BN_CTX_get() can fail - consistently check its return value.

There are currently cases where the return from each call is checked,
the return from only the last call is checked and cases where it is not
checked at all (including code in bn, ec and engine).

Checking the last return value is valid as once the function fails it will
continue to return NULL. However, in order to be consistent check each
call with the same idiom. This makes it easy to verify.

Note there are still a handful of cases that do not follow the idiom -
these will be handled separately.

ok beck@ doug@

12 files changed, 140 insertions, 110 deletions

diff --git a/src/lib/libcrypto/bn/bn_div.c b/src/lib/libcrypto/bn/bn_div.c
index f4deccf77f..fefc53f9fa 100644
--- a/src/lib/libcrypto/bn/bn_div.c
+++ b/src/lib/libcrypto/bn/bn_div.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_div.c,v 1.22 2014/07/11 08:44:47 jsing Exp $ */
+/* $OpenBSD: bn_div.c,v 1.23 2015/02/09 15:49:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -170,7 +170,7 @@ BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,
                 res = BN_CTX_get(ctx);
         else
                 res = dv;
-        if (sdiv == NULL || res == NULL || tmp == NULL || snum == NULL)
+        if (tmp == NULL || snum == NULL || sdiv == NULL || res == NULL)
                 goto err;
 
         /* First we normalise the numbers */
diff --git a/src/lib/libcrypto/bn/bn_exp.c b/src/lib/libcrypto/bn/bn_exp.c
index 1aa5503dae..eecab5163b 100644
--- a/src/lib/libcrypto/bn/bn_exp.c
+++ b/src/lib/libcrypto/bn/bn_exp.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_exp.c,v 1.19 2014/07/11 15:01:49 miod Exp $ */
+/* $OpenBSD: bn_exp.c,v 1.20 2015/02/09 15:49:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -272,9 +272,9 @@ BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
         }
 
         BN_CTX_start(ctx);
-        aa = BN_CTX_get(ctx);
-        val[0] = BN_CTX_get(ctx);
-        if (!aa || !val[0])
+        if ((aa = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((val[0] = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         BN_RECP_CTX_init(&recp);
@@ -408,10 +408,11 @@ BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
         }
 
         BN_CTX_start(ctx);
-        d = BN_CTX_get(ctx);
-        r = BN_CTX_get(ctx);
-        val[0] = BN_CTX_get(ctx);
-        if (!d || !r || !val[0])
+        if ((d = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((r = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((val[0] = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         /* If this is not done, things will break in the montgomery
@@ -885,10 +886,11 @@ BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p, const BIGNUM *m,
         }
 
         BN_CTX_start(ctx);
-        d = BN_CTX_get(ctx);
-        r = BN_CTX_get(ctx);
-        t = BN_CTX_get(ctx);
-        if (d == NULL || r == NULL || t == NULL)
+        if ((d = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((r = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((t = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (in_mont != NULL)
@@ -1003,9 +1005,9 @@ BN_mod_exp_simple(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, const BIGNUM *m,
         }
 
         BN_CTX_start(ctx);
-        d = BN_CTX_get(ctx);
-        val[0] = BN_CTX_get(ctx);
-        if (!d || !val[0])
+        if ((d = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((val[0] = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (!BN_nnmod(val[0],a,m,ctx))
diff --git a/src/lib/libcrypto/bn/bn_exp2.c b/src/lib/libcrypto/bn/bn_exp2.c
index c8f0294f7a..38bf467a38 100644
--- a/src/lib/libcrypto/bn/bn_exp2.c
+++ b/src/lib/libcrypto/bn/bn_exp2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_exp2.c,v 1.9 2014/07/11 08:44:47 jsing Exp $ */
+/* $OpenBSD: bn_exp2.c,v 1.10 2015/02/09 15:49:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -150,11 +150,13 @@ BN_mod_exp2_mont(BIGNUM *rr, const BIGNUM *a1, const BIGNUM *p1,
         bits = (bits1 > bits2) ? bits1 : bits2;
 
