TSUtil.m

#import <Foundation/Foundation.h>
#import <spawn.h>
#import "TSUtil.h"

#define POSIX_SPAWN_PERSONA_FLAGS_OVERRIDE 1
extern int posix_spawnattr_set_persona_np(const posix_spawnattr_t* __restrict, uid_t, uint32_t);
extern int posix_spawnattr_set_persona_uid_np(const posix_spawnattr_t* __restrict, uid_t);
extern int posix_spawnattr_set_persona_gid_np(const posix_spawnattr_t* __restrict, uid_t);

NSString* getNSStringFromFile(int fd) {
    NSMutableString* ms = [NSMutableString new];
    ssize_t num_read;
    char c;
    while((num_read = read(fd, &c, sizeof(c))))
    {
        [ms appendString:[NSString stringWithFormat:@"%c", c]];
    }
    return ms.copy;
}

NSString* spawnRoot(NSString* path, NSArray* args) {
    NSMutableArray* argsM = args.mutableCopy ?: [NSMutableArray new];
    [argsM insertObject:path.lastPathComponent atIndex:0];
    
    NSUInteger argCount = [argsM count];
    char **argsC = (char **)malloc((argCount + 1) * sizeof(char*));

    for (NSUInteger i = 0; i < argCount; i++)
    {
        argsC[i] = strdup([[argsM objectAtIndex:i] UTF8String]);
    }
    argsC[argCount] = NULL;

    posix_spawnattr_t attr;
    posix_spawnattr_init(&attr);

    posix_spawnattr_set_persona_np(&attr, 99, POSIX_SPAWN_PERSONA_FLAGS_OVERRIDE);
    posix_spawnattr_set_persona_uid_np(&attr, 0);
    posix_spawnattr_set_persona_gid_np(&attr, 0);

    posix_spawn_file_actions_t action;
    posix_spawn_file_actions_init(&action);

    //int outErr[2];

    int out[2];
    pipe(out);
    posix_spawn_file_actions_adddup2(&action, out[1], STDOUT_FILENO);
    posix_spawn_file_actions_addclose(&action, out[0]);
    
    pid_t task_pid;
    int status = -200;
    int spawnError = posix_spawn(&task_pid, [path UTF8String], &action, &attr, (char* const*)argsC, NULL);
    posix_spawnattr_destroy(&attr);
    for (NSUInteger i = 0; i < argCount; i++)
    {
        free(argsC[i]);
    }
    free(argsC);
    
    if(spawnError != 0)
    {
        return @"0";
    }

    do
    {
        if (waitpid(task_pid, &status, 0) != -1) {
        } else
        {
            return @"-222";
        }
    } while (!WIFEXITED(status) && !WIFSIGNALED(status));
    close(out[1]);
    NSString* output = getNSStringFromFile(out[0]);
    printf("%s\n", output.UTF8String);
    return output;
}