improve drop root code; remove reliance on C
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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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57
server.go
57
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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@ -280,11 +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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@ -310,36 +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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