croc: Overwrite-confirmation bypass via a crafted "croc-stdin-" filename on receive

croc is a tool that allows any two computers to simply and securely transfer files and folders. Prior to 11.5.2, the receive-side file-readiness loop in src/croc/croc.go treats any sender-controlled basename beginning with croc-stdin- as a trusted text-transfer artifact even when SendingText is false. This skips askReceiveOverwrite and rename handling for a predictable exact-name collision in the receiver's working directory, allowing a remote sender whose transfer the user accepts to overwrite or truncate a matching regular file through recipientInitializeFile, or to remove and replace a matching destination with an empty file or an in-directory symlink through createEmptyFileAndFinish, without confirmation. The impact is limited to pre-existing names in the croc-stdin- namespace that the sender can predict; other filenames retain the prompt, dotfiles outside that namespace are not reachable, and symlink targets remain confined to the receive directory. This issue is fixed in version 11.5.2.

An issue was discovered in Croc through 9.6.5. The shared secret, located on a command line, can be read by local users who list all processes and their arguments.

An issue was discovered in Croc through 9.6.5. A sender may place ANSI or CSI escape sequences in a filename to attack the terminal device of a receiver.

An issue was discovered in Croc through 9.6.5. A sender may send dangerous new files to a receiver, such as executable content or a .ssh/authorized_keys file.

An issue was discovered in Croc through 9.6.5. The protocol requires a sender to provide its local IP addresses in cleartext via an ips? message.

An issue was discovered in Croc through 9.6.5. When a custom shared secret is used, the sender and receiver may divulge parts of this secret to an untrusted Relay, as part of composing a room name.

An issue was discovered in Croc through 9.6.5. A sender can cause a receiver to overwrite files during ZIP extraction.