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kill: refuse to kill/stop the session you're currently inside (mirrors attach's self-check) #51

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kill: refuse to kill/stop the session you're currently inside (mirrors attach's self-check) #51

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75 changes: 46 additions & 29 deletions attach.c
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Original file line number Diff line number Diff line change
Expand Up @@ -256,6 +256,34 @@ int replay_session_log(int saved_errno)
return 1;
}

/* Returns 1 if sockname appears in the current process's atch session
** ancestry chain (SESSION_ENVVAR, colon-separated, outermost first).
** Shared by attach_main and kill_main to refuse both direct self-
** attach/self-kill and indirect loops like A -> B -> A. */
static int session_in_ancestry(const char *sockname)
{
const char *chain = getenv(SESSION_ENVVAR);
size_t slen;
const char *p;

if (!chain || !*chain)
return 0;

slen = strlen(sockname);
p = chain;
while (*p) {
const char *colon = strchr(p, ':');
size_t tlen = colon ? (size_t)(colon - p) : strlen(p);

if (tlen == slen && strncmp(p, sockname, tlen) == 0)
return 1;
if (!colon)
break;
p = colon + 1;
}
return 0;
}

int attach_main(int noerror)
{
struct packet pkt;
Expand All @@ -264,35 +292,13 @@ int attach_main(int noerror)
int s;

/* Refuse to attach to any session in our ancestry chain (catches both
* direct self-attach and indirect loops like A -> B -> A).
* SESSION_ENVVAR is the colon-separated chain, so scanning it covers
* all ancestors. */
{
const char *tosearch = getenv(SESSION_ENVVAR);

if (tosearch && *tosearch) {
size_t slen = strlen(sockname);
const char *p = tosearch;

while (*p) {
const char *colon = strchr(p, ':');
size_t tlen =
colon ? (size_t)(colon - p) : strlen(p);

if (tlen == slen
&& strncmp(p, sockname, tlen) == 0) {
if (!noerror)
printf
("%s: cannot attach to session '%s' from within itself\n",
progname,
session_shortname());
return 1;
}
if (!colon)
break;
p = colon + 1;
}
}
* direct self-attach and indirect loops like A -> B -> A). */
if (session_in_ancestry(sockname)) {
if (!noerror)
printf
("%s: cannot attach to session '%s' from within itself\n",
progname, session_shortname());
return 1;
}

/* Attempt to open the socket. Don't display an error if noerror is
Expand Down Expand Up @@ -537,6 +543,17 @@ int kill_main(int force)
const char *name = session_shortname();
int i;

/* Refuse to kill/stop any session in our ancestry chain — same check
* as attach_main, see session_in_ancestry(). Previously unchecked:
* killing your own controlling session from within it just made the
* signal race the caller's own exit, with no explanatory message. */
if (session_in_ancestry(sockname)) {
printf
("%s: cannot kill/stop session '%s' from within itself — run this from another session or terminal instead\n",
progname, name);
return 1;
}

signal(SIGPIPE, SIG_IGN);

if (force) {
Expand Down
31 changes: 31 additions & 0 deletions tests/test.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -276,6 +276,37 @@ run "$ATCH" kill -f s-noexist-force
assert_exit "kill -f: nonexistent → exit 1" 1 "$rc"
assert_contains "kill -f: nonexistent → message" "does not exist" "$out"

# kill/stop refuses to target the session in the caller's own ancestry chain
# (ATCH_SESSION), same guard as attach's self-attach check.
# NOTE: `VAR=val run ...` would leak VAR into the rest of this script, since
# `run` is a shell function -- a temporary assignment before a function call
# persists after it returns (POSIX behavior, unlike prefixing an external
# command). Export/unset explicitly instead.
"$ATCH" start s-selfkill sleep 999
export ATCH_SESSION="$HOME/.cache/atch/s-selfkill"
run "$ATCH" kill s-selfkill
unset ATCH_SESSION
assert_exit "kill: self → exit 1" 1 "$rc"
assert_contains "kill: self → message" "from within itself" "$out"
tidy s-selfkill

"$ATCH" start s-selfkillf sleep 999
export ATCH_SESSION="$HOME/.cache/atch/s-selfkillf"
run "$ATCH" kill -f s-selfkillf
unset ATCH_SESSION
assert_exit "kill -f: self → exit 1" 1 "$rc"
assert_contains "kill -f: self → message" "from within itself" "$out"
tidy s-selfkillf

# a mismatched ATCH_SESSION (different session, not an ancestor) must not
# trip the guard -- only an exact ancestry-chain match refuses the kill
"$ATCH" start s-notself sleep 999
export ATCH_SESSION="$HOME/.cache/atch/some-other-session"
run "$ATCH" kill s-notself
unset ATCH_SESSION
assert_exit "kill: non-ancestor session unaffected → exit 0" 0 "$rc"
assert_contains "kill: non-ancestor session unaffected → stopped" "stopped" "$out"

# ── 6. clear command ─────────────────────────────────────────────────────────

run "$ATCH" clear
Expand Down