1 // termux-api.c - helper binary for calling termux api classes
2 // Usage: termux-api ${API_METHOD} ${ADDITIONAL_FLAGS}
4 // am broadcast com.termux.api/.TermuxApiReceiver --es socket_input ${INPUT_SOCKET}
5 // --es socket_output ${OUTPUT_SOCKET}
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.
19 #include <sys/socket.h>
21 #include <sys/types.h>
26 // Function which execs "am broadcast ..".
27 void exec_am_broadcast(int argc
, char** argv
, char* input_address_string
, char* output_address_string
)
29 // Redirect stdout to /dev/null (but leave stderr open):
31 open("/dev/null", O_RDONLY
);
35 char const* const file
= "/system/bin/am";
36 // Avoid the system am binary from linking to wrong libraries:
37 unsetenv("LD_LIBRARY_PATH");
39 // The user is calculated from the uid in android.os.UserHandle#getUserId(int uid) as "uid / 100000", so we do the same:
40 uid_t current_uid
= getuid();
41 int android_user_id
= current_uid
/ 100000;
42 char* android_user_id_string
;
43 if (asprintf(&android_user_id_string
, "%d", android_user_id
) == -1) {
44 fprintf(stderr
, "asprintf() error");
48 int const extra_args
= 15; // Including ending NULL.
49 char** child_argv
= malloc((sizeof(char*)) * (argc
+ extra_args
));
52 child_argv
[1] = "broadcast";
53 child_argv
[2] = "--user";
54 child_argv
[3] = android_user_id_string
;
56 child_argv
[5] = "com.termux.api/.TermuxApiReceiver";
57 child_argv
[6] = "--es";
58 // Input/output are reversed for the java process (our output is its input):
59 child_argv
[7] = "socket_input";
60 child_argv
[8] = output_address_string
;
61 child_argv
[9] = "--es";
62 child_argv
[10] = "socket_output";
63 child_argv
[11] = input_address_string
;
64 child_argv
[12] = "--es";
65 child_argv
[13] = "api_method";
66 child_argv
[14] = argv
[1];
68 // Copy the remaining arguments -2 for first binary and second api name:
69 memcpy(child_argv
+ extra_args
, argv
+ 2, (argc
-1) * sizeof(char*));
72 child_argv
[argc
+ extra_args
] = NULL
;
74 execv(file
, child_argv
);
75 perror("execv(\"/system/bin/am\")");
79 void generate_uuid(char* str
) {
80 sprintf(str
, "%x%x-%x-%x-%x-%x%x%x",
81 rand(), rand(), // Generates a 64-bit Hex number
82 (uint32_t) getpid(), // Generates a 32-bit Hex number
83 ((rand() & 0x0fff) | 0x4000), // Generates a 32-bit Hex number of the form 4xxx (4 indicates the UUID version)
84 rand() % 0x3fff + 0x8000, // Generates a 32-bit Hex number in the range [0x8000, 0xbfff]
85 rand(), rand(), rand()); // Generates a 96-bit Hex number
88 // Thread function which reads from stdin and writes to socket.
89 void* transmit_stdin_to_socket(void* arg
) {
90 int output_server_socket
= *((int*) arg
);
91 struct sockaddr_un remote_addr
;
92 socklen_t addrlen
= sizeof(remote_addr
);
93 int output_client_socket
= accept(output_server_socket
, (struct sockaddr
*) &remote_addr
, &addrlen
);
97 while (len
= read(STDIN_FILENO
, &buffer
, sizeof(buffer
)-1), len
> 0) {
98 if (write(output_client_socket
, buffer
, len
) < 0) break;
100 // Close output socket on end of input:
101 close(output_client_socket
);
105 // Main thread function which reads from input socket and writes to stdout.
106 void transmit_socket_to_stdout(int input_socket_fd
) {
109 while ((len
= read(input_socket_fd
, &buffer
, sizeof(buffer
)-1)) > 0) {
111 write(STDOUT_FILENO
, buffer
, len
);
113 if (len
< 0) perror("read()");
116 int main(int argc
, char** argv
) {
117 // Do not transform children into zombies when they terminate:
118 struct sigaction sigchld_action
= { .sa_handler
= SIG_DFL
, .sa_flags
= SA_RESTART
| SA_NOCLDSTOP
| SA_NOCLDWAIT
};
119 sigaction(SIGCHLD
, &sigchld_action
, NULL
);
121 char input_address_string
[100]; // This program reads from it.
122 char output_address_string
[100]; // This program writes to it.
124 // Seed the random number generator:
126 gettimeofday(&time
,NULL
);
127 srand((time
.tv_sec
* 1000) + (time
.tv_usec
/ 1000));
129 generate_uuid(input_address_string
);
130 generate_uuid(output_address_string
);
132 struct sockaddr_un input_address
= { .sun_family
= AF_UNIX
};
133 struct sockaddr_un output_address
= { .sun_family
= AF_UNIX
};
134 // Leave struct sockaddr_un.sun_path[0] as 0 and use the UUID string as abstract linux namespace:
135 strncpy(&input_address
.sun_path
[1], input_address_string
, strlen(input_address_string
));
136 strncpy(&output_address
.sun_path
[1], output_address_string
, strlen(output_address_string
));
138 int input_server_socket
= socket(AF_UNIX
, SOCK_STREAM
|SOCK_CLOEXEC
, 0);
139 if (input_server_socket
== -1) { perror("socket()"); return 1; }
140 int output_server_socket
= socket(AF_UNIX
, SOCK_STREAM
|SOCK_CLOEXEC
, 0);
141 if (output_server_socket
== -1) { perror("socket()"); return 1; }
143 if (bind(input_server_socket
, (struct sockaddr
*) &input_address
, sizeof(sa_family_t
) + strlen(input_address_string
) + 1) == -1) {
144 perror("bind(input)");
147 if (bind(output_server_socket
, (struct sockaddr
*) &output_address
, sizeof(sa_family_t
) + strlen(output_address_string
) + 1) == -1) {
148 perror("bind(output)");
152 if (listen(input_server_socket
, 1) == -1) { perror("listen()"); return 1; }
153 if (listen(output_server_socket
, 1) == -1) { perror("listen()"); return 1; }
155 pid_t fork_result
= fork();
156 switch (fork_result
) {
157 case -1: perror("fork()"); return 1;
158 case 0: exec_am_broadcast(argc
, argv
, input_address_string
, output_address_string
); return 0;
161 struct sockaddr_un remote_addr
;
162 socklen_t addrlen
= sizeof(remote_addr
);
163 int input_client_socket
= accept(input_server_socket
, (struct sockaddr
*) &remote_addr
, &addrlen
);
165 pthread_t transmit_thread
;
166 pthread_create(&transmit_thread
, NULL
, transmit_stdin_to_socket
, &output_server_socket
);
168 transmit_socket_to_stdout(input_client_socket
);