We're trying to gut 90% of the ipnserver package. A lot will get deleted, some will move to LocalBackend, and a lot is being moved into this new ipn/ipnauth package which will be leaf-y and testable. This is a baby step towards moving some stuff to ipnauth. Update #6417 Updates tailscale/corp#8051 Change-Id: I28bc2126764f46597d92a2d72565009dc6927ee0 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>main
Brad Fitzpatrick
3 years ago
committed by
Brad Fitzpatrick
parent
5f6fec0eba
commit
7bff7345cc
@ -0,0 +1,204 @@ |
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// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package ipnauth controls access to the LocalAPI.
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package ipnauth |
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import ( |
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"errors" |
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"fmt" |
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"net" |
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"net/netip" |
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"os" |
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"os/user" |
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"runtime" |
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"strconv" |
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"syscall" |
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"inet.af/peercred" |
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"tailscale.com/net/netstat" |
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"tailscale.com/safesocket" |
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"tailscale.com/types/logger" |
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"tailscale.com/util/groupmember" |
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"tailscale.com/util/pidowner" |
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"tailscale.com/util/winutil" |
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"tailscale.com/version/distro" |
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) |
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// ConnIdentity represents the owner of a localhost TCP or unix socket connection
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// connecting to the LocalAPI.
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type ConnIdentity struct { |
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conn net.Conn |
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notWindows bool // runtime.GOOS != "windows"
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// Fields used when NotWindows:
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isUnixSock bool // Conn is a *net.UnixConn
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creds *peercred.Creds // or nil
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// Used on Windows:
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// TODO(bradfitz): merge these into the peercreds package and
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// use that for all.
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pid int |
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userID string |
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user *user.User |
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} |
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func (ci *ConnIdentity) UserID() string { return ci.userID } |
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func (ci *ConnIdentity) User() *user.User { return ci.user } |
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func (ci *ConnIdentity) Pid() int { return ci.pid } |
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func (ci *ConnIdentity) IsUnixSock() bool { return ci.isUnixSock } |
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func (ci *ConnIdentity) NotWindows() bool { return ci.notWindows } |
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func (ci *ConnIdentity) Creds() *peercred.Creds { return ci.creds } |
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// GetConnIdentity returns the localhost TCP connection's identity information
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// (pid, userid, user). If it's not Windows (for now), it returns a nil error
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// and a ConnIdentity with NotWindows set true. It's only an error if we expected
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// to be able to map it and couldn't.
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func GetConnIdentity(logf logger.Logf, c net.Conn) (ci *ConnIdentity, err error) { |
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ci = &ConnIdentity{conn: c} |
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if runtime.GOOS != "windows" { // for now; TODO: expand to other OSes
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ci.notWindows = true |
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_, ci.isUnixSock = c.(*net.UnixConn) |
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ci.creds, _ = peercred.Get(c) |
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return ci, nil |
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} |
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la, err := netip.ParseAddrPort(c.LocalAddr().String()) |
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if err != nil { |
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return ci, fmt.Errorf("parsing local address: %w", err) |
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} |
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ra, err := netip.ParseAddrPort(c.RemoteAddr().String()) |
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if err != nil { |
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return ci, fmt.Errorf("parsing local remote: %w", err) |
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} |
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if !la.Addr().IsLoopback() || !ra.Addr().IsLoopback() { |
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return ci, errors.New("non-loopback connection") |
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} |
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tab, err := netstat.Get() |
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if err != nil { |
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return ci, fmt.Errorf("failed to get local connection table: %w", err) |
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} |
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pid := peerPid(tab.Entries, la, ra) |
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if pid == 0 { |
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return ci, errors.New("no local process found matching localhost connection") |
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} |
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ci.pid = pid |
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uid, err := pidowner.OwnerOfPID(pid) |
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if err != nil { |
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var hint string |
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if runtime.GOOS == "windows" { |
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hint = " (WSL?)" |
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} |
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return ci, fmt.Errorf("failed to map connection's pid to a user%s: %w", hint, err) |
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} |
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ci.userID = uid |
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u, err := LookupUserFromID(logf, uid) |
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if err != nil { |
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return ci, fmt.Errorf("failed to look up user from userid: %w", err) |
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} |
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ci.user = u |
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return ci, nil |
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} |
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// LookupUserFromID is a wrapper around os/user.LookupId that works around some
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// issues on Windows. On non-Windows platforms it's identical to user.LookupId.
