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Author | SHA1 | Date |
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nervuri | 8cf7b02e1b | |
nervuri | da4f262454 | |
nervuri | a37d9a5198 |
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@ -2,10 +2,10 @@
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## Install
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Start by installing Go, Git, GCC and glibc (the program is written in Go, but a tiny bit of C code is used to drop privileges when running as root). On Debian, run:
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Start by installing Go and Git. On Debian, run:
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```
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apt install golang git gcc libc6-dev
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apt install golang git
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```
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Then fetch and build the program:
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@ -66,7 +66,7 @@ systemctl start client-hello-mirror.service
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## Drop root
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A standard web-facing setup involves using a CA-signed certificate and binding to privileged port 443. For security reasons, the program will drop root privileges imediately after loading the certificate and binding to the specified port. Use the `-u` option to select a user to switch to; the default is `www-data`.
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A standard web-facing setup involves using a CA-signed certificate and binding to privileged port 443. For security reasons, the program will drop root privileges imediately after loading the certificate and binding to the specified port. Use the `-u` option to select a user to switch to. If you really want to run as root, set `-u root` (not recommended).
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## Redirect http:// to https://
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@ -0,0 +1,5 @@
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module tildegit.org/nervuri/client-hello-mirror
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go 1.19
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require golang.org/x/crypto v0.5.0
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@ -0,0 +1,2 @@
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golang.org/x/crypto v0.5.0 h1:U/0M97KRkSFvyD/3FSmdP5W5swImpNgle/EHFhOsQPE=
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golang.org/x/crypto v0.5.0/go.mod h1:NK/OQwhpMQP3MwtdjgLlYHnH9ebylxKWv3e0fK+mkQU=
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70
server.go
70
server.go
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@ -14,6 +14,7 @@ import (
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"log"
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"net"
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"net/url"
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"os"
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"os/user"
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"strconv"
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"strings"
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@ -21,12 +22,6 @@ import (
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"time"
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)
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import (
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//#include <unistd.h>
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//#include <errno.h>
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"C"
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)
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type tlsConnectionInfo struct {
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TlsVersion uint16 `json:"tls_version"`
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CipherSuite uint16 `json:"cipher_suite"`
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@ -129,21 +124,24 @@ _____________________
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=> https://tildegit.org/nervuri/client-hello-mirror Source (contributions welcome)
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=> https://www.gnu.org/licenses/agpl-3.0.en.html License: AGPL-3.0-or-later`
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// Copy the Client Hello message before starting the TLS handshake.
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func peek(conn net.Conn, tlsConfig *tls.Config) {
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// Copy the Client Hello before starting the TLS handshake.
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defer conn.Close()
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var buf bytes.Buffer
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_, err := io.CopyN(&buf, conn, 5) // TLS record header
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// Copy TLS record header.
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_, err := io.CopyN(&buf, conn, 5)
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if err != nil {
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log.Println(err)
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return
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}
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// Check if this is a TLS handshake record.
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if buf.Bytes()[0] != 0x16 {
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// Not a Client Hello message.
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return
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}
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length := binary.BigEndian.Uint16(buf.Bytes()[3:5])
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_, err = io.CopyN(&buf, conn, int64(length))
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// Extract handshake message length.
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handshakeMessageLength := binary.BigEndian.Uint16(buf.Bytes()[3:5])
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// Copy handshake message (should be a Client Hello).
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_, err = io.CopyN(&buf, conn, int64(handshakeMessageLength))
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if err != nil {
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log.Println(err)
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return
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@ -277,11 +275,11 @@ func main() {
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// Parse arguments
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flag.StringVar(&certFile, "c", "", "path to certificate file")
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flag.StringVar(&keyFile, "k", "", "path to private key file")
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flag.StringVar(&userToSwitchTo, "u", "www-data", "user to switch to, if running as root")
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flag.StringVar(&userToSwitchTo, "u", "", "user to switch to, if running as root")
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flag.Parse()
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hostAndPort = flag.Arg(0)
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if certFile == "" || keyFile == "" || hostAndPort == "" {
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fmt.Println("usage: client-hello-mirror -c cert.pem -k key.pem host:port")
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fmt.Println("usage: client-hello-mirror -c cert.pem -k key.pem [-u user] host:port")
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return
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}
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@ -307,36 +305,48 @@ func main() {
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defer ln.Close()
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// Drop root
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if syscall.Getuid() == 0 {
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if syscall.Getuid() == 0 { // running as root
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if userToSwitchTo == "" {
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fmt.Println("Running as root. Please specify an unprivileged user to switch to, using the -u flag")
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return
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fmt.Println("When running as root, use the -u option to switch to an unprivileged user.")
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os.Exit(1)
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}
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// Get user and group IDs for the user we want to switch to.
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userInfo, err := user.Lookup(userToSwitchTo)
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if err != nil {
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fmt.Println(err)
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if userToSwitchTo == "www-data" {
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fmt.Println("Running as root. Please specify an unprivileged user to switch to, using the -u flag")
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}
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return
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os.Exit(1)
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}
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uid, err := strconv.ParseInt(userInfo.Uid, 10, 32)
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// Convert group id and user id from string to int.
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gid, err := strconv.Atoi(userInfo.Gid)
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if err != nil {
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fmt.Println(err)
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return
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os.Exit(1)
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}
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gid, err := strconv.ParseInt(userInfo.Gid, 10, 32)
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uid, err := strconv.Atoi(userInfo.Uid)
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if err != nil {
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fmt.Println(err)
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return
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os.Exit(1)
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}
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cerr, errno := C.setgid(C.__gid_t(gid))
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if cerr != 0 {
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log.Fatalln("Unable to set GID due to error:", errno)
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if uid == 0 {
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fmt.Println("WARNING: running as root is not recommended!")
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}
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cerr, errno = C.setuid(C.__uid_t(uid))
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if cerr != 0 {
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log.Fatalln("Unable to set UID due to error:", errno)
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// Unset supplementary group IDs.
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err = syscall.Setgroups([]int{})
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if err != nil {
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fmt.Println("Failed to unset supplementary group IDs: " + err.Error())
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os.Exit(1)
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}
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// Set group ID.
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err = syscall.Setgid(gid)
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if err != nil {
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fmt.Println("Failed to set group ID: " + err.Error())
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os.Exit(1)
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}
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// Set user ID.
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err = syscall.Setuid(uid)
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if err != nil {
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fmt.Println("Failed to set user ID: " + err.Error())
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os.Exit(1)
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}
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}
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