Fix issue with pid://../run/foo..pid parser

Unfortunately we cannot use realpath(3) here since the the PID files
usually do not yet exist at this point.

Add and modify my ugly de_dotdot() from Merecat httpd.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

TODO.org

@@ -1,4 +1,4 @@
-* TODO fix pid parser, //run/foo.pid -> /var/run///run/foo.pid
+* DONE fix pid parser, //run/foo.pid -> /var/run///run/foo.pid
 ** DONE test framework refactor 'texec sh -c ...' -> 'run ...'
 * TODO Clean up tests a bit
 * TODO Drop tenv or common and rename tenv-root

src/pid.c

@@ -149,6 +149,8 @@ int pid_file_create(svc_t *svc)
 
 int pid_file_set(svc_t *svc, char *file, int not)
 {
+	char buf[sizeof(svc->pidfile)];
+
 	if (!file) {
 		file = pid_file(svc);
 		if (!file)
@@ -165,7 +167,9 @@ int pid_file_set(svc_t *svc, char *file, int not)
 		not = 1;
 	}
 
-	pid_runpath(file, &svc->pidfile[not], sizeof(svc->pidfile) - not);
+	de_dotdot(file);
+	pid_runpath(file, buf, sizeof(buf));
+	strlcpy(&svc->pidfile[not], buf, sizeof(svc->pidfile) - not);
 	if (not)
 		svc->pidfile[0] = '!';
 

src/pid.h

@@ -51,6 +51,7 @@ static inline char *pid_runpath(const char *file, char *path, size_t len)
 {
 	static char *prefix = "/var/run";
 	static int unknown = 1;
+	char *ptr;
 	int rc;
 
 	if (unknown) {
@@ -59,10 +60,9 @@ static inline char *pid_runpath(const char *file, char *path, size_t len)
 		unknown = 0;
 	}
 
-	if (!strncmp(file, "/var/run/", 9))
-		file += 9;
-	else if (!strncmp(file, "/run/", 5))
-		file += 5;
+	ptr = strstr(file, "/run/");
+	if (ptr)
+		file = ptr + 5;
 
 	rc = paste(path, len, prefix, file);
 	if (rc < 0 || (size_t)rc >= len)

src/util.c

@@ -467,6 +467,47 @@ char *sanitize(char *arg, size_t len)
 	return arg;
 }
 
+void de_dotdot(char *file)
+{
+        char *cp, *cp2;
+        int l;
+
+        /* Remove leading ./ and any /./ sequences. */
+        while (strncmp(file, "./", 2) == 0)
+                memmove(file, file + 2, strlen(file) - 1);
+        while ((cp = strstr(file, "/./")))
+                memmove(cp, cp + 2, strlen(cp) - 1);
+
+        /* Alternate between removing leading ../ and removing xxx/../ */
+        for (;;) {
+                while (strncmp(file, "../", 3) == 0)
+                        memmove(file, file + 3, strlen(file) - 2);
+                cp = strstr(file, "/../");
+                if (!cp)
+                        break;
+
+                for (cp2 = cp - 1; cp2 >= file && *cp2 != '/'; --cp2)
+                        continue;
+
+                memmove(cp2 + 1, cp + 4, strlen(cp + 3));
+        }
+
+        /* Also elide any xxx/.. at the end. */
+        while ((l = strlen(file)) > 3 && strcmp((cp = file + l - 3), "/..") == 0) {
+                for (cp2 = cp - 1; cp2 >= file && *cp2 != '/'; --cp2)
+                        continue;
+                if (cp2 < file)
+                        break;
+                *cp2 = '\0';
+        }
+
+        /* Collapse any multiple / sequences. */
+        while ((cp = strstr(file, "//"))) {
+                cp2 = cp + 1;
+                memmove(cp, cp2, strlen(cp2) + 1);
+        }
+}
+
 static int hasopt(char *opts, char *opt)
 {
 	char buf[strlen(opts) + 1];

src/util.h

@@ -72,6 +72,7 @@ char *uptime       (long secs, char *buf, size_t len);
 char *memsz        (uint64_t sz, char *buf, size_t len);
 
 char *sanitize     (char *arg, size_t len);
+void  de_dotdot    (char *file);
 
 int   ismnt        (char *file, char *dir, char *mode);
 int   fismnt       (char *dir);