cmd: Split unix sockets for admin endpoint addresses (#5696)

* cmd: fix cli when admin endpoint uses new unix socket permission format

Fixes a bug where the following Caddyfile

```Caddyfile
{
	admin unix/admin.sock|0660
}
```

and `caddy reload --config Caddyfile`
would throw the following error instead of reloading it:

```
INFO    using provided configuration    {"config_file": "Caddyfile", "config_adapter": ""}
Error: sending configuration to instance: performing request: Post "http://127.0.0.1/load": dial unix admin.sock|0660: connect: no such file or directory
[ERROR] exit status 1
```

---

This bug also affected `caddy start` and `caddy stop`.

* Move splitter function to internal

---------

Co-authored-by: Matthew Holt <mholt@users.noreply.github.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/internal/sockets.go b/internal/sockets.go
new file mode 100644
index 0000000..761f920
--- /dev/null
+++ b/internal/sockets.go
@@ -0,0 +1,56 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal
+
+import (
+	"fmt"
+	"io/fs"
+	"strconv"
+	"strings"
+)
+
+// SplitUnixSocketPermissionsBits takes a unix socket address in the
+// unusual "path|bits" format (e.g. /run/caddy.sock|0222) and tries
+// to split it into socket path (host) and permissions bits (port).
+// Colons (":") can't be used as separator, as socket paths on Windows
+// may include a drive letter (e.g. `unix/c:\absolute\path.sock`).
+// Permission bits will default to 0200 if none are specified.
+// Throws an error, if the first carrying bit does not
+// include write perms (e.g. `0422` or `022`).
+// Symbolic permission representation (e.g. `u=w,g=w,o=w`)
+// is not supported and will throw an error for now!
+func SplitUnixSocketPermissionsBits(addr string) (path string, fileMode fs.FileMode, err error) {
+	addrSplit := strings.SplitN(addr, "|", 2)
+
+	if len(addrSplit) == 2 {
+		// parse octal permission bit string as uint32
+		fileModeUInt64, err := strconv.ParseUint(addrSplit[1], 8, 32)
+		if err != nil {
+			return "", 0, fmt.Errorf("could not parse octal permission bits in %s: %v", addr, err)
+		}
+		fileMode = fs.FileMode(fileModeUInt64)
+
+		// FileMode.String() returns a string like `-rwxr-xr--` for `u=rwx,g=rx,o=r` (`0754`)
+		if string(fileMode.String()[2]) != "w" {
+			return "", 0, fmt.Errorf("owner of the socket requires '-w-' (write, octal: '2') permissions at least; got '%s' in %s", fileMode.String()[1:4], addr)
+		}
+
+		return addrSplit[0], fileMode, nil
+	}
+
+	// default to 0200 (symbolic: `u=w,g=,o=`)
+	// if no permission bits are specified
+	return addr, 0200, nil
+}