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stunnel使用详解

發布時間：2023/12/10 编程问答 21 豆豆

生活随笔收集整理的這篇文章主要介紹了 stunnel使用详解小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

http://www.stunnel.org/faq/args.html

http://www.colasoft.com.cn/support/monitor_stunnel.php

科來網絡分析系統與stunnel結合使用

科來網絡分析系統是一款強大的網絡檢測分析工具，可對網絡中未加密的數據傳輸進行檢測分析并實時顯示分析結果，包括用戶的郵件收發、Web訪問以及各種網絡登錄等操作。所以，未經加密的數據傳輸是不安全的，存在被別人竊聽的安全隱患。

圖一顯示的是科來網絡分析系統對網絡數據傳輸捕獲的結果，從中可以看出，當前網絡中的敏感數據傳輸都未經過任何的加密保護，存在安全隱患。為加強網絡本身的安全性，在使用科來網絡分析系統進行網絡管理的同時，我們建議用戶對重要的數據傳輸進行加密保護，以達到管理和保護的有效結合。在這種情況下，即使數據被竊取，攻擊者也無法分析數據的真實內容，從而保證了數據傳輸的安全性。

圖一，網絡事務分析結果

圖二所示為常見的網絡傳輸情況，在這種情況下，數據在網絡中的傳輸沒有經過任何保護，當網絡在遭受黑客攻擊或黑客入侵時，重要數據很容易被竊取。為了使我們局域網傳輸的重要數據都是安全的，我們可以利用Stunnel工具對數據進行加密。

圖二，普通網絡

Stunnel (http://www.stunnel.org/)是一款可以加密網絡數據的TCP連接，并可工作在Unix和Windows平臺上，它采用Client/Server模式，將Client端的網絡數據采用SSL(Secure Sockets Layer)加密后，安全的傳輸到指定的Server端再進行解密還原，然后再發送到訪問的服務器。在加密傳輸過程中，可充分確保數據的安全性，我們只要把Server端程序安裝在局域網外面的一臺服務器上，即可保證傳輸的數據在局域網內是安全的，如圖三所示。

圖三，Stunnel加密后的網絡

操作過程：

Stunnel是一款免費的工具，可以在這里下載。下面我們介紹一下具體的使用。

下載Stunnel Client端程序，并解壓到本機的C:/Program Files目錄下。

下載Stunnel Server端程序，并解壓后放在外網的服務器上。

分別配置stunnel.conf文件。

更改本機應用程序的網絡連接配置。

分別運行stunnel.-4.04.exe執行文件。

說明：
我們使用Stunnel，需要在外網有一臺有管理權限的服務器，來運行Stunnel的Server程序。配置好Stunnel.conf后，可將執行文件在啟動菜單中建立快捷方式，這樣讓每次開機時，能自動運行。Stunnel技術是將傳輸的信息加密后，通過Server端的服務器進行解密才到達的目的主機，所以在選擇Server端服務器的時候，對服務器的帶寬速度有一定的要求。

Stunnel的配置：

Client和Server端都包含stunnel.conf配置文件，格式如下表所示：

Client端stunnel.conf文件內容	Server端stunnel.conf文件內容
# Use it for client mode ????????client = yes #Client-level configuration ????????[ 應用服務名稱 ] ????????accept ??=本地IP : 目標端口 ????????connect =Server端IP : 指定的端口	# Use it for server mode ????????client = no #Server-level configuration ????????[ 應用服務名稱 ] ????????accept ??= 指定的端口 ????????connect =目標服務器IP : 目標端口

常見應用實例：

Stunnel.conf文件配置比較簡單，下面我們介紹一些常見應用配置，其中Client端是放在本機，IP是127.0.0.1，Server端是放在外網的服務器上，IP是202.151.90.28。

1.加密郵件傳輸：

加密郵件，需要將發送和接收的過程都要進行保護，那么我們就要對POP3和SMTP傳送方式進行加密。如果我們有一個xxx@colasoft.com.cn信箱，服務器的IP是202.108.44.153，配置文件stunnel.conf如下：

Client端SMTP和POP3文件內容	Server端SMTP和POP3文件內容
????????[smtp.colasoft.com.cn] ????????accept ??= 127.0.0.1:25 ????????connect = 202.151.90.28:125 ????????[pop3.colasoft.com.cn] ????????accept ??= 127.0.0.1:110 ????????connect = 202.151.90.28:1110	????????[smtp.colasoft.com.cn] ????????accept ??= 125 ????????connect = 202.108.44.170:25 ????????[pop3.colasoft.com.cn] ????????accept ??= 1110 ????????connect = 202.108.44.153:110

