path: root/libselinux/src/label_file.c

/*
 * File contexts backend for labeling system
 *
 * Author : Eamon Walsh <ewalsh@tycho.nsa.gov>
 * Author : Stephen Smalley <sds@tycho.nsa.gov>
 *
 * This library derived in part from setfiles and the setfiles.pl script
 * developed by Secure Computing Corporation.
 */

#include <assert.h>
#include <fcntl.h>
#include <stdarg.h>
#include <string.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <stdint.h>
#include <pcre.h>

#include <linux/limits.h>

#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include "callbacks.h"
#include "label_internal.h"
#include "label_file.h"

/*
 * Internals, mostly moved over from matchpathcon.c
 */

/* return the length of the text that is the stem of a file name */
static int get_stem_from_file_name(const char *const buf)
{
	const char *tmp = strchr(buf + 1, '/');

	if (!tmp)
		return 0;
	return tmp - buf;
}

/* find the stem of a file name, returns the index into stem_arr (or -1 if
 * there is no match - IE for a file in the root directory or a regex that is
 * too complex for us).  Makes buf point to the text AFTER the stem. */
static int find_stem_from_file(struct saved_data *data, const char **buf)
{
	int i;
	int stem_len = get_stem_from_file_name(*buf);

	if (!stem_len)
		return -1;
	for (i = 0; i < data->num_stems; i++) {
		if (stem_len == data->stem_arr[i].len
		    && !strncmp(*buf, data->stem_arr[i].buf, stem_len)) {
			*buf += stem_len;
			return i;
		}
	}
	return -1;
}

/*
 * Warn about duplicate specifications.
 */
static int nodups_specs(struct saved_data *data, const char *path)
{
	int rc = 0;
	unsigned int ii, jj;
	struct spec *curr_spec, *spec_arr = data->spec_arr;

	for (ii = 0; ii < data->nspec; ii++) {
		curr_spec = &spec_arr[ii];
		for (jj = ii + 1; jj < data->nspec; jj++) {
			if ((!strcmp(spec_arr[jj].regex_str, curr_spec->regex_str))
			    && (!spec_arr[jj].mode || !curr_spec->mode
				|| spec_arr[jj].mode == curr_spec->mode)) {
				rc = -1;
				errno = EINVAL;
				if (strcmp(spec_arr[jj].lr.ctx_raw, curr_spec->lr.ctx_raw)) {
					COMPAT_LOG
						(SELINUX_ERROR,
						 "%s: Multiple different specifications for %s  (%s and %s).\n",
						 path, curr_spec->regex_str,
						 spec_arr[jj].lr.ctx_raw,
						 curr_spec->lr.ctx_raw);
				} else {
					COMPAT_LOG
						(SELINUX_ERROR,
						 "%s: Multiple same specifications for %s.\n",
						 path, curr_spec->regex_str);
				}
			}
		}
	}
	return rc;
}

static int compile_regex(struct saved_data *data, struct spec *spec, const char **errbuf)
{
	const char *tmperrbuf;
	char *reg_buf, *anchored_regex, *cp;
	struct stem *stem_arr = data->stem_arr;
	size_t len;
	int erroff;

	if (spec->regcomp)
		return 0; /* already done */

	/* Skip the fixed stem. */
	reg_buf = spec->regex_str;
	if (spec->stem_id >= 0)
		reg_buf += stem_arr[spec->stem_id].len;

	/* Anchor the regular expression. */
	len = strlen(reg_buf);
	cp = anchored_regex = malloc(len + 3);
	if (!anchored_regex)
		return -1;

	/* Create ^...$ regexp.  */
	*cp++ = '^';
	cp = mempcpy(cp, reg_buf, len);
	*cp++ = '$';
	*cp = '\0';

	/* Compile the regular expression. */
	spec->regex = pcre_compile(anchored_regex, 0, &tmperrbuf, &erroff, NULL);
	free(anchored_regex);
	if (!spec->regex) {
		if (errbuf)
			*errbuf=tmperrbuf;
		return -1;
	}

	spec->sd = pcre_study(spec->regex, 0, &tmperrbuf);
	if (!spec->sd) {
		if (errbuf)
			*errbuf=tmperrbuf;
		return -1;
	}

