| 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 | |