From d1d376a30f13b340d9e81e1a8964b44693e55c19 Mon Sep 17 00:00:00 2001
From: Alexey Sheplyakov <asheplyakov@altlinux.org>
Date: Tue, 24 Aug 2021 15:29:38 +0400
Subject: [PATCH] cifsmount: retry with older protocol versions on failure

* An old server might not support the (cifs.ko) default protocol version
* Crypto modules required for new(er) protocol versions might be missing
  in initramfs

Related: #40554
---
 mount.c | 44 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 41 insertions(+), 3 deletions(-)

diff --git a/mount.c b/mount.c
index e2edd7f..0404672 100644
--- a/mount.c
+++ b/mount.c
@@ -181,12 +181,26 @@ out:
 }
 
 #ifdef ENABLE_CIFS
-static int cifsmount(char *dev, char *location)
+static int cifsmount3(char *dev, char *location, const char *extra_opts)
 {
 	char spec[PATH_MAX + 19], *sep, *ptr = dev;
 	struct sockaddr_in saddr;
 	pid_t pid;
 	int n, status, ret = -1;
+	const char *default_opts = "guest";
+	char *opts = NULL;
+	if (extra_opts) {
+		if (asprintf(&opts, "%s,%s", default_opts, extra_opts) < 0) {
+			log_message("%s: error: asprintf", __func__);
+			return -1;
+		}
+	} else {
+		opts = strdup(default_opts);
+		if (!opts) {
+			log_message("%s: error: strdup", __func__);
+			return -1;
+		}
+	}
 
 	while (*ptr == '/') ptr++;
 
@@ -211,14 +225,15 @@ static int cifsmount(char *dev, char *location)
 	strcat(spec, inet_ntoa(saddr.sin_addr));
 	n = strlen(spec);
 	strncpy(spec + n, sep, sizeof(spec) - n);
-	log_message("cifsmount %s %s", spec, location);
+
+	log_message("/sbin/mount.cifs %s %s --verbose -o %s", spec, location, opts);
 
 	pid = fork();
 	if (pid < 0) {
 		log_message("%s: error: fork: %s", __func__, strerror(errno));
 		goto out;
 	} else if (pid == 0) {
-		char * argv[] = {"/sbin/mount.cifs", spec, location, "-oguest", NULL};
+		char * argv[] = {"/sbin/mount.cifs", spec, location, "--verbose", "-o", opts, NULL};
 		redirect2log(STDOUT_FILENO);
 		redirect2log(STDERR_FILENO);
 		redirect2null(STDIN_FILENO);
@@ -232,8 +247,31 @@ static int cifsmount(char *dev, char *location)
 		ret = (WIFEXITED(status) && !WEXITSTATUS(status)) ? 0 : -1;
 	}
 out:
+	free(opts);
 	return ret;
 }
+
+static int cifsmount(char *dev, char *location)
+{
+	int rc = 0;
+	static const char *fallbacks[] = {
+		"vers=2.1,sec=none",
+		"vers=2.0,sec=none",
+		"vers=1.0,sec=none",
+		NULL
+	};
+	const char **opts = NULL;
+	log_message("%s: attempting to mount %s with default protocol version", __func__, dev);
+	rc = cifsmount3(dev, location, NULL);
+	for (opts = fallbacks; rc < 0 && *opts; opts++) {
+		log_message("%s: failed, retrying with %s", __func__, *opts);
+		rc = cifsmount3(dev, location, *opts);
+	}
+	if (rc < 0) {
+		log_message("%s: sorry, nothing worked", __func__);
+	}
+	return rc;
+}
 #endif
 
 #endif