	/* Done. */
	spec->regcomp = 1;

	return 0;
}

static int process_line(struct selabel_handle *rec,
			const char *path, const char *prefix,
			char *line_buf, unsigned lineno)
{
	int items, len, rc;
	char *buf_p, *regex, *type, *context;
	struct saved_data *data = (struct saved_data *)rec->data;
	struct spec *spec_arr;
	unsigned int nspec = data->nspec;
	const char *errbuf = NULL;

	len = strlen(line_buf);
	if (line_buf[len - 1] == '\n')
		line_buf[len - 1] = 0;
	buf_p = line_buf;
	while (isspace(*buf_p))
		buf_p++;
	/* Skip comment lines and empty lines. */
	if (*buf_p == '#' || *buf_p == 0)
		return 0;
	items = sscanf(line_buf, "%as %as %as", &regex, &type, &context);
	if (items < 2) {
		COMPAT_LOG(SELINUX_WARNING,
			    "%s:  line %d is missing fields, skipping\n", path,
			    lineno);
		if (items == 1)
			free(regex);
		return 0;
	} else if (items == 2) {
		/* The type field is optional. */
		free(context);
		context = type;
		type = 0;
	}

	len = get_stem_from_spec(regex);
	if (len && prefix && strncmp(prefix, regex, len)) {
		/* Stem of regex does not match requested prefix, discard. */
		free(regex);
		free(type);
		free(context);
		return 0;
	}

	rc = grow_specs(data);
	if (rc)
		return rc;

	spec_arr = data->spec_arr;

	/* process and store the specification in spec. */
	spec_arr[nspec].stem_id = find_stem_from_spec(data, regex);
	spec_arr[nspec].regex_str = regex;
	if (rec->validating && compile_regex(data, &spec_arr[nspec], &errbuf)) {
		COMPAT_LOG(SELINUX_WARNING, "%s:  line %d has invalid regex %s:  %s\n",
			   path, lineno, regex, (errbuf ? errbuf : "out of memory"));
	}

	/* Convert the type string to a mode format */
	spec_arr[nspec].type_str = type;
	spec_arr[nspec].mode = 0;
	if (type) {
		mode_t mode = string_to_mode(type);
		if (mode == -1) {
			COMPAT_LOG(SELINUX_WARNING, "%s:  line %d has invalid file type %s\n",
				   path, lineno, type);
			mode = 0;
		}
		spec_arr[nspec].mode = mode;
	}

	spec_arr[nspec].lr.ctx_raw = context;

	/* Determine if specification has
	 * any meta characters in the RE */
	spec_hasMetaChars(&spec_arr[nspec]);

	if (strcmp(context, "<<none>>") && rec->validating)
		compat_validate(rec, &spec_arr[nspec].lr, path, lineno);

	data->nspec = ++nspec;

	return 0;
}

static int load_mmap(struct selabel_handle *rec, const char *path, struct stat *sb)
{
	struct saved_data *data = (struct saved_data *)rec->data;
	char mmap_path[PATH_MAX + 1];
	int mmapfd;
	int rc, i;
	struct stat mmap_stat;
	char *addr;
	size_t len;
	int stem_map_len, *stem_map;
	struct mmap_area *mmap_area;

	uint32_t *magic;
	uint32_t *section_len;
	uint32_t *plen;

	rc = snprintf(mmap_path, sizeof(mmap_path), "%s.bin", path);
	if (rc >= sizeof(mmap_path))
		return -1;

	mmapfd = open(mmap_path, O_RDONLY | O_CLOEXEC);
	if (mmapfd < 0)
		return -1;

	rc = fstat(mmapfd, &mmap_stat);
	if (rc < 0) {
		close(mmapfd);
		return -1;
	}

	/* if mmap is old, ignore it */
	if (mmap_stat.st_mtime < sb->st_mtime) {
		close(mmapfd);
		return -1;
	}

	if (mmap_stat.st_mtime == sb->st_mtime &&
	    mmap_stat.st_mtim.tv_nsec < sb->st_mtim.tv_nsec) {
		close(mmapfd);
		return -1;
	}

