Initial commit.

3 files changed, 162 insertions, 0 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..b9509e1
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,15 @@
+CFLAGS ?= -O3 -march=native -pipe -fomit-frame-pointer -fPIE -fstack-protector-all
+LDFLAGS ?= -Wl,-z,now -Wl,-z,relro
+PREFIX ?= /usr/local
+
+.PHONY: clean install
+
+all: clean-mosh
+
+clean:
+	rm -f clean-mosh
+
+install:
+	install -m 0100 -o 0 -g 0 -t $(PREFIX)/sbin/ clean-mosh
+
+clean-mosh:
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..7b9a9e6
--- /dev/null
+++ b/README.md
@@ -0,0 +1,31 @@
+# Mosh Cleaner
+
+Mosh cleaner kills stale mosh sessions, according to this algorithm:
+
+    For each user:
+    	If user only has one mosh session:
+    		continue
+    	For each mosh session other than the most recent of that user:
+    		If session is currently connected:
+    			continue
+    		If session is older than kill-time:
+    			kill session
+
+`kill-time` begins at 24 hours and splits in half each time, until a minimum of 1 hour. This amounts to the following semantics:
+
+* Most recent session: never killed
+* Any currently connected session: never killed
+* Second most recent session: killed if not used for 24 hours
+* Third most recent session: killed if not used for 12 hours
+* Forth most recent session: killed if not used for 6 hours
+* Fifth most recent session: killed if not used for 3 hours
+* Sixth most recent session: killed if not used for 1.5 hours
+* Seventh most recent session: killed if not used for 1 hour
+* Eighth most recent session: killed if not used for 1 hour
+* Ninth most recent session: killed if not used for 1 hour
+
+### Usage
+
+    $ make
+    $ sudo make install
+    $ sudo clean-mosh
diff --git a/clean-mosh.c b/clean-mosh.c
new file mode 100644
index 0000000..3a512c9
--- /dev/null
+++ b/clean-mosh.c
@@ -0,0 +1,116 @@
+#include <stdio.h>
+#include <signal.h>
+#include <time.h>
+#include <utmp.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+struct mosh {
+	time_t last_used;
+	int has_ip;
+	int pid;
+	struct mosh *next;
+};
+
+struct user {
+	char username[UT_NAMESIZE];
+	struct mosh *head;
+	struct user *next;
+};
+
+static inline struct user *new_user(char *username)
+{
+	struct user *user;
+	user = malloc(sizeof(struct user));
+	if (!user) {
+		perror("user");
+		exit(EXIT_FAILURE);
+	}
+	strcpy(user->username, username);
+	user->head = NULL;
+	user->next = NULL;
+	return user;
+}
+
+#define ONE_HOUR (60 * 60)
+#define ONE_DAY (ONE_HOUR * 24)
+
+int main(int argc, char *argv[])
+{
+	FILE *utmp;
+	struct utmp entry;
+	struct user *user_head = NULL, *user;
+	struct mosh *parsed, *insert, **prev;
+	char *bracket_open, *bracket_close;
+	int kill_time;
+
+	utmp = fopen("/var/run/utmp", "r");
+	if (!utmp) {
+		perror("fopen");
+		return EXIT_FAILURE;
+	}
+	while (fread(&entry, sizeof(entry), 1, utmp)) {
+		if (!strcmp(entry.ut_host, "mosh"))
+			continue;
+		bracket_open = strrchr(entry.ut_host, '[');
+		bracket_close = strrchr(entry.ut_host, ']');
+		if (!bracket_open || !bracket_close || bracket_open >= bracket_close)
+			continue;
+
+		parsed = malloc(sizeof(struct mosh));
+		if (!parsed) {
+			perror("malloc");
+			return EXIT_FAILURE;
+		}
+		parsed->next = NULL;
+		parsed->has_ip = strstr(entry.ut_host, "via mosh") != NULL;
+		*bracket_close = '\0';
+		parsed->pid = atoi(bracket_open + 1);
+		parsed->last_used = entry.ut_tv.tv_sec;
+
+
+		if (!user_head)
+			user_head = user = new_user(entry.ut_user);
+		else {
+			for (user = user_head; user; user = user->next) {
+				if (!strcmp(entry.ut_user, user->username))
+					break;
+				if (!user->next) {
+					user->next = new_user(entry.ut_user);
+					user = user->next;
+					break;
+				}
+			}
+		}
+		if (!user->head)
+			user->head = parsed;
+		else {
+			for (prev = &user->head, insert = user->head; insert; prev = &insert->next, insert = insert->next) {
+				if ((parsed->has_ip && !insert->has_ip) || parsed->last_used > insert->last_used)
+					break;
+			}
+			*prev = parsed;
+			parsed->next = insert;
+		}
+	}
+	fclose(utmp);
+
+	for (user = user_head; user; user = user->next) {
+		if (!user->head->next) /* If the user only has one mosh process running, we don't kill anything. */
+			continue;
+		for (parsed = user->head->next, kill_time = ONE_DAY; parsed; parsed = parsed->next, kill_time /= 2) {
+			if (kill_time < ONE_HOUR)
+				kill_time = ONE_HOUR;
+			if (parsed->has_ip) /* If the user is currently connected, we don't kill it. */
+				continue;
+			if (time(NULL) - parsed->last_used < kill_time) /* If the connection is less than an hour old, we don't kill it. */
+				continue;
+			printf("[+] Killing %s's mosh instance %d, last used on %s", user->username, parsed->pid, ctime(&parsed->last_used));
+			if (kill(parsed->pid, SIGTERM))
+				perror("kill");
+		}
+	}
+
+	return EXIT_SUCCESS;
+}