Inital import.

Initial fork from f2d678e6e89b6508147086610e985d4e8416e867 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)

1 files changed, 704 insertions, 0 deletions

diff --git a/crypto/bn/gcd.c b/crypto/bn/gcd.c
new file mode 100644
index 00000000..2dce296c
--- /dev/null
+++ b/crypto/bn/gcd.c
@@ -0,0 +1,704 @@
+/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
+ * All rights reserved.
+ *
+ * This package is an SSL implementation written
+ * by Eric Young (eay@cryptsoft.com).
+ * The implementation was written so as to conform with Netscapes SSL.
+ *
+ * This library is free for commercial and non-commercial use as long as
+ * the following conditions are aheared to.  The following conditions
+ * apply to all code found in this distribution, be it the RC4, RSA,
+ * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
+ * included with this distribution is covered by the same copyright terms
+ * except that the holder is Tim Hudson (tjh@cryptsoft.com).
+ *
+ * Copyright remains Eric Young's, and as such any Copyright notices in
+ * the code are not to be removed.
+ * If this package is used in a product, Eric Young should be given attribution
+ * as the author of the parts of the library used.
+ * This can be in the form of a textual message at program startup or
+ * in documentation (online or textual) provided with the package.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *    "This product includes cryptographic software written by
+ *     Eric Young (eay@cryptsoft.com)"
+ *    The word 'cryptographic' can be left out if the rouines from the library
+ *    being used are not cryptographic related :-).
+ * 4. If you include any Windows specific code (or a derivative thereof) from
+ *    the apps directory (application code) you must include an acknowledgement:
+ *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * The licence and distribution terms for any publically available version or
+ * derivative of this code cannot be changed.  i.e. this code cannot simply be
+ * copied and put under another distribution licence
+ * [including the GNU Public Licence.]
+ */
+/* ====================================================================
+ * Copyright (c) 1998-2001 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This product includes cryptographic software written by Eric Young
+ * (eay@cryptsoft.com).  This product includes software written by Tim
+ * Hudson (tjh@cryptsoft.com). */
+
+#include <openssl/bn.h>
+
+#include <openssl/err.h>
+
+#include "internal.h"
+
+static BIGNUM *euclid(BIGNUM *a, BIGNUM *b) {
+  BIGNUM *t;
+  int shifts = 0;
+
+  /* 0 <= b <= a */
+  while (!BN_is_zero(b)) {
+    /* 0 < b <= a */
+
+    if (BN_is_odd(a)) {
+      if (BN_is_odd(b)) {
+        if (!BN_sub(a, a, b)) {
+          goto err;
+        }
+        if (!BN_rshift1(a, a)) {
+          goto err;
+        }
+        if (BN_cmp(a, b) < 0) {
+          t = a;
+          a = b;
+          b = t;
+        }
+      } else {
+        /* a odd - b even */
+        if (!BN_rshift1(b, b)) {
+          goto err;
+        }
+        if (BN_cmp(a, b) < 0) {
+          t = a;
+          a = b;
+          b = t;
+        }
+      }
+    } else {
+      /* a is even */
+      if (BN_is_odd(b)) {
+        if (!BN_rshift1(a, a)) {
+          goto err;
+        }
+        if (BN_cmp(a, b) < 0) {
+          t = a;
+          a = b;
+          b = t;
+        }
+      } else {
+        /* a even - b even */
+        if (!BN_rshift1(a, a)) {
+          goto err;
+        }
+        if (!BN_rshift1(b, b)) {
+          goto err;
+        }
+        shifts++;
+      }
+    }
+    /* 0 <= b <= a */
+  }
+
+  if (shifts) {
+    if (!BN_lshift(a, a, shifts)) {
