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cli: add 'ssh' commands to log onto other devices and manage keys

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Add three SSH-related commands to the operational CLI:

  ssh [user <name>] [port <num>] <host>
      Connect to a remote device over SSH, running as the
      CLI user (not root) by dropping privileges before exec.

  set ssh known-hosts <host> <keytype> <pubkey>
      Pre-enroll a host public key received out-of-band (e.g.
      via email after a factory reset) into ~/.ssh/known_hosts,
      avoiding a TOFU prompt on first connect.

  no ssh known-hosts <host>
      Remove a stale host key entry using ssh-keygen -R, e.g.
      after a device factory reset causes a key mismatch.

Tab completion is provided for key types (ssh-ed25519,
ecdsa-sha2-nistp256, etc.) and for known host names/IPs.

A new run_as_user() helper is introduced alongside the existing
run(), factoring out the fork+setuid+execvp pattern used by
infix_shell() so it can be shared across the SSH functions.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
This commit is contained in:
Joachim Wiberg
2026-03-09 19:26:03 +01:00
parent b9a8014e41
commit 290c03b2b5
2 changed files with 294 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/klish-plugin-infix/src/infix.c
+245 -3
View File
@@ -1,9 +1,12 @@
#include <errno.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
@@ -79,6 +82,53 @@ static int run(char *const argv[])
return -1;
}
/*
* Like run(), but drops privileges to the given user before exec.
* Use for commands that must run as the CLI user, not root (klishd).
*/
static int run_as_user(const char *user, char *const argv[])
{
struct passwd *pw;
pid_t pid;
int rc;
pw = getpwnam(user);
if (!pw) {
fprintf(stderr, ERRMSG "unknown user: %s\n", user);
return -1;
}
pid = fork();
if (pid == -1)
return -1;
if (!pid) {
if (initgroups(user, pw->pw_gid) || setgid(pw->pw_gid) || setuid(pw->pw_uid)) {
fprintf(stderr, "Aborting, failed dropping privileges to "
"(UID:%d GID:%d): %s\n",
pw->pw_uid, pw->pw_gid, strerror(errno));
_exit(1);
}
execvp(argv[0], argv);
_exit(127);
}
while (waitpid(pid, &rc, 0) < 0) {
if (errno != EINTR)
return -1;
}
if (WIFEXITED(rc))
return WEXITSTATUS(rc);
if (WIFSIGNALED(rc)) {
errno = EINTR;
return -1;
}
return -1;
}
/*
* Shell command execution - only use with hardcoded commands or when
* shell features (pipes, redirects) are needed. Never use with user input.
@@ -304,7 +354,7 @@ int infix_shell(kcontext_t *ctx)
};
pw = getpwnam(user);
if (setgid(pw->pw_gid) || setuid(pw->pw_uid)) {
if (initgroups(user, pw->pw_gid) || setgid(pw->pw_gid) || setuid(pw->pw_uid)) {
fprintf(stderr, "Aborting, failed dropping privileges to (UID:%d GID:%d): %s\n",
pw->pw_uid, pw->pw_gid, strerror(errno));
_exit(1);
@@ -313,8 +363,10 @@ int infix_shell(kcontext_t *ctx)
_exit(execvp(args[0], args));
}
while (waitpid(pid, &rc, 0) != pid)
;
while (waitpid(pid, &rc, 0) < 0) {
if (errno != EINTR)
return -1;
}
if (WIFEXITED(rc))
rc = WEXITSTATUS(rc);
@@ -427,6 +479,192 @@ int infix_asym_keys(kcontext_t *ctx)
"| jq -r '.\"ietf-keystore:keystore\".\"asymmetric-keys\".\"asymmetric-key\"[].name'");
}
/*
* Create ~/.ssh/known_hosts with correct ownership if it doesn't exist.
* Must be called as root before dropping privileges, since ~/.ssh/ is
* owned by root on Infix (the system manages authorized_keys via YANG).
