Fix initialization sequence to prevent freeing of unitialized objects.

Submitted by: Nils Larsch <nla@trustcenter.de>

PR: 459

diff --git a/CHANGES b/CHANGES
index 85bd963ae91c6b72e818d481265c1230a17e756c..863a975a88f7df8118973c6542767a4c621a3be7 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,12 @@
 
  Changes between 0.9.7 and 0.9.7a  [XX xxx 2003]
 
+  *) DSA routines: under certain error conditions uninitialized BN objects
+     could be freed. Solution: make sure initialization is performed early
+     enough. (Reported and fix supplied by Ivan D Nestlerode <nestler@MIT.EDU>,
+     Nils Larsch <nla@trustcenter.de> via PR#459)
+     [Lutz Jaenicke]
+
   *) Another fix for SSLv2 session ID handling: the session ID was incorrectly
      checked on reconnect on the client side, therefore session resumption
      could still fail with a "ssl session id is different" error. This

diff --git a/crypto/dsa/dsa_ossl.c b/crypto/dsa/dsa_ossl.c
index 37dd5fc994092968b3606579825b1bd3df1e6e9b..11da570ddb9331ae6efb49a548affab173b7aa69 100644 (file)
--- a/crypto/dsa/dsa_ossl.c
+++ b/crypto/dsa/dsa_ossl.c
@@ -106,13 +106,15 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
        int i,reason=ERR_R_BN_LIB;
        DSA_SIG *ret=NULL;
 
+       BN_init(&m);
+       BN_init(&xr);
+
        if (!dsa->p || !dsa->q || !dsa->g)
                {
                reason=DSA_R_MISSING_PARAMETERS;
                goto err;
                }
-       BN_init(&m);
-       BN_init(&xr);
+
        s=BN_new();
        if (s == NULL) goto err;
 
@@ -178,6 +180,9 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
                DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
                return 0;
                }
+
+       BN_init(&k);
+
        if (ctx_in == NULL)
                {
                if ((ctx=BN_CTX_new()) == NULL) goto err;
@@ -185,7 +190,6 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
        else
                ctx=ctx_in;
 
-       BN_init(&k);
        if ((r=BN_new()) == NULL) goto err;
        kinv=NULL;
 
@@ -241,11 +245,12 @@ static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
                return -1;
                }
 
-       if ((ctx=BN_CTX_new()) == NULL) goto err;
        BN_init(&u1);
        BN_init(&u2);
        BN_init(&t1);
 
+       if ((ctx=BN_CTX_new()) == NULL) goto err;
+
        if (BN_is_zero(sig->r) || sig->r->neg || BN_ucmp(sig->r, dsa->q) >= 0)
                {
                ret = 0;