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applied, deadlock detection and statement_timeout now works. The file timer.c goes into src/backend/port/win32/. The patch also removes two lines of "printf debugging" accidentally left in pqsignal.h, in the console control handler. Magnus Hagander |
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auth.c | ||
be-fsstubs.c | ||
be-secure.c | ||
crypt.c | ||
hba.c | ||
ip.c | ||
Makefile | ||
md5.c | ||
pg_hba.conf.sample | ||
pg_ident.conf.sample | ||
pqcomm.c | ||
pqformat.c | ||
pqsignal.c | ||
README.SSL |
>From the servers perspective: Receives StartupPacket | | (Is SSL_NEGOTIATE_CODE?) ----------- Normal startup | No | | Yes | | (Server compiled with USE_SSL?) ------- Send 'N' | No | | | | Yes Normal startup | | Send 'S' | | Establish SSL | | Normal startup >From the clients perspective (v6.6 client _with_ SSL): Connect | | Send packet with SSL_NEGOTIATE_CODE | | Receive single char ------- 'S' -------- Establish SSL | | | '<else>' | | Normal startup | | Is it 'E' for error ------------------- Retry connection | Yes without SSL | No | Is it 'N' for normal ------------------- Normal startup | Yes | Fail with unknown --------------------------------------------------------------------------- COMMENTS FROM BEAR GILES On a related note, I had mentioned this before but it's a subtle point and I'm sure that it's slipped everyone's mind... - if you need to have confidence in the identity of the database server, e.g., you're storing sensitive information and you absolutely must prevent any "man in the middle" attacks, use the SSL code I provided with server-side certs. To many users, the key issue is not whether the data is encrypted, it's whether the other party can be trusted to be who they claim to be. - if you just need confidentiality, but you don't need to verify the identity of the database server (e.g., because you trust the IP address, but worry about packet sniffers), SSH tunnels are much easier to set up and maintain than the embedded SSL code. You can set up the database server so it doesn't require a certificate (hell, you can hard code a fallback certificate into the server!), *but that violates the common practice of SSL-enabled servers.* I cannot overemphasize this - every other SSL-enabled server requires a certificate, and most provide installation scripts to create a "snake oil" temporary certificate. I can't think of any server (apache+mod_ssl, courier-imap, postfix(+tls), etc.) that uses anonymous servers. - if you don't need confidentiality, e.g., you're on a trusted network segment, then use direct access to the server port. --------------------------------------------------------------------------- EMAIL ABOUT DOCUMENTATION From: Bear Giles <bgiles@coyotesong.com> Subject: [HACKERS] 2nd cut at SSL documentation To: pgsql-hackers@postgresql.org Date: Tue, 21 May 2002 14:27:00 -0600 (MDT) A second cut at SSL documentation.... SSL Support in PostgreSQL ========================= Who needs it? ============= The sites that require SSL fall into one (or more) of several broad categories. *) They have insecure networks. Examples of insecure networks are anyone in a "corporate hotel," any network with 802.11b wireless access points (WAP) (in 2002, this protocol has many well-known security weaknesses and even 'gold' connections can be broken within 8 hours), or anyone accessing their database over the internet. These sites need a Virtual Private Network (VPN), and either SSH tunnels or direct SSL connections can be used. *) They are storing extremely sensitive information. An example of extremely sensitive information is logs from network intrusion detection systems. This information *must* be fully encrypted between front- and back-end since an attacker is presumably sniffing all traffic within the VPN, and if they learn that you know what they are doing they may attempt to cover their tracks with a quick 'rm -rf /' and 'dropdb' In the extreme case, the contents of the database itself may be encrypted with either the crypt package (which provides symmetrical encryption of the records) or the PKIX package (which provides public-key encryption of the records). *) They are storing information which is considered confidential by custom, law or regulation. This includes all records held by your doctor, lawyer, accountant, etc. In these cases, the motivation for using encryption is not a conscious evaulation of risk, but the fear of liability for 'failure to perform due diligence' if encryption is available but unused and an attacker gains unauthorized access to the harm of others. *) They have 'road warriors.' This includes all sites where people need to have direct access to the database (not through a proxy such as a secure web page) from changing remote addresses. Client certificates provide a clean way to grant this access without opening up the database to the