74 lines
1.9 KiB
C
74 lines
1.9 KiB
C
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#include <stdbool.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/random.h>
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#include <monocypher.h>
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#include "epic_drm.h"
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#define log(what) printf("[epic_drm] " what "\n")
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/**
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* sends a protected command to the client
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*/
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void get_cmd(struct command_channel* chan, const uint8_t* key) {
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log("sending encrypted DRM command");
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uint8_t cmd[CMD_SIZE] = "echo 'sharks'";
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getrandom(chan->data.nonce, 24, 0);
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crypto_lock(chan->data.mac, chan->data.exec_cmd, key, chan->data.nonce, cmd, CMD_SIZE);
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chan->command = SUCCESS;
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}
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/**
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* unprotects and executes data from the client
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*/
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void execute_cmd(struct command_channel* chan, const uint8_t* key) {
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log("decrypting command");
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uint8_t cmd[CMD_SIZE];
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int res = crypto_unlock(cmd, key, chan->data.nonce, chan->data.mac, chan->data.exec_cmd, CMD_SIZE);
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if (res != 0) {
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log("decryption error");
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chan->command = ERROR;
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} else {
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log("executing command");
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system((const char*)cmd);
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chan->command = SUCCESS;
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}
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}
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int main() {
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// create random key
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uint8_t key[16];
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log("generating random key");
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getrandom(key, sizeof(key), 0);
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// initialize memory
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log("opening shm");
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shm_unlink(SHM_NAME);
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int shm = shm_open(SHM_NAME, O_RDWR | O_CREAT | O_EXCL, 0644);
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ftruncate(shm, SHM_SIZE);
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struct command_channel* chan = mmap(NULL, SHM_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, shm, 0);
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sem_init(&chan->sem_c2s, 1, 0);
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sem_init(&chan->sem_s2c, 1, 0);
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// process commands
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log("ready");
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while (true) {
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sem_wait(&chan->sem_c2s);
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switch (chan->command) {
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case GET_CMD:
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get_cmd(chan, key);
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break;
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case EXECUTE_CMD:
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execute_cmd(chan, key);
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break;
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default:
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log("unexpected command");
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}
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sem_post(&chan->sem_s2c);
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}
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}
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