clean homedir pathname

fixes #2137 and similar issues with the /proc/self/mountinfo checks

3 files changed, 44 insertions, 4 deletions

diff --git a/src/firejail/firejail.h b/src/firejail/firejail.h
index 1d74dc8dc..cae767667 100644
--- a/src/firejail/firejail.h
+++ b/src/firejail/firejail.h
@@ -522,6 +522,7 @@ int is_link(const char *fname);
 void trim_trailing_slash_or_dot(char *path);
 char *line_remove_spaces(const char *buf);
 char *split_comma(char *str);
+char *clean_pathname(const char *path);
 void check_unsigned(const char *str, const char *msg);
 int find_child(pid_t parent, pid_t *child);
 void check_private_dir(void);
diff --git a/src/firejail/main.c b/src/firejail/main.c
index 123fe96a1..315a7260a 100644
--- a/src/firejail/main.c
+++ b/src/firejail/main.c
@@ -233,9 +233,8 @@ static void init_cfg(int argc, char **argv) {
         // build home directory name
         cfg.homedir = NULL;
         if (pw->pw_dir != NULL) {
-                cfg.homedir = strdup(pw->pw_dir);
-                if (!cfg.homedir)
-                        errExit("strdup");
+                cfg.homedir = clean_pathname(pw->pw_dir);
+                assert(cfg.homedir);
         }
         else {
                 fprintf(stderr, "Error: user %s doesn't have a user directory assigned\n", cfg.username);
diff --git a/src/firejail/util.c b/src/firejail/util.c
index ae07a42b0..0d1418b43 100644
--- a/src/firejail/util.c
+++ b/src/firejail/util.c
@@ -533,6 +533,46 @@ char *split_comma(char *str) {
 }
 
 
+// remove consecutive and trailing slashes
+// and return allocated memory
+// e.g. /home//user/ -> /home/user
+char *clean_pathname(const char *path) {
+        assert(path);
+        size_t len = strlen(path);
+        char *rv = calloc(len + 1, 1);
+        if (!rv)
+                errExit("calloc");
+
+        if (len > 0) {
+                int i, j, cnt;
+                for (i = 0, j = 0, cnt = 0; i < len; i++) {
+                        if (path[i] == '/')
+                                cnt++;
+                        else
+                                cnt = 0;
+
+                        if (cnt < 2) {
+                                rv[j] = path[i];
+                                j++;
+                        }
+                }
+
+                // remove a trailing slash
+                if (j > 1 && rv[j - 1] == '/')
+                        rv[j - 1] = '\0';
+
+                size_t new_len = strlen(rv);
+                if (new_len < len) {
+                        rv = realloc(rv, new_len + 1);
+                        if (!rv)
+                                errExit("realloc");
+                }
+        }
+
+        return rv;
+}
+
+
 void check_unsigned(const char *str, const char *msg) {
         EUID_ASSERT();
         const char *ptr = str;
@@ -656,7 +696,7 @@ void extract_command_name(int index, char **argv) {
         // command name is a substring of cfg.command_name
         if (basename != cfg.command_name || *ptr != '\0') {
                 *ptr = '\0';
-                
+
                 basename = strdup(basename);
                 if (!basename)
                         errExit("strdup");