	/* ok, read it in... */
	len = mmap_stat.st_size;
	len += (sysconf(_SC_PAGE_SIZE) - 1);
	len &= ~(sysconf(_SC_PAGE_SIZE) - 1);

	mmap_area = malloc(sizeof(*mmap_area));
	if (!mmap_area) {
		close(mmapfd);
		return -1;
	}

	addr = mmap(NULL, len, PROT_READ, MAP_PRIVATE, mmapfd, 0);
	close(mmapfd);
	if (addr == MAP_FAILED) {
		free(mmap_area);
		perror("mmap");
		return -1;
	}

	/* save where we mmap'd the file to cleanup on close() */
	mmap_area->addr = addr;
	mmap_area->len = len;
	mmap_area->next = data->mmap_areas;
	data->mmap_areas = mmap_area;

	/* check if this looks like an fcontext file */
	magic = (uint32_t *)addr;
	if (*magic != SELINUX_MAGIC_COMPILED_FCONTEXT)
		return -1;
	addr += sizeof(uint32_t);

	/* check if this version is higher than we understand */
	section_len = (uint32_t *)addr;
	if (*section_len > SELINUX_COMPILED_FCONTEXT_MAX_VERS)
		return -1;
	addr += sizeof(uint32_t);

	/* allocate the stems_data array */
	section_len = (uint32_t *)addr;
	addr += sizeof(uint32_t);

	/*
	 * map indexed by the stem # in the mmap file and contains the stem
	 * number in the data stem_arr
	 */
	stem_map_len = *section_len;
	stem_map = calloc(stem_map_len, sizeof(*stem_map));
	if (!stem_map)
		return -1;

	for (i = 0; i < *section_len; i++) {
		char *buf;
		uint32_t stem_len;
		int newid;

		/* the length does not inlude the nul */
		plen = (uint32_t *)addr;
		addr += sizeof(uint32_t);

		stem_len = *plen;
		buf = (char *)addr;
		addr += (stem_len + 1); // +1 is the nul

		/* store the mapping between old and new */
		newid = find_stem(data, buf, stem_len);
		if (newid < 0) {
			newid = store_stem(data, buf, stem_len);
			if (newid < 0) {
				rc = newid;
				goto err;
			}
			data->stem_arr[newid].from_mmap = 1;
		}
		stem_map[i] = newid;
	}

	/* allocate the regex array */
	section_len = (uint32_t *)addr;
	addr += sizeof(*section_len);

	for (i = 0; i < *section_len; i++) {
		struct spec *spec;
		int32_t stem_id;

		rc = grow_specs(data);
		if (rc < 0)
			goto err;

		spec = &data->spec_arr[data->nspec];
		spec->from_mmap = 1;
		spec->regcomp = 1;

		plen = (uint32_t *)addr;
		addr += sizeof(uint32_t);
		rc = -1;
		spec->lr.ctx_raw = strdup((char *)addr);
		if (!spec->lr.ctx_raw)
			goto err;

		addr += *plen;

		plen = (uint32_t *)addr;
		addr += sizeof(uint32_t);
		spec->regex_str = (char *)addr;
		addr += *plen;

		spec->mode = *(mode_t *)addr;
		addr += sizeof(mode_t);

		/* map the stem id from the mmap file to the data->stem_arr */
		stem_id = *(int32_t *)addr;
		if (stem_id == -1 || stem_id >= stem_map_len)
			spec->stem_id = -1;
		else
			spec->stem_id = stem_map[stem_id];
		addr += sizeof(int32_t);

		/* retrieve the hasMetaChars bit */
		spec->hasMetaChars = *(uint32_t *)addr;
		addr += sizeof(uint32_t);

		plen = (uint32_t *)addr;
		addr += sizeof(uint32_t);
		spec->regex = (pcre *)addr;
		addr += *plen;

		plen = (uint32_t *)addr;
		addr += sizeof(uint32_t);
		spec->lsd.study_data = (void *)addr;
		spec->lsd.flags |= PCRE_EXTRA_STUDY_DATA;
		addr += *plen;

		data->nspec++;
	}
	/* win */
	rc = 0;
err:
	free(stem_map);

	return rc;
}

static int process_file(const char *path, const char *suffix, struct selabel_handle *rec, const char *prefix)
{
	FILE *fp;
	struct stat sb;
	unsigned int lineno;
	size_t line_len;
	char *line_buf = NULL;
	int rc;
	char stack_path[PATH_MAX + 1];

