This document summarizes techniques for securing data in Postgres, including host-based authentication, access control lists, row-level security, SSL/TLS, auditing, and encryption. It also discusses upcoming features in Postgres 10 like SSL configuration reload and more restrictive row-level security policies. Desired future features mentioned include data redaction, Active Directory support, and features similar to Oracle TDE for encryption key management.

1. Securing Data in Postgres
Payal Singh
@pallureshu
OmniTI Computer Consulting
https://omniti.com 1

2. Agenda
Host Based Authentication
Access Control Lists
Row-Level Security
SSL/TLS
Auditing
Encryption
PCI Compliance
Upcoming Features in pg10
Desired Features
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3. Host Based Authentication
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4. HBA
Host Based Authentication
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5. HBA
Reloading authentication changes - pg_reload_conf()
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6. HBA
Monitoring authentication - tail_n_mail
[1] (from line 262,856)
2017-05-30 17:35:39 EDT [[local]] [13667]: [2-1] user=marion,db=postgres,
e=28P01 FATAL: password authentication failed for user "marion" e=28P01
DETAIL: Connection matched pg_hba.conf line 18: "local all all md5"
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7. HBA
Password file - .pgpass in $HOME
postgres@thinkpad ~ $ whoami
postgres
postgres@thinkpad ~ $ pwd
/home/postgres
postgres@thinkpad~ $ ls -l .pgpass
-rw------- 1 postgres postgres 29 Jul 9 11:23 .pgpass
postgres@thinkpad ~ $ cat .pgpass
*:*:*:postgres:HuyYheDAfqVq7
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8. Access Control Lists
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9. ACL
Access Control List
“list of permissions attached to an object. An ACL specifies which users or system processes are granted access to
objects, as well as what operations are allowed on given objects.”
GRANT - define access privileges
REVOKE - revoke access privileges
https://www.postgresql.org/docs/current/static/sql-grant.html
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10. ACL
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11. ACL
ACL commands are transactional in Postgres:
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12. ACL
Not so much in MySQL:
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13. ACL
Passwords In MySQL:
Passwords In Postgres:
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14. ACL
SHOW GRANTS in MySQL
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15. ACL
Roles and role membership
A role has privileges of all roles it is a member of
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16. ACL
SET DEFAULT PRIVILEGES
ALTER DEFAULT PRIVILEGES IN SCHEMA <schema_name> GRANT <privilege> ON TABLES TO <role>;
Only applies to objects created in future
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17. ACL
USAGE:
Roles must have usage on schema to access tables, functions
Usage on public schema granted by default to public role
Usage granted by default on all roles in MySQL
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18. ACL - USAGE Example
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19. Column Level ACLs
Grant privileges only on specific column(s)
NOTE: UPDATE privilege in practice requires SELECT as well
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20. Row-Level Security
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21. RLS
User-based or command-based row level access restrictions
Disabled by default
Exceptions - TRUNCATE, REFERENCES
Not a SQL Standard
Watch for performance improvements in pg10!
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22. RLS
When enabled, all traffic goes through policies
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23. RLS
Default Policy - all deny
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24. RLS
Does not apply to table owner unless forced
BYPASSRLS attribute
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25. RLS
In case of multiple policies, access is determined if any one or more of the policies
allow it (OR)
Referential integrity checks - covert channel leaks should be avoided
Race conditions - e.g. SELECT … FOR UPDATE
Solutions - SELECT … FOR SHARE; Exclusive locks on referenced
table
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26. SSL/TLS
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27. SSL/TLS
ssl = on # (change requires restart)
#ssl_ciphers = 'ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH' # allowed SSL ciphers
#ssl_prefer_server_ciphers = on # (change requires restart)
#ssl_ecdh_curve = 'prime256v1' # (change requires restart)
ssl_cert_file = '/etc/ssl/postgres/starry.io.crt' # (change requires restart)
ssl_key_file = '/etc/ssl/postgres/starry.io.key' # (change requires restart)
ssl_ca_file = '' # (change requires restart)
#ssl_crl_file = '' # (change requires restart)
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28. SSL/TLS
Requirement: OpenSSL
At build time: --with-openssl
Authentication without encryption overhead: NULL-SHA or NULL-MD5
Not recommended: less secure
Overhead is minimal compared to authentication overhead
Certificate file permissions must be 600
Restart required for certs change
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29. Event Triggers
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30. Event Triggers
Database wide DDL event capture
Useful for:
Auditing
Unwanted modification of data
Accidental data loss
Trigger-based replication
http://tapoueh.org/images/confs/Fosdem2013_Event_Triggers.pdf
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31. Event Triggers
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32. Event Triggers
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33. Event Triggers
Events:
ddl_command_start
ddl_command_end
sql_drop
table_rewrite in pg10!
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34. Auditing
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35. Auditing
Trigger based diff tracking
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36. Auditing
Hstore - delta capture
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37. Auditing
Delta function:
GIST and GIN index support for most operations
BTree and Hash index support useful for equivalence operations
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38. Auditing
pgAudit extension
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39. Auditing
PgAudit:
Shared_preload_libraries
Postgres development packages
Installation is a bit weird
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40. Encryption and PCI Compliance
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41. Encryption
pg_crypto extension - encrypts data
Encrypted backups
Postgres instance-level Encryption - 3rd party patch!
https://www.postgresql.org/message-
id/CA%2BCSw_tb3bk5i7if6inZFc3yyf%2B9HEVNTy51QFBoeUk7UE_V%3Dw@mail.gmail.com
http://www.cybertec.at/postgresql-instance-level-encryption/
SSL/TLS
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42. PCI Compliance
pg_stat_statements extension
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43. PCI Compliance
Monitors
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44. PCI Compliance
Monitored queries:
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45. PCI Compliance
pg_crypto
Key management
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46. Upcoming Features in PG10
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47. Upcoming
SSL - reload instead of a restart
SCRAM-SHA-256 authentication
Restrictive RLS Policies (AND)
New monitoring roles:
pg_monitor, pg_read_all_settings, pg_read_all_stats, and pg_stat_scan_tables
pg_hba_file_rules view
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48. Desired Features
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49. Desired
Data Redaction
Active Directory support
Oracle TDE - key management
http://www.oracle.com/technetwork/database/security/twp-transparent-data-encryption-bes-130696.pdf
SHOW GRANTS
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50. Thank you!
Questions?
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Twitter: @pallureshu
Email: payal@omniti.com