+/*-
+ * Bignum consistency macros
+ * There is one "API" macro, bn_fix_top(), for stripping leading zeroes from
+ * bignum data after direct manipulations on the data. There is also an
+ * "internal" macro, bn_check_top(), for verifying that there are no leading
+ * zeroes. Unfortunately, some auditing is required due to the fact that
+ * bn_fix_top() has become an overabused duct-tape because bignum data is
+ * occasionally passed around in an inconsistent state. So the following
+ * changes have been made to sort this out;
+ * - bn_fix_top()s implementation has been moved to bn_correct_top()
+ * - if BN_DEBUG isn't defined, bn_fix_top() maps to bn_correct_top(), and
+ * bn_check_top() is as before.
+ * - if BN_DEBUG *is* defined;
+ * - bn_check_top() tries to pollute unused words even if the bignum 'top' is
+ * consistent. (ed: only if BN_DEBUG_RAND is defined)
+ * - bn_fix_top() maps to bn_check_top() rather than "fixing" anything.
+ * The idea is to have debug builds flag up inconsistent bignums when they
+ * occur. If that occurs in a bn_fix_top(), we examine the code in question; if
+ * the use of bn_fix_top() was appropriate (ie. it follows directly after code
+ * that manipulates the bignum) it is converted to bn_correct_top(), and if it
+ * was not appropriate, we convert it permanently to bn_check_top() and track
+ * down the cause of the bug. Eventually, no internal code should be using the
+ * bn_fix_top() macro. External applications and libraries should try this with
+ * their own code too, both in terms of building against the openssl headers
+ * with BN_DEBUG defined *and* linking with a version of OpenSSL built with it
+ * defined. This not only improves external code, it provides more test
+ * coverage for openssl's own code.
+ */
+
+# ifdef BN_DEBUG
+
+/* We only need assert() when debugging */
+# include <assert.h>
+
+# ifdef BN_DEBUG_RAND
+/* To avoid "make update" cvs wars due to BN_DEBUG, use some tricks */
+# ifndef RAND_pseudo_bytes
+int RAND_pseudo_bytes(unsigned char *buf, int num);
+# define BN_DEBUG_TRIX
+# endif
+# define bn_pollute(a) \
+ do { \
+ const BIGNUM *_bnum1 = (a); \
+ if(_bnum1->top < _bnum1->dmax) { \
+ unsigned char _tmp_char; \
+ /* We cast away const without the compiler knowing, any \
+ * *genuinely* constant variables that aren't mutable \
+ * wouldn't be constructed with top!=dmax. */ \
+ BN_ULONG *_not_const; \
+ memcpy(&_not_const, &_bnum1->d, sizeof(_not_const)); \
+ RAND_bytes(&_tmp_char, 1); /* Debug only - safe to ignore error return */\
+ memset(_not_const + _bnum1->top, _tmp_char, \
+ sizeof(*_not_const) * (_bnum1->dmax - _bnum1->top)); \
+ } \
+ } while(0)
+# ifdef BN_DEBUG_TRIX
+# undef RAND_pseudo_bytes
+# endif
+# else
+# define bn_pollute(a)
+# endif
+# define bn_check_top(a) \
+ do { \
+ const BIGNUM *_bnum2 = (a); \
+ if (_bnum2 != NULL) { \
+ assert((_bnum2->top == 0) || \
+ (_bnum2->d[_bnum2->top - 1] != 0)); \
+ bn_pollute(_bnum2); \
+ } \
+ } while(0)
+
+# define bn_fix_top(a) bn_check_top(a)
+
+# define bn_check_size(bn, bits) bn_wcheck_size(bn, ((bits+BN_BITS2-1))/BN_BITS2)
+# define bn_wcheck_size(bn, words) \
+ do { \
+ const BIGNUM *_bnum2 = (bn); \
+ assert((words) <= (_bnum2)->dmax && (words) >= (_bnum2)->top); \
+ /* avoid unused variable warning with NDEBUG */ \
+ (void)(_bnum2); \
+ } while(0)
+
+# else /* !BN_DEBUG */
+
+# define bn_pollute(a)
+# define bn_check_top(a)
+# define bn_fix_top(a) bn_correct_top(a)
+# define bn_check_size(bn, bits)
+# define bn_wcheck_size(bn, words)
+
+# endif
+
+BN_ULONG bn_mul_add_words(BN_ULONG *rp, const BN_ULONG *ap, int num,
+ BN_ULONG w);
+BN_ULONG bn_mul_words(BN_ULONG *rp, const BN_ULONG *ap, int num, BN_ULONG w);
+void bn_sqr_words(BN_ULONG *rp, const BN_ULONG *ap, int num);
+BN_ULONG bn_div_words(BN_ULONG h, BN_ULONG l, BN_ULONG d);
+BN_ULONG bn_add_words(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,
+ int num);
+BN_ULONG bn_sub_words(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,
+ int num);
+
+struct bignum_st {
+ BN_ULONG *d; /* Pointer to an array of 'BN_BITS2' bit
+ * chunks. */
+ int top; /* Index of last used d +1. */
+ /* The next are internal book keeping for bn_expand. */
+ int dmax; /* Size of the d array. */
+ int neg; /* one if the number is negative */
+ int flags;
+};
+
+/* Used for montgomery multiplication */
+struct bn_mont_ctx_st {
+ int ri; /* number of bits in R */
+ BIGNUM RR; /* used to convert to montgomery form */
+ BIGNUM N; /* The modulus */
+ BIGNUM Ni; /* R*(1/R mod N) - N*Ni = 1 (Ni is only
+ * stored for bignum algorithm) */
+ BN_ULONG n0[2]; /* least significant word(s) of Ni; (type
+ * changed with 0.9.9, was "BN_ULONG n0;"
+ * before) */
+ int flags;
+};