	/* append the path suffix if we have one */
	if (suffix) {
		rc = snprintf(stack_path, sizeof(stack_path), "%s.%s", path, suffix);
		if (rc >= sizeof(stack_path)) {
			errno = ENAMETOOLONG;
			return -1;
		}
		path = stack_path;
	}

	/* Open the specification file. */
	if ((fp = fopen(path, "r")) == NULL)
		return -1;
	__fsetlocking(fp, FSETLOCKING_BYCALLER);

	if (fstat(fileno(fp), &sb) < 0)
		return -1;
	if (!S_ISREG(sb.st_mode)) {
		errno = EINVAL;
		return -1;
	}

	rc = load_mmap(rec, path, &sb);
	if (rc == 0)
		goto out;

	/*
	 * The do detailed validation of the input and fill the spec array
	 */
	lineno = 0;
	while (getline(&line_buf, &line_len, fp) > 0) {
		rc = process_line(rec, path, prefix, line_buf, ++lineno);
		if (rc)
			return rc;
	}
out:
	free(line_buf);
	fclose(fp);

	return 0;
}

static int init(struct selabel_handle *rec, struct selinux_opt *opts,
		unsigned n)
{
	struct saved_data *data = (struct saved_data *)rec->data;
	const char *path = NULL;
	const char *prefix = NULL;
	char subs_file[PATH_MAX + 1];
	int status = -1, baseonly = 0;

	/* Process arguments */
	while (n--)
		switch(opts[n].type) {
		case SELABEL_OPT_PATH:
			path = opts[n].value;
			break;
		case SELABEL_OPT_SUBSET:
			prefix = opts[n].value;
			break;
		case SELABEL_OPT_BASEONLY:
			baseonly = !!opts[n].value;
			break;
		}

	/* Process local and distribution substitution files */
	if (!path) {
		rec->dist_subs = selabel_subs_init(selinux_file_context_subs_dist_path(), rec->dist_subs);
		rec->subs = selabel_subs_init(selinux_file_context_subs_path(), rec->subs);
		path = selinux_file_context_path();
	} else {
		snprintf(subs_file, sizeof(subs_file), "%s.subs_dist", path);
		rec->dist_subs = selabel_subs_init(subs_file, rec->dist_subs);
		snprintf(subs_file, sizeof(subs_file), "%s.subs", path);
		rec->subs = selabel_subs_init(subs_file, rec->subs);
	}

	rec->spec_file = strdup(path);

	/* 
	 * The do detailed validation of the input and fill the spec array
	 */
	status = process_file(path, NULL, rec, prefix);
	if (status)
		goto finish;

	if (rec->validating) {
		status = nodups_specs(data, path);
		if (status)
			goto finish;
	}

	if (!baseonly) {
		status = process_file(path, "homedirs", rec, prefix);
		if (status && errno != ENOENT)
			goto finish;

		status = process_file(path, "local", rec, prefix);
		if (status && errno != ENOENT)
			goto finish;
	}

	status = sort_specs(data);

	status = 0;
finish:
	if (status)
		free(data->spec_arr);
	return status;
}

/*
 * Backend interface routines
 */
static void closef(struct selabel_handle *rec)
{
	struct saved_data *data = (struct saved_data *)rec->data;
	struct mmap_area *area, *last_area;
	struct spec *spec;
	struct stem *stem;
	unsigned int i;

	for (i = 0; i < data->nspec; i++) {
		spec = &data->spec_arr[i];
		free(spec->lr.ctx_trans);
		free(spec->lr.ctx_raw);
		if (spec->from_mmap)
			continue;
		free(spec->regex_str);
		free(spec->type_str);
		if (spec->regcomp) {
			pcre_free(spec->regex);
			pcre_free_study(spec->sd);
		}
	}

	for (i = 0; i < (unsigned int)data->num_stems; i++) {
		stem = &data->stem_arr[i];
		if (stem->from_mmap)
			continue;
		free(stem->buf);
	}

	if (data->spec_arr)
		free(data->spec_arr);
	if (data->stem_arr)
		free(data->stem_arr);