world. Who does not need it? --------------------- It's at least as important to know who does not need SSL as it is to know who does. Sites that do not need SSL fall into several broad categories. *) Access is limited to the Unix socket. *) Access is limited to a physically secure network. "Physically secure" networks are common in the clusters and colocation sites - all database traffic is restricted to dedicated NIC cards and hubs, and all servers and cabling are maintained in locked cabinets. Using SSH/OpenSSH as a Virtual Private Network (VPN) ==================================================== SSH and OpenSSH can be used to construct a Virtual Private Network (VPN) to provide confidentiality of PostgreSQL communications. These tunnels are widely available and fairly well understood, but do not provide any application-level authentication information. To set up a SSH/OpenSSH tunnel, a shell account for each user should be set up on the database server. It is acceptable for the shell program to be bogus (e.g., /bin/false), if the tunnel is set up in to avoid launching a remote shell. On each client system the $HOME/.ssh/config file should contain an additional line similiar to LocalForward 5555 psql.example.com:5432 (replacing psql.example.com with the name of your database server). By putting this line in the configuration file, instead of specifying it on the command line, the tunnel will be created whenever a connection is made to the remote system. The psql(1) client (or any client) should be wrapped with a script that establishes an SSH tunnel when the program is launched: #!/bin/sh HOST=psql.example.com IDENTITY=$HOME/.ssh/identity.psql /usr/bin/ssh -1 -i $IDENTITY -n $HOST 'sleep 60' & \ /usr/bin/psql -h $HOST -p 5555 $1 Alternately, the system could run a daemon that establishes and maintains the tunnel. This is preferrable when multiple users need to establish similar tunnels to the same remote site. Unfortunately, there are many potential drawbacks to SSL tunnels: *) the SSH implementation or protocol may be flawed. Serious problems are discovered about once every 18- to 24- months. *) the systems may be misconfigured by accident. *) the database server must provide shell accounts for all users needing access. This can be a chore to maintain, esp. in if all other user access should be denied. *) neither the front- or back-end can determine the level of encryption provided by the SSH tunnel - or even whether an SSH tunnel is in use. This prevents security-aware clients from refusing any connection with unacceptly weak encryption. *) neither the front- or back-end can get any authentication information pertaining to the SSH tunnel. Bottom line: if you just need a VPN, SSH tunnels are a good solution. But if you explicitly need a secure connection they're inadequate. Direct SSL Support ================== Insecure Channel: ANONYMOUS DH Server ------------------------------------- "ANONYMOUS DH" is the most basic SSL implementation. It does not require a server certificate, but it is vulnerable to "man-in-the-middle" attacks. The PostgreSQL backend does not support ANONYMOUS DH sessions. Secure Channel: Server Authentication ------------------------------------- Server Authentication requires that the server authenticate itself to clients (via certificates), but clients can remain anonymous. This protects clients from "man-in-the-middle" attacks (where a bogus server either captures all data or provides bogus data), but does not protect the server from bad data injected by false clients. The community has established a set of criteria for secure communications: *) the server must provide a certificate identifying itself via its own fully qualified domain name (FDQN) in the certificate's Common Name (CN) field. *) the FQDN in the server certificate must resolve to the IP address used in the connection. *) the certificate must be valid. (The current date must be no earlier than the 'notBefore' date, and no later than the 'notAfter' date.) *) the server certificate must be signed by an issuer certificate known to the clients. This issuer can be a known public CA (e.g., Verisign), a locally generated root cert installed with the database client, or the self-signed server cert installed with the database client. Another approach (used by SSH and most web clients) is for the client to prompt the user whether to accept a new root cert when it is encountered for the first time. psql(1) does not currently support this mechanism. *) the client *should* check the issuer's Certificate Revocation List (CRL) to verify that the server's certificate hasn't been revoked for some reason, but in practice this step is often skipped. *) the server private key must be owned by the database process and not world-accessible. It is recommended that the server key be encrypted, but it is not required if necessary for the operation of the system. (Primarily