         BN_CTX_start(ctx);
-        d = BN_CTX_get(ctx);
-        r = BN_CTX_get(ctx);
-        val1[0] = BN_CTX_get(ctx);
-        val2[0] = BN_CTX_get(ctx);
-        if (!d || !r || !val1[0] || !val2[0])
+        if ((d = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((r = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((val1[0] = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((val2[0] = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (in_mont != NULL)
diff --git a/src/lib/libcrypto/bn/bn_gcd.c b/src/lib/libcrypto/bn/bn_gcd.c
index 379bea99ad..da9c29a8e5 100644
--- a/src/lib/libcrypto/bn/bn_gcd.c
+++ b/src/lib/libcrypto/bn/bn_gcd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_gcd.c,v 1.9 2014/07/11 08:44:47 jsing Exp $ */
+/* $OpenBSD: bn_gcd.c,v 1.10 2015/02/09 15:49:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -125,9 +125,9 @@ BN_gcd(BIGNUM *r, const BIGNUM *in_a, const BIGNUM *in_b, BN_CTX *ctx)
         bn_check_top(in_b);
 
         BN_CTX_start(ctx);
-        a = BN_CTX_get(ctx);
-        b = BN_CTX_get(ctx);
-        if (a == NULL || b == NULL)
+        if ((a = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((b = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (BN_copy(a, in_a) == NULL)
@@ -247,14 +247,19 @@ BN_mod_inverse(BIGNUM *in, const BIGNUM *a, const BIGNUM *n, BN_CTX *ctx)
         bn_check_top(n);
 
         BN_CTX_start(ctx);
-        A = BN_CTX_get(ctx);
-        B = BN_CTX_get(ctx);
-        X = BN_CTX_get(ctx);
-        D = BN_CTX_get(ctx);
-        M = BN_CTX_get(ctx);
-        Y = BN_CTX_get(ctx);
-        T = BN_CTX_get(ctx);
-        if (T == NULL)
+        if ((A = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((B = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((X = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((D = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((M = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((Y = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((T = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (in == NULL)
@@ -537,14 +542,19 @@ BN_mod_inverse_no_branch(BIGNUM *in, const BIGNUM *a, const BIGNUM *n,
         bn_check_top(n);
 
         BN_CTX_start(ctx);
-        A = BN_CTX_get(ctx);
-        B = BN_CTX_get(ctx);
-        X = BN_CTX_get(ctx);
-        D = BN_CTX_get(ctx);
-        M = BN_CTX_get(ctx);
-        Y = BN_CTX_get(ctx);
-        T = BN_CTX_get(ctx);
-        if (T == NULL)
+        if ((A = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((B = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((X = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((D = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((M = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((Y = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((T = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (in == NULL)
diff --git a/src/lib/libcrypto/bn/bn_gf2m.c b/src/lib/libcrypto/bn/bn_gf2m.c
index 1cd38c7797..4544369248 100644
--- a/src/lib/libcrypto/bn/bn_gf2m.c
+++ b/src/lib/libcrypto/bn/bn_gf2m.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_gf2m.c,v 1.16 2014/10/28 07:35:58 jsg Exp $ */
+/* $OpenBSD: bn_gf2m.c,v 1.17 2015/02/09 15:49:22 jsing Exp $ */
 /* ====================================================================
  * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
  *
@@ -840,8 +840,7 @@ BN_GF2m_mod_div(BIGNUM *r, const BIGNUM *y, const BIGNUM *x, const BIGNUM *p,
         bn_check_top(p);
 
         BN_CTX_start(ctx);
-        xinv = BN_CTX_get(ctx);
-        if (xinv == NULL)
+        if ((xinv = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (!BN_GF2m_mod_inv(xinv, x, p, ctx))
@@ -875,11 +874,13 @@ BN_GF2m_mod_div(BIGNUM *r, const BIGNUM *y, const BIGNUM *x, const BIGNUM *p,
 
         BN_CTX_start(ctx);
 
