31st of July 2014

HTTPS and Certificates explainedWhat is it? How does it work?

by Pierre Cornic

31st of July 2014

Table of content

1. Why HTTPS?2. Public/private key, encrypt, sign3. Certificate authority & PKI4. Let’s use it

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Bi-directional encryption of communication

For example: ARP spoofing

Attacker cannot decrypt data

Why HTTPS

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Validate identity of remote server

For example: DNS poisoning

Client sees a certificate warning when accessing fake site

Why HTTPS

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Table of content

1. Why HTTPS?2. Public/private key, encrypt, sign3. Certificate authority & PKI4. Let’s use it

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Source: wikipedia

● Encrypt with public key● Decrypt with private key

Public/private key encryption

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Source: wikipedia

● Encrypt hash with private key● Decrypt with public key

Public/private key encryption

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Table of content

1. Why HTTPS?2. Public/private key, encrypt, sign3. Certificate authority & PKI4. Let’s use it

31st of July 2014

● Binds a certificate to an identity

Inovia-Team

Certificate Authority(Trusted Tier Party)

Private key

Checks that the person that owns private key is Inovia-Team

Public key + Inovia-Team =Certificate

Creates & signs

Certificate Authority

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Version: 3 (0x2)

Serial Number: 92675 (0x16a03)

Signature Algorithm: sha1WithRSAEncryption

Issuer: C=IL, O=StartCom Ltd., OU=Secure Digital Certificate Signing, CN=StartCom Class 2 Primary Intermediate Server CA

Validity

Not Before: May 23 01:18:37 2013 GMT

Not After : May 23 19:03:12 2015 GMT

Subject: description=zyBDci1AcdG79M0X, C=FR, ST=Ile-de-France, L=PARIS, O=Inovia-Team SARL, CN=inovia.fr/emailAddress=webmaster@inovia-team.com

Subject Public Key Info:

Public Key Algorithm: rsaEncryption

RSA Public Key: (2048 bit)

Modulus (2048 bit):

00:e5:2b:b0:66:ac:f5:22:5b:64:b5:19:58:25:c3:

[………]

Exponent: 65537 (0x10001)

X509v3 extensions:

X509v3 Basic Constraints:

CA:FALSE

X509v3 Key Usage:

Digital Signature, Key Encipherment, Key Agreement

X509v3 Extended Key Usage:

TLS Web Client Authentication, TLS Web Server Authentication

X509v3 Subject Key Identifier:

E7:39:36:3C:96:C6:AA:C2:83:73:7E:8A:4E:1B:9C:9B:34:C6:52:7D

X509v3 Authority Key Identifier:

keyid:11:DB:23:45:FD:54:CC:6A:71:6F:84:8A:03:D7:BE:F7:01:2F:26:86

What is inside a x509 certificate?$ openssl x509 -in inovia.fr.crt -noout -text

Certificate authority

Subject: Inovia-Team

Public key

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X509v3 Subject Alternative Name:

DNS:inovia.fr, DNS:inovia-team.com, DNS:*.inovia-team.com, DNS:*.inovia-team.com, DNS:*.inovia.fr

X509v3 Certificate Policies:

Policy: 2.23.140.1.2.2

Policy: 1.3.6.1.4.1.23223.1.2.3

CPS: http://www.startssl.com/policy.pdf

User Notice:

Organization: StartCom Certification Authority

Number: 1

Explicit Text: This certificate was issued according to the Class 2 Validation requirements of the StartCom CA policy, reliance only for the intended purpose in compliance of the relying party obligations.

X509v3 CRL Distribution Points:

URI:http://crl.startssl.com/crt2-crl.crl

Authority Information Access:

OCSP - URI:http://ocsp.startssl.com/sub/class2/server/ca

CA Issuers - URI:http://aia.startssl.com/certs/sub.class2.server.ca.crt

X509v3 Issuer Alternative Name:

URI:http://www.startssl.com/

Signature Algorithm: sha1WithRSAEncryption

7d:a9:eb:10:28:6a:75:a2:65:f6:7b:38:13:c4:f4:61:f6:43:

[...]

46:72:3f:e8:b3:1f:0f:ab:56:25:1d:6a:cb:5d:78:c0:b8:e1:

b5:58:95:bd

What is inside a x509 certificate?

Subject other names

Signature using CA private key

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Verify certificate

● Retrieve CA certificate● Decrypt CA_to_validate signature using CA public key● Hash CA_to_validate data● Check that both hash are the same

To verify a certificate I need another certificate.HOW CAN I TRUST IT???

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Public Key Infrastructure

● Chain of trust

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Public Key Infrastructure

Major Root Certificates are preinstalled in browsers and operating systems

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Public Key Infrastructure

Major Root Certificates are preinstalled in browsers and operating systems

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Table of content

1. Why HTTPS?2. Public/private key, encrypt, sign3. Certificate authority & PKI4. Let’s use it

31st of July 2014

Use case: enable SSL for a team of developers

● 10 devs● Application installed on each workstation● Each dev must be able to access another dev

workstation without certificate warning● Do not want to pay 10 certificates!

