wpa_supplicant: add patch to fix ext_passwords_file bug

This fixes inconsistent behaviour in ext_passwords_file that makes
impossible to input passphrases containing certain characters.

Closes #342140

pkgs/os-specific/linux/wpa_supplicant/default.nix

@@ -22,6 +22,7 @@ stdenv.mkDerivation rec {
       hash = "sha256-X6mBbj7BkW66aYeSCiI3JKBJv10etLQxaTRfRgwsFmM=";
       revert = true;
     })
+    ./unsurprising-ext-password.patch
   ];
 
   # TODO: Patch epoll so that the dbus actually responds

pkgs/os-specific/linux/wpa_supplicant/unsurprising-ext-password.patch

@@ -0,0 +1,66 @@
+From e5ac0dd1af48e085bb824082ef3b64afba673ded Mon Sep 17 00:00:00 2001
+From: rnhmjoj <rnhmjoj@inventati.org>
+Date: Wed, 18 Sep 2024 13:43:44 +0200
+Subject: [PATCH] ext_password_file: do not use wpa_config_get_line
+To: hostap@lists.infradead.org
+
+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@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
+