-        a = BN_CTX_get(ctx);
-        b = BN_CTX_get(ctx);
-        u = BN_CTX_get(ctx);
-        v = BN_CTX_get(ctx);
-        if (v == NULL)
+        if ((a = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((b = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((u = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((v = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         /* reduce x and y mod p */
@@ -1137,10 +1138,11 @@ BN_GF2m_mod_solve_quad_arr(BIGNUM *r, const BIGNUM *a_, const int p[],
         }
 
         BN_CTX_start(ctx);
-        a = BN_CTX_get(ctx);
-        z = BN_CTX_get(ctx);
-        w = BN_CTX_get(ctx);
-        if (w == NULL)
+        if ((a = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((z = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((w = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (!BN_GF2m_mod_arr(a, a_, p))
@@ -1169,10 +1171,11 @@ BN_GF2m_mod_solve_quad_arr(BIGNUM *r, const BIGNUM *a_, const int p[],
         }
         else /* m is even */
         {
-                rho = BN_CTX_get(ctx);
-                w2 = BN_CTX_get(ctx);
-                tmp = BN_CTX_get(ctx);
-                if (tmp == NULL)
+                if ((rho = BN_CTX_get(ctx)) == NULL)
+                        goto err;
+                if ((w2 = BN_CTX_get(ctx)) == NULL)
+                        goto err;
+                if ((tmp = BN_CTX_get(ctx)) == NULL)
                         goto err;
                 do {
                         if (!BN_rand(rho, p[0], 0, 0))
diff --git a/src/lib/libcrypto/bn/bn_kron.c b/src/lib/libcrypto/bn/bn_kron.c
index 699cda55f0..274da5d186 100644
--- a/src/lib/libcrypto/bn/bn_kron.c
+++ b/src/lib/libcrypto/bn/bn_kron.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_kron.c,v 1.5 2014/07/11 08:44:48 jsing Exp $ */
+/* $OpenBSD: bn_kron.c,v 1.6 2015/02/09 15:49:22 jsing Exp $ */
 /* ====================================================================
  * Copyright (c) 1998-2000 The OpenSSL Project.  All rights reserved.
  *
@@ -79,9 +79,9 @@ BN_kronecker(const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
         bn_check_top(b);
 
         BN_CTX_start(ctx);
-        A = BN_CTX_get(ctx);
-        B = BN_CTX_get(ctx);
-        if (B == NULL)
+        if ((A = BN_CTX_get(ctx)) == NULL)
+                goto end;
+        if ((B = BN_CTX_get(ctx)) == NULL)
                 goto end;
 
         err = !BN_copy(A, a);
diff --git a/src/lib/libcrypto/bn/bn_mont.c b/src/lib/libcrypto/bn/bn_mont.c
index 5803ca493d..3eb9913a9e 100644
--- a/src/lib/libcrypto/bn/bn_mont.c
+++ b/src/lib/libcrypto/bn/bn_mont.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_mont.c,v 1.23 2014/07/11 08:44:48 jsing Exp $ */
+/* $OpenBSD: bn_mont.c,v 1.24 2015/02/09 15:49:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -149,8 +149,7 @@ BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
 #endif
 
         BN_CTX_start(ctx);
-        tmp = BN_CTX_get(ctx);
-        if (tmp == NULL)
+        if ((tmp = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         bn_check_top(tmp);
@@ -288,9 +287,9 @@ BN_from_montgomery(BIGNUM *ret, const BIGNUM *a, BN_MONT_CTX *mont, BN_CTX *ctx)
         BIGNUM *t1, *t2;
 