如果有多個郵件傳輸需要加密，則增加相應的POP3和SMTP設置即可。設置好了配置文件，我們還需要將郵件客戶端（常見的為Foxmail或Outlook）與其對應，設置如下：
發送的郵件地址改為：127.0.0.1????????端口改為：125
接收的郵件地址改為：127.0.0.1????????端口改為：1110

2.加密FTP傳輸：

FTP是比較早的文件傳輸協議，內容都是以明文方式傳輸，我們利用Stunnel后，也可以讓FTP的傳輸非常安全，現在我們只需要在前面的stunnel.conf內容里面增加以下配置信息：

Client端FTP的配置	Server端FTP的配置
????????[ftp.net130.com] ????????accept ??= 127.0.0.1:21 ????????connect = 202.151.90.28:121	???????? [ftp.net130.com] ???????? accept ??= 121 ???????? connect = 218.7.9.73:21

FTP軟件（如CuteFTP）也要做相應更改：
登錄的遠程地址改為：127.0.0.1????????端口改為121

3.加密HTTP網站訪問傳輸：

我們不能對所有的網站訪問都進行加密，因為太多，但對于很重要的網站，我們也可以用Stunnel來保護訪問的內容不受到監聽。例如我們要訪問www.colasoft.com.cn，網站IP地址是202.108.36.172，HTTP的配置如下：

Client端HTTP的配置	Server端HTTP的配置
????????[www.colasoft.com.cn] ????????accept ??= 127.0.0.1:80 ????????connect = 202.151.90.28:8080	????????[www.colasoft.com.cn] ????????accept ??= 8080 ????????connect = 202.108.36.172:80

通過結合使用科來網絡分析系統與Stunnel，既可以做到對網絡的安全檢測，并找出網絡內的潛在安全隱患，又能從防護的角度出發，保護公司內部網絡的重要信息。此方案成本低，不改變當前網絡內的結構，容易實施，是一個簡單有效的安全管理方案。

Stunnel-4.10 Man Page

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
CONFIGURATION FILE
- GLOBAL OPTIONS
- SERVICE-LEVEL OPTIONS
RETURN VALUE
EXAMPLES
FILES
BUGS
RESTRICTIONS
NOTES
- INETD MODE
- CERTIFICATES
- RANDOMNESS
SEE ALSO
AUTHOR

NAME

stunnel - universal SSL tunnel

SYNOPSIS

Unix:

stunnel [<filename>] | -fd?n | -help | -version | -sockets

WIN32:

stunnel [ [-install | -uninstall] [-quiet] [<filename>] ] | -help | -version | -sockets

DESCRIPTION

The stunnel program is designed to work as SSL encryption wrapper between remote clients and local (inetd-startable) or remote servers. The concept is that having non-SSL aware daemons running on your system you can easily set them up to communicate with clients over secure SSL channels.

stunnel can be used to add SSL functionality to commonly used Inetd daemons like POP-2, POP-3, and IMAP servers, to standalone daemons like NNTP, SMTP and HTTP, and in tunneling PPP over network sockets without changes to the source code.

This product includes cryptographic software written by Eric Young (eay@cryptsoft.com)

OPTIONS

<filename>

Use specified configuration file

-fd n (Unix only)

Read the config file from specified file descriptor

-help

Print stunnel help menu

-version

Print stunnel version and compile time defaults

-sockets

Print default socket options

-install (NT/2000/XP only)

Install NT Service

-uninstall (NT/2000/XP only)

Uninstall NT Service

-quiet (NT/2000/XP only)

Don't display a message box when successfully installed or uninstalled NT service

CONFIGURATION FILE

Each line of the configuration file can be either:

an empty line (ignored)
a comment starting with ';' (ignored)
an 'option_name = option_value' pair
'[service_name]' indicating a start of a service definition

GLOBAL OPTIONS

CApath = directory

Certificate Authority directory

This is the directory in which stunnel will look for certificates when using the verify. Note that the certificates in this directory should be named XXXXXXXX.0 where XXXXXXXX is the hash value of the cert.

CApath path is relative to chroot directory if specified.

