curve25519: do everything on the stack

With MIPS now supporting a separate IRQ stack, and with these changes
being backported into OpenWRT (and likely the stable mainline releases),
we no longer need to kmalloc more space for temporary variables.

1 files changed, 0 insertions, 171 deletions

diff --git a/src/crypto/curve25519.c b/src/crypto/curve25519.c
index 28dddcd..6a1bcd0 100644
--- a/src/crypto/curve25519.c
+++ b/src/crypto/curve25519.c
@@ -10,12 +10,6 @@
 #include <linux/random.h>
 #include <crypto/algapi.h>
 
-#define ARCH_HAS_SEPARATE_IRQ_STACK
-
-#if defined(CONFIG_MIPS) /* TODO: add other archs that are missing a separate IRQ stack. */
-#undef ARCH_HAS_SEPARATE_IRQ_STACK
-#endif
-
 static __always_inline void normalize_secret(u8 secret[CURVE25519_POINT_SIZE])
 {
 	secret[0] &= 248;
@@ -1070,7 +1064,6 @@ static void crecip(limb *out, const limb *z)
 }
 
 
-#ifdef ARCH_HAS_SEPARATE_IRQ_STACK
 /* Input: Q, Q', Q-Q'
  * Output: 2Q, Q+Q'
  *
@@ -1230,170 +1223,6 @@ void curve25519(u8 mypublic[CURVE25519_POINT_SIZE], const u8 secret[CURVE25519_P
 	memzero_explicit(z, sizeof(z));
 	memzero_explicit(zmone, sizeof(zmone));
 }
-#else
-struct other_stack {
-	limb origx[10], origxprime[10], zzz[19], xx[19], zz[19], xxprime[19], zzprime[19], zzzprime[19], xxxprime[19];
-	limb a[19], b[19], c[19], d[19], e[19], f[19], g[19], h[19];
-	limb bp[10], x[10], z[11], zmone[10];
-	u8 ee[32];
-};
-
-/* Input: Q, Q', Q-Q'
- * Output: 2Q, Q+Q'
- *
- *   x2 z3: long form
- *   x3 z3: long form
- *   x z: short form, destroyed
- *   xprime zprime: short form, destroyed
- *   qmqp: short form, preserved
- *
- * On entry and exit, the absolute value of the limbs of all inputs and outputs
- * are < 2^26. */
-static void fmonty(struct other_stack *s,
-		   limb *x2, limb *z2,  /* output 2Q */
-		   limb *x3, limb *z3,  /* output Q + Q' */
-		   limb *x, limb *z,    /* input Q */
-		   limb *xprime, limb *zprime,  /* input Q' */
-		   const limb *qmqp /* input Q - Q' */)
-{
-	memcpy(s->origx, x, 10 * sizeof(limb));
-	fsum(x, z);
-	/* |x[i]| < 2^27 */
-	fdifference(z, s->origx);  /* does x - z */
-	/* |z[i]| < 2^27 */
-
-	memcpy(s->origxprime, xprime, sizeof(limb) * 10);
-	fsum(xprime, zprime);
-	/* |xprime[i]| < 2^27 */
-	fdifference(zprime, s->origxprime);
-	/* |zprime[i]| < 2^27 */
-	fproduct(s->xxprime, xprime, z);
-	/* |s->xxprime[i]| < 14*2^54: the largest product of two limbs will be <
-	 * 2^(27+27) and fproduct adds together, at most, 14 of those products.
-	 * (Approximating that to 2^58 doesn't work out.) */
-	fproduct(s->zzprime, x, zprime);
-	/* |s->zzprime[i]| < 14*2^54 */
-	freduce_degree(s->xxprime);
-	freduce_coefficients(s->xxprime);
-	/* |s->xxprime[i]| < 2^26 */
-	freduce_degree(s->zzprime);
-	freduce_coefficients(s->zzprime);
-	/* |s->zzprime[i]| < 2^26 */
-	memcpy(s->origxprime, s->xxprime, sizeof(limb) * 10);
-	fsum(s->xxprime, s->zzprime);
-	/* |s->xxprime[i]| < 2^27 */
-	fdifference(s->zzprime, s->origxprime);
-	/* |s->zzprime[i]| < 2^27 */
-	fsquare(s->xxxprime, s->xxprime);
