RSA, DSA, DH: Allow some given input to be NULL on already initialised keys

The diverse {RSA,DSA,DH}_set0_* functions are made to allow some
parameters to be NULL IF the corresponding numbers in the given key
structure have already been previously initialised.  Specifically,
this allows the addition of private components to be added to a key
that already has the public half, approximately like this:

    RSA_get0_key(rsa, NULL, &e, NULL);
    RSA_get0_factors(rsa, &p, &q);
    /* calculate new d */
    RSA_set0_key(rsa, NULL, NULL, d);

Reviewed-by: Matt Caswell <matt@openssl.org>

1 files changed, 37 insertions, 14 deletions

diff --git a/crypto/dh/dh_lib.c b/crypto/dh/dh_lib.c
index bf9f8d3317..644508d784 100644
--- a/crypto/dh/dh_lib.c
+++ b/crypto/dh/dh_lib.c
@@ -245,15 +245,27 @@ void DH_get0_pqg(const DH *dh, BIGNUM **p, BIGNUM **q, BIGNUM **g)
 
 int DH_set0_pqg(DH *dh, BIGNUM *p, BIGNUM *q, BIGNUM *g)
 {
-    /* q is optional */
-    if (p == NULL || g == NULL)
+    /* If the fields p and g in d are NULL, the corresponding input
+     * parameters MUST be non-NULL.  q may remain NULL.
+     *
+     * It is an error to give the results from get0 on d
+     * as input parameters.
+     */
+    if (p == dh->p || (dh->q != NULL && q == dh->q) || g == dh->g)
         return 0;
-    BN_free(dh->p);
-    BN_free(dh->q);
-    BN_free(dh->g);
-    dh->p = p;
-    dh->q = q;
-    dh->g = g;
+
+    if (p != NULL) {
+        BN_free(dh->p);
+        dh->p = p;
+    }
+    if (q != NULL) {
+        BN_free(dh->q);
+        dh->q = q;
+    }
+    if (g != NULL) {
+        BN_free(dh->g);
+        dh->g = g;
+    }
 
     if (q != NULL) {
         dh->length = BN_num_bits(q);
@@ -283,14 +295,25 @@ void DH_get0_key(const DH *dh, BIGNUM **pub_key, BIGNUM **priv_key)
 
 int DH_set0_key(DH *dh, BIGNUM *pub_key, BIGNUM *priv_key)
 {
-    /* Note that it is valid for priv_key to be NULL */
-    if (pub_key == NULL)
+    /* If the pub_key in dh is NULL, the corresponding input
+     * parameters MUST be non-NULL.  The priv_key field may
+     * be left NULL.
+     *
+     * It is an error to give the results from get0 on dh
+     * as input parameters.
+     */
+    if (dh->pub_key == pub_key
+        || (dh->priv_key != NULL && priv_key != dh->priv_key))
         return 0;
 
-    BN_free(dh->pub_key);
-    BN_free(dh->priv_key);
-    dh->pub_key = pub_key;
-    dh->priv_key = priv_key;
+    if (pub_key != NULL) {
+        BN_free(dh->pub_key);
+        dh->pub_key = pub_key;
+    }
+    if (priv_key != NULL) {
+        BN_free(dh->priv_key);
+        dh->priv_key = priv_key;
+    }
 
     return 1;
 }