obmc-console-ssh@.service: add ECDSA and ED25519 keys

With RSA-SHA1 being deprecated, have our dropbear server also support
ECDSA and ED25519 keys.

The key generation and support within our standard ssh port 22 was added
via commit [1].

This commit adds support for our virtual console ports that come in via
ssh.

The service files have a somewhat unfortunately named variable,
DROPBEAR_RSAKEY_DIR, which assumed dropbear was only going to support
RSA keys. As this commit shows, dropbear supports multiple key types and
the directory, /etc/dropbear/, has no limitations on the type of key
that can go in that directory. Initially, we changed this variable name
to DROPBEAR_KEY_DIR but upon further investigation we saw that this
naming convention was utilized heavily in the dropbear recipes. To keep
things consistent with dropbear, we left it as DROPBEAR_RSAKEY_DIR even
though other key types will be stored in that directory.

Tested:
- Confirmed port 2200 and 2201 dropbear services loaded new RSA keys
  (via 'ps' command) on p10bmc machine
- Confirmed when an ssh was done to port 2200, it connected, properly
  and listed the following as supported via "ssh -vv":
    host key algorithms: ssh-ed25519,ecdsa-sha2-nistp384,rsa-sha2-256

[1]: https://gerrit.openbmc.org/c/openbmc/openbmc/+/70265

Change-Id: I76dd742654a67645d12856ae8fd15dfe71876b9d
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
2 files changed
tree: 2030f7ded94cb1d1ef8fe25c6322e0b21c61d4e9
  1. conf/
  2. test/
  3. .clang-format
  4. .clang-tidy
  5. .gitignore
  6. .travis.yml
  7. CHANGELOG.md
  8. config.c
  9. console-client.c
  10. console-dbus.c
  11. console-server.c
  12. console-server.h
  13. console-socket.c
  14. LICENSE
  15. log-handler.c
  16. meson.build
  17. meson.options
  18. OWNERS
  19. README.md
  20. ringbuffer.c
  21. socket-handler.c
  22. tty-handler.c
  23. util.c
README.md

To Build

To build this project, run the following shell commands:

meson setup build
meson compile -C build

To test:

meson test -C build

To Run Server

Running the server requires a serial port (e.g. /dev/ttyS0):

touch obmc-console.conf
./obmc-console-server --config obmc-console.conf ttyS0

To Connect Client

To connect to the server, simply run the client:

./obmc-console-client

To disconnect the client, use the standard ~. combination.

Underlying design

This shows how the host UART connection is abstracted within the BMC as a Unix domain socket.

               +---------------------------------------------------------------------------------------------+
               |                                                                                             |
               |       obmc-console-client       unix domain socket         obmc-console-server              |
               |                                                                                             |
               |     +----------------------+                           +------------------------+           |
               |     |   client.2200.conf   |  +---------------------+  | server.ttyVUART0.conf  |           |
           +---+--+  +----------------------+  |                     |  +------------------------+  +--------+-------+
Network    | 2200 +-->                      +->+ @obmc-console.host0 +<-+                        <--+ /dev/ttyVUART0 |   UARTs
           +---+--+  | console-id = "host0" |  |                     |  |  console-id = "host0"  |  +--------+-------+
               |     |                      |  +---------------------+  |                        |           |
               |     +----------------------+                           +------------------------+           |
               |                                                                                             |
               |                                                                                             |
               |                                                                                             |
               +---------------------------------------------------------------------------------------------+

This supports multiple independent consoles. The console-id is a unique portion for the unix domain socket created by the obmc-console-server instance. The server needs to know this because it needs to know what to name the pipe; the client needs to know it as it needs to form the abstract socket name to which to connect.