More secure storage of key material.

Add secure heap for storage of private keys (when possible).
Add BIO_s_secmem(), CBIGNUM, etc.
Add BIO_CTX_secure_new so all BIGNUM's in the context are secure.
Contributed by Akamai Technologies under the Corporate CLA.

Reviewed-by: Richard Levitte <levitte@openssl.org>

1 files changed, 39 insertions, 3 deletions

diff --git a/crypto/buffer/buffer.c b/crypto/buffer/buffer.c
index 2beacce6d7..5ee11f4c70 100644
--- a/crypto/buffer/buffer.c
+++ b/crypto/buffer/buffer.c
@@ -67,6 +67,16 @@
  */
 #define LIMIT_BEFORE_EXPANSION 0x5ffffffc
 
+BUF_MEM *BUF_MEM_new_ex(unsigned long flags)
+{
+    BUF_MEM *ret;
+
+    ret = BUF_MEM_new();
+    if (ret != NULL)
+        ret->flags = flags;
+    return (ret);
+}
+
 BUF_MEM *BUF_MEM_new(void)
 {
     BUF_MEM *ret;
@@ -76,6 +86,7 @@ BUF_MEM *BUF_MEM_new(void)
         BUFerr(BUF_F_BUF_MEM_NEW, ERR_R_MALLOC_FAILURE);
         return (NULL);
     }
+    ret->flags = 0;
     ret->length = 0;
     ret->max = 0;
     ret->data = NULL;
@@ -88,11 +99,30 @@ void BUF_MEM_free(BUF_MEM *a)
         return;
 
     if (a->data != NULL) {
-        OPENSSL_clear_free(a->data, a->max);
+        memset(a->data, 0, (unsigned int)a->max);
+        if (a->flags & BUF_MEM_FLAG_SECURE)
+            OPENSSL_secure_free(a->data);
+        else
+            OPENSSL_clear_free(a->data, a->max);
     }
     OPENSSL_free(a);
 }
 
+/* Allocate a block of secure memory; copy over old data if there
+ * was any, and then free it. */
+static char *sec_alloc_realloc(BUF_MEM *str, size_t len)
+{
+    char *ret;
+
+    ret = OPENSSL_secure_malloc(len);
+    if (str->data != NULL) {
+        if (ret != NULL)
+            memcpy(ret, str->data, str->length);
+        OPENSSL_secure_free(str->data);
+    }
+    return (ret);
+}
+
 size_t BUF_MEM_grow(BUF_MEM *str, size_t len)
 {
     char *ret;
@@ -113,7 +143,10 @@ size_t BUF_MEM_grow(BUF_MEM *str, size_t len)
         return 0;
     }
     n = (len + 3) / 3 * 4;
-    ret = OPENSSL_realloc(str->data, n);
+    if ((str->flags & BUF_MEM_FLAG_SECURE))
+        ret = sec_alloc_realloc(str, n);
+    else
+        ret = OPENSSL_realloc(str->data, n);
     if (ret == NULL) {
         BUFerr(BUF_F_BUF_MEM_GROW, ERR_R_MALLOC_FAILURE);
         len = 0;
@@ -147,7 +180,10 @@ size_t BUF_MEM_grow_clean(BUF_MEM *str, size_t len)
         return 0;
     }
     n = (len + 3) / 3 * 4;
-    ret = OPENSSL_realloc_clean(str->data, str->max, n);
+    if ((str->flags & BUF_MEM_FLAG_SECURE))
+        ret = sec_alloc_realloc(str, n);
+    else
+        ret = OPENSSL_realloc_clean(str->data, str->max, n);
     if (ret == NULL) {
         BUFerr(BUF_F_BUF_MEM_GROW_CLEAN, ERR_R_MALLOC_FAILURE);
         len = 0;