         BN_CTX_start(ctx);
-        t1 = BN_CTX_get(ctx);
-        t2 = BN_CTX_get(ctx);
-        if (t1 == NULL || t2 == NULL)
+        if ((t1 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((t2 = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (!BN_copy(t1, a))
diff --git a/src/lib/libcrypto/bn/bn_mul.c b/src/lib/libcrypto/bn/bn_mul.c
index daba02d6ca..7794d59707 100644
--- a/src/lib/libcrypto/bn/bn_mul.c
+++ b/src/lib/libcrypto/bn/bn_mul.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_mul.c,v 1.19 2014/07/11 08:44:48 jsing Exp $ */
+/* $OpenBSD: bn_mul.c,v 1.20 2015/02/09 15:49:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1012,8 +1012,7 @@ BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
                         j = 1 << (j - 1);
                         assert(j <= al || j <= bl);
                         k = j + j;
-                        t = BN_CTX_get(ctx);
-                        if (t == NULL)
+                        if ((t = BN_CTX_get(ctx)) == NULL)
                                 goto err;
                         if (al > j || bl > j) {
                                 if (bn_wexpand(t, k * 4) == NULL)
@@ -1057,7 +1056,8 @@ BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
                         j = BN_num_bits_word((BN_ULONG)al);
                         j = 1 << (j - 1);
                         k = j + j;
-                        t = BN_CTX_get(ctx);
+                        if ((t = BN_CTX_get(ctx)) == NULL)
+                                goto err;
                         if (al == j) /* exact multiple */
                         {
                                 if (bn_wexpand(t, k * 2) == NULL)
diff --git a/src/lib/libcrypto/bn/bn_prime.c b/src/lib/libcrypto/bn/bn_prime.c
index e5cd315e47..02780d32e6 100644
--- a/src/lib/libcrypto/bn/bn_prime.c
+++ b/src/lib/libcrypto/bn/bn_prime.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_prime.c,v 1.12 2014/10/18 17:20:40 jsing Exp $ */
+/* $OpenBSD: bn_prime.c,v 1.13 2015/02/09 15:49:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -170,8 +170,7 @@ BN_generate_prime_ex(BIGNUM *ret, int bits, int safe, const BIGNUM *add,
         if (ctx == NULL)
                 goto err;
         BN_CTX_start(ctx);
-        t = BN_CTX_get(ctx);
-        if (!t)
+        if ((t = BN_CTX_get(ctx)) == NULL)
                 goto err;
 loop:
         /* make a random number and set the top and bottom bits */
@@ -287,10 +286,11 @@ BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed,
                 A = t;
         } else
                 A = a;
-        A1 = BN_CTX_get(ctx);
-        A1_odd = BN_CTX_get(ctx);
-        check = BN_CTX_get(ctx);
-        if (check == NULL)
+        if ((A1 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((A1_odd = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((check = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         /* compute A1 := A - 1 */
@@ -461,10 +461,11 @@ probable_prime_dh_safe(BIGNUM *p, int bits, const BIGNUM *padd,
 
         bits--;
         BN_CTX_start(ctx);
-        t1 = BN_CTX_get(ctx);
-        q = BN_CTX_get(ctx);
-        qadd = BN_CTX_get(ctx);
-        if (qadd == NULL)
+        if ((t1 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((q = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((qadd = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (!BN_rshift1(qadd, padd))
diff --git a/src/lib/libcrypto/bn/bn_sqr.c b/src/lib/libcrypto/bn/bn_sqr.c
index 5ea9fb083d..a0dce6ea81 100644
--- a/src/lib/libcrypto/bn/bn_sqr.c
+++ b/src/lib/libcrypto/bn/bn_sqr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_sqr.c,v 1.11 2014/07/11 13:26:31 miod Exp $ */
+/* $OpenBSD: bn_sqr.c,v 1.12 2015/02/09 15:49:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -85,7 +85,7 @@ BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
         BN_CTX_start(ctx);
         rr = (a != r) ? r : BN_CTX_get(ctx);
         tmp = BN_CTX_get(ctx);
-        if (!rr || !tmp)
+        if (rr == NULL || tmp == NULL)
                 goto err;
 
         max = 2 * al; /* Non-zero (from above) */
diff --git a/src/lib/libcrypto/bn/bn_sqrt.c b/src/lib/libcrypto/bn/bn_sqrt.c
index 9a59d56b3f..f94fa41094 100644
--- a/src/lib/libcrypto/bn/bn_sqrt.c
+++ b/src/lib/libcrypto/bn/bn_sqrt.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_sqrt.c,v 1.5 2014/07/11 08:44:48 jsing Exp $ */
+/* $OpenBSD: bn_sqrt.c,v 1.6 2015/02/09 15:49:22 jsing Exp $ */
 /* Written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
  * and Bodo Moeller for the OpenSSL project. */
 /* ====================================================================
@@ -108,13 +108,17 @@ BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
         }
 