* Once the file exists with the user's ownership, ssh(1) can update it.
*/
static void ensure_known_hosts(const struct passwd *pw)
{
char path[512];
int fd;
snprintf(path, sizeof(path), "%s/.ssh/known_hosts", pw->pw_dir);
fd = open(path, O_CREAT | O_EXCL | O_WRONLY, 0600);
if (fd < 0)
return; /* Already exists, or unrecoverable error */
fchown(fd, pw->pw_uid, pw->pw_gid);
close(fd);
}
int infix_ssh_connect(kcontext_t *ctx)
{
kpargv_t *pargv = kcontext_pargv(ctx);
const char *host, *ruser, *port, *user;
struct passwd *pw;
kparg_t *parg;
char *argv[8];
int i = 0;
host = kparg_value(kpargv_find(pargv, "host"));
parg = kpargv_find(pargv, "user");
ruser = parg ? kparg_value(parg) : NULL;
parg = kpargv_find(pargv, "port");
port = parg ? kparg_value(parg) : NULL;
if (!host) {
fprintf(stderr, ERRMSG "missing host argument.\n");
return -1;
}
user = cd_home(ctx);
pw = getpwnam(user);
if (pw)
ensure_known_hosts(pw);
argv[i++] = "ssh";
if (ruser) { argv[i++] = "-l"; argv[i++] = (char *)ruser; }
if (port) { argv[i++] = "-p"; argv[i++] = (char *)port; }
argv[i++] = (char *)host;
argv[i] = NULL;
return run_as_user(user, argv);
}
/*
* Completion: list hostnames from the current user's ~/.ssh/known_hosts.
*/
int infix_ssh_known_hosts(kcontext_t *ctx)
{
char path[512], line[4096];
const char *user;
struct passwd *pw;
FILE *f;
user = cd_home(ctx);
pw = getpwnam(user);
if (!pw)
return 0;
snprintf(path, sizeof(path), "%s/.ssh/known_hosts", pw->pw_dir);
f = fopen(path, "r");
if (!f)
return 0;
while (fgets(line, sizeof(line), f)) {
char *sp;
/* Skip comments, blank lines, and hashed entries */
if (line[0] == '#' || line[0] == '\n' || line[0] == '|')
continue;
sp = strchr(line, ' ');
if (!sp)
continue;
*sp = '\0';
/* Entries may be comma-separated: "host,ip algo key" */
for (char *tok = strtok(line, ","); tok; tok = strtok(NULL, ","))
puts(tok);
}
fclose(f);
return 0;
}
/*
* Pre-enroll a host public key received out-of-band into ~/.ssh/known_hosts.
* Runs as the CLI user to ensure correct file ownership.
*/
int infix_ssh_add_known_host(kcontext_t *ctx)
{
kpargv_t *pargv = kcontext_pargv(ctx);
const char *host, *keytype, *pubkey, *user;
char path[512];
struct passwd *pw;
pid_t pid;
int rc;
host = kparg_value(kpargv_find(pargv, "host"));
keytype = kparg_value(kpargv_find(pargv, "keytype"));
pubkey = kparg_value(kpargv_find(pargv, "pubkey"));
if (!host || !keytype || !pubkey) {
fprintf(stderr, ERRMSG "missing arguments.\n");
return -1;
}
user = cd_home(ctx);
pw = getpwnam(user);
if (!pw) {
fprintf(stderr, ERRMSG "unknown user: %s\n", user);
return -1;
}
snprintf(path, sizeof(path), "%s/.ssh/known_hosts", pw->pw_dir);
ensure_known_hosts(pw);
pid = fork();
if (pid == -1)
return -1;
if (!pid) {
FILE *f;
if (setgid(pw->pw_gid) || setuid(pw->pw_uid)) {
fprintf(stderr, "Aborting, failed dropping privileges: %s\n",
strerror(errno));
_exit(1);
}
f = fopen(path, "a");
if (!f) {
fprintf(stderr, ERRMSG "cannot open %s: %s\n", path, strerror(errno));
_exit(1);
}
fprintf(f, "%s %s %s\n", host, keytype, pubkey);
fclose(f);
printf("Host %s added to %s\n", host, path);
_exit(0);
}
while (waitpid(pid, &rc, 0) != pid)
;
if (WIFEXITED(rc))
return WEXITSTATUS(rc);
if (WIFSIGNALED(rc)) {
errno = EINTR;
return -1;
}
return -1;
}
int infix_ssh_remove_known_host(kcontext_t *ctx)
{
kpargv_t *pargv = kcontext_pargv(ctx);
const char *host;
