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, 47 insertions, 32 deletions

diff --git a/crypto/bn/bn_ctx.c b/crypto/bn/bn_ctx.c
index c023303..660e626 100644
--- a/crypto/bn/bn_ctx.c
+++ b/crypto/bn/bn_ctx.c
@@ -103,7 +103,7 @@ typedef struct bignum_pool {
 } BN_POOL;
 static void BN_POOL_init(BN_POOL *);
 static void BN_POOL_finish(BN_POOL *);
-static BIGNUM *BN_POOL_get(BN_POOL *);
+static BIGNUM *BN_POOL_get(BN_POOL *, int);
 static void BN_POOL_release(BN_POOL *, unsigned int);
 
 /************/
@@ -138,6 +138,8 @@ struct bignum_ctx {
     int err_stack;
     /* Block "gets" until an "end" (compatibility behaviour) */
     int too_many;
+    /* Flags. */
+    int flags;
 };
 
 /* Enable this to find BN_CTX bugs */
@@ -186,8 +188,9 @@ static void ctxdbg(BN_CTX *ctx)
 
 BN_CTX *BN_CTX_new(void)
 {
-    BN_CTX *ret = OPENSSL_malloc(sizeof(*ret));
-    if (!ret) {
+    BN_CTX *ret;
+
+    if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) {
         BNerr(BN_F_BN_CTX_NEW, ERR_R_MALLOC_FAILURE);
         return NULL;
     }
@@ -197,6 +200,16 @@ BN_CTX *BN_CTX_new(void)
     ret->used = 0;
     ret->err_stack = 0;
     ret->too_many = 0;
+    ret->flags = 0;
+    return ret;
+}
+
+BN_CTX *BN_CTX_secure_new(void)
+{
+    BN_CTX *ret = BN_CTX_new();
+
+    if (ret)
+        ret->flags = BN_FLG_SECURE;
     return ret;
 }
 
@@ -258,10 +271,11 @@ void BN_CTX_end(BN_CTX *ctx)
 BIGNUM *BN_CTX_get(BN_CTX *ctx)
 {
     BIGNUM *ret;
+
     CTXDBG_ENTRY("BN_CTX_get", ctx);
     if (ctx->err_stack || ctx->too_many)
         return NULL;
-    if ((ret = BN_POOL_get(&ctx->pool)) == NULL) {
+    if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {
         /*
          * Setting too_many prevents repeated "get" attempts from cluttering
          * the error stack.
@@ -289,26 +303,23 @@ static void BN_STACK_init(BN_STACK *st)
 
 static void BN_STACK_finish(BN_STACK *st)
 {
-    if (st->size)
-        OPENSSL_free(st->indexes);
+    OPENSSL_free(st->indexes);
+    st->indexes = NULL;
 }
 
 
 static int BN_STACK_push(BN_STACK *st, unsigned int idx)
 {
-    if (st->depth == st->size)
+    if (st->depth == st->size) {
         /* Need to expand */
-    {
-        unsigned int newsize = (st->size ?
-                                (st->size * 3 / 2) : BN_CTX_START_FRAMES);
-        unsigned int *newitems = OPENSSL_malloc(newsize *
-                                                sizeof(unsigned int));
-        if (!newitems)
+        unsigned int newsize =
+            st->size ? (st->size * 3 / 2) : BN_CTX_START_FRAMES;
+        unsigned int *newitems = OPENSSL_malloc(sizeof(*newitems) * newsize);
+        if (newitems == NULL)
             return 0;
         if (st->depth)
-            memcpy(newitems, st->indexes, st->depth * sizeof(unsigned int));
-        if (st->size)
-            OPENSSL_free(st->indexes);
+            memcpy(newitems, st->indexes, sizeof(*newitems) * st->depth);
+        OPENSSL_free(st->indexes);
         st->indexes = newitems;
         st->size = newsize;
     }
@@ -333,14 +344,13 @@ static void BN_POOL_init(BN_POOL *p)
 
 static void BN_POOL_finish(BN_POOL *p)
 {
+    unsigned int loop;
+    BIGNUM *bn;
+
     while (p->head) {
-        unsigned int loop = 0;
-        BIGNUM *bn = p->head->vals;
-        while (loop++ < BN_CTX_POOL_SIZE) {
+        for (loop = 0, bn = p->head->vals; loop++ < BN_CTX_POOL_SIZE; bn++)
             if (bn->d)
                 BN_clear_free(bn);
-            bn++;
-        }
         p->current = p->head->next;
         OPENSSL_free(p->head);
         p->head = p->current;
@@ -348,22 +358,25 @@ static void BN_POOL_finish(BN_POOL *p)
 }
 
 
-static BIGNUM *BN_POOL_get(BN_POOL *p)
+static BIGNUM *BN_POOL_get(BN_POOL *p, int flag)
 {
+    BIGNUM *bn;
+    unsigned int loop;
+
+    /* Full; allocate a new pool item and link it in. */
     if (p->used == p->size) {
-        BIGNUM *bn;
-        unsigned int loop = 0;
         BN_POOL_ITEM *item = OPENSSL_malloc(sizeof(*item));
-        if (!item)
+        if (item == NULL)
             return NULL;
-        /* Initialise the structure */
-        bn = item->vals;
-        while (loop++ < BN_CTX_POOL_SIZE)
-            BN_init(bn++);
+        for (loop = 0, bn = item->vals; loop++ < BN_CTX_POOL_SIZE; bn++) {
+            BN_init(bn);
+            if ((flag & BN_FLG_SECURE) != 0)
+                BN_set_flags(bn, BN_FLG_SECURE);
+        }
         item->prev = p->tail;
         item->next = NULL;
-        /* Link it in */
-        if (!p->head)
+
+        if (p->head == NULL)
             p->head = p->current = p->tail = item;
         else {
             p->tail->next = item;
@@ -375,6 +388,7 @@ static BIGNUM *BN_POOL_get(BN_POOL *p)
         /* Return the first bignum from the new pool */
         return item->vals;
     }
+
     if (!p->used)
         p->current = p->head;
     else if ((p->used % BN_CTX_POOL_SIZE) == 0)
@@ -385,10 +399,11 @@ static BIGNUM *BN_POOL_get(BN_POOL *p)
 static void BN_POOL_release(BN_POOL *p, unsigned int num)
 {
     unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
+
     p->used -= num;
     while (num--) {
         bn_check_top(p->current->vals + offset);
-        if (!offset) {
+        if (offset == 0) {
             offset = BN_CTX_POOL_SIZE - 1;
             p->current = p->current->prev;
         } else