+      goto err;
+    }
+  }
+
+  return a;
+
+err:
+  return NULL;
+}
+
+int BN_gcd(BIGNUM *r, const BIGNUM *in_a, const BIGNUM *in_b, BN_CTX *ctx) {
+  BIGNUM *a, *b, *t;
+  int ret = 0;
+
+  BN_CTX_start(ctx);
+  a = BN_CTX_get(ctx);
+  b = BN_CTX_get(ctx);
+
+  if (a == NULL || b == NULL) {
+    goto err;
+  }
+  if (BN_copy(a, in_a) == NULL) {
+    goto err;
+  }
+  if (BN_copy(b, in_b) == NULL) {
+    goto err;
+  }
+
+  a->neg = 0;
+  b->neg = 0;
+
+  if (BN_cmp(a, b) < 0) {
+    t = a;
+    a = b;
+    b = t;
+  }
+  t = euclid(a, b);
+  if (t == NULL) {
+    goto err;
+  }
+
+  if (BN_copy(r, t) == NULL) {
+    goto err;
+  }
+  ret = 1;
+
+err:
+  BN_CTX_end(ctx);
+  return ret;
+}
+
+/* solves ax == 1 (mod n) */
+static BIGNUM *BN_mod_inverse_no_branch(BIGNUM *out, const BIGNUM *a,
+                                        const BIGNUM *n, BN_CTX *ctx);
+
+BIGNUM *BN_mod_inverse(BIGNUM *out, const BIGNUM *a, const BIGNUM *n,
+                       BN_CTX *ctx) {
+  BIGNUM *A, *B, *X, *Y, *M, *D, *T, *R = NULL;
+  BIGNUM *ret = NULL;
+  int sign;
+
+  if ((a->flags & BN_FLG_CONSTTIME) != 0 ||
+      (n->flags & BN_FLG_CONSTTIME) != 0) {
+    return BN_mod_inverse_no_branch(out, a, n, ctx);
+  }
+
+  BN_CTX_start(ctx);
+  A = BN_CTX_get(ctx);
+  B = BN_CTX_get(ctx);
+  X = BN_CTX_get(ctx);
+  D = BN_CTX_get(ctx);
+  M = BN_CTX_get(ctx);
+  Y = BN_CTX_get(ctx);
+  T = BN_CTX_get(ctx);
+  if (T == NULL) {
+    goto err;
+  }
+
+  if (out == NULL) {
+    R = BN_new();
+  } else {
+    R = out;
+  }
+  if (R == NULL) {
+    goto err;
+  }
+
+  BN_one(X);
+  BN_zero(Y);
+  if (BN_copy(B, a) == NULL) {
+    goto err;
+  }
+  if (BN_copy(A, n) == NULL) {
+    goto err;
+  }
+  A->neg = 0;
+  if (B->neg || (BN_ucmp(B, A) >= 0)) {
+    if (!BN_nnmod(B, B, A, ctx)) {
+      goto err;
+    }
+  }
+  sign = -1;
+  /* From  B = a mod |n|,  A = |n|  it follows that
+   *
+   *      0 <= B < A,
+   *     -sign*X*a  ==  B   (mod |n|),
+   *      sign*Y*a  ==  A   (mod |n|).
+   */
+
+  if (BN_is_odd(n) && (BN_num_bits(n) <= (BN_BITS <= 32 ? 450 : 2048))) {
+    /* Binary inversion algorithm; requires odd modulus.
+     * This is faster than the general algorithm if the modulus
+     * is sufficiently small (about 400 .. 500 bits on 32-bit
+     * sytems, but much more on 64-bit systems) */
+    int shift;
+
+    while (!BN_is_zero(B)) {
+      /*      0 < B < |n|,
+       *      0 < A <= |n|,
+       * (1) -sign*X*a  ==  B   (mod |n|),
+       * (2)  sign*Y*a  ==  A   (mod |n|) */
+
+      /* Now divide  B  by the maximum possible power of two in the integers,
+       * and divide  X  by the same value mod |n|.
+       * When we're done, (1) still holds. */
+      shift = 0;
+      while (!BN_is_bit_set(B, shift)) {
+        /* note that 0 < B */
+        shift++;
+
+        if (BN_is_odd(X)) {
+          if (!BN_uadd(X, X, n)) {
+            goto err;
+          }
+        }
+        /* now X is even, so we can easily divide it by two */
+        if (!BN_rshift1(X, X)) {
+          goto err;
+        }
+      }
+      if (shift > 0) {
+        if (!BN_rshift(B, B, shift)) {
+          goto err;
+        }
+      }
+
+      /* Same for A and Y. Afterwards, (2) still holds. */
+      shift = 0;
+      while (!BN_is_bit_set(A, shift)) {
+        /* note that 0 < A */
+        shift++;
+
+        if (BN_is_odd(Y)) {
+          if (!BN_uadd(Y, Y, n)) {
+            goto err;
+          }
+        }
+        /* now Y is even */
+        if (!BN_rshift1(Y, Y)) {
+          goto err;
+        }
+      }
+      if (shift > 0) {
+        if (!BN_rshift(A, A, shift)) {
+          goto err;
+        }
+      }
+
+      /* We still have (1) and (2).
