rework fix for empty spaces in mountinfo fields

cf. 949b924fba58dc05f1c21d6621f05047be5397f0 and 5c69440cc943f530830b8534d99d2061bdcfaf40

1 files changed, 129 insertions, 0 deletions

diff --git a/src/firejail/mountinfo.c b/src/firejail/mountinfo.c
new file mode 100644
index 000000000..4a7816901
--- /dev/null
+++ b/src/firejail/mountinfo.c
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2014-2018 Firejail Authors
+ *
+ * This file is part of firejail project
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "firejail.h"
+
+#define MAX_BUF 4096
+static char mbuf[MAX_BUF];
+static MountData mdata;
+
+// Convert octal escape sequence to decimal value
+static int read_oct(const char *path) {
+        int decimal = 0;
+        int digit, i;
+        // there are always three octal digits
+        for (i = 1; i < 4; i++) {
+                digit = *(path + i);
+                if (digit < '0' || digit > '7') {
+                        fprintf(stderr, "Error: cannot read /proc/self/mountinfo\n");
+                        exit(1);
+                }
+                decimal = (decimal + digit - '0') * 8;
+        }
+        decimal /= 8;
+        return decimal;
+}
+
+// Restore empty spaces in pathnames extracted from /proc/self/mountinfo
+static void unmangle_path(char *path) {
+        char *p = strchr(path, '\\');
+        if (p) {
+                if (read_oct(p) == ' ') {
+                        *p = ' ';
+                        int i = 3;
+                        do {
+                                p++;
+                                if (*(p + i) == '\\' && read_oct(p + i) == ' ') {
+                                        *p = ' ';
+                                        i += 3;
+                                }
+                                else
+                                        *p = *(p + i);
+                        } while (*p);
+                }
+        }
+}
+
+// Get info regarding the last kernel mount operation.
+// The return value points to a static area, and will be overwritten by subsequent calls.
+// The function does an exit(1) if anything goes wrong.
+MountData *get_last_mount(void) {
+        // open /proc/self/mountinfo
+        FILE *fp = fopen("/proc/self/mountinfo", "r");
+        if (!fp)
+                goto errexit;
+
+        mbuf[0] = '\0';
+        while (fgets(mbuf, MAX_BUF, fp));
+        fclose(fp);
+        if (arg_debug)
+                printf("%s", mbuf);
+
+        // extract filesystem name, directory and filesystem type
+        // examples:
+        //      587 543 8:1 /tmp /etc rw,relatime master:1 - ext4 /dev/sda1 rw,errors=remount-ro,data=ordered
+        //              mdata.fsname: /tmp
+        //              mdata.dir: /etc
+        //              mdata.fstype: ext4
+        //      585 564 0:76 / /home/netblue/.cache rw,nosuid,nodev - tmpfs tmpfs rw
+        //              mdata.fsname: /
+        //              mdata.dir: /home/netblue/.cache
+        //              mdata.fstype: tmpfs
+        memset(&mdata, 0, sizeof(mdata));
+        char *ptr = strtok(mbuf, " ");
+        if (!ptr)
+                goto errexit;
+
+        int cnt = 1;
+        while ((ptr = strtok(NULL, " ")) != NULL) {
+                cnt++;
+                if (cnt == 4)
+                        mdata.fsname = ptr;
+                else if (cnt == 5) {
+                        mdata.dir = ptr;
+                        break;
+                }
+        }
+
+        ptr = strtok(NULL, "-");
+        if (!ptr)
+                goto errexit;
+
+        ptr = strtok(NULL, " ");
+        if (!ptr)
+                goto errexit;
+        mdata.fstype = ptr++;
+
+        if (mdata.fsname == NULL ||
+            mdata.dir == NULL ||
+            mdata.fstype == NULL)
+                goto errexit;
+
+        unmangle_path(mdata.fsname);
+        unmangle_path(mdata.dir);
+
+        if (arg_debug)
+                printf("fsname=%s dir=%s fstype=%s\n", mdata.fsname, mdata.dir, mdata.fstype);
+        return &mdata;
+
+errexit:
+        fprintf(stderr, "Error: cannot read /proc/self/mountinfo\n");
+        exit(1);
+}