Invalid memcpy in `SharedSecret::new`

[TheBlueMatt]

Haven't seen this on x86, but it may be because the memcpy is being optimized away and hidden from valgrind, but on ppcel64 I see the following errors in valgrind. The various rust-lightning and C bits on the outside shouldn't be relevant, ultimately we call SharedSecret::new with two safely-constructed objects. Note that this is built against the HEAD of pull #279 though that shouldn't be related either.

==525==    at 0x487F4D4: memcpy (vg_replace_strmem.c:1034)
==525==    by 0x514D023: rustsecp256k1_v0_4_0_ge_neg (group_impl.h:84)
==525==    by 0x5151FBF: rustsecp256k1_v0_4_0_ecmult_const (ecmult_const_impl.h:242)
==525==    by 0x515D00F: rustsecp256k1_v0_4_0_ecdh (main_impl.h:53)
==525==    by 0x5091ECF: secp256k1::ecdh::SharedSecret::new (ecdh.rs:108)
==525==    by 0x5096C37: lightning::ln::peer_channel_encryptor::PeerChannelEncryptor::outbound_noise_act (peer_channel_encryptor.rs:192)
==525==    by 0x5041B9F: lightning::ln::peer_channel_encryptor::PeerChannelEncryptor::get_act_one (peer_channel_encryptor.rs:248)
==525==    by 0x4E9F69F: lightning::ln::peer_handler::PeerManager<Descriptor,CM,RM,L>::new_outbound_connection (peer_handler.rs:464)
==525==    by 0x4FCFD3B: PeerManager_new_outbound_connection (peer_handler.rs:751)
==525==    by 0x114E83: PeersConnection::PeersConnection(LDK::ChannelManager&, LDK::ChannelManager&, LDK::PeerManager&, LDK::PeerManager&) (demo.cpp:261)
==525==    by 0x10DDAF: main (demo.cpp:406)
==525== 
==525== Source and destination overlap in memcpy(0x1ffeffc808, 0x1ffeffc808, 88)
==525==    at 0x487F4D4: memcpy (vg_replace_strmem.c:1034)
==525==    by 0x514D023: rustsecp256k1_v0_4_0_ge_neg (group_impl.h:84)
==525==    by 0x5152007: rustsecp256k1_v0_4_0_ecmult_const (ecmult_const_impl.h:247)
==525==    by 0x515D00F: rustsecp256k1_v0_4_0_ecdh (main_impl.h:53)
==525==    by 0x5091ECF: secp256k1::ecdh::SharedSecret::new (ecdh.rs:108)
==525==    by 0x5096C37: lightning::ln::peer_channel_encryptor::PeerChannelEncryptor::outbound_noise_act (peer_channel_encryptor.rs:192)
==525==    by 0x5041B9F: lightning::ln::peer_channel_encryptor::PeerChannelEncryptor::get_act_one (peer_channel_encryptor.rs:248)
==525==    by 0x4E9F69F: lightning::ln::peer_handler::PeerManager<Descriptor,CM,RM,L>::new_outbound_connection (peer_handler.rs:464)
==525==    by 0x4FCFD3B: PeerManager_new_outbound_connection (peer_handler.rs:751)
==525==    by 0x114E83: PeersConnection::PeersConnection(LDK::ChannelManager&, LDK::ChannelManager&, LDK::PeerManager&, LDK::PeerManager&) (demo.cpp:261)
==525==    by 0x10DDAF: main (demo.cpp:406)
==525== 
==525== Source and destination overlap in memcpy(0x1ffeffc808, 0x1ffeffc808, 88)
==525==    at 0x487F4D4: memcpy (vg_replace_strmem.c:1034)
==525==    by 0x514F84F: rustsecp256k1_v0_4_0_ge_mul_lambda (group_impl.h:654)
==525==    by 0x515201B: rustsecp256k1_v0_4_0_ecmult_const (ecmult_const_impl.h:248)
==525==    by 0x515D00F: rustsecp256k1_v0_4_0_ecdh (main_impl.h:53)
==525==    by 0x5091ECF: secp256k1::ecdh::SharedSecret::new (ecdh.rs:108)
==525==    by 0x5096C37: lightning::ln::peer_channel_encryptor::PeerChannelEncryptor::outbound_noise_act (peer_channel_encryptor.rs:192)
==525==    by 0x5041B9F: lightning::ln::peer_channel_encryptor::PeerChannelEncryptor::get_act_one (peer_channel_encryptor.rs:248)
==525==    by 0x4E9F69F: lightning::ln::peer_handler::PeerManager<Descriptor,CM,RM,L>::new_outbound_connection (peer_handler.rs:464)
==525==    by 0x4FCFD3B: PeerManager_new_outbound_connection (peer_handler.rs:751)
==525==    by 0x114E83: PeersConnection::PeersConnection(LDK::ChannelManager&, LDK::ChannelManager&, LDK::PeerManager&, LDK::PeerManager&) (demo.cpp:261)
==525==    by 0x10DDAF: main (demo.cpp:406)

[TheBlueMatt]

This appears to be a gcc mis-compilation moved to bitcoin-core/secp256k1#949.

[tcharding]

If this is to be fixed in bitcoin core can we close this issue @TheBlueMatt?

[apoelstra]

Yep, let's close it.