lib: Fix OpenSSL includes and explicit_bzero on OSX

The include headers and NIDs are different on macOS X. It also doesn't
have explicit_bzero.

The crypt.h includes are now guarded to work on OS X (trying to avoid
the includes by defining the OpenSSL mac header guard led to a whole
list of other issues).

The explicit zero'ing of buffers temporarily holding secrets has now
been abstracted in a crypt_secure_clear() function defaulting to
OpenSSL_cleanse, explicit_bzero (if present) or a best-effort option
using a volatile pointer.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

6 files changed, 35 insertions, 4 deletions

diff --git a/src/lib/config.h.in b/src/lib/config.h.in
index b2b17669..6065ac41 100644
--- a/src/lib/config.h.in
+++ b/src/lib/config.h.in
@@ -21,6 +21,7 @@
  */
 
 #cmakedefine HAVE_SYS_RANDOM
+#cmakedefine HAVE_EXPLICIT_BZERO
 #cmakedefine HAVE_LIBGCRYPT
 #cmakedefine HAVE_OPENSSL
 #ifdef HAVE_OPENSSL
diff --git a/src/lib/crypt.c b/src/lib/crypt.c
index fdbae776..38dd9f29 100644
--- a/src/lib/crypt.c
+++ b/src/lib/crypt.c
@@ -1064,3 +1064,24 @@ void crypt_secure_free(void * ptr,
         free(ptr);
 #endif
 }
+
+void crypt_secure_clear(void * ptr,
+                        size_t size)
+{
+        volatile uint8_t * p;
+
+        if (ptr == NULL)
+                return;
+
+#ifdef HAVE_OPENSSL
+        (void) p;
+        openssl_secure_clear(ptr, size);
+#elif defined(HAVE_EXPLICIT_BZERO)
+        (void) p;
+        explicit_bzero(ptr, size);
+#else /* best effort to avoid optimizing out */
+        p = ptr;
+        while (size-- > 0)
+                *p++ = 0;
+#endif
+}
diff --git a/src/lib/crypt/openssl.c b/src/lib/crypt/openssl.c
index b8233593..232aa6c9 100644
--- a/src/lib/crypt/openssl.c
+++ b/src/lib/crypt/openssl.c
@@ -1872,3 +1872,9 @@ void openssl_secure_free(void * ptr)
 {
         OPENSSL_secure_free(ptr);
 }
+
+void openssl_secure_clear(void * ptr,
+                          size_t size)
+{
+        OPENSSL_cleanse(ptr, size);
+}
diff --git a/src/lib/crypt/openssl.h b/src/lib/crypt/openssl.h
index 083e8dde..a6bb5840 100644
--- a/src/lib/crypt/openssl.h
+++ b/src/lib/crypt/openssl.h
@@ -166,4 +166,7 @@ void *  openssl_secure_malloc(size_t size);
 void    openssl_secure_free(void * ptr,
                             size_t size);
 
+void    openssl_secure_clear(void * ptr,
+                             size_t size);
+
 #endif /* OUROBOROS_LIB_CRYPT_OPENSSL_H */
diff --git a/src/lib/dev.c b/src/lib/dev.c
index 35ea701b..fb06c496 100644
--- a/src/lib/dev.c
+++ b/src/lib/dev.c
@@ -870,7 +870,7 @@ int flow_accept(qosspec_t *             qs,
 
         fd = flow_init(&flow, &crypt);
 
-        explicit_bzero(key, SYMMKEYSZ);
+        crypt_secure_clear(key, SYMMKEYSZ);
 
         if (qs != NULL)
                 *qs = flow.qs;
@@ -917,7 +917,7 @@ int flow_alloc(const char *            dst,
 
         fd = flow_init(&flow, &crypt);
 
-        explicit_bzero(key, SYMMKEYSZ);
+        crypt_secure_clear(key, SYMMKEYSZ);
 
         if (qs != NULL)
                 *qs = flow.qs;
@@ -956,7 +956,7 @@ int flow_join(const char *            dst,
 
         fd = flow_init(&flow, &crypt);
 
-        explicit_bzero(key, SYMMKEYSZ);
+        crypt_secure_clear(key, SYMMKEYSZ);
 
         return fd;
 }
diff --git a/src/lib/tests/kex_test.c b/src/lib/tests/kex_test.c
index 58cf8b43..0a588550 100644
--- a/src/lib/tests/kex_test.c
+++ b/src/lib/tests/kex_test.c
@@ -574,7 +574,7 @@ static int test_kex_parse_config_empty(void)
 
         memset(&kex, 0, sizeof(kex));
 
-        fp = FMEMOPEN_STR("");
+        fp = FMEMOPEN_STR("\n");
         if (fp == NULL) {
                 printf("Failed to open memory stream.\n");
                 goto fail;