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Allow pasta to take a command to execute

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When not given an existing PID or network namspace to attach to, pasta
spawns a shell.  Most commands which can spawn a shell in an altered
environment can also run other commands in that same environment, which can
be useful in automation.

Allow pasta to do the same thing; it can be given an arbitrary command to
run in the network and user namespace which pasta creates.  If neither a
command nor an existing PID or netns to attach to is given, continue to
spawn a default shell, as before.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson
2022-08-26 14:58:39 +10:00
committed by Stefano Brivio
parent c188736cd8
commit 1392bc5ca0
4 changed files with 51 additions and 25 deletions
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33
pasta.c
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@@ -108,6 +108,7 @@ netns:
struct pasta_setup_ns_arg {
struct ctx *c;
int euid;
char **argv;
};
/**
@@ -119,7 +120,6 @@ struct pasta_setup_ns_arg {
static int pasta_setup_ns(void *arg)
{
struct pasta_setup_ns_arg *a = (struct pasta_setup_ns_arg *)arg;
char *shell;
if (!a->c->netns_only) {
char buf[BUFSIZ];
@@ -139,29 +139,42 @@ static int pasta_setup_ns(void *arg)
FWRITE("/proc/sys/net/ipv4/ping_group_range", "0 0",
"Cannot set ping_group_range, ICMP requests might fail");
shell = getenv("SHELL") ? getenv("SHELL") : "/bin/sh";
if (strstr(shell, "/bash"))
execve(shell, ((char *[]) { shell, "-l", NULL }), environ);
else
execve(shell, ((char *[]) { shell, NULL }), environ);
execvp(a->argv[0], a->argv);
perror("execve");
perror("execvp");
exit(EXIT_FAILURE);
}
/**
* pasta_start_ns() - Fork shell in new namespace if target ns is not given
* pasta_start_ns() - Fork command in new namespace if target ns is not given
* @c: Execution context
* @argc: Number of arguments for spawned command
* @argv: Command to spawn and arguments
*/
void pasta_start_ns(struct ctx *c)
void pasta_start_ns(struct ctx *c, int argc, char *argv[])
{
struct pasta_setup_ns_arg arg = { .c = c, .euid = geteuid() };
struct pasta_setup_ns_arg arg = {
.c = c,
.euid = geteuid(),
.argv = argv,
};
char *shell = getenv("SHELL") ? getenv("SHELL") : "/bin/sh";
char *sh_argv[] = { shell, NULL };
char *bash_argv[] = { shell, "-l", NULL };
char ns_fn_stack[NS_FN_STACK_SIZE];
c->foreground = 1;
if (!c->debug)
c->quiet = 1;
if (argc == 0) {
if (strstr(shell, "/bash")) {
arg.argv = bash_argv;
} else {
arg.argv = sh_argv;
}
}
pasta_child_pid = clone(pasta_setup_ns,
ns_fn_stack + sizeof(ns_fn_stack) / 2,
(c->netns_only ? 0 : CLONE_NEWNET) |