[PATCH 3/3] libselinux: labeling support (try 3)

[Eamon Walsh <ewalsh@tycho.nsa.gov>]

This patch includes the file contexts backend code.

Signed-off-by: Eamon Walsh <ewalsh@tycho.nsa.gov>
---

 label_file.c |  637 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 637 insertions(+)


Index: libselinux/src/label_file.c
===================================================================
--- libselinux/src/label_file.c	(revision 0)
+++ libselinux/src/label_file.c	(revision 0)
@@ -0,0 +1,637 @@
+/*
+ * 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 <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 <regex.h>
+#include "callbacks.h"
+#include "label_internal.h"
+
+/*
+ * Internals, mostly moved over from matchpathcon.c
+ */
+
+/* A file security context specification. */
+typedef struct spec {
+	struct selabel_lookup_rec lr;	/* holds contexts for lookup result */
+	char *regex_str;	/* regular expession string for diagnostics */
+	char *type_str;		/* type string for diagnostic messages */
+	regex_t regex;		/* compiled regular expression */
+	mode_t mode;		/* mode format value */
+	int matches;		/* number of matching pathnames */
+	int hasMetaChars;	/* regular expression has meta-chars */
+	int stem_id;		/* indicates which stem-compression item */
+} spec_t;
+
+/* A regular expression stem */
+typedef struct stem {
+	char *buf;
+	int len;
+} stem_t;
+
+/* Our stored configuration */
+struct saved_data {
+	/*
+	 * The array of specifications, initially in the same order as in 
+	 * the specification file. Sorting occurs based on hasMetaChars.
+	 */
+	spec_t *spec_arr;
+	unsigned int nspec;
+
+	/*
+	 * The array of regular expression stems.
+	 */
+	stem_t *stem_arr;
+	int num_stems;
+	int alloc_stems;
+};
+
+/* Return the length of the text that can be considered the stem, returns 0
+ * if there is no identifiable stem */
+static int get_stem_from_spec(const char *const buf)
+{
+	const char *tmp = strchr(buf + 1, '/');
+	const char *ind;
+
+	if (!tmp)
+		return 0;
+
+	for (ind = buf; ind < tmp; ind++) {
+		if (strchr(".^$?*+|[({", (int)*ind))
+			return 0;
+	}
+	return tmp - buf;
+}
+
+/* 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 spec, returns the index into stem_arr for a new
+ * or existing stem, (or -1 if there is no possible stem - 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_spec(struct saved_data *data, const char **buf)
+{
+	int i, num = data->num_stems;
+	int stem_len = get_stem_from_spec(*buf);
+
+	if (!stem_len)
+		return -1;
+	for (i = 0; i < num; i++) {
+		if (stem_len == data->stem_arr[i].len
+		    && !strncmp(*buf, data->stem_arr[i].buf, stem_len)) {
+			*buf += stem_len;
+			return i;
+		}
+	}
+	if (data->alloc_stems == num) {
+		stem_t *tmp_arr;
+		data->alloc_stems = data->alloc_stems * 2 + 16;
+		tmp_arr = realloc(data->stem_arr,
+				  sizeof(stem_t) * data->alloc_stems);
+		if (!tmp_arr)
+			return -1;
+		data->stem_arr = tmp_arr;
+	}
+	data->stem_arr[num].len = stem_len;
+	data->stem_arr[num].buf = malloc(stem_len + 1);
+	if (!data->stem_arr[num].buf)
+		return -1;
+	memcpy(data->stem_arr[num].buf, *buf, stem_len);
+	data->stem_arr[num].buf[stem_len] = '\0';
+	data->num_stems++;
+	*buf += stem_len;
+	return num;
+}
+
+/* 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 void nodups_specs(struct saved_data *data, const char *path)
+{
+	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)) {
