Fixed: Fix exit code handling

strtol() returns 0 on conversion failure and errno is not set, which resulted in wrong exit codes passed by server to be assumed to be exit code 0.

Moreover, shell exit codes are limited to 0-255 and that was not being checked. Out of bound exit codes would return with exit code `44` `Channel number out of range`.

Author: agnostic-apollo

termux-am.cpp

@@ -65,6 +65,11 @@ bool recv_part(const int fd, char* data, int len) {
     return false;
 }
 
+bool is_number(const std::string& s) {
+    std::string::const_iterator it = s.begin();
+    while (it != s.end() && std::isdigit(*it)) ++it;
+    return !s.empty() && it == s.end();
+}
 
 int main(int argc, char* argv[]) {
     struct sockaddr_un adr = {.sun_family = AF_UNIX};
@@ -99,15 +104,28 @@ int main(int argc, char* argv[]) {
     {
         char tmp[10];
         memset(tmp, '\0', sizeof(tmp));
-        if (! recv_part(fd, tmp, sizeof(tmp)-1)) {
-            fputs("Exit code too long", stderr);
+        if (!recv_part(fd, tmp, sizeof(tmp) - 1)) {
+            std::string errmsg = "Exit code \"" + std::string(tmp) + "\" is too long. It must be valid number between 0-255";
+            if (errno == 0)
+                std::cerr << errmsg << std::endl;
+            else
+                perror(errmsg.c_str());
             close(fd);
             return 1;
         }
+
+        // strtol returns 0 if conversion failed and allows leading whitespaces
         errno = 0;
         exit_code = strtol(tmp, NULL, 10);
-        if (errno != 0) {
-            perror("Exit code not a valid number");
+        if (!is_number(std::string(tmp)) || (exit_code == 0 && std::string(tmp) != "0")) {
+            std::cerr << "Exit code \"" + std::string(tmp) + "\" is not a valid number between 0-255" << std::endl;
+            close(fd);
+            return 1;
+        }
+
+        // Out of bound exit codes would return with exit code `44` `Channel number out of range`.
+        if (exit_code < 0 || exit_code > 255) {
+            std::cerr << "Exit code \"" << std::string(tmp) << "\" is not a valid exit code between 0-255" << std::endl;
             close(fd);
             return 1;
         }