File openssl-add-BN_FLG_FIXED_TOP-flag.patch of Package openssl.24728

From b7862891fed4cfb5ec36a31d35e14b51bf26d01e Mon Sep 17 00:00:00 2001
From: Andy Polyakov <appro@openssl.org>
Date: Fri, 6 Jul 2018 15:02:29 +0200
Subject: [PATCH] bn/bn_lib.c: add BN_FLG_FIXED_TOP flag.

The new flag marks vectors that were not treated with bn_correct_top,
in other words such vectors are permitted to be zero padded. For now
it's BN_DEBUG-only flag, as initial use case for zero-padded vectors
would be controlled Montgomery multiplication/exponentiation, not
general purpose. For general purpose use another type might be more
appropriate. Advantage of this suggestion is that it's possible to
back-port it...

bn/bn_div.c: fix memory sanitizer problem.
bn/bn_sqr.c: harmonize with BN_mul.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6707)

(cherry picked from commit 305b68f1a2b6d4d0aa07a6ab47ac372f067a40bb)

Resolved conflicts:
	crypto/bn/bn_lcl.h
---
 crypto/bn/bn_div.c |  1 +
 crypto/bn/bn_lcl.h | 18 +++++++++++++++---
 crypto/bn/bn_lib.c | 15 +++++++++++----
 crypto/bn/bn_sqr.c | 10 ++--------
 4 files changed, 29 insertions(+), 15 deletions(-)

Index: openssl-1.0.2j/crypto/bn/bn_div.c
===================================================================
--- openssl-1.0.2j.orig/crypto/bn/bn_div.c
+++ openssl-1.0.2j/crypto/bn/bn_div.c
@@ -290,6 +290,7 @@ int BN_div(BIGNUM *dv, BIGNUM *rm, const
     wnum.neg = 0;
     wnum.d = &(snum->d[loop]);
     wnum.top = div_n;
+    wnum.flags = BN_FLG_STATIC_DATA;
     /*
      * only needed when BN_ucmp messes up the values between top and max
      */
Index: openssl-1.0.2j/crypto/bn/bn_lib.c
===================================================================
--- openssl-1.0.2j.orig/crypto/bn/bn_lib.c
+++ openssl-1.0.2j/crypto/bn/bn_lib.c
@@ -524,9 +524,10 @@ BIGNUM *BN_copy(BIGNUM *a, const BIGNUM
     memcpy(a->d, b->d, sizeof(b->d[0]) * b->top);
 #endif
 
-    a->top = b->top;
     a->neg = b->neg;
+    a->top = b->top;
+    a->flags |= b->flags & BN_FLG_FIXED_TOP;
     bn_check_top(a);
     return (a);
 }
 
@@ -570,8 +574,9 @@ void BN_clear(BIGNUM *a)
     bn_check_top(a);
     if (a->d != NULL)
         OPENSSL_cleanse(a->d, a->dmax * sizeof(a->d[0]));
-    a->top = 0;
     a->neg = 0;
+    a->top = 0;
+    a->flags &= ~BN_FLG_FIXED_TOP;
 }
 
 BN_ULONG BN_get_word(const BIGNUM *a)
@@ -592,6 +597,7 @@ int BN_set_word(BIGNUM *a, BN_ULONG w)
     a->neg = 0;
     a->d[0] = w;
     a->top = (w ? 1 : 0);
+    a->flags &= ~BN_FLG_FIXED_TOP;
     bn_check_top(a);
     return (1);
 }
@@ -787,6 +793,7 @@ int BN_set_bit(BIGNUM *a, int n)
         for (k = a->top; k < i + 1; k++)
             a->d[k] = 0;
         a->top = i + 1;
+        a->flags &= ~BN_FLG_FIXED_TOP;
     }
 
     a->d[i] |= (((BN_ULONG)1) << j);
Index: openssl-1.0.2j/crypto/bn/bn.h
===================================================================
--- openssl-1.0.2j.orig/crypto/bn/bn.h
+++ openssl-1.0.2j/crypto/bn/bn.h
@@ -410,8 +410,9 @@ int BN_GENCB_call(BN_GENCB *cb, int a, i
 # define BN_zero_ex(a) \
         do { \
                 BIGNUM *_tmp_bn = (a); \
-                _tmp_bn->top = 0; \
                 _tmp_bn->neg = 0; \
+                _tmp_bn->top = 0; \
+                (a)->flags &= ~BN_FLG_FIXED_TOP; \
         } while(0)
 # ifdef OPENSSL_NO_DEPRECATED
 #  define BN_zero(a)      BN_zero_ex(a)
@@ -829,9 +830,10 @@ int RAND_pseudo_bytes(unsigned char *buf
         do { \
                 const BIGNUM *_bnum2 = (a); \
                 if (_bnum2 != NULL) { \
-                        assert((_bnum2->top == 0) || \
-			        (_bnum2->flags & BN_FLG_FIXED_TOP) || \
-                               (_bnum2->d[_bnum2->top - 1] != 0)); \
+			 int _top = _bnum2->top; \
+			 OPENSSL_assert((_top == 0 && !_bnum2->neg) || \
+				(_top && ((_bnum2->flags & BN_FLG_FIXED_TOP) \
+					  || _bnum2->d[_top - 1] != 0))); \
                         bn_pollute(_bnum2); \
                 } \
         } while(0)
@@ -870,6 +872,7 @@ int RAND_pseudo_bytes(unsigned char *buf
                 } \
         if ((a)->top == 0) \
             (a)->neg = 0; \
+        (a)->flags &= ~BN_FLG_FIXED_TOP; \
         bn_pollute(a); \
         }