char *argv[4];
host = kparg_value(kpargv_find(pargv, "host"));
if (!host) {
fprintf(stderr, ERRMSG "missing host argument.\n");
return -1;
}
argv[0] = "ssh-keygen";
argv[1] = "-R";
argv[2] = (char *)host;
argv[3] = NULL;
return run_as_user(cd_home(ctx), argv);
}
int kplugin_infix_fini(kcontext_t *ctx)
{
(void)ctx;
@@ -453,6 +691,10 @@ int kplugin_infix_init(kcontext_t *ctx)
kplugin_add_syms(plugin, ksym_new("firewall_services", infix_firewall_services));
kplugin_add_syms(plugin, ksym_new("set_boot_order", infix_set_boot_order));
kplugin_add_syms(plugin, ksym_new("shell", infix_shell));
kplugin_add_syms(plugin, ksym_new("ssh_connect", infix_ssh_connect));
kplugin_add_syms(plugin, ksym_new("ssh_known_hosts", infix_ssh_known_hosts));
kplugin_add_syms(plugin, ksym_new("ssh_add_known_host", infix_ssh_add_known_host));
kplugin_add_syms(plugin, ksym_new("ssh_remove_known_host", infix_ssh_remove_known_host));
return 0;
}
src/klish-plugin-infix/xml/infix.xml
+49
View File
@@ -169,6 +169,24 @@
<ACTION sym="STRING"/>
</PTYPE>
<PTYPE name="SSH_KNOWN_HOSTS">
<COMPL>
<ACTION sym="ssh_known_hosts@infix"/>
</COMPL>
<ACTION sym="STRING"/>
</PTYPE>
<PTYPE name="SSH_KEY_TYPE">
<COMPL>
<ACTION sym="printl">ecdsa-sha2-nistp256</ACTION>
<ACTION sym="printl">ecdsa-sha2-nistp384</ACTION>
<ACTION sym="printl">ecdsa-sha2-nistp521</ACTION>
<ACTION sym="printl">ssh-ed25519</ACTION>
<ACTION sym="printl">ssh-rsa</ACTION>
</COMPL>
<ACTION sym="STRING"/>
</PTYPE>
<VIEW name="main">
<HOTKEY key="^D" cmd="exit"/>
@@ -300,6 +318,15 @@ echo "Public: $pub"
<PARAM name="third" ptype="/BOOT_TARGET" help="Third boot target" min="0"/>
<ACTION sym="set_boot_order@infix"/>
</COMMAND>
<COMMAND name="ssh" help="SSH client settings" mode="switch">
<COMMAND name="known-hosts" help="Pre-enroll a host public key received out-of-band">
<PARAM name="host" ptype="/STRING" help="Hostname or IP address"/>
<PARAM name="keytype" ptype="/SSH_KEY_TYPE" help="Public key algorithm"/>
<PARAM name="pubkey" ptype="/STRING" help="Base64-encoded public key"/>
<ACTION sym="ssh_add_known_host@infix"/>
</COMMAND>
</COMMAND>
</COMMAND>
<COMMAND name="dhcp-server" help="DHCP server tools" mode="switch">
@@ -875,6 +902,28 @@ echo "Public: $pub"
</ACTION>
</COMMAND>
<COMMAND name="ssh" help="Connect to a remote device over SSH">
<SWITCH name="optional" min="0" max="2">
<COMMAND name="user" help="Login with a different username">
<PARAM name="user" ptype="/STRING" help="Remote username"/>
</COMMAND>
<COMMAND name="port" help="Connect to a non-standard port">
<PARAM name="port" ptype="/UINT" help="TCP port number"/>
</COMMAND>
</SWITCH>
<PARAM name="host" ptype="/STRING" help="Hostname or IP address"/>
<ACTION sym="ssh_connect@infix" in="tty" out="tty" interrupt="true"/>
</COMMAND>
<COMMAND name="no" help="Remove a setting or entry" mode="switch">
<COMMAND name="ssh" help="SSH client settings" mode="switch">
<COMMAND name="known-hosts" help="Remove a host from the SSH known_hosts file">
<PARAM name="host" ptype="/SSH_KNOWN_HOSTS" help="Hostname or IP to remove"/>
<ACTION sym="ssh_remove_known_host@infix"/>
</COMMAND>
</COMMAND>
</COMMAND>
<COMMAND name="upgrade" help="Install a software update bundle from remote or local file">
<PARAM name="URI" ptype="/STRING" help="[(ftp|tftp|http|https|sftp)://(dns.name | ip.address)/path/to/]upgrade-bundle.pkg"/>
<SWITCH name="optional" min="0" max="2">