-	/* |s->xxxprime[i]| < 2^26 */
-	fsquare(s->zzzprime, s->zzprime);
-	/* |s->zzzprime[i]| < 2^26 */
-	fproduct(s->zzprime, s->zzzprime, qmqp);
-	/* |s->zzprime[i]| < 14*2^52 */
-	freduce_degree(s->zzprime);
-	freduce_coefficients(s->zzprime);
-	/* |s->zzprime[i]| < 2^26 */
-	memcpy(x3, s->xxxprime, sizeof(limb) * 10);
-	memcpy(z3, s->zzprime, sizeof(limb) * 10);
-
-	fsquare(s->xx, x);
-	/* |s->xx[i]| < 2^26 */
-	fsquare(s->zz, z);
-	/* |s->zz[i]| < 2^26 */
-	fproduct(x2, s->xx, s->zz);
-	/* |x2[i]| < 14*2^52 */
-	freduce_degree(x2);
-	freduce_coefficients(x2);
-	/* |x2[i]| < 2^26 */
-	fdifference(s->zz, s->xx);  // does s->zz = s->xx - s->zz
-	/* |s->zz[i]| < 2^27 */
-	memset(s->zzz + 10, 0, sizeof(limb) * 9);
-	fscalar_product(s->zzz, s->zz, 121665);
-	/* |s->zzz[i]| < 2^(27+17) */
-	/* No need to call freduce_degree here:
-		 fscalar_product doesn't increase the degree of its input. */
-	freduce_coefficients(s->zzz);
-	/* |s->zzz[i]| < 2^26 */
-	fsum(s->zzz, s->xx);
-	/* |s->zzz[i]| < 2^27 */
-	fproduct(z2, s->zz, s->zzz);
-	/* |z2[i]| < 14*2^(26+27) */
-	freduce_degree(z2);
-	freduce_coefficients(z2);
-	/* |z2|i| < 2^26 */
-}
-
-/* Calculates nQ where Q is the x-coordinate of a point on the curve
- *
- *   resultx/resultz: the x coordinate of the resulting curve point (short form)
- *   n: a little endian, 32-byte number
- *   q: a point of the curve (short form) */
-static void cmult(struct other_stack *s, limb *resultx, limb *resultz, const u8 *n, const limb *q)
-{
-	unsigned i, j;
-	limb *nqpqx = s->a, *nqpqz = s->b, *nqx = s->c, *nqz = s->d, *t;
-	limb *nqpqx2 = s->e, *nqpqz2 = s->f, *nqx2 = s->g, *nqz2 = s->h;
-
-	*nqpqz = *nqx = *nqpqz2 = *nqz2 = 1;
-	memcpy(nqpqx, q, sizeof(limb) * 10);
-
-	for (i = 0; i < 32; ++i) {
-		u8 byte = n[31 - i];
-		for (j = 0; j < 8; ++j) {
-			const limb bit = byte >> 7;
-
-			swap_conditional(nqx, nqpqx, bit);
-			swap_conditional(nqz, nqpqz, bit);
-			fmonty(s,
-			       nqx2, nqz2,
-			       nqpqx2, nqpqz2,
-			       nqx, nqz,
-			       nqpqx, nqpqz,
-			       q);
-			swap_conditional(nqx2, nqpqx2, bit);
-			swap_conditional(nqz2, nqpqz2, bit);
-
-			t = nqx;
-			nqx = nqx2;
-			nqx2 = t;
-			t = nqz;
-			nqz = nqz2;
-			nqz2 = t;
-			t = nqpqx;
-			nqpqx = nqpqx2;
-			nqpqx2 = t;
-			t = nqpqz;
-			nqpqz = nqpqz2;
-			nqpqz2 = t;
-
-			byte <<= 1;
-		}
-	}
-
-	memcpy(resultx, nqx, sizeof(limb) * 10);
-	memcpy(resultz, nqz, sizeof(limb) * 10);
-}
-
-void curve25519(u8 mypublic[CURVE25519_POINT_SIZE], const u8 secret[CURVE25519_POINT_SIZE], const u8 basepoint[CURVE25519_POINT_SIZE])
-{
-	struct other_stack *s = kzalloc(sizeof(struct other_stack), GFP_KERNEL);
-	if (unlikely(!s)) {
-		memset(mypublic, 0, CURVE25519_POINT_SIZE);
-		return;
-	}
-
-	memcpy(s->ee, secret, 32);
-	normalize_secret(s->ee);
-
-	fexpand(s->bp, basepoint);
-	cmult(s, s->x, s->z, s->ee, s->bp);
-	crecip(s->zmone, s->z);
-	fmul(s->z, s->x, s->zmone);
-	fcontract(mypublic, s->z);
-
-	kzfree(s);
-}
-#endif
 #endif
 
 void curve25519_generate_secret(u8 secret[CURVE25519_POINT_SIZE])