Magisk/sepolicy-inject.c

/* 
 * This was derived from public domain works with updates to 
 * work with more modern SELinux libraries. 
 * 
 * It is released into the public domain.
 * 
 */

#include <getopt.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <sepol/policydb/policydb.h>
#include <sepol/policydb/services.h>

void usage(char *arg0) {
	fprintf(stderr, "%s -s <source type> -t <target type> -c <class> -p <perm> -P <policy file> -o <output file>\n", arg0);
	exit(1);
}

void *cmalloc(size_t s) {
	void *t = malloc(s);
	if (t == NULL) {
		fprintf(stderr, "Out of memory\n");
		exit(1);
	}
	return t;
}

int add_rule(char *s, char *t, char *c, char *p, policydb_t *policy) {
	type_datum_t *src, *tgt;
	class_datum_t *cls;
	perm_datum_t *perm;
	avtab_datum_t *av;
	avtab_key_t key;
	
	src = hashtab_search(policy->p_types.table, s);
	if (src == NULL) {
		fprintf(stderr, "source type %s does not exist\n", s);
		return 1;
	}
	tgt = hashtab_search(policy->p_types.table, t);
	if (tgt == NULL) {
		fprintf(stderr, "target type %s does not exist\n", t);
		return 1;
	}
	cls = hashtab_search(policy->p_classes.table, c);
	if (cls == NULL) {
		fprintf(stderr, "class %s does not exist\n", c);
		return 1;
	}
	perm = hashtab_search(cls->permissions.table, p);
	if (perm == NULL) {
		if (cls->comdatum == NULL) {
			fprintf(stderr, "perm %s does not exist in class %s\n", p, c);
			return 1;
		}
		perm = hashtab_search(cls->comdatum->permissions.table, p);
		if (perm == NULL) {
			fprintf(stderr, "perm %s does not exist in class %s\n", p, c);
			return 1;
		}
	}

	// See if there is already a rule
	key.source_type = src->s.value;
	key.target_type = tgt->s.value;
	key.target_class = cls->s.value;
	key.specified = AVTAB_ALLOWED;
	av = avtab_search(&policy->te_avtab, &key);

	if (av == NULL) {
		av = cmalloc(sizeof av);
		av->data |= 1U << (perm->s.value - 1);
		int ret = avtab_insert(&policy->te_avtab, &key, av);
		if (ret) {
			fprintf(stderr, "Error inserting into avtab\n");
			return 1;
		}	
	}

	av->data |= 1U << (perm->s.value - 1);

	return 0;
}
	

int load_policy(char *filename, policydb_t *policydb, struct policy_file *pf) {
	int fd;
	struct stat sb;
	void *map;
	int ret;

	fd = open(filename, O_RDONLY);
	if (fd < 0) {
		fprintf(stderr, "Can't open '%s':  %s\n",
				filename, strerror(errno));
		return 1;
	}
	if (fstat(fd, &sb) < 0) {
		fprintf(stderr, "Can't stat '%s':  %s\n",
				filename, strerror(errno));
		return 1;
	}
	map = mmap(NULL, sb.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE,
				fd, 0);
	if (map == MAP_FAILED) {
		fprintf(stderr, "Can't mmap '%s':  %s\n",
				filename, strerror(errno));
		return 1;
	}

	policy_file_init(pf);
	pf->type = PF_USE_MEMORY;
	pf->data = map;
	pf->len = sb.st_size;
	if (policydb_init(policydb)) {
		fprintf(stderr, "policydb_init: Out of memory!\n");
		return 1;
	}
	ret = policydb_read(policydb, pf, 1);
	if (ret) {
		fprintf(stderr, "error(s) encountered while parsing configuration\n");
		return 1;
	}

	return 0;
}
	

int main(int argc, char **argv)
{
	char *policy = NULL, *source = NULL, *target = NULL, *class = NULL, *perm = NULL, *outfile = NULL;
	policydb_t policydb;
	struct policy_file pf, outpf;
	sidtab_t sidtab;
	char ch;
	FILE *fp;
	
	
        struct option long_options[] = {
                {"source", required_argument, NULL, 's'},
                {"target", required_argument, NULL, 't'},
                {"class", required_argument, NULL, 'c'},
                {"perm", required_argument, NULL, 'p'},
                {"policy", required_argument, NULL, 'P'},
                {"output", required_argument, NULL, 'o'},
                {NULL, 0, NULL, 0}
        };

        while ((ch = getopt_long(argc, argv, "s:t:c:p:P:o:", long_options, NULL)) != -1) {
                switch (ch) {
                case 's':
                        source = optarg;
                        break;
                case 't':
                        target = optarg;
                        break;
                case 'c':
                        class = optarg;
                        break;
                case 'p':
                        perm = optarg;
                        break;
                case 'P':
                        policy = optarg;
                        break;
		case 'o':
			outfile = optarg;
			break;
		default:
			usage(argv[0]);
		}
	}

	if (!source || !target || !class || !perm || !policy)
		usage(argv[0]);

	sepol_set_policydb(&policydb);
        sepol_set_sidtab(&sidtab);

	if (load_policy(policy, &policydb, &pf)) {
		fprintf(stderr, "Could not load policy\n");
		return 1;
	}

        if (policydb_load_isids(&policydb, &sidtab))
		return 1;

	if (add_rule(source, target, class, perm, &policydb)) {
		fprintf(stderr, "Could not add rule\n");
		return 1;
	}

	fp = fopen(outfile, "w");
	if (!fp) {
		fprintf(stderr, "Could not open outfile\n");
		return 1;
	}
	
	policy_file_init(&outpf);
	outpf.type = PF_USE_STDIO;
	outpf.fp = fp;
	

	if (policydb_write(&policydb, &outpf)) {
		fprintf(stderr, "Could not write policy\n");
		return 1;
	}
	
	policydb_destroy(&policydb);
	fclose(fp);
	
	return 0;
}