CAfile = certfile

Certificate Authority file

This file contains multiple CA certificates, used with the verify.

cert = pemfile

certificate chain PEM file name

A PEM is always needed in server mode. Specifying this flag in client mode will use this certificate chain as a client side certificate chain. Using client side certs is optional. The certificates must be in PEM format and must be sorted starting with the certificate to the highest level (root CA).

chroot = directory (Unix only)

directory to chroot stunnel process

chroot keeps stunnel in chrooted jail. CApath, CRLpath, pid and exec are located inside the jail and the patches have to be relative to the directory specified with chroot.

To have libwrap (TCP Wrappers) control effective in a chrooted environment you also have to copy its configuration files (/etc/hosts.allow and /etc/hosts.deny) there.

ciphers = cipherlist

Select permitted SSL ciphers

A colon delimited list of the ciphers to allow in the SSL connection. For example DES-CBC3-SHA:IDEA-CBC-MD5

client = yes | no

client mode (remote service uses SSL)

default: no (server mode)

compression = zlib | rle

select data compression algorithm

default: no compression

CRLpath = directory

Certificate Revocation Lists directory

This is the directory in which stunnel will look for CRLs when using the verify. Note that the CRLs in this directory should be named XXXXXXXX.0 where XXXXXXXX is the hash value of the CRL.

CRLpath path is relative to chroot directory if specified.

CRLfile = certfile

Certificate Revocation Lists file

This file contains multiple CRLs, used with the verify.

debug = [facility.]level

debugging level

Level is a one of the syslog level names or numbers emerg (0), alert (1), crit (2), err (3), warning (4), notice (5), info (6), or debug (7). All logs for the specified level and all levels numerically less than it will be shown. Use debug = debug or debug = 7 for greatest debugging output. The default is notice (5).

The syslog facility 'daemon' will be used unless a facility name is supplied. (Facilities are not supported on Win32.)

Case is ignored for both facilities and levels.

EGD = egd path (Unix only)

path to Entropy Gathering Daemon socket

Entropy Gathering Daemon socket to use to feed OpenSSL random number generator. (Available only if compiled with OpenSSL 0.9.5a or higher)

engine = auto | <engine id>

select hardware engine

default: software-only cryptography

foreground = yes | no (Unix only)

foreground mode

Stay in foreground (don't fork) and log to stderr instead of via syslog (unless output is specified).

default: background in daemon mode

key = keyfile

private key for certificate specified with cert option

Private key is needed to authenticate certificate owner. Since this file should be kept secret it should only be readable to its owner. On Unix systems you can use the following command:

??? chmod 600 keyfile

default: value of cert option

options = SSL_options

OpenSSL library options

The parameter is the OpenSSL option name as described in the SSL_CTX_set_options(3ssl) manual, but without SSL_OP_ prefix. Several options can be used to specify multiple options.

For example for compatibility with erroneous Eudora SSL implementation the following option can be used:

??? options = DONT_INSERT_EMPTY_FRAGMENTS

output = file

append log messages to a file instead of using syslog

/dev/stdout device can be used to redirect log messages to the standard output (for example to log them with daemontools splogger).

pid = file (Unix only)

pid file location

If the argument is empty, then no pid file will be created.

pid path is relative to chroot directory if specified.

RNDbytes = bytes

bytes to read from random seed files

Number of bytes of data read from random seed files. With SSL versions less than 0.9.5a, also determines how many bytes of data are considered sufficient to seed the PRNG. More recent OpenSSL versions have a builtin function to determine when sufficient randomness is available.

RNDfile = file

path to file with random seed data

The SSL library will use data from this file first to seed the random number generator.

RNDoverwrite = yes | no

overwrite the random seed files with new random data

default: yes

service = servicename

use specified string as the service name

On Unix: inetd mode service name for TCP Wrapper library.

On NT/2000/XP: NT service name in the Control Panel.

default: stunnel

session = timeout

session cache timeout

setgid = groupname (Unix only)

setgid() to groupname in daemon mode and clears all other groups

setuid = username (Unix only)

setuid() to username in daemon mode

socket = a|l|r:option=value[:value]

Set an option on accept/local/remote socket

The values for linger option are l_onof:l_linger. The values for time are tv_sec:tv_usec.

