if (pPin && ulPinLen) {
-		login->pPin = calloc((sizeof *pPin), ulPinLen);
+		login->pPin = sc_mem_secure_alloc((sizeof *pPin)*ulPinLen);
 		if (login->pPin == NULL) {
 			goto err;
 		}
@@ -207,7 +207,7 @@ err:
 	if (login) {
 		if (login->pPin) {
 			sc_mem_clear(login->pPin, login->ulPinLen);
-			free(login->pPin);
+			sc_mem_secure_free(login->pPin, login->ulPinLen);
 		}
 		free(login);
 	}
@@ -223,7 +223,7 @@ void pop_login_state(struct sc_pkcs11_slot *slot)
 			struct sc_pkcs11_login *login = list_get_at(&slot->logins, size-1);
 			if (login) {
 				sc_mem_clear(login->pPin, login->ulPinLen);
-				free(login->pPin);
+				sc_mem_secure_free(login->pPin, login->ulPinLen);
 				free(login);
 			}
 			if (0 > list_delete_at(&slot->logins, size-1))
@@ -238,7 +238,7 @@ void pop_all_login_states(struct sc_pkcs11_slot *slot)
 		struct sc_pkcs11_login *login = list_fetch(&slot->logins);
 		while (login) {
 			sc_mem_clear(login->pPin, login->ulPinLen);
-			free(login->pPin);
+			sc_mem_secure_free(login->pPin, login->ulPinLen);
 			free(login);
 			login = list_fetch(&slot->logins);
 		}