Solution: Create your own CA!

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Let’s use it: create your own CA

$ openssl genrsa -out rootCA.key 2048 -des3

● Generate password-protected CA Key

$ openssl req -x509 -new -nodes -key rootCA.key -days 1024 -out rootCA.pemYou are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN.There are quite a few fields but you can leave some blankFor some fields there will be a default value,If you enter '.', the field will be left blank.-----Country Name (2 letter code) [AU]:FRState or Province Name (full name) [Some-State]:Ile-de-FranceLocality Name (eg, city) []:ParisOrganization Name (eg, company) [Internet Widgits Pty Ltd]:Inovia-TeamOrganizational Unit Name (eg, section) []:IT DepartmentCommon Name (e.g. server FQDN or YOUR name) []:Inovia Certificate AuthorityEmail Address []:

● Generate CA Certificate

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Signature flow

Obtaining certificate from a CA

Certificate signing request

Certificate Authority

HTTP Server <- Certificate

Client Application <- CA’s credentials

CA receives a Certificate Signing Request

CA creates a Certificate which is placed on the HTTP server

Client connects to the server over HTTPS and verifies that the server’s Certificate signature

matches the trusted CA’s credentials.

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Create Certificate Signing Request

$ openssl genrsa -out mywebsite.key 2048

● Generate Key

$ openssl req -new -key mywebsite.key -days -out mywebsite.csrYou are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN.There are quite a few fields but you can leave some blankFor some fields there will be a default value,If you enter '.', the field will be left blank.-----Country Name (2 letter code) [AU]:FRState or Province Name (full name) [Some-State]:Ile-de-FranceLocality Name (eg, city) []:ParisOrganization Name (eg, company) [Internet Widgits Pty Ltd]:Inovia-TeamOrganizational Unit Name (eg, section) []:MyTeamCommon Name (e.g. server FQDN or YOUR name) []:*.myhostname.localEmail Address []:

● Generate Certificate Signing Request (CSR)

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Generate certificate from CSR

● Send CSR to IT Department

$ openssl x509 -req -in mywebsite.csr -CA rootCA.pem -CAkey rootCA.key -CAcreateserial -out mywebsite.crt -days 500Signature oksubject=/C=FR/ST=Ile-de-France/L=Paris/O=Inovia-Team/OU=MyTeam/CN=*.myhostname.localGetting CA Private Key

● Generate Certificate

● Verify certificate using your CA$ openssl verify -CAfile rootCA.pem mywebsite.crtmywebsite.crt: OK

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Verify certificate

Certificate: Data: Version: 1 (0x0) Serial Number: 92:72:d1:12:be:f4:07:8e Signature Algorithm: sha1WithRSAEncryption Issuer: C=FR, ST=Ile-de-France, L=Paris, O=Inovia-Team, OU=IT Department, CN=Inovia Certificate Authority Validity Not Before: Jul 31 12:32:41 2014 GMT Not After : Dec 13 12:32:41 2015 GMT Subject: C=FR, ST=Ile-de-France, L=Paris, O=Inovia-Team, OU=MyTeam, CN=*.myhostname.local Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (2048 bit) Modulus (2048 bit): 00:d0:bd:82:bc:9c:36:ea:7e:a3:ee:c5:86:70:e5: [...] 22:0b:72:fc:46:ac:aa:6d:76:e4:2b:1c:09:1e:78: 6e:bd:81:a1:57:03:f8:91:7e:54:8b:38:9e:ec:19: e3:27 Exponent: 65537 (0x10001) Signature Algorithm: sha1WithRSAEncryption b6:d5:74:81:26:96:8a:37:51:c0:33:97:c5:65:c3:8a:f5:94: [...] 90:fc:c8:8d:e1:2b:4f:c7:fd:6d:8c:f7:3b:0e:fd:42:86:8e:

$ openssl x509 -in mywebsite.crt -noout -text

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Install in Apache

<VirtualHost *:443>ServerName mywebsite.myhostname.localDocumentRoot /var/www/mywebsite/

SSLEngine onSSLCertificateFile /etc/apache2/ssl/mywebsite.crtSSLCertificateKeyFile /etc/apache2/ssl/mywebsite.keySSLCertificateChainFile /etc/apache2/ssl/rootCA.pem

</VirtualHost>

● Create a VirtualHost

● Enable virtualhost & restart apache# a2ensite mywebsite# a2enmod ssl# apache2ctl -t# apache2ctl restart

Is that all?

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Install CA certificate on all browsers

● Chrome: Parameters > Display advanced parameters > Manage certificates > Root certificates > Import

● Firefox: Tools > Preferences > Advanced > Certificates > Display certificates > Import

● OS: If you use Webservices for example$ sudo cp rootCA.crt /usr/share/ca-certificates/$ sudo update-ca-certificates

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For online questions, please leave a comment on the article.

Questions ?

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31st of July 2014

http://securitymusings.com (images)http://www.technicalinfo.net/papers/images/pharming030.jpg (images)http://dm3.github.io/(images)http://technet.microsoft.com/ (images)http://icons.iconarchive.com (images)www.flaticon.com (images)

Sources