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func LookupUserFromID(logf logger.Logf, uid string) (*user.User, error) { |
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u, err := user.LookupId(uid) |
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if err != nil && runtime.GOOS == "windows" && errors.Is(err, syscall.Errno(0x534)) { |
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// The below workaround is only applicable when uid represents a
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// valid security principal. Omitting this check causes us to succeed
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// even when uid represents a deleted user.
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if !winutil.IsSIDValidPrincipal(uid) { |
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return nil, err |
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} |
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logf("[warning] issue 869: os/user.LookupId failed; ignoring") |
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// Work around https://github.com/tailscale/tailscale/issues/869 for
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// now. We don't strictly need the username. It's just a nice-to-have.
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// So make up a *user.User if their machine is broken in this way.
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return &user.User{ |
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Uid: uid, |
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Username: "unknown-user-" + uid, |
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Name: "unknown user " + uid, |
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}, nil |
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} |
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return u, err |
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} |
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// IsReadonlyConn reports whether the connection should be considered read-only,
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// meaning it's not allowed to change the state of the node.
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//
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// Read-only also means it's not allowed to access sensitive information, which
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// admittedly doesn't follow from the name. Consider this "IsUnprivileged".
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// Also, Windows doesn't use this. For Windows it always returns false.
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//
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// TODO(bradfitz): rename it? Also make Windows use this.
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func (ci *ConnIdentity) IsReadonlyConn(operatorUID string, logf logger.Logf) bool { |
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if runtime.GOOS == "windows" { |
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// Windows doesn't need/use this mechanism, at least yet. It
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// has a different last-user-wins auth model.
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return false |
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} |
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const ro = true |
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const rw = false |
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if !safesocket.PlatformUsesPeerCreds() { |
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return rw |
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} |
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creds := ci.creds |
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if creds == nil { |
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logf("connection from unknown peer; read-only") |
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return ro |
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} |
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uid, ok := creds.UserID() |
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if !ok { |
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logf("connection from peer with unknown userid; read-only") |
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return ro |
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} |
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if uid == "0" { |
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logf("connection from userid %v; root has access", uid) |
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return rw |
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} |
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if selfUID := os.Getuid(); selfUID != 0 && uid == strconv.Itoa(selfUID) { |
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logf("connection from userid %v; connection from non-root user matching daemon has access", uid) |
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return rw |
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} |
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if operatorUID != "" && uid == operatorUID { |
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logf("connection from userid %v; is configured operator", uid) |
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return rw |
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} |
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if yes, err := isLocalAdmin(uid); err != nil { |
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logf("connection from userid %v; read-only; %v", uid, err) |
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return ro |
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} else if yes { |
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logf("connection from userid %v; is local admin, has access", uid) |
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return rw |
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} |
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logf("connection from userid %v; read-only", uid) |
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return ro |
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} |
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func isLocalAdmin(uid string) (bool, error) { |
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u, err := user.LookupId(uid) |
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if err != nil { |
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return false, err |
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} |
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var adminGroup string |
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switch { |
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case runtime.GOOS == "darwin": |
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adminGroup = "admin" |
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case distro.Get() == distro.QNAP: |
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adminGroup = "administrators" |
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default: |
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return false, fmt.Errorf("no system admin group found") |
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} |
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return groupmember.IsMemberOfGroup(adminGroup, u.Username) |
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} |
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func peerPid(entries []netstat.Entry, la, ra netip.AddrPort) int { |
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for _, e := range entries { |
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if e.Local == ra && e.Remote == la { |
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return e.Pid |
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} |
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} |
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return 0 |
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} |
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