ringct: fix dummy bulletproofs on ledger in fake mode

Ledger does some basic checks on them

src/ringct/rctSigs.cpp

@@ -46,13 +46,34 @@ using namespace std;
 
 namespace
 {
-    rct::Bulletproof make_dummy_bulletproof(size_t n_outs)
+    rct::Bulletproof make_dummy_bulletproof(const std::vector<uint64_t> &outamounts, rct::keyV &C, rct::keyV &masks)
     {
+        const size_t n_outs = outamounts.size();
         const rct::key I = rct::identity();
         size_t nrl = 0;
         while ((1u << nrl) < n_outs)
           ++nrl;
         nrl += 6;
+
+        C.resize(n_outs);
+        masks.resize(n_outs);
+        for (size_t i = 0; i < n_outs; ++i)
+        {
+            masks[i] = I;
+            rct::key sv8, sv;
+            sv = rct::zero();
+            sv.bytes[0] = outamounts[i] & 255;
+            sv.bytes[1] = (outamounts[i] >> 8) & 255;
+            sv.bytes[2] = (outamounts[i] >> 16) & 255;
+            sv.bytes[3] = (outamounts[i] >> 24) & 255;
+            sv.bytes[4] = (outamounts[i] >> 32) & 255;
+            sv.bytes[5] = (outamounts[i] >> 40) & 255;
+            sv.bytes[6] = (outamounts[i] >> 48) & 255;
+            sv.bytes[7] = (outamounts[i] >> 56) & 255;
+            sc_mul(sv8.bytes, sv.bytes, rct::INV_EIGHT.bytes);
+            rct::addKeys2(C[i], rct::INV_EIGHT, sv8, rct::H);
+        }
+
         return rct::Bulletproof{rct::keyV(n_outs, I), I, I, I, I, I, I, rct::keyV(nrl, I), rct::keyV(nrl, I), I, I, I};
     }
 }
@@ -769,9 +790,7 @@ namespace rct {
                 if (hwdev.get_mode() == hw::device::TRANSACTION_CREATE_FAKE)
                 {
                     // use a fake bulletproof for speed
-                    rv.p.bulletproofs.push_back(make_dummy_bulletproof(outamounts.size()));
-                    C = rct::keyV(outamounts.size(), I);
-                    masks = rct::keyV(outamounts.size(), I);
+                    rv.p.bulletproofs.push_back(make_dummy_bulletproof(outamounts, C, masks));
                 }
                 else
                 {
@@ -799,9 +818,7 @@ namespace rct {
                 if (hwdev.get_mode() == hw::device::TRANSACTION_CREATE_FAKE)
                 {
                     // use a fake bulletproof for speed
-                    rv.p.bulletproofs.push_back(make_dummy_bulletproof(batch_amounts.size()));
-                    C = rct::keyV(batch_amounts.size(), I);
-                    masks = rct::keyV(batch_amounts.size(), I);
+                    rv.p.bulletproofs.push_back(make_dummy_bulletproof(batch_amounts, C, masks));
                 }
                 else
                 {