SSH crashes FN device when trying to close a session

[markjfisher]

Using netcat with ssh to a machine, when the session completes, the fujinet crashes:

21:04:25.731 > [2023/06/27 21:04:23.975347, 1] ssh_packet_userauth_failure:  Access denied for 'password'. Authentication that can continue: publickey,password
21:04:25.732 > [2023/06/27 21:04:23.975978, 2] ssh_packet_userauth_failure:  Access denied for 'password'. Authentication that can continue: publickey,password
21:04:25.733 > NetworkProtocolSSH::open() - Unable to authorise with given password, error: Access denied for 'password'. Authentication that can continue: publickey,password.
21:04:25.738 >
21:04:25.738 > assert failed: heap_caps_free heap_caps.c:351 (heap != NULL && "free() target pointer is outside heap areas")
21:04:25.739 >
21:04:25.739 >
21:04:25.739 > Backtrace: 0x4008425d:0x3ffd9ab0 0x40092d55:0x3ffd9ad0 0x40099ef9:0x3ffd9af0 0x400852f7:0x3ffd9c20 0x40099f29:0x3ffd9c40 0x40217cba:0x3ffd9c60 0x401d0066:0x3ffd9c80 0x400e0344:0x3ffd9cb0 0x400de862:0x3ffd9cf0 0x400ef14d:0x3ffd9d10 0x400ef26b:0x3ffd9d50 0x400d2ca4:0x3ffd9d70 0x40096b15:0x3ffd9d90
21:04:25.887 >
21:04:25.887 >   #0  0x4008425d:0x3ffd9ab0 in panic_abort at /home/fenrock/.platformio/packages/framework-espidf/components/esp_system/panic.c:423
21:04:25.887 >   #1  0x40092d55:0x3ffd9ad0 in esp_system_abort at /home/fenrock/.platformio/packages/framework-espidf/components/esp_system/esp_system.c:153
21:04:25.887 >   #2  0x40099ef9:0x3ffd9af0 in __assert_func at /home/fenrock/.platformio/packages/framework-espidf/components/newlib/assert.c:78
21:04:25.887 >   #3  0x400852f7:0x3ffd9c20 in heap_caps_free at /home/fenrock/.platformio/packages/framework-espidf/components/heap/heap_caps.c:351 (discriminator 1)
21:04:25.887 >   #4  0x40099f29:0x3ffd9c40 in free at /home/fenrock/.platformio/packages/framework-espidf/components/newlib/heap.c:39
21:04:25.887 >   #5  0x40217cba:0x3ffd9c60 in ssh_free at lib/libssh/src/session.c:310 (discriminator 1)
21:04:25.887 >   #6  0x401d0066:0x3ffd9c80 in NetworkProtocolSSH::open(EdUrlParser*, cmdFrame_t*) at lib/network-protocol/SSH.cpp:154
21:04:25.887 >   #7  0x400e0344:0x3ffd9cb0 in sioNetwork::sio_open() at lib/device/sio/network.cpp:120
21:04:25.887 >   #8  0x400de862:0x3ffd9cf0 in sioNetwork::sio_process(unsigned long, unsigned char) at lib/device/sio/network.cpp:799
21:04:25.887 >   #9  0x400ef14d:0x3ffd9d10 in systemBus::_sio_process_cmd() at lib/bus/sio/sio.cpp:233
21:04:25.887 >   #10 0x400ef26b:0x3ffd9d50 in systemBus::service() at lib/bus/sio/sio.cpp:341
21:04:25.887 >   #11 0x400d2ca4:0x3ffd9d70 in fn_service_loop(void*) at src/main.cpp:324 (discriminator 1)
21:04:25.887 >   #12 0x40096b15:0x3ffd9d90 in vPortTaskWrapper at /home/fenrock/.platformio/packages/framework-espidf/components/freertos/FreeRTOS-Kernel/portable/xtensa/port.c:154

The above is a log for when the password is wrong, which closes the session at the end, so it's easy to reproduce. Also happens after a successful connection, then terminating the connection.

The part that's failing is trying to free memory for the known_hosts file, which I didn't implement.
So there are logs mentioning it trying to use the known hosts earlier:

21:04:20.506 > [2023/06/27 21:04:18.751251, 1] ssh_known_hosts_read_entries:  Failed to open the known_hosts file '': No such file or directory
21:04:20.507 > [2023/06/27 21:04:18.751907, 1] ssh_known_hosts_read_entries:  Failed to open the known_hosts file '': No such file or directory

And the code mentioned above is trying to safely free the memory, but clearly something is wrong:

// line 310 session.c:
  SAFE_FREE(session->opts.knownhosts);

which is mentioned in the crash log.