Examples:

??? socket = l:SO_LINGER=1:60??????? set one minute timeout for closing local socket??? socket = r:TCP_NODELAY=1??????? turn off the Nagle algorithm for remote sockets??? socket = r:SO_OOBINLINE=1??????? place out-of-band data directly into the??????? receive data stream for remote sockets??? socket = a:SO_REUSEADDR=0??????? disable address reuse (enabled by default)??? socket = a:SO_BINDTODEVICE=lo??????? only accept connections on loopback interface

taskbar = yes | no (WIN32 only)

enable the taskbar icon

default: yes

verify = level

verify peer certificate

??? level 1 - verify peer certificate if present??? level 2 - verify peer certificate??? level 3 - verify peer with locally installed certificate??? default - no verify

SERVICE-LEVEL OPTIONS

Each configuration section begins with service name in square brackets. The service name is used for libwrap (TCP Wrappers) access control and lets you distinguish stunnel services in your log files.

Note that if you wish to run stunnel in inetd mode (where it is provided a network socket by a server such as inetd, xinetd, or tcpserver) then you should read the section entitled INETD MODE below.

accept = [host:]port

accept connections on specified host:port

If no host specified, defaults to all IP addresses for the local host.

connect = [host:]port

connect to remote host:port

If no host specified, defaults to localhost.

delay = yes | no

delay DNS lookup for 'connect' option

exec = executable_path (Unix only)

execute local inetd-type program

exec path is relative to chroot directory if specified.

execargs = $0 $1 $2 ... (Unix only)

arguments for exec including program name ($0)

Quoting is currently not supported. Arguments are separated with arbitrary number of whitespaces.

ident = username

use IDENT (RFC 1413) username checking

local = host

IP of the outgoing interface is used as source for remote connections. Use this option to bind a static local IP address, instead.

protocol = proto

Negotiate SSL with specified protocol

currently supported: cifs, nntp, pop3, smtp

pty = yes | no (Unix only)

allocate pseudo terminal for 'exec' option

TIMEOUTbusy = seconds

time to wait for expected data

TIMEOUTclose = seconds

time to wait for close_notify (set to 0 for buggy MSIE)

TIMEOUTconnect = seconds

time to wait to connect a remote host

TIMEOUTidle = seconds

time to keep an idle connection

transparent = yes | no (Unix only)

transparent proxy mode

Re-write address to appear as if wrapped daemon is connecting from the SSL client machine instead of the machine running stunnel. This option is only available in local mode (exec option) by LD_PRELOADing env.so shared library or in remote mode (connect option) on Linux 2.2 kernel compiled with transparent proxy option and then only in server mode. Note that this option will not combine with proxy mode (connect) unless the client's default route to the target machine lies through the host running stunnel, which cannot be localhost.

RETURN VALUE

stunnel returns zero on success, non-zero on error.

EXAMPLES

In order to provide SSL encapsulation to your local imapd service, use

??? [imapd]??? accept = 993??? exec = /usr/sbin/imapd??? execargs = imapd

If you want to provide tunneling to your pppd daemon on port 2020, use something like

??? [vpn]??? accept = 2020??? exec = /usr/sbin/pppd??? execargs = pppd local??? pty = yes

If you want to use stunnel in inetd mode to launch your imapd process, you'd use this stunnel.conf. Note there must be no [service_name] section.

??? exec = /usr/sbin/imapd??? execargs = imapd

FILES

stunnel.conf

stunnel configuration file

stunnel.pem

stunnel certificate and private key

BUGS

Option execargs does not support quoting.

RESTRICTIONS

stunnel cannot be used for the FTP daemon because of the nature of the FTP protocol which utilizes multiple ports for data transfers. There are available SSL enabled versions of FTP and telnet daemons, however.

NOTES

INETD MODE

The most common use of stunnel is to listen on a network port and establish communication with either a new port via the connect option, or a new program via the exec option. However there is a special case when you wish to have some other program accept incoming connections and launch stunnel, for example with inetd, xinetd, or tcpserver.

For example, if you have the following line in inetd.conf:

??? imaps stream tcp nowait root /usr/sbin/stunnel stunnel /etc/stunnel/imaps.conf

In these cases, the inetd-style program is responsible for binding a network socket (imaps above) and handing it to stunnel when a connection is received. Thus you do not want stunnel to have any accept option. All the Service Level Options should be placed in the global options section, and no [service_name] section will be present. See the EXAMPLES section for example configurations.

CERTIFICATES

Each SSL enabled daemon needs to present a valid X.509 certificate to the peer. It also needs a private key to decrypt the incoming data. The easiest way to obtain a certificate and a key is to generate them with the free OpenSSL package. You can find more information on certificates generation on pages listed below.

Two things are important when generating certificate-key pairs for stunnel. The private key cannot be encrypted, because the server has no way to obtain the password from the user. To produce an unencrypted key add the -nodes option when running the req command from the OpenSSL kit.

