[PATCH] ext_password_file: do not use wpa_config_get_line

[rnhmjoj]

The file-based backed of the ext_password framework uses
`wpa_config_get_line` to read the passwords line-by-line from a file.
This function is meant to parse a single line from the
wpa_supplicant.conf file, so it handles whitespace, quotes and other
characters specially.

Its behavior, however, it's not compatible with the rest of the
ext_password framework implementation. For example, if a passphrase
contains a `#` character it must be quoted to prevent parsing the
remaining characters as an inline comment, but the code handling the
external password in `wpa_supplicant_get_psk` does not handle quotes.
The result is that either it will hash the enclosing quotes, producing a
wrong PSK, or if the passphrase is long enough, fail the length check.
As a consequence, some passphrases are impossible to input correctly.

To solve this and other issues, this patch changes the behaviour of the
`ext_password_file_get` function (which was not documented in details,
at least w.r.t. special characters) to simply treat all characters
literally: including trailing whitespaces (except CR and LF), `#` for
inline comments, etc. Empty lines and full-line comments are still
supported.

Signed-off-by: Michele Guerini Rocco <rnhmjoj at inventati.org>
---
 src/utils/ext_password_file.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/utils/ext_password_file.c b/src/utils/ext_password_file.c
index 4bb0095f3..f631ff15c 100644
--- a/src/utils/ext_password_file.c
+++ b/src/utils/ext_password_file.c
@@ -9,7 +9,6 @@
 #include "includes.h"
 
 #include "utils/common.h"
-#include "utils/config.h"
 #include "ext_password_i.h"
 
 
@@ -97,7 +96,16 @@ static struct wpabuf * ext_password_file_get(void *ctx, const char *name)
 
 	wpa_printf(MSG_DEBUG, "EXT PW FILE: get(%s)", name);
 
-	while (wpa_config_get_line(buf, sizeof(buf), f, &line, &pos)) {
+	while ((pos = fgets(buf, sizeof(buf), f))) {
+		line++;
+
+		/* Strip newline characters */
+		pos[strcspn(pos, "\r\n")] = 0;
+
+		/* Skip comments and empty lines */
+		if (*pos == '#' || *pos == '\0')
+		  continue;
+
 		char *sep = os_strchr(pos, '=');
 
 		if (!sep) {
-- 
2.44.1

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