BN_div bugfix. The q-- loop should not be entered in the n0==d0 case. (4a6222d7) · Commits · CYBER - Cyber Security / TS 103 523 MSP / TLMSP / TLMSP OpenSSL

CHANGES

+4 −0

Original line number	Diff line number	Diff line
		@@ -4,6 +4,10 @@

		Changes between 0.9.4 and 0.9.5 [xx XXX 2000]

		*) Bug fix for BN_div() when the first words of num and divsor are
		equal (it gave wrong results if (rem=(n1-q*d0)&BN_MASK2) < d0).
		[Ulf Möller]

		*) Add support for various broken PKCS#8 formats, and command line
		options to produce them.
		[Steve Henson]

crypto/bn/bn_div.c

+71 −76

Original line number	Diff line number	Diff line
		@@ -62,7 +62,7 @@
		#include "bn_lcl.h"

		/* The old slow way */
		#if 1
		#if 0
		int BN_div(BIGNUM dv, BIGNUM rem, const BIGNUM m, const BIGNUM d,
		BN_CTX *ctx)
		{
		@@ -126,6 +126,32 @@ int BN_div(BIGNUM dv, BIGNUM rem, const BIGNUM m, const BIGNUM d,

		#else

		#if !defined(NO_ASM) && !defined(PEDANTIC) && !defined(BN_DIV3W)
		# if defined(__GNUC__) && __GNUC__>=2
		# if defined(__i386)
		/*
		* There were two reasons for implementing this template:
		* - GNU C generates a call to a function (__udivdi3 to be exact)
		* in reply to ((((BN_ULLONG)n0)<<BN_BITS2)\|n1)/d0 (I fail to
		* understand why...);
		* - divl doesn't only calculate quotient, but also leaves
		* remainder in %edx which we can definitely use here:-)
		*
		* <appro@fy.chalmers.se>
		*/
		# define bn_div_words(n0,n1,d0) \
		({ asm volatile ( \
		"divl %4" \
		: "=a"(q), "=d"(rem) \
		: "a"(n1), "d"(n0), "g"(d0) \
		: "cc"); \
		q; \
		})
		# define REMAINDER_IS_ALREADY_CALCULATED
		# endif /* __<cpu> */
		# endif /* __GNUC__ */
		#endif /* NO_ASM */

		int BN_div(BIGNUM dv, BIGNUM rm, const BIGNUM num, const BIGNUM divisor,
		BN_CTX *ctx)
		{
		@@ -214,52 +240,22 @@ int BN_div(BIGNUM dv, BIGNUM rm, const BIGNUM num, const BIGNUM divisor,
		#ifdef BN_DIV3W
		q=bn_div_3_words(wnump,d1,d0);
		#else

		#if !defined(NO_ASM) && !defined(PEDANTIC)
		# if defined(__GNUC__) && __GNUC__>=2
		# if defined(__i386)
		/*
		* There were two reasons for implementing this template:
		* - GNU C generates a call to a function (__udivdi3 to be exact)
		* in reply to ((((BN_ULLONG)n0)<<BN_BITS2)\|n1)/d0 (I fail to
		* understand why...);
		* - divl doesn't only calculate quotient, but also leaves
		* remainder in %edx which we can definitely use here:-)
		*
		* <appro@fy.chalmers.se>
		*/
		# define bn_div_words(n0,n1,d0) \
		({ asm volatile ( \
		"divl %4" \
		: "=a"(q), "=d"(rem) \
		: "a"(n1), "d"(n0), "g"(d0) \
		: "cc"); \
		q; \
		})
		# define REMAINDER_IS_ALREADY_CALCULATED
		# endif /* __<cpu> */
		# endif /* __GNUC__ */
		#endif /* NO_ASM */
		BN_ULONG n0,n1,rem=0;

		n0=wnump[0];
		n1=wnump[-1];
		if (n0 == d0)
		{
		q=BN_MASK2;
		#ifdef REMAINDER_IS_ALREADY_CALCULATED /* in this case it isn't */
		rem=(n1-q*d0)&BN_MASK2;
		#endif
		}
		else /* n0 < d0 */
		{
		#ifdef BN_LLONG
		BN_ULLONG t2;

		#if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)
		q=(BN_ULONG)(((((BN_ULLONG)n0)<<BN_BITS2)\|n1)/d0);
		#else
		q=bn_div_words(n0,n1,d0);
		#endif
		{
		#ifdef BN_LLONG
		BN_ULLONG t2;

		#ifndef REMAINDER_IS_ALREADY_CALCULATED
		/*
		@@ -279,16 +275,14 @@ int BN_div(BIGNUM dv, BIGNUM rm, const BIGNUM num, const BIGNUM divisor,
		if (rem < d0) break; /* don't let rem overflow */
		t2 -= d1;
		}
		#else
		#else /* !BN_LLONG */
		BN_ULONG t2l,t2h,ql,qh;

		q=bn_div_words(n0,n1,d0);
		#ifndef REMAINDER_IS_ALREADY_CALCULATED
		/*
		* It's more than enough with the only multiplication.
		* See the comment above in BN_LLONG section...
		*/
		rem=(n1-q*d0)&BN_MASK2;
		#endif

		#ifdef BN_UMULT_HIGH
		t2l = d1 * q;
		t2h = BN_UMULT_HIGH(d1,q);
		@@ -308,9 +302,10 @@ int BN_div(BIGNUM dv, BIGNUM rm, const BIGNUM num, const BIGNUM divisor,
		if (rem < d0) break; /* don't let rem overflow */
		if (t2l < d1) t2h--; t2l -= d1;
		}
		#endif
		#endif /* !BN_LLONG */
		}
		#endif /* !BN_DIV3W */

		l0=bn_mul_words(tmp->d,sdiv->d,div_n,q);
		wnum.d--; wnum.top++;
		tmp->d[div_n]=l0;
		@@ -341,7 +336,7 @@ int BN_div(BIGNUM dv, BIGNUM rm, const BIGNUM num, const BIGNUM divisor,
		BN_CTX_end(ctx);
		return(1);
		err:
		BN_CX_end(ctx);
		BN_CTX_end(ctx);
		return(0);
		}