The order of contents of the .pem file is also important. It should contain the unencrypted private key first, then a signed certificate (not certificate request). There should be also empty lines after certificate and private key. Plaintext certificate information appended on the top of generated certificate should be discarded. So the file should look like this:

??? -----BEGIN RSA PRIVATE KEY-----??? [encoded key]??? -----END RSA PRIVATE KEY-----??? [empty line]??? -----BEGIN CERTIFICATE-----??? [encoded certificate]??? -----END CERTIFICATE-----??? [empty line]

RANDOMNESS

stunnel needs to seed the PRNG (pseudo random number generator) in order for SSL to use good randomness. The following sources are loaded in order until sufficient random data has been gathered:

The file specified with the RNDfile flag.
The file specified by the RANDFILE environment variable, if set.
The file .rnd in your home directory, if RANDFILE not set.
The file specified with '--with-random' at compile time.
The contents of the screen if running on Windows.
The egd socket specified with the EGD flag.
The egd socket specified with '--with-egd-sock' at compile time.
The /dev/urandom device.

With recent (>=OpenSSL 0.9.5a) version of SSL it will stop loading random data automatically when sufficient entropy has been gathered. With previous versions it will continue to gather from all the above sources since no SSL function exists to tell when enough data is available.

Note that on Windows machines that do not have console user interaction (mouse movements, creating windows, etc) the screen contents are not variable enough to be sufficient, and you should provide a random file for use with the RNDfile flag.

Note that the file specified with the RNDfile flag should contain random data -- that means it should contain different information each time stunnel is run. This is handled automatically unless the RNDoverwrite flag is used. If you wish to update this file manually, the openssl rand command in recent versions of OpenSSL, would be useful.

One important note -- if /dev/urandom is available, OpenSSL has a habit of seeding the PRNG with it even when checking the random state, so on systems with /dev/urandom you're likely to use it even though it's listed at the very bottom of the list above. This isn't stunnel's behaviour, it's OpenSSLs.

AUTHOR

Michal Trojnara

<Michal.Trojnara@mirt.net>

The Ubiquitous Miscellaneous Section

Those things that don't have a proper home yet may end up here. Or they may stay here. I've heard that many answers prefer to be in the miscellaneous sections. Maybe they're just shy.

What are the offical SSL ports?

These are the officially 'registered' ports for various SSL-ified protocols. note that listing them here doesn't mean that they can be used with stunnel.

??? nsiiops????? 261/tcp?? # IIOP Name Service over TLS/SSL??? https??????? 443/tcp?? # http protocol over TLS/SSL??? smtps??????? 465/tcp?? # smtp protocol over TLS/SSL (was ssmtp)??? nntps??????? 563/tcp?? # nntp protocol over TLS/SSL (was snntp)??? imap4-ssl??? 585/tcp?? # IMAP4+SSL (use 993 instead)??? sshell?????? 614/tcp?? # SSLshell??? ldaps??????? 636/tcp?? # ldap protocol over TLS/SSL (was sldap)??? ftps-data??? 989/tcp?? # ftp protocol, data, over TLS/SSL??? ftps???????? 990/tcp?? # ftp protocol, control, over TLS/SSL??? telnets????? 992/tcp?? # telnet protocol over TLS/SSL??? imaps??????? 993/tcp?? # imap4 protocol over TLS/SSL??? ircs???????? 994/tcp?? # irc protocol over TLS/SSL??? pop3s??????? 995/tcp?? # pop3 protocol over TLS/SSL (was spop3)??? msft-gc-ssl? 3269/tcp? # Microsoft Global Catalog with LDAP/SSL

How do I know which encryption ciphers are available?

The ciphers that are availabre to stunnel (and usable by the '-C' flag) are determined by your OpenSSL library. To list the available ciphers, run the following:

??? openssl ciphers -v

How can I delay DNS lookups until connect time?

If you're using Stunnel-4.0 or later, add the following to your Stunnel configuration file:

? delay = yes

If you are using older versions, there are several different patches available for this in the patches directory on this site you may try.

Another option is to launch redir (a TCP redirector) dynamically instead of using the "-r host:port" option, like this:

?? -l /usr/bin/redir -- redir --inetd --caddr host --cport port

How can I convert a certificate from der format (.cer) to PEM format?

Some institutions that supply certificates will send them to you in der format instead of PEM format. You can use the openssl command line tool to convert from one to the other:

? openssl x509 -in file.cer -inform d -out file.pem???????????

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