to allow automatic restarts after the system is rebooted.) The 'mkcert.sh' script can be used to generate and install suitable certificates Finally, the client library can have one or more trusted root certificates compiled into it. This allows clients to verify certificates without the need for local copies. To do this, the source file src/interfaces/libpq/fe-ssl.c must be edited and the database recompiled. Secure Channel: Mutual Authentication ------------------------------------- Mutual authentication requires that servers and clients each authenticate to the other. This protects the server from false clients in addition to protecting the clients from false servers. The community has established a set of criteria for client authentication similar to the list above. *) the client must provide a certificate identifying itself. The certificate's Common Name (CN) field should contain the client's usual name. *) the client certificate must be signed by a certificate known to the server. If a local root cert was used to sign the server's cert, the client certs can be signed by the issuer. *) the certificate must be valid. (The current date must be no earlier than the 'notBefore' date, and no later than the 'notAfter' date.) *) the server *should* check the issuer's Certificate Revocation List (CRL) to verify that the clients's certificate hasn't been revoked for some reason, but in practice this step is often skipped. *) the client's private key must be owned by the client process and not world-accessible. It is recommended that the client key be encrypted, but because of technical reasons in the architecture of the client library this is not yet supported. PostgreSQL can generate client certificates via a four-step process. 1. The "client.conf" file must be copied from the server. Certificates can be highly localizable, and this file contains information that will be needed later. The client.conf file is normally installed in /etc/postgresql/root.crt. The client should also copy the server's root.crt file to $HOME/.postgresql/root.crt. 2. If the user has the OpenSSL applications installed, they can run pgkeygen.sh. (An equivalent compiled program will be available in the future.) They should provide a copy of the $HOME/.postgresql/postgresql.pem file to their DBA. 3. The DBA should sign this file the OpenSSL applications: $ openssl ca -config root.conf -ss_cert .... and return the signed cert (postgresql.crt) to the user. 4. The user should install this file in $HOME/.postgresql/postgresql.crt. The server will log every time a client certificate has been used, but there is not yet a mechanism provided for using client certificates as PostgreSQL authentication at the application level. ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html ------------------------------------------------------------------------------ Date: Tue, 21 May 2002 19:50:38 -0400 From: Neil Conway <nconway@klamath.dyndns.org> To: "Bear Giles" <bgiles@coyotesong.com> cc: pgsql-hackers@postgresql.org Subject: Re: [HACKERS] 2nd cut at SSL documentation On Tue, 21 May 2002 14:27:00 -0600 (MDT) "Bear Giles" <bgiles@coyotesong.com> wrote: > A second cut at SSL documentation.... I've pointed out some minor things I noticed while reading through. Yeah, I was bored :-) > The sites that require SSL fall into one (or more) of several broad > categories. > > *) They have insecure networks. > > Examples of insecure networks are anyone in a "corporate hotel," What's a corporate hotel? > *) They have 'road warriors.' This section title sounds confusingly similar to the 1st item. Perhaps "They need to authentication clients securely" or something similar? The need to use client certificates does not apply only to "road warriors" -- I've seen situations where client-certs are used for clients to connecting to a server over a LAN. > *) Access is limited to the Unix socket. "the" sounds wrong, there's more than just 1 :-) > *) Access is limited to a physically secure network. > > "Physically secure" networks are common in the clusters and > colocation sites - all database traffic is restricted to dedicated > NIC cards and hubs, and all servers and cabling are maintained in > locked cabinets. Perhaps add a note on the performance hit here? > Using SSH/OpenSSH as a Virtual Private Network (VPN) I'm unsure why you're bothering to differentiate between SSH and OpenSSH. > SSH and OpenSSH can be used to construct a Virtual Private Network > (VPN) No need to include the abbreviation for VPN here, you've explained the term before. > to provide confidentiality of PostgreSQL communications. > These tunnels are widely available and fairly well understood, but > do not provide any application-level authentication information. You might want to clarify what "application-level authentication information" means, or else leave out all discussion of drawbacks until later. > To set up a SSH/OpