wpa_supplicant: Move wpa_config_get_line() into utils

The function wpa_config_get_line() is used by the wpa_supplicant config
file parser to retrieve the next non-comment non-blank line. We'll need
the same kind of functionality to implement the file-based external
password backend, so as a preparatory step this commit extracts the
function into its own standalone file in the utils package.

No functional changes are expected from this commit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>

src/utils/Makefile

@@ -6,6 +6,7 @@ LIB_OBJS= \
 	base64.o \
 	bitfield.o \
 	common.o \
+	config.o \
 	crc32.o \
 	ip_addr.o \
 	json.o \

src/utils/config.c

@@ -0,0 +1,97 @@
+/*
+ * Configuration parsing
+ * Copyright (c) 2003-2019, Jouni Malinen <j@w1.fi>
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+#include "includes.h"
+
+#include "utils/config.h"
+#include "common.h"
+
+
+static int newline_terminated(const char *buf, size_t buflen)
+{
+	size_t len = os_strlen(buf);
+	if (len == 0)
+		return 0;
+	if (len == buflen - 1 && buf[buflen - 1] != '\r' &&
+	    buf[len - 1] != '\n')
+		return 0;
+	return 1;
+}
+
+
+static void skip_line_end(FILE *stream)
+{
+	char buf[100];
+	while (fgets(buf, sizeof(buf), stream)) {
+		buf[sizeof(buf) - 1] = '\0';
+		if (newline_terminated(buf, sizeof(buf)))
+			return;
+	}
+}
+
+
+char * wpa_config_get_line(char *s, int size, FILE *stream, int *line,
+			   char **_pos)
+{
+	char *pos, *end, *sstart;
+
+	while (fgets(s, size, stream)) {
+		(*line)++;
+		s[size - 1] = '\0';
+		if (!newline_terminated(s, size)) {
+			/*
+			 * The line was truncated - skip rest of it to avoid
+			 * confusing error messages.
+			 */
+			wpa_printf(MSG_INFO, "Long line in configuration file "
+				   "truncated");
+			skip_line_end(stream);
+		}
+		pos = s;
+
+		/* Skip white space from the beginning of line. */
+		while (*pos == ' ' || *pos == '\t' || *pos == '\r')
+			pos++;
+
+		/* Skip comment lines and empty lines */
+		if (*pos == '#' || *pos == '\n' || *pos == '\0')
+			continue;
+
+		/*
+		 * Remove # comments unless they are within a double quoted
+		 * string.
+		 */
+		sstart = os_strchr(pos, '"');
+		if (sstart)
+			sstart = os_strrchr(sstart + 1, '"');
+		if (!sstart)
+			sstart = pos;
+		end = os_strchr(sstart, '#');
+		if (end)
+			*end-- = '\0';
+		else
+			end = pos + os_strlen(pos) - 1;
+
+		/* Remove trailing white space. */
+		while (end > pos &&
+		       (*end == '\n' || *end == ' ' || *end == '\t' ||
+			*end == '\r'))
+			*end-- = '\0';
+
+		if (*pos == '\0')
+			continue;
+
+		if (_pos)
+			*_pos = pos;
+		return pos;
+	}
+
+	if (_pos)
+		*_pos = NULL;
+	return NULL;
+}

src/utils/config.h

@@ -0,0 +1,29 @@
+/*
+ * Configuration parsing
+ * Copyright (c) 2003-2019, Jouni Malinen <j@w1.fi>
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+#ifndef UTILS_CONFIG_H
+#define UTILS_CONFIG_H
+
+/**
+ * wpa_config_get_line - Read the next configuration file line
+ * @s: Buffer for the line
+ * @size: The buffer length
+ * @stream: File stream to read from
+ * @line: Pointer to a variable storing the file line number
+ * @_pos: Buffer for the pointer to the beginning of data on the text line or
+ * %NULL if not needed (returned value used instead)
+ * Returns: Pointer to the beginning of data on the text line or %NULL if no
+ * more text lines are available.
+ *
+ * This function reads the next non-empty line from the configuration file and
+ * removes comments. The returned string is guaranteed to be null-terminated.
+ */
+char * wpa_config_get_line(char *s, int size, FILE *stream, int *line,
+			   char **_pos);
+
+#endif /* UTILS_CONFIG_H */