+				if (strcmp
+				    (spec_arr[jj].lr.ctx_raw,
+				     curr_spec->lr.ctx_raw)) {
+					selinux_log
+						(SELINUX_WARNING,
+						 "%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 {
+					selinux_log
+						(SELINUX_WARNING,
+						 "%s: Multiple same specifications for %s.\n",
+						 path, curr_spec->regex_str);
+				}
+			}
+		}
+	}
+}
+
+/* Determine if the regular expression specification has any meta characters. */
+static void spec_hasMetaChars(struct spec *spec)
+{
+	char *c;
+	int len;
+	char *end;
+
+	c = spec->regex_str;
+	len = strlen(spec->regex_str);
+	end = c + len;
+
+	spec->hasMetaChars = 0;
+
+	/* Look at each character in the RE specification string for a 
+	 * meta character. Return when any meta character reached. */
+	while (c != end) {
+		switch (*c) {
+		case '.':
+		case '^':
+		case '$':
+		case '?':
+		case '*':
+		case '+':
+		case '|':
+		case '[':
+		case '(':
+		case '{':
+			spec->hasMetaChars = 1;
+			return;
+		case '\\':	/* skip the next character */
+			c++;
+			break;
+		default:
+			break;
+
+		}
+		c++;
+	}
+	return;
+}
+
+static int process_line(struct saved_data *data,
+			const char *path, const char *prefix,
+			char *line_buf, int pass, unsigned lineno)
+{
+	int items, len, regerr;
+	char *buf_p, *regex, *anchored_regex, *type, *context;
+	const char *reg_buf;
+	spec_t *spec_arr = data->spec_arr;
+	unsigned int nspec = data->nspec;
+
+	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) {
+		selinux_log(SELINUX_WARNING,
+			  "%s:  line %d is missing fields, skipping\n", path,
+			  lineno);
+		return 0;
+	} else if (items == 2) {
+		/* The type field is optional. */
+		free(context);
+		context = type;
+		type = 0;
+	}
+
+	reg_buf = regex;
+	len = get_stem_from_spec(reg_buf);
+	if (len && prefix && strncmp(prefix, regex, len)) {
+		/* Stem of regex does not match requested prefix, discard. */
+		free(regex);
+		free(type);
+		free(context);
+		return 0;
+	}
+
+	if (pass == 1) {
+		/* On the second pass, compile and store the specification in spec. */
+		char *cp;
+		spec_arr[nspec].stem_id = find_stem_from_spec(data, &reg_buf);
+		spec_arr[nspec].regex_str = regex;
+
+		/* 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. */
+		regerr =
+			regcomp(&spec_arr[nspec].regex,
+				anchored_regex, REG_EXTENDED | REG_NOSUB);
+		if (regerr != 0) {
+			size_t errsz = 0;
+			char *errbuf = NULL;
+			errsz = regerror(regerr, &spec_arr[nspec].regex,
+					 errbuf, errsz);
+			if (errsz)
+				errbuf = malloc(errsz);
+			if (errbuf)
+				(void)regerror(regerr,
+					       &spec_arr[nspec].regex,
+					       errbuf, errsz);
+			selinux_log(SELINUX_WARNING,
+				  "%s:  line %d has invalid regex %s:  %s\n",
+				  path, lineno, anchored_regex,
+				  (errbuf ? errbuf : "out of memory"));
+			free(anchored_regex);
+			return 0;
+		}
+		free(anchored_regex);
+
+		/* Convert the type string to a mode format */
+		spec_arr[nspec].type_str = type;
+		spec_arr[nspec].mode = 0;
+		if (!type)
+			goto skip_type;
+		len = strlen(type);
+		if (type[0] != '-' || len != 2) {
+			selinux_log(SELINUX_WARNING,
+				  "%s:  line %d has invalid file type %s\n",
+				  path, lineno, type);
+			return 0;
+		}
+		switch (type[1]) {
+		case 'b':
+			spec_arr[nspec].mode = S_IFBLK;
+			break;
+		case 'c':
+			spec_arr[nspec].mode = S_IFCHR;
+			break;
+		case 'd':
+			spec_arr[nspec].mode = S_IFDIR;
+			break;
