search

mkj / dropbear

Dropbear SSH
https://matt.ucc.asn.au/dropbear/dropbear.html
Other
1.68k stars 399 forks source link

curve255.19.c:91:12: runtime error: left shift of negative value -329 #312

Open sbytnar opened 2 months ago

sbytnar commented 2 months ago

To reproduce this, build curve25519.c with -fsanitize=undefined. gcc version 9.4.0 (Ubuntu 9.4.0-1ubuntu1~20.04.2)

Run the dropbear server from the command line. Connect to the dropbear server. The message is printed on the console.

mkj commented 2 months ago

Putting if (c < 0) printf at line 91 I can reproduce it, though I couldn't get ubsan to catch it. It certainly looks like undefined behaviour, I'll figure how to fix that.

The curve25519 implementation is from tweetnacl, I'm surprised the problem hasn't been reported elsewhere (that I can find).