mdw@git.distorted.org.uk Git - termux-packages/blob - packages/termux-api/termux-api.c

   1 // termux-api.c - helper binary for calling termux api classes
   2 // Usage: termux-api ${API_METHOD} ${ADDITIONAL_FLAGS}
   3 //        This executes
   4 //          am broadcast com.termux.api/.TermuxApiReceiver --es socket_input ${INPUT_SOCKET}
   5 //                                                        --es socket_output ${OUTPUT_SOCKET}
   6 //                                                        --es ${API_METHOD}
   7 //                                                        ${ADDITIONAL_FLAGS}
   8 //        where ${INPUT_SOCKET} and ${OUTPUT_SOCKET} are addresses to linux abstract namespace sockets,
   9 //        used to pass on stdin to the java implementation and pass back output from java to stdout.
  10 #define _POSIX_SOURCE
  11 #define _GNU_SOURCE
  12 #include <fcntl.h>
  13 #include <pthread.h>
  14 #include <signal.h>
  15 #include <stdbool.h>
  16 #include <stdio.h>
  17 #include <stdlib.h>
  18 #include <string.h>
  19 #include <sys/socket.h>
  20 #include <sys/stat.h>
  21 #include <sys/types.h>
  22 #include <sys/un.h>
  23 #include <time.h>
  24 #include <unistd.h>
  25
  26 // Function which execs "am broadcast ..".
  27 _Noreturn void exec_am_broadcast(int argc, char** argv, char* input_address_string, char* output_address_string)
  28 {
  29     // Redirect stdout to /dev/null (but leave stderr open):
  30     close(STDOUT_FILENO);
  31     open("/dev/null", O_RDONLY);
  32     // Close stdin:
  33     close(STDIN_FILENO);
  34
  35     int const extra_args = 15; // Including ending NULL.
  36     char** child_argv = malloc((sizeof(char*)) * (argc + extra_args));
  37
  38     child_argv[0] = "am";
  39     child_argv[1] = "broadcast";
  40     child_argv[2] = "--user";
  41     child_argv[3] = "0";
  42     child_argv[4] = "-n";
  43     child_argv[5] = "com.termux.api/.TermuxApiReceiver";
  44     child_argv[6] = "--es";
  45     // Input/output are reversed for the java process (our output is its input):
  46     child_argv[7] = "socket_input";
  47     child_argv[8] = output_address_string;
  48     child_argv[9] = "--es";
  49     child_argv[10] = "socket_output";
  50     child_argv[11] = input_address_string;
  51     child_argv[12] = "--es";
  52     child_argv[13] = "api_method";
  53     child_argv[14] = argv[1];
  54
  55     // Copy the remaining arguments -2 for first binary and second api name:
  56     memcpy(child_argv + extra_args, argv + 2, (argc-1) * sizeof(char*));
  57
  58     // End with NULL:
  59     child_argv[argc + extra_args] = NULL;
  60
  61     // Use an a executable taking care of PATH and LD_LIBRARY_PATH:
  62     execv("/data/data/com.termux/files/usr/bin/am", child_argv);
  63
  64     perror("execv(\"/data/data/com.termux/files/usr/bin/am\")");
  65     exit(1);
  66 }
  67
  68 void generate_uuid(char* str) {
  69     sprintf(str, "%x%x-%x-%x-%x-%x%x%x",
  70             arc4random(), arc4random(),                 // Generates a 64-bit Hex number
  71             (uint32_t) getpid(),                        // Generates a 32-bit Hex number
  72             ((arc4random() & 0x0fff) | 0x4000),         // Generates a 32-bit Hex number of the form 4xxx (4 indicates the UUID version)
  73             arc4random() % 0x3fff + 0x8000,             // Generates a 32-bit Hex number in the range [0x8000, 0xbfff]
  74             arc4random(), arc4random(), arc4random());  // Generates a 96-bit Hex number
  75 }
  76
  77 // Thread function which reads from stdin and writes to socket.
  78 void* transmit_stdin_to_socket(void* arg) {
  79     int output_server_socket = *((int*) arg);
  80     struct sockaddr_un remote_addr;
  81     socklen_t addrlen = sizeof(remote_addr);
  82     int output_client_socket = accept(output_server_socket, (struct sockaddr*) &remote_addr, &addrlen);
  83
  84     ssize_t len;
  85     char buffer[1024];
  86     while (len = read(STDIN_FILENO, &buffer, sizeof(buffer)), len > 0) {
  87         if (write(output_client_socket, buffer, len) < 0) break;
  88     }
  89     // Close output socket on end of input:
  90     close(output_client_socket);
  91     return NULL;
  92 }
  93
  94 // Main thread function which reads from input socket and writes to stdout.
  95 void transmit_socket_to_stdout(int input_socket_fd) {
  96     ssize_t len;
  97     char buffer[1024];
  98     while ((len = read(input_socket_fd, &buffer, sizeof(buffer))) > 0) {
  99         write(STDOUT_FILENO, buffer, len);
 100     }
 101     if (len < 0) perror("read()");
 102 }
 103
 104 int main(int argc, char** argv) {
 105     // Do not transform children into zombies when they terminate:
 106     struct sigaction sigchld_action = { .sa_handler = SIG_DFL, .sa_flags = SA_RESTART | SA_NOCLDSTOP | SA_NOCLDWAIT };
 107     sigaction(SIGCHLD, &sigchld_action, NULL);
 108
 109     char input_address_string[100];  // This program reads from it.
 110     char output_address_string[100]; // This program writes to it.
 111
 112     generate_uuid(input_address_string);
 113     generate_uuid(output_address_string);
 114
 115     struct sockaddr_un input_address = { .sun_family = AF_UNIX };
 116     struct sockaddr_un output_address = { .sun_family = AF_UNIX };
 117     // Leave struct sockaddr_un.sun_path[0] as 0 and use the UUID string as abstract linux namespace:
 118     strncpy(&input_address.sun_path[1], input_address_string, strlen(input_address_string));
 119     strncpy(&output_address.sun_path[1], output_address_string, strlen(output_address_string));
 120
 121     int input_server_socket = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
 122     if (input_server_socket == -1) { perror("socket()"); return 1; }
 123     int output_server_socket = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
 124     if (output_server_socket == -1) { perror("socket()"); return 1; }
 125
 126     if (bind(input_server_socket, (struct sockaddr*) &input_address, sizeof(sa_family_t) + strlen(input_address_string) + 1) == -1) {
 127         perror("bind(input)");
 128         return 1;
 129     }
 130     if (bind(output_server_socket, (struct sockaddr*) &output_address, sizeof(sa_family_t) + strlen(output_address_string) + 1) == -1) {
 131         perror("bind(output)");
 132         return 1;
 133     }
 134
 135     if (listen(input_server_socket, 1) == -1) { perror("listen()"); return 1; }
 136     if (listen(output_server_socket, 1) == -1) { perror("listen()"); return 1; }
 137
 138     pid_t fork_result = fork();
 139     switch (fork_result) {
 140         case -1: perror("fork()"); return 1;
 141         case 0: exec_am_broadcast(argc, argv, input_address_string, output_address_string);
 142     }
 143
 144     struct sockaddr_un remote_addr;
 145     socklen_t addrlen = sizeof(remote_addr);
 146     int input_client_socket = accept(input_server_socket, (struct sockaddr*) &remote_addr, &addrlen);
 147
 148     pthread_t transmit_thread;
 149     pthread_create(&transmit_thread, NULL, transmit_stdin_to_socket, &output_server_socket);
 150
 151     transmit_socket_to_stdout(input_client_socket);
 152
 153     return 0;
 154 }
 155