+		case 'p':
+			spec_arr[nspec].mode = S_IFIFO;
+			break;
+		case 'l':
+			spec_arr[nspec].mode = S_IFLNK;
+			break;
+		case 's':
+			spec_arr[nspec].mode = S_IFSOCK;
+			break;
+		case '-':
+			spec_arr[nspec].mode = S_IFREG;
+			break;
+		default:
+			selinux_log(SELINUX_WARNING,
+				  "%s:  line %d has invalid file type %s\n",
+				  path, lineno, type);
+			return 0;
+		}
+
+	skip_type:
+		spec_arr[nspec].lr.ctx_raw = context;
+
+		/* Determine if specification has 
+		 * any meta characters in the RE */
+		spec_hasMetaChars(&spec_arr[nspec]);
+	}
+
+	data->nspec = ++nspec;
+	if (pass == 0) {
+		free(regex);
+		if (type)
+			free(type);
+		free(context);
+	}
+	return 0;
+}
+
+static int init(struct selabel_rec *rec, struct selabel_opt *opts, size_t n)
+{
+	struct saved_data *data = (struct saved_data *)rec->data;
+	const char *path = NULL;
+	const char *prefix = NULL;
+	FILE *fp;
+	FILE *localfp = NULL;
+	FILE *homedirfp = NULL;
+	char local_path[PATH_MAX + 1];
+	char homedir_path[PATH_MAX + 1];
+	char *line_buf = NULL;
+	size_t line_len = 0;
+	unsigned int lineno, pass, i, j, maxnspec;
+	spec_t *spec_copy = NULL;
+	int status = -1, baseonly = 0;
+	struct stat sb;
+
+	/* Process arguments */
+	while (n--)
+		switch(opts[n].type) {
+		case SELABEL_OPT_PATH:
+			path = opts[n].value;
+			break;
+		case SELABEL_OPT_PREFIX:
+			prefix = opts[n].value;
+			break;
+		case SELABEL_OPT_BASEONLY:
+			baseonly = !!opts[n].value;
+			break;
+		}
+
+	/* Open the specification file. */
+	if (!path)
+		path = selinux_file_context_path();
+	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;
+	}
+
+	if (!baseonly) {
+		snprintf(homedir_path, sizeof(homedir_path), "%s.homedirs",
+			 path);
+		homedirfp = fopen(homedir_path, "r");
+		if (homedirfp != NULL)
+			__fsetlocking(homedirfp, FSETLOCKING_BYCALLER);
+
+		snprintf(local_path, sizeof(local_path), "%s.local", path);
+		localfp = fopen(local_path, "r");
+		if (localfp != NULL)
+			__fsetlocking(localfp, FSETLOCKING_BYCALLER);
+	}
+
+	/* 
+	 * Perform two passes over the specification file.
+	 * The first pass counts the number of specifications and
+	 * performs simple validation of the input.  At the end
+	 * of the first pass, the spec array is allocated.
+	 * The second pass performs detailed validation of the input
+	 * and fills in the spec array.
+	 */
+	maxnspec = UINT_MAX / sizeof(spec_t);
+	for (pass = 0; pass < 2; pass++) {
+		lineno = 0;
+		data->nspec = 0;
+		while (getline(&line_buf, &line_len, fp) > 0
+		       && data->nspec < maxnspec) {
+			if (process_line(data, path, prefix, line_buf,
+					 pass, ++lineno) != 0)
+				goto finish;
+		}
+		lineno = 0;
+		if (homedirfp)
+			while (getline(&line_buf, &line_len, homedirfp) > 0
+			       && data->nspec < maxnspec) {
+				if (process_line
+				    (data, homedir_path, prefix,
+				     line_buf, pass, ++lineno) != 0)
+					goto finish;
+			}
+
+		lineno = 0;
+		if (localfp)
+			while (getline(&line_buf, &line_len, localfp) > 0
+			       && data->nspec < maxnspec) {
+				if (process_line
+				    (data, local_path, prefix, line_buf,
+				     pass, ++lineno) != 0)
+					goto finish;
+			}
+
+		if (pass == 0) {
+			if (data->nspec == 0) {
+				status = 0;
+				goto finish;
+			}
+			if (NULL == (data->spec_arr =
+				     malloc(sizeof(spec_t) * data->nspec)))
+				goto finish;
+			memset(data->spec_arr, 0, sizeof(spec_t)*data->nspec);