+       * Both  A  and  B  are odd.
+       * The following computations ensure that
+       *
+       *     0 <= B < |n|,
+       *      0 < A < |n|,
+       * (1) -sign*X*a  ==  B   (mod |n|),
+       * (2)  sign*Y*a  ==  A   (mod |n|),
+       *
+       * and that either  A  or  B  is even in the next iteration. */
+      if (BN_ucmp(B, A) >= 0) {
+        /* -sign*(X + Y)*a == B - A  (mod |n|) */
+        if (!BN_uadd(X, X, Y)) {
+          goto err;
+        }
+        /* NB: we could use BN_mod_add_quick(X, X, Y, n), but that
+         * actually makes the algorithm slower */
+        if (!BN_usub(B, B, A)) {
+          goto err;
+        }
+      } else {
+        /*  sign*(X + Y)*a == A - B  (mod |n|) */
+        if (!BN_uadd(Y, Y, X)) {
+          goto err;
+        }
+        /* as above, BN_mod_add_quick(Y, Y, X, n) would slow things down */
+        if (!BN_usub(A, A, B)) {
+          goto err;
+        }
+      }
+    }
+  } else {
+    /* general inversion algorithm */
+
+    while (!BN_is_zero(B)) {
+      BIGNUM *tmp;
+
+      /*
+       *      0 < B < A,
+       * (*) -sign*X*a  ==  B   (mod |n|),
+       *      sign*Y*a  ==  A   (mod |n|) */
+
+      /* (D, M) := (A/B, A%B) ... */
+      if (BN_num_bits(A) == BN_num_bits(B)) {
+        if (!BN_one(D)) {
+          goto err;
+        }
+        if (!BN_sub(M, A, B)) {
+          goto err;
+        }
+      } else if (BN_num_bits(A) == BN_num_bits(B) + 1) {
+        /* A/B is 1, 2, or 3 */
+        if (!BN_lshift1(T, B)) {
+          goto err;
+        }
+        if (BN_ucmp(A, T) < 0) {
+          /* A < 2*B, so D=1 */
+          if (!BN_one(D)) {
+            goto err;
+          }
+          if (!BN_sub(M, A, B)) {
+            goto err;
+          }
+        } else {
+          /* A >= 2*B, so D=2 or D=3 */
+          if (!BN_sub(M, A, T)) {
+            goto err;
+          }
+          if (!BN_add(D, T, B)) {
+            goto err; /* use D (:= 3*B) as temp */
+          }
+          if (BN_ucmp(A, D) < 0) {
+            /* A < 3*B, so D=2 */
+            if (!BN_set_word(D, 2)) {
+              goto err;
+            }
+            /* M (= A - 2*B) already has the correct value */
+          } else {
+            /* only D=3 remains */
+            if (!BN_set_word(D, 3)) {
+              goto err;
+            }
+            /* currently  M = A - 2*B,  but we need  M = A - 3*B */
+            if (!BN_sub(M, M, B)) {
+              goto err;
+            }
+          }
+        }
+      } else {
+        if (!BN_div(D, M, A, B, ctx)) {
+          goto err;
+        }
+      }
+
+      /* Now
+       *      A = D*B + M;
+       * thus we have
+       * (**)  sign*Y*a  ==  D*B + M   (mod |n|). */
+
+      tmp = A; /* keep the BIGNUM object, the value does not matter */
+
+      /* (A, B) := (B, A mod B) ... */
+      A = B;
+      B = M;
+      /* ... so we have  0 <= B < A  again */
+
+      /* Since the former  M  is now  B  and the former  B  is now  A,
+       * (**) translates into
+       *       sign*Y*a  ==  D*A + B    (mod |n|),
+       * i.e.
+       *       sign*Y*a - D*A  ==  B    (mod |n|).
