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Diffstat (limited to 'crypto/openssl/crypto/bn/bn_sqrt.c')
-rw-r--r--crypto/openssl/crypto/bn/bn_sqrt.c76
1 files changed, 41 insertions, 35 deletions
diff --git a/crypto/openssl/crypto/bn/bn_sqrt.c b/crypto/openssl/crypto/bn/bn_sqrt.c
index e2a1105dc838..6beaf9e5e5dd 100644
--- a/crypto/openssl/crypto/bn/bn_sqrt.c
+++ b/crypto/openssl/crypto/bn/bn_sqrt.c
@@ -1,4 +1,4 @@
-/* crypto/bn/bn_mod.c */
+/* crypto/bn/bn_sqrt.c */
/* Written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
* and Bodo Moeller for the OpenSSL project. */
/* ====================================================================
@@ -65,14 +65,12 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
* using the Tonelli/Shanks algorithm (cf. Henri Cohen, "A Course
* in Algebraic Computational Number Theory", algorithm 1.5.1).
* 'p' must be prime!
- * If 'a' is not a square, this is not necessarily detected by
- * the algorithms; a bogus result must be expected in this case.
*/
{
BIGNUM *ret = in;
int err = 1;
int r;
- BIGNUM *b, *q, *t, *x, *y;
+ BIGNUM *A, *b, *q, *t, *x, *y;
int e, i, j;
if (!BN_is_odd(p) || BN_abs_is_word(p, 1))
@@ -85,9 +83,11 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
goto end;
if (!BN_set_word(ret, BN_is_bit_set(a, 0)))
{
- BN_free(ret);
+ if (ret != in)
+ BN_free(ret);
return NULL;
}
+ bn_check_top(ret);
return ret;
}
@@ -103,23 +103,16 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
goto end;
if (!BN_set_word(ret, BN_is_one(a)))
{
- BN_free(ret);
+ if (ret != in)
+ BN_free(ret);
return NULL;
}
+ bn_check_top(ret);
return ret;
}
-#if 0 /* if BN_mod_sqrt is used with correct input, this just wastes time */
- r = BN_kronecker(a, p, ctx);
- if (r < -1) return NULL;
- if (r == -1)
- {
- BNerr(BN_F_BN_MOD_SQRT, BN_R_NOT_A_SQUARE);
- return(NULL);
- }
-#endif
-
BN_CTX_start(ctx);
+ A = BN_CTX_get(ctx);
b = BN_CTX_get(ctx);
q = BN_CTX_get(ctx);
t = BN_CTX_get(ctx);
@@ -131,6 +124,9 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
ret = BN_new();
if (ret == NULL) goto end;
+ /* A = a mod p */
+ if (!BN_nnmod(A, a, p, ctx)) goto end;
+
/* now write |p| - 1 as 2^e*q where q is odd */
e = 1;
while (!BN_is_bit_set(p, e))
@@ -149,9 +145,9 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
if (!BN_rshift(q, p, 2)) goto end;
q->neg = 0;
if (!BN_add_word(q, 1)) goto end;
- if (!BN_mod_exp(ret, a, q, p, ctx)) goto end;
+ if (!BN_mod_exp(ret, A, q, p, ctx)) goto end;
err = 0;
- goto end;
+ goto vrfy;
}
if (e == 2)
@@ -182,15 +178,8 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
* November 1992.)
*/
- /* make sure that a is reduced modulo p */
- if (a->neg || BN_ucmp(a, p) >= 0)
- {
- if (!BN_nnmod(x, a, p, ctx)) goto end;
- a = x; /* use x as temporary variable */
- }
-
/* t := 2*a */
- if (!BN_mod_lshift1_quick(t, a, p)) goto end;
+ if (!BN_mod_lshift1_quick(t, A, p)) goto end;
/* b := (2*a)^((|p|-5)/8) */
if (!BN_rshift(q, p, 3)) goto end;
@@ -205,12 +194,12 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
if (!BN_sub_word(t, 1)) goto end;
/* x = a*b*t */
- if (!BN_mod_mul(x, a, b, p, ctx)) goto end;
+ if (!BN_mod_mul(x, A, b, p, ctx)) goto end;
if (!BN_mod_mul(x, x, t, p, ctx)) goto end;
if (!BN_copy(ret, x)) goto end;
err = 0;
- goto end;
+ goto vrfy;
}
/* e > 2, so we really have to use the Tonelli/Shanks algorithm.
@@ -297,11 +286,11 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
/* x := a^((q-1)/2) */
if (BN_is_zero(t)) /* special case: p = 2^e + 1 */
{
- if (!BN_nnmod(t, a, p, ctx)) goto end;
+ if (!BN_nnmod(t, A, p, ctx)) goto end;
if (BN_is_zero(t))
{
/* special case: a == 0 (mod p) */
- if (!BN_zero(ret)) goto end;
+ BN_zero(ret);
err = 0;
goto end;
}
@@ -310,11 +299,11 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
}
else
{
- if (!BN_mod_exp(x, a, t, p, ctx)) goto end;
+ if (!BN_mod_exp(x, A, t, p, ctx)) goto end;
if (BN_is_zero(x))
{
/* special case: a == 0 (mod p) */
- if (!BN_zero(ret)) goto end;
+ BN_zero(ret);
err = 0;
goto end;
}
@@ -322,10 +311,10 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
/* b := a*x^2 (= a^q) */
if (!BN_mod_sqr(b, x, p, ctx)) goto end;
- if (!BN_mod_mul(b, b, a, p, ctx)) goto end;
+ if (!BN_mod_mul(b, b, A, p, ctx)) goto end;
/* x := a*x (= a^((q+1)/2)) */
- if (!BN_mod_mul(x, x, a, p, ctx)) goto end;
+ if (!BN_mod_mul(x, x, A, p, ctx)) goto end;
while (1)
{
@@ -342,7 +331,7 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
{
if (!BN_copy(ret, x)) goto end;
err = 0;
- goto end;
+ goto vrfy;
}
@@ -373,6 +362,22 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
e = i;
}
+ vrfy:
+ if (!err)
+ {
+ /* verify the result -- the input might have been not a square
+ * (test added in 0.9.8) */
+
+ if (!BN_mod_sqr(x, ret, p, ctx))
+ err = 1;
+
+ if (!err && 0 != BN_cmp(x, A))
+ {
+ BNerr(BN_F_BN_MOD_SQRT, BN_R_NOT_A_SQUARE);
+ err = 1;
+ }
+ }
+
end:
if (err)
{
@@ -383,5 +388,6 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
ret = NULL;
}
BN_CTX_end(ctx);
+ bn_check_top(ret);
return ret;
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-06 11:38:49 +0000