	area = data->mmap_areas;
	while (area) {
		munmap(area->addr, area->len);
		last_area = area;
		area = area->next;
		free(last_area);
	}
	free(data);
}

static struct selabel_lookup_rec *lookup(struct selabel_handle *rec,
					 const char *key, int type)
{
	struct saved_data *data = (struct saved_data *)rec->data;
	struct spec *spec_arr = data->spec_arr;
	int i, rc, file_stem;
	mode_t mode = (mode_t)type;
	const char *buf;
	struct selabel_lookup_rec *ret = NULL;
	char *clean_key = NULL;
	const char *prev_slash, *next_slash;
	unsigned int sofar = 0;

	if (!data->nspec) {
		errno = ENOENT;
		goto finish;
	}

	/* Remove duplicate slashes */
	if ((next_slash = strstr(key, "//"))) {
		clean_key = malloc(strlen(key) + 1);
		if (!clean_key)
			goto finish;
		prev_slash = key;
		while (next_slash) {
			memcpy(clean_key + sofar, prev_slash, next_slash - prev_slash);
			sofar += next_slash - prev_slash;
			prev_slash = next_slash + 1;
			next_slash = strstr(prev_slash, "//");
		}
		strcpy(clean_key + sofar, prev_slash);
		key = clean_key;
	}

	buf = key;
	file_stem = find_stem_from_file(data, &buf);
	mode &= S_IFMT;

	/* 
	 * Check for matching specifications in reverse order, so that
	 * the last matching specification is used.
	 */
	for (i = data->nspec - 1; i >= 0; i--) {
		struct spec *spec = &spec_arr[i];
		/* if the spec in question matches no stem or has the same
		 * stem as the file AND if the spec in question has no mode
		 * specified or if the mode matches the file mode then we do
		 * a regex check        */
		if ((spec->stem_id == -1 || spec->stem_id == file_stem) &&
		    (!mode || !spec->mode || mode == spec->mode)) {
			if (compile_regex(data, spec, NULL) < 0)
				goto finish;
			if (spec->stem_id == -1)
				rc = pcre_exec(spec->regex, get_pcre_extra(spec), key, strlen(key), 0, 0, NULL, 0);
			else
				rc = pcre_exec(spec->regex, get_pcre_extra(spec), buf, strlen(buf), 0, 0, NULL, 0);

			if (rc == 0) {
				spec->matches++;
				break;
			} else if (rc == PCRE_ERROR_NOMATCH)
				continue;

			errno = ENOENT;
			/* else it's an error */
			goto finish;
		}
	}

	if (i < 0 || strcmp(spec_arr[i].lr.ctx_raw, "<<none>>") == 0) {
		/* No matching specification. */
		errno = ENOENT;
		goto finish;
	}

	errno = 0;
	ret = &spec_arr[i].lr;

finish:
	free(clean_key);
	return ret;
}

static void stats(struct selabel_handle *rec)
{
	struct saved_data *data = (struct saved_data *)rec->data;
	unsigned int i, nspec = data->nspec;
	struct spec *spec_arr = data->spec_arr;

	for (i = 0; i < nspec; i++) {
		if (spec_arr[i].matches == 0) {
			if (spec_arr[i].type_str) {
				COMPAT_LOG(SELINUX_WARNING,
				    "Warning!  No matches for (%s, %s, %s)\n",
				    spec_arr[i].regex_str,
				    spec_arr[i].type_str,
				    spec_arr[i].lr.ctx_raw);
			} else {
				COMPAT_LOG(SELINUX_WARNING,
				    "Warning!  No matches for (%s, %s)\n",
				    spec_arr[i].regex_str,
				    spec_arr[i].lr.ctx_raw);
			}
		}
	}
}

int selabel_file_init(struct selabel_handle *rec, struct selinux_opt *opts,
		      unsigned nopts)
{
	struct saved_data *data;

	data = (struct saved_data *)malloc(sizeof(*data));
	if (!data)
		return -1;
	memset(data, 0, sizeof(*data));

	rec->data = data;
	rec->func_close = &closef;
	rec->func_stats = &stats;
	rec->func_lookup = &lookup;

	return init(rec, opts, nopts);
}