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- <span class="productname">PostgreSQL</span> offers encryption at several
- levels, and provides flexibility in protecting data from disclosure
- due to database server theft, unscrupulous administrators, and
- insecure networks. Encryption might also be required to secure
- sensitive data such as medical records or financial transactions.
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">Password Encryption</span></dt><dd><p>
- Database user passwords are stored as hashes (determined by the setting
- <a class="xref" href="runtime-config-connection.html#GUC-PASSWORD-ENCRYPTION">password_encryption</a>), so the administrator cannot
- determine the actual password assigned to the user. If SCRAM or MD5
- encryption is used for client authentication, the unencrypted password is
- never even temporarily present on the server because the client encrypts
- it before being sent across the network. SCRAM is preferred, because it
- is an Internet standard and is more secure than the PostgreSQL-specific
- MD5 authentication protocol.
- </p></dd><dt><span class="term">Encryption For Specific Columns</span></dt><dd><p>
- The <a class="xref" href="pgcrypto.html" title="F.25. pgcrypto">pgcrypto</a> module allows certain fields to be
- stored encrypted.
- This is useful if only some of the data is sensitive.
- The client supplies the decryption key and the data is decrypted
- on the server and then sent to the client.
- </p><p>
- The decrypted data and the decryption key are present on the
- server for a brief time while it is being decrypted and
- communicated between the client and server. This presents a brief
- moment where the data and keys can be intercepted by someone with
- complete access to the database server, such as the system
- administrator.
- </p></dd><dt><span class="term">Data Partition Encryption</span></dt><dd><p>
- Storage encryption can be performed at the file system level or the
- block level. Linux file system encryption options include eCryptfs
- and EncFS, while FreeBSD uses PEFS. Block level or full disk
- encryption options include dm-crypt + LUKS on Linux and GEOM
- modules geli and gbde on FreeBSD. Many other operating systems
- support this functionality, including Windows.
- </p><p>
- This mechanism prevents unencrypted data from being read from the
- drives if the drives or the entire computer is stolen. This does
- not protect against attacks while the file system is mounted,
- because when mounted, the operating system provides an unencrypted
- view of the data. However, to mount the file system, you need some
- way for the encryption key to be passed to the operating system,
- and sometimes the key is stored somewhere on the host that mounts
- the disk.
- </p></dd><dt><span class="term">Encrypting Data Across A Network</span></dt><dd><p>
- SSL connections encrypt all data sent across the network: the
- password, the queries, and the data returned. The
- <code class="filename">pg_hba.conf</code> file allows administrators to specify
- which hosts can use non-encrypted connections (<code class="literal">host</code>)
- and which require SSL-encrypted connections
- (<code class="literal">hostssl</code>). Also, clients can specify that they
- connect to servers only via SSL.
- </p><p>
- GSSAPI-encrypted connections encrypt all data sent across the network,
- including queries and data returned. (No password is sent across the
- network.) The <code class="filename">pg_hba.conf</code> file allows
- administrators to specify which hosts can use non-encrypted connections
- (<code class="literal">host</code>) and which require GSSAPI-encrypted connections
- (<code class="literal">hostgssenc</code>). Also, clients can specify that they
- connect to servers only on GSSAPI-encrypted connections
- (<code class="literal">gssencmode=require</code>).
- </p><p>
- <span class="application">Stunnel</span> or
- <span class="application">SSH</span> can also be used to encrypt
- transmissions.
- </p></dd><dt><span class="term">SSL Host Authentication</span></dt><dd><p>
- It is possible for both the client and server to provide SSL
- certificates to each other. It takes some extra configuration
- on each side, but this provides stronger verification of identity
- than the mere use of passwords. It prevents a computer from
- pretending to be the server just long enough to read the password
- sent by the client. It also helps prevent <span class="quote">“<span class="quote">man in the middle</span>”</span>
- attacks where a computer between the client and server pretends to
- be the server and reads and passes all data between the client and
- server.
- </p></dd><dt><span class="term">Client-Side Encryption</span></dt><dd><p>
- If the system administrator for the server's machine cannot be trusted,
- it is necessary
- for the client to encrypt the data; this way, unencrypted data
- never appears on the database server. Data is encrypted on the
- client before being sent to the server, and database results have
- to be decrypted on the client before being used.
- </p></dd></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="preventing-server-spoofing.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="runtime.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ssl-tcp.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">18.7. Preventing Server Spoofing </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 18.9. Secure TCP/IP Connections with SSL</td></tr></table></div></body></html>
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