facts: server.Mounts: fix whitespaces and escaped characters

The `mount` command can not be parsed unambigiously. Whitespaces in paths
and , in option lists are not escaped. See the new tests for examples
the old code can not handle.

This patch switches to reading from `/proc/self/mountinfo` instead (see man 5
proc for documentation) where strings are properly escaped.

While `/proc/self/mountinfo` provides a lot more details, these are
ignored to keep compatibility with the old type. If there is a need, the
missing fields can be easily added.

Author: lemmi

pyinfra/facts/server.py

@@ -206,34 +206,53 @@ class Mounts(FactBase[Dict[str, MountsDict]]):
 
     @override
     def command(self):
-        return "mount"
+        return "cat /proc/self/mountinfo"
 
     @override
     def process(self, output) -> dict[str, MountsDict]:
         devices: dict[str, MountsDict] = {}
 
-        for line in output:
-            is_map = False
-            if line.startswith("map "):
-                line = line[4:]
-                is_map = True
-
-            device, _, path, other_bits = line.split(" ", 3)
+        def unescape_octal(match: re.Match) -> str:
+            s = match.group(0)[1:]  # skip the backslash
+            return chr(int(s, base=8))
 
-            if is_map:
-                device = "map {0}".format(device)
+        def replace_octal(s: str) -> str:
+            """
+            Unescape strings encoded by linux's string_escape_mem with ESCAPE_OCTAL flag.
+            """
+            return re.sub(r"\\[0-7]{3}", unescape_octal, s)
 
-            if other_bits.startswith("type"):
-                _, type_, options = other_bits.split(" ", 2)
-                options = options.strip("()").split(",")
-            else:
-                options = other_bits.strip("()").split(",")
-                type_ = options.pop(0)
-
-            devices[path] = {
-                "device": device,
-                "type": type_,
-                "options": [option.strip() for option in options],
+        for line in output:
+            # ignore mount ID, parent ID, major:minor, root
+            _, _, _, _, mount_point, mount_options, line = line.split(sep=" ", maxsplit=6)
+
+            # ignore optional tags "shared", "master", "propagate_from" and "unbindable"
+            while True:
+                optional, line = line.split(sep=" ", maxsplit=1)
+                if optional == "-":
+                    break
+
+            fs_type, mount_source, super_options = line.split(sep=" ")
+
+            mount_options = mount_options.split(sep=",")
+
+            # escaped: mount_point, mount_source, super_options
+            # these strings can contain characters encoded in octal, e.g. '\054' for ','
+            mount_point = replace_octal(mount_point)
+            mount_source = replace_octal(mount_source)
+
+            # mount_options will override ro/rw and can be different than the super block options
+            # filter them, so they don't appear twice
+            super_options = [
+                replace_octal(opt)
+                for opt in super_options.split(sep=",")
+                if opt not in ["ro", "rw"]
+            ]
+
+            devices[mount_point] = {
+                "device": mount_source,
+                "type": fs_type,
+                "options": mount_options + super_options,
             }
 
         return devices

tests/facts/server.Mounts/mounts.json

@@ -1,39 +1,44 @@
 {
-    "command": "mount",
+    "command": "cat /proc/self/mountinfo",
     "output": [
-        "/dev/sda1 on /boot type ext2 (rw,relatime,block_validity,barrier,user_xattr,acl)",
-        "/dev/disk1s4 on /private/var/vm (apfs, local, noexec, journaled, noatime, nobrowse)",
-        "map thing on / type something ()"
+        "2 1 0:26 / / ro,noatime - ext4 /dev/sdb1 rw",
+        "33 29 8:1 / /boot rw,relatime - vfat /dev/sda1 rw,lazytime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro",
+        "408 35 0:352 / /mnt/overlay/overlay,dir\\040with\\040spaces\\040and\\040\\134backslashes ro,relatime shared:27 - overlay none ro,lowerdir=lower\\054dir,upperdir=upper\\054dir,workdir=work\\054dir"
     ],
     "fact": {
+        "/": {
+            "device": "/dev/sdb1",
+            "type": "ext4",
+            "options": [
+                "ro",
+                "noatime"
+            ]
+        },
         "/boot": {
             "device": "/dev/sda1",
-            "type": "ext2",
+            "type": "vfat",
             "options": [
                 "rw",
                 "relatime",
-                "block_validity",
-                "barrier",
-                "user_xattr",
-                "acl"
+                "lazytime",
+                "fmask=0022",
+                "dmask=0022",
+                "codepage=437",
+                "iocharset=iso8859-1",
+                "shortname=mixed",
+                "utf8",
+                "errors=remount-ro"
             ]
         },
-        "/private/var/vm": {
-            "device": "/dev/disk1s4",
-            "type": "apfs",
+        "/mnt/overlay/overlay,dir with spaces and \\backslashes": {
+            "device": "none",
+            "type": "overlay",
             "options": [
-                "local",
-                "noexec",
-                "journaled",
-                "noatime",
-                "nobrowse"
-            ]
-        },
-        "/": {
-            "device": "map thing",
-            "type": "something",
-            "options": [
-                ""
+                "ro",
+                "relatime",
+                "lowerdir=lower,dir",
+                "upperdir=upper,dir",
+                "workdir=work,dir"
             ]
         }
     }