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This shows you the differences between two versions of the page.
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ac:laboratoare:05 [2018/10/24 15:29] tiberiu.iorgulescu |
ac:laboratoare:05 [2022/11/03 17:05] (current) marios.choudary |
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| ===== Lab 05 - PKI and TLS ===== | ===== Lab 05 - PKI and TLS ===== | ||
| + | |||
| + | <hidden> | ||
| + | ==== Task 0: Implement DH + AES-GCM encryption === | ||
| + | |||
| + | Implement DH + AES-GCM encryption starting from the code from previous lab (see bonus 2). | ||
| + | |||
| + | Use the secret key to encrypt some data and check that the other party can decrypt it. You can use | ||
| + | the code available [[https://paste.ubuntu.com/p/4XZpMtt9ZZ/ | here]] for AES-GCM. | ||
| + | </hidden> | ||
| + | |||
| ==== Public Key Infrastructure ==== | ==== Public Key Infrastructure ==== | ||
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| {{ :ac:laboratoare:chain-of-trust.png?500 |Chain of trust}} | {{ :ac:laboratoare:chain-of-trust.png?500 |Chain of trust}} | ||
| - | ==== Task 1: Investigate certficates for ocw.cs.pub.ro ==== | + | === Task 1: Investigate certficates for ocw.cs.pub.ro === |
| Using your browser's 'View Certificate' functionality, try to find information about the certificate presented by https://ocw.cs.pub.ro. We are interested in: | Using your browser's 'View Certificate' functionality, try to find information about the certificate presented by https://ocw.cs.pub.ro. We are interested in: | ||
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| Export server and issuer certificates, or download them from here: {{:ac:laboratoare:certificates.tar}}. We will use ''openssl'' command line tool to investigate certificate files. | Export server and issuer certificates, or download them from here: {{:ac:laboratoare:certificates.tar}}. We will use ''openssl'' command line tool to investigate certificate files. | ||
| + | <note tip> | ||
| + | You can download a website certificate with this command: | ||
| + | <code> | ||
| + | true | openssl s_client -connect ocw.cs.pub.ro:443 2>/dev/null | openssl x509 > ocwcspubro.crt | ||
| + | </code> | ||
| + | </note> | ||
| <note tip> | <note tip> | ||
| You can connect to a HTTPS website using: | You can connect to a HTTPS website using: | ||
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| $ openssl x509 -in ocwcspubro.crt -noout -subject | $ openssl x509 -in ocwcspubro.crt -noout -subject | ||
| $ openssl x509 -in ocwcspubro.crt -noout -pubkey | $ openssl x509 -in ocwcspubro.crt -noout -pubkey | ||
| + | </code> | ||
| + | |||
| + | In order to download the lasters version of TERENASSLCA3.crt, you need to check CA Issuers - URI field of ocw's certificate. | ||
| + | If you download it, it might be in DER format (binary). You can convert it with the following command: | ||
| + | <code> | ||
| + | openssl x509 -inform der -in TERENASSLCA3.crt -out TERENASSLCA3pem.crt | ||
| </code> | </code> | ||
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| ==== TLS ==== | ==== TLS ==== | ||
| + | |||
| The Transport Layer Security protocol aims primarily to provide privacy and data integrity between two communicating computer applications. When secured by TLS, connections between a client (e.g., a web browser) and a server (e.g., wikipedia.org) have one or more of the following properties: | The Transport Layer Security protocol aims primarily to provide privacy and data integrity between two communicating computer applications. When secured by TLS, connections between a client (e.g., a web browser) and a server (e.g., wikipedia.org) have one or more of the following properties: | ||
| * The connection is private because symmetric cryptography is used to encrypt the data transmitted. The keys for this symmetric encryption are based on a shared secret negotiated at the start of the session. | * The connection is private because symmetric cryptography is used to encrypt the data transmitted. The keys for this symmetric encryption are based on a shared secret negotiated at the start of the session. | ||
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| The TLS protocol comprises two layers: the TLS record protocol and the TLS handshake protocol. TLS handshake protocol (both RSA key exchange and Diffie-Hellman key exchange) can be seen in the pictures below: | The TLS protocol comprises two layers: the TLS record protocol and the TLS handshake protocol. TLS handshake protocol (both RSA key exchange and Diffie-Hellman key exchange) can be seen in the pictures below: | ||
| - | {{:ac:laboratoare:ssl-rsa-handshake.jpeg?500 }} | + | * {{:ac:laboratoare:ssl-rsa-handshake.jpeg?500}} |
| - | {{ :ac:laboratoare:ssl-dh-handshake.jpeg?500}} | + | * {{:ac:laboratoare:ssl-dh-handshake.jpeg?500}} |
| - | ==== Task 2: Investigate the TLS handshake protocol ==== | + | |
| + | === Task 2: Investigate the TLS cryptographic parameters === | ||
| + | |||
| + | Use your browser to inspect the TLS version and cryptoparameters of popular websites: google.com, amazon.com, microsoft.com. Report any differences. | ||
| + | |||
| + | * Can you tell what is the root certificate, the intermediate certificate and the target/server certificate ? | ||
| + | * How do you differentiate a root certificate from an intermediate certificate ? | ||
| + | |||
| + | === Task 3: Investigate the TLS handshake protocol === | ||
| Using Wireshark, investigate the two traffic captures ({{:ac:laboratoare:traffic-captures.tar}}). In both cases try to find: | Using Wireshark, investigate the two traffic captures ({{:ac:laboratoare:traffic-captures.tar}}). In both cases try to find: | ||
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| <note important>The property that compromise of long-term keys does not compromise past session keys is called **Forward Secrecy**. DH key exchange has this property, while RSA key exchange does not.</note> | <note important>The property that compromise of long-term keys does not compromise past session keys is called **Forward Secrecy**. DH key exchange has this property, while RSA key exchange does not.</note> | ||
| - | ==== Task 3: Create your own CA ==== | + | <hidden> |
| + | ==== Task 3-5: Create your own CA ==== | ||
| - Create directories for CA and for server files <code>mkdir ca-files server-files</code> | - Create directories for CA and for server files <code>mkdir ca-files server-files</code> | ||
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| <note warning>Keeping ''root-ca.key'' private is **very important**. Describe what an attacker with access to private key can do. What about ''server.key''?</note> | <note warning>Keeping ''root-ca.key'' private is **very important**. Describe what an attacker with access to private key can do. What about ''server.key''?</note> | ||
| + | |||
| + | </hidden> | ||
