gcloud-compute-ssh

Patches to PuTTY for gcloud compute ssh on Windows.

overview

Patches PuTTY for Windows source code (2014-05-21 snapshot) so that after renaming

• copy pscp.exe scp.exe
• copy plink.exe ssh.exe
• copy pkeygen.exe ssh-keygen.exe

scp, ssh and ssh-keygen, from the command line, behave more like the OpenSSH counterparts. Some behaviors are not covered -- mainly just enough to support internal gcloud usage patterns.

details

Changes fall into a few categories:

• Change cmdgen.c to generate pkeygen.exe which acts like ssh-keygen from the command line. Most of the changes are in this file. Major changes:
  • use Windows libraries to generate cryptographic random data
  • output refactored to a loop that can generate more than one file
  • id, id.pub and id.ppk all generated by default
• Change all identity file read acceses to first check for a .ppk variant, e.g., -i id will first check for id.ppk. This preserves the ssh and scp -i usage pattern.
• Change the default TERM environment variable value passed to the server by plink to check the local TERM setting (instead of "xterm"). If TERM is not set then "dumb" is used. This gives the proper hint to remote .profiles to refrain from colorizing prompts and ls(1) output.
• Eliminate the low hanging fruit of the MSVC 32 and 64 bit warnings. Most of these involve mixed combinations of [unsigned] int, [unsigned] long, size_t, and ssize_t. Some only show up in 64 bit compilers. Other culprits are strcpy(), strcat(), and sprintf() into fixed size buffers - they are handled by a homebrew szprintf() that supports a clean sized buffer paradigm. Much more work is needed in this area. A lot of the (int) and (size_t) casts should be replaced by proper variable and function typing, but that would require a meticulous code walkthrough.

patch authors

Glenn S. Fowler, Google, 2014.

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