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pasta: More general way of starting spawned shell as a login shell

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When invoked so as to spawn a shell, pasta checks explicitly for the
shell being bash and if so, adds a "-l" option to make it a login shell.
This is not ideal, since this is a bash specific option and requires pasta
to know about specific shell variants.

There's a general convention for starting a login shell, which is to
prepend a "-" to argv[0].  Use this approach instead, so we don't need bash
specific logic.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2022-10-14 15:25:28 +11:00 committed by Stefano Brivio
parent f99e9a3338
commit 672a8cd80e
1 changed files with 20 additions and 12 deletions
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32
pasta.c
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@ -149,10 +149,12 @@ void pasta_open_ns(struct ctx *c, const char *netns)
/** /**
* struct pasta_setup_ns_arg - Argument for pasta_setup_ns() * struct pasta_setup_ns_arg - Argument for pasta_setup_ns()
* @exe: Executable to run
* @argv: Command and arguments to run * @argv: Command and arguments to run
*/ */
struct pasta_setup_ns_arg { struct pasta_setup_ns_arg {
char **argv; const char *exe;
char *const *argv;
}; };
/** /**
@ -163,12 +165,13 @@ struct pasta_setup_ns_arg {
*/ */
static int pasta_setup_ns(void *arg) static int pasta_setup_ns(void *arg)
{ {
struct pasta_setup_ns_arg *a = (struct pasta_setup_ns_arg *)arg; const struct pasta_setup_ns_arg *a;
FWRITE("/proc/sys/net/ipv4/ping_group_range", "0 0", FWRITE("/proc/sys/net/ipv4/ping_group_range", "0 0",
"Cannot set ping_group_range, ICMP requests might fail"); "Cannot set ping_group_range, ICMP requests might fail");
execvp(a->argv[0], a->argv); a = (const struct pasta_setup_ns_arg *)arg;
execvp(a->exe, a->argv);
perror("execvp"); perror("execvp");
exit(EXIT_FAILURE); exit(EXIT_FAILURE);
@ -183,26 +186,31 @@ static int pasta_setup_ns(void *arg)
void pasta_start_ns(struct ctx *c, int argc, char *argv[]) void pasta_start_ns(struct ctx *c, int argc, char *argv[])
{ {
struct pasta_setup_ns_arg arg = { struct pasta_setup_ns_arg arg = {
.exe = argv[0],
.argv = argv, .argv = argv,
}; };
char *shell = getenv("SHELL");
char *sh_argv[] = { shell, NULL };
char *bash_argv[] = { shell, "-l", NULL };
char ns_fn_stack[NS_FN_STACK_SIZE]; char ns_fn_stack[NS_FN_STACK_SIZE];
char *sh_argv[] = { NULL, NULL };
char sh_arg0[PATH_MAX + 1];
c->foreground = 1; c->foreground = 1;
if (!c->debug) if (!c->debug)
c->quiet = 1; c->quiet = 1;
if (!shell)
shell = "/bin/sh";
if (argc == 0) { if (argc == 0) {
if (strstr(shell, "/bash")) { arg.exe = getenv("SHELL");
arg.argv = bash_argv; if (!arg.exe)
} else { arg.exe = "/bin/sh";
arg.argv = sh_argv;
if ((size_t)snprintf(sh_arg0, sizeof(sh_arg0),
"-%s", arg.exe) >= sizeof(sh_arg0)) {
err("$SHELL is too long (%u bytes)",
strlen(arg.exe));
exit(EXIT_FAILURE);
} }
sh_argv[0] = sh_arg0;
arg.argv = sh_argv;
} }
pasta_child_pid = clone(pasta_setup_ns, pasta_child_pid = clone(pasta_setup_ns,