Return Result from BigNum::mod_inverse.

4 files changed, 16 insertions, 7 deletions

diff --git a/td/mtproto/TlsInit.cpp b/td/mtproto/TlsInit.cpp
index 38fdf0720..f1418f356 100644
--- a/td/mtproto/TlsInit.cpp
+++ b/td/mtproto/TlsInit.cpp
@@ -452,7 +452,12 @@ class TlsHelloStore {
     BigNum::mod_sub(numerator, numerator, one, mod, big_num_context);
     BigNum::mod_mul(numerator, numerator, numerator, mod, big_num_context);
 
-    BigNum::mod_inverse(denominator, denominator, mod, big_num_context);
+    auto r_inverse = BigNum::mod_inverse(denominator, mod, big_num_context);
+    if (r_inverse.is_error()) {
+      LOG(ERROR) << r_inverse.error();
+    } else {
+      denominator = r_inverse.move_as_ok();
+    }
     BigNum::mod_mul(numerator, numerator, denominator, mod, big_num_context);
     return numerator;
   }
diff --git a/tdutils/td/utils/BigNum.cpp b/tdutils/td/utils/BigNum.cpp
index b8c1290e7..3bfd10204 100644
--- a/tdutils/td/utils/BigNum.cpp
+++ b/tdutils/td/utils/BigNum.cpp
@@ -281,9 +281,14 @@ void BigNum::mod_mul(BigNum &r, BigNum &a, BigNum &b, const BigNum &m, BigNumCon
   LOG_IF(FATAL, result != 1);
 }
 
-void BigNum::mod_inverse(BigNum &r, BigNum &a, const BigNum &m, BigNumContext &context) {
-  auto result = BN_mod_inverse(r.impl_->big_num, a.impl_->big_num, m.impl_->big_num, context.impl_->big_num_context);
-  LOG_IF(FATAL, result != r.impl_->big_num);
+Result<BigNum> BigNum::mod_inverse(BigNum &a, const BigNum &m, BigNumContext &context) {
+  BigNum r;
+  auto *result = BN_mod_inverse(r.impl_->big_num, a.impl_->big_num, m.impl_->big_num, context.impl_->big_num_context);
+  if (result != r.impl_->big_num) {
+    CHECK(result == nullptr);
+    return Status::Error("Failed to compute modulo inverse");
+  }
+  return std::move(r);
 }
 
 void BigNum::div(BigNum *quotient, BigNum *remainder, const BigNum &dividend, const BigNum &divisor,
diff --git a/tdutils/td/utils/BigNum.h b/tdutils/td/utils/BigNum.h
index 6967d87ec..0219d145d 100644
--- a/tdutils/td/utils/BigNum.h
+++ b/tdutils/td/utils/BigNum.h
@@ -97,7 +97,7 @@ class BigNum {
 
   static void mod_mul(BigNum &r, BigNum &a, BigNum &b, const BigNum &m, BigNumContext &context);
 
-  static void mod_inverse(BigNum &r, BigNum &a, const BigNum &m, BigNumContext &context);
+  static Result<BigNum> mod_inverse(BigNum &a, const BigNum &m, BigNumContext &context);
 
   static void div(BigNum *quotient, BigNum *remainder, const BigNum &dividend, const BigNum &divisor,
                   BigNumContext &context);
diff --git a/tdutils/td/utils/Ed25519.cpp b/tdutils/td/utils/Ed25519.cpp
index f0c497d2d..e498a09a1 100644
--- a/tdutils/td/utils/Ed25519.cpp
+++ b/tdutils/td/utils/Ed25519.cpp
@@ -288,8 +288,7 @@ Result<SecureString> Ed25519::compute_shared_secret(const PublicKey &public_key,
 
   BigNum::mod_sub(y2, p, y2, p, context);
 
-  BigNum inverse_y_plus_1;
-  BigNum::mod_inverse(inverse_y_plus_1, y2, p, context);
+  TRY_RESULT(inverse_y_plus_1, BigNum::mod_inverse(y2, p, context));
 
   BigNum u;
   BigNum::mod_mul(u, y, inverse_y_plus_1, p, context);