+       * Similarly, (*) translates into
+       *      -sign*X*a  ==  A          (mod |n|).
+       *
+       * Thus,
+       *   sign*Y*a + D*sign*X*a  ==  B  (mod |n|),
+       * i.e.
+       *        sign*(Y + D*X)*a  ==  B  (mod |n|).
+       *
+       * So if we set  (X, Y, sign) := (Y + D*X, X, -sign),  we arrive back at
+       *      -sign*X*a  ==  B   (mod |n|),
+       *       sign*Y*a  ==  A   (mod |n|).
+       * Note that  X  and  Y  stay non-negative all the time. */
+
+      /* most of the time D is very small, so we can optimize tmp := D*X+Y */
+      if (BN_is_one(D)) {
+        if (!BN_add(tmp, X, Y)) {
+          goto err;
+        }
+      } else {
+        if (BN_is_word(D, 2)) {
+          if (!BN_lshift1(tmp, X)) {
+            goto err;
+          }
+        } else if (BN_is_word(D, 4)) {
+          if (!BN_lshift(tmp, X, 2)) {
+            goto err;
+          }
+        } else if (D->top == 1) {
+          if (!BN_copy(tmp, X)) {
+            goto err;
+          }
+          if (!BN_mul_word(tmp, D->d[0])) {
+            goto err;
+          }
+        } else {
+          if (!BN_mul(tmp, D, X, ctx)) {
+            goto err;
+          }
+        }
+        if (!BN_add(tmp, tmp, Y)) {
+          goto err;
+        }
+      }
+
+      M = Y; /* keep the BIGNUM object, the value does not matter */
+      Y = X;
+      X = tmp;
+      sign = -sign;
+    }
+  }
+
+  /* The while loop (Euclid's algorithm) ends when
+   *      A == gcd(a,n);
+   * we have
+   *       sign*Y*a  ==  A  (mod |n|),
+   * where  Y  is non-negative. */
+
+  if (sign < 0) {
+    if (!BN_sub(Y, n, Y)) {
+      goto err;
+    }
+  }
+  /* Now  Y*a  ==  A  (mod |n|).  */
+
+  if (BN_is_one(A)) {
+    /* Y*a == 1  (mod |n|) */
+    if (!Y->neg && BN_ucmp(Y, n) < 0) {
+      if (!BN_copy(R, Y)) {
+        goto err;
+      }
+    } else {
+      if (!BN_nnmod(R, Y, n, ctx)) {
+        goto err;
+      }
+    }
+  } else {
+    OPENSSL_PUT_ERROR(BN, BN_mod_inverse, BN_R_NO_INVERSE);
+    goto err;
+  }
+  ret = R;
+
+err:
+  if (ret == NULL && out == NULL) {
+    BN_free(R);
+  }
+  BN_CTX_end(ctx);
+  return ret;
+}
+
+/* BN_mod_inverse_no_branch is a special version of BN_mod_inverse.
+ * It does not contain branches that may leak sensitive information. */
+static BIGNUM *BN_mod_inverse_no_branch(BIGNUM *out, const BIGNUM *a,
+                                        const BIGNUM *n, BN_CTX *ctx) {
+  BIGNUM *A, *B, *X, *Y, *M, *D, *T, *R = NULL;
+  BIGNUM local_A, local_B;
+  BIGNUM *pA, *pB;
+  BIGNUM *ret = NULL;
+  int sign;
+
+  BN_CTX_start(ctx);
+  A = BN_CTX_get(ctx);
+  B = BN_CTX_get(ctx);
+  X = BN_CTX_get(ctx);
+  D = BN_CTX_get(ctx);
+  M = BN_CTX_get(ctx);
+  Y = BN_CTX_get(ctx);
+  T = BN_CTX_get(ctx);
+  if (T == NULL) {
+    goto err;
+  }
+
+  if (out == NULL) {
+    R = BN_new();
+  } else {
+    R = out;
+  }
+  if (R == NULL) {
+    goto err;
+  }
+
+  BN_one(X);
+  BN_zero(Y);
+  if (BN_copy(B, a) == NULL) {
+    goto err;
+  }
+  if (BN_copy(A, n) == NULL) {
+    goto err;
+  }
+  A->neg = 0;
+
+  if (B->neg || (BN_ucmp(B, A) >= 0)) {
+    /* Turn BN_FLG_CONSTTIME flag on, so that when BN_div is invoked,
+     * BN_div_no_branch will be called eventually.
