libselinux: Add read_spec_entries function to replace sscanf

Currently sscanf is used with %ms parameters that are not supported
on all platforms. The new read_spec_entries function may be used
to replace these where required. This patch updates
sefcontext_compile, label_file and label_android_property services
to use the new function.

The file and property services have been tested on Android emulator
and the file service on Fedora 21.

Signed-off-by: Richard Haines <richard_c_haines@btinternet.com>

1 files changed, 88 insertions, 0 deletions

diff --git a/libselinux/src/label_support.c b/libselinux/src/label_support.c
new file mode 100644
index 00000000..7464f430
--- /dev/null
+++ b/libselinux/src/label_support.c
@@ -0,0 +1,88 @@
+/*
+ * This file contains helper functions for labeling support.
+ *
+ * Author : Richard Haines <richard_c_haines@btinternet.com>
+ */
+
+#include <stdlib.h>
+#include <stdarg.h>
+#include <ctype.h>
+#include <string.h>
+#include "label_internal.h"
+
+/*
+ * The read_spec_entries and read_spec_entry functions may be used to
+ * replace sscanf to read entries from spec files. The file and
+ * property services now use these.
+ */
+
+/* Read an entry from a spec file (e.g. file_contexts) */
+static inline int read_spec_entry(char **entry, char **ptr)
+{
+	int entry_len = 0;
+	*entry = NULL;
+	char *tmp_buf = NULL;
+
+	while (isspace(**ptr) && **ptr != '\0')
+		(*ptr)++;
+
+	tmp_buf = *ptr;
+
+	while (!isspace(**ptr) && **ptr != '\0') {
+		(*ptr)++;
+		entry_len++;
+	}
+
+	*entry = strndup(tmp_buf, entry_len);
+	if (!*entry)
+		return -1;
+
+	return 0;
+}
+
+/*
+ * line_buf - Buffer containing the spec entries .
+ * num_args - The number of spec parameter entries to process.
+ * ...      - A 'char **spec_entry' for each parameter.
+ * returns  - The number of items processed.
+ *
+ * This function calls read_spec_entry() to do the actual string processing.
+ */
+int read_spec_entries(char *line_buf, int num_args, ...)
+{
+	char **spec_entry, *buf_p;
+	int len, rc, items;
+	va_list ap;
+
+	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;
+
+	/* Process the spec file entries */
+	va_start(ap, num_args);
+
+	for (items = 0; items < num_args; items++) {
+		spec_entry = va_arg(ap, char **);
+
+		if (len - 1 == buf_p - line_buf) {
+			va_end(ap);
+			return items;
+		}
+
+		rc = read_spec_entry(spec_entry, &buf_p);
+		if (rc < 0) {
+			va_end(ap);
+			return rc;
+		}
+	}
+	va_end(ap);
+	return items;
+}