+			maxnspec = data->nspec;
+			rewind(fp);
+			if (homedirfp)
+				rewind(homedirfp);
+			if (localfp)
+				rewind(localfp);
+		}
+	}
+	free(line_buf);
+
+	/* Move exact pathname specifications to the end. */
+	spec_copy = malloc(sizeof(spec_t) * data->nspec);
+	if (!spec_copy)
+		goto finish;
+	j = 0;
+	for (i = 0; i < data->nspec; i++)
+		if (data->spec_arr[i].hasMetaChars)
+			memcpy(&spec_copy[j++],
+			       &data->spec_arr[i], sizeof(spec_t));
+	for (i = 0; i < data->nspec; i++)
+		if (!data->spec_arr[i].hasMetaChars)
+			memcpy(&spec_copy[j++],
+			       &data->spec_arr[i], sizeof(spec_t));
+	free(data->spec_arr);
+	data->spec_arr = spec_copy;
+
+	nodups_specs(data, path);
+
+	status = 0;
+finish:
+	fclose(fp);
+	if (data->spec_arr != spec_copy)
+		free(data->spec_arr);
+	if (homedirfp)
+		fclose(homedirfp);
+	if (localfp)
+		fclose(localfp);
+	return status;
+}
+
+/*
+ * Backend interface routines
+ */
+static void close(struct selabel_rec *rec)
+{
+	struct saved_data *data = (struct saved_data *)rec->data;
+	struct spec *spec;
+	struct stem *stem;
+	unsigned int i;
+
+	for (i = 0; i < data->nspec; i++) {
+		spec = &data->spec_arr[i];
+		free(spec->regex_str);
+		free(spec->type_str);
+		free(spec->lr.ctx_raw);
+		free(spec->lr.ctx_trans);
+		regfree(&spec->regex);
+	}
+
+	for (i = 0; i < (unsigned int)data->num_stems; i++) {
+		stem = &data->stem_arr[i];
+		free(stem->buf);
+	}
+
+	if (data->spec_arr)
+		free(data->spec_arr);
+	if (data->stem_arr)
+		free(data->stem_arr);
+	
+	memset(data, 0, sizeof(*data));
+}
+
+static struct selabel_lookup_rec *lookup(struct selabel_rec *rec,
+					 const char *key, int type)
+{
+	struct saved_data *data = (struct saved_data *)rec->data;
+	spec_t *spec_arr = data->spec_arr;
+	int i, rc, file_stem;
+	mode_t mode = (mode_t)type;
+	const char *buf = key;
+
+	if (!data->nspec) {
+		errno = ENOENT;
+		return NULL;
+	}
+
+	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--) {
+		/* 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_arr[i].stem_id == -1
+		     || spec_arr[i].stem_id == file_stem)
+		    && (!mode || !spec_arr[i].mode
+			|| mode == spec_arr[i].mode)) {
+			if (spec_arr[i].stem_id == -1)
+				rc = regexec(&spec_arr[i].regex, key, 0, 0, 0);
+			else
+				rc = regexec(&spec_arr[i].regex, buf, 0, 0, 0);
+
+			if (rc == 0) {
+				spec_arr[i].matches++;
+				break;
+			}
+			if (rc == REG_NOMATCH)
+				continue;
+			/* else it's an error */
+			return NULL;
+		}
+	}
+
+	if (i < 0 || strcmp(spec_arr[i].lr.ctx_raw, "<<none>>") == 0) {
+		/* No matching specification. */
+		errno = ENOENT;
+		return NULL;
+	}
+
+	return &spec_arr[i].lr;
+}
+
+static void stats(struct selabel_rec *rec)
+{
+	struct saved_data *data = (struct saved_data *)rec->data;
+	unsigned int i, nspec = data->nspec;
+	spec_t *spec_arr = data->spec_arr;
+
+	for (i = 0; i < nspec; i++) {
+		if (spec_arr[i].matches == 0) {
+			if (spec_arr[i].type_str) {
+				selinux_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 {
+				selinux_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_rec *rec, struct selabel_opt *opts,
+		      size_t 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 = &close;
+	rec->func_stats = &stats;
+	rec->func_lookup = &lookup;
+
+	return init(rec, opts, nopts);
+}


-- 
Eamon Walsh <ewalsh@tycho.nsa.gov>
National Security Agency


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