+     */
+    pB = &local_B;
+    BN_with_flags(pB, B, BN_FLG_CONSTTIME);
+    if (!BN_nnmod(B, pB, A, ctx))
+      goto err;
+  }
+  sign = -1;
+  /* From  B = a mod |n|,  A = |n|  it follows that
+   *
+   *      0 <= B < A,
+   *     -sign*X*a  ==  B   (mod |n|),
+   *      sign*Y*a  ==  A   (mod |n|).
+   */
+
+  while (!BN_is_zero(B)) {
+    BIGNUM *tmp;
+
+    /*
+     *      0 < B < A,
+     * (*) -sign*X*a  ==  B   (mod |n|),
+     *      sign*Y*a  ==  A   (mod |n|)
+     */
+
+    /* Turn BN_FLG_CONSTTIME flag on, so that when BN_div is invoked,
+     * BN_div_no_branch will be called eventually.
+     */
+    pA = &local_A;
+    BN_with_flags(pA, A, BN_FLG_CONSTTIME);
+
+    /* (D, M) := (A/B, A%B) ... */
+    if (!BN_div(D, M, pA, B, ctx)) {
+      goto err;
+    }
+
+    /* Now
+     *      A = D*B + M;
+     * thus we have
+     * (**)  sign*Y*a  ==  D*B + M   (mod |n|).
+     */
+
+    tmp = A; /* keep the BIGNUM object, the value does not matter */
+
+    /* (A, B) := (B, A mod B) ... */
+    A = B;
+    B = M;
+    /* ... so we have  0 <= B < A  again */
+
+    /* Since the former  M  is now  B  and the former  B  is now  A,
+     * (**) translates into
+     *       sign*Y*a  ==  D*A + B    (mod |n|),
+     * i.e.
+     *       sign*Y*a - D*A  ==  B    (mod |n|).
+     * Similarly, (*) translates into
+     *      -sign*X*a  ==  A          (mod |n|).
+     *
+     * Thus,
+     *   sign*Y*a + D*sign*X*a  ==  B  (mod |n|),
+     * i.e.
+     *        sign*(Y + D*X)*a  ==  B  (mod |n|).
+     *
+     * So if we set  (X, Y, sign) := (Y + D*X, X, -sign),  we arrive back at
+     *      -sign*X*a  ==  B   (mod |n|),
+     *       sign*Y*a  ==  A   (mod |n|).
+     * Note that  X  and  Y  stay non-negative all the time.
+     */
+
+    if (!BN_mul(tmp, D, X, ctx)) {
+      goto err;
+    }
+    if (!BN_add(tmp, tmp, Y)) {
+      goto err;
+    }
+
+    M = Y; /* keep the BIGNUM object, the value does not matter */
+    Y = X;
+    X = tmp;
+    sign = -sign;
+  }
+
+  /*
+   * The while loop (Euclid's algorithm) ends when
+   *      A == gcd(a,n);
+   * we have
+   *       sign*Y*a  ==  A  (mod |n|),
+   * where  Y  is non-negative.
+   */
+
+  if (sign < 0) {
+    if (!BN_sub(Y, n, Y)) {
+      goto err;
+    }
+  }
+  /* Now  Y*a  ==  A  (mod |n|).  */
+
+  if (BN_is_one(A)) {
+    /* Y*a == 1  (mod |n|) */
+    if (!Y->neg && BN_ucmp(Y, n) < 0) {
+      if (!BN_copy(R, Y)) {
+        goto err;
+      }
+    } else {
+      if (!BN_nnmod(R, Y, n, ctx)) {
+        goto err;
+      }
+    }
+  } else {
+    OPENSSL_PUT_ERROR(BN, BN_mod_inverse_no_branch, BN_R_NO_INVERSE);
+    goto err;
+  }
+  ret = R;
+
+err:
+  if (ret == NULL && out == NULL) {
+    BN_free(R);
+  }
+
+  BN_CTX_end(ctx);
+  return ret;
+}