         BN_CTX_start(ctx);
-        A = BN_CTX_get(ctx);
-        b = BN_CTX_get(ctx);
-        q = BN_CTX_get(ctx);
-        t = BN_CTX_get(ctx);
-        x = BN_CTX_get(ctx);
-        y = BN_CTX_get(ctx);
-        if (y == NULL)
+        if ((A = BN_CTX_get(ctx)) == NULL)
+                goto end;
+        if ((b = BN_CTX_get(ctx)) == NULL)
+                goto end;
+        if ((q = BN_CTX_get(ctx)) == NULL)
+                goto end;
+        if ((t = BN_CTX_get(ctx)) == NULL)
+                goto end;
+        if ((x = BN_CTX_get(ctx)) == NULL)
+                goto end;
+        if ((y = BN_CTX_get(ctx)) == NULL)
                 goto end;
 
         if (ret == NULL)
diff --git a/src/lib/libcrypto/bn/bn_x931p.c b/src/lib/libcrypto/bn/bn_x931p.c
index fc8d4c3c49..89c86c1ff7 100644
--- a/src/lib/libcrypto/bn/bn_x931p.c
+++ b/src/lib/libcrypto/bn/bn_x931p.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_x931p.c,v 1.5 2014/06/12 15:49:28 deraadt Exp $ */
+/* $OpenBSD: bn_x931p.c,v 1.6 2015/02/09 15:49:22 jsing Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2005.
  */
@@ -107,17 +107,21 @@ BN_X931_derive_prime_ex(BIGNUM *p, BIGNUM *p1, BIGNUM *p2, const BIGNUM *Xp,
                 return 0;
 
         BN_CTX_start(ctx);
-        if (!p1)
-                p1 = BN_CTX_get(ctx);
-
-        if (!p2)
-                p2 = BN_CTX_get(ctx);
-
-        t = BN_CTX_get(ctx);
-
-        p1p2 = BN_CTX_get(ctx);
+        if (p1 != NULL) {
+                if ((p1 = BN_CTX_get(ctx)) == NULL)
+                        goto err;
+        }
+        if (p2 != NULL) {
+                if ((p2 = BN_CTX_get(ctx)) == NULL)
+                        goto err;
+        }
 
-        pm1 = BN_CTX_get(ctx);
+        if ((t = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((p1p2 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((pm1 = BN_CTX_get(ctx)) == NULL)
+                goto err;
 
         if (!bn_x931_derive_pi(p1, Xp1, ctx, cb))
                 goto err;
@@ -213,7 +217,8 @@ BN_X931_generate_Xpq(BIGNUM *Xp, BIGNUM *Xq, int nbits, BN_CTX *ctx)
                 return 0;
 
         BN_CTX_start(ctx);
-        t = BN_CTX_get(ctx);
+        if ((t = BN_CTX_get(ctx)) == NULL)
+                return 0;
 
         for (i = 0; i < 1000; i++) {
                 if (!BN_rand(Xq, nbits, 1, 0))
@@ -247,10 +252,14 @@ BN_X931_generate_prime_ex(BIGNUM *p, BIGNUM *p1, BIGNUM *p2, BIGNUM *Xp1,
         int ret = 0;
 
         BN_CTX_start(ctx);
-        if (!Xp1)
-                Xp1 = BN_CTX_get(ctx);
-        if (!Xp2)
-                Xp2 = BN_CTX_get(ctx);
+        if (Xp1 != NULL) {
+                if ((Xp1 = BN_CTX_get(ctx)) == NULL)
+                        goto error;
+        }
+        if (Xp2 != NULL) {
+                if ((Xp2 = BN_CTX_get(ctx)) == NULL)
+                        goto error;
+        }
 
         if (!BN_rand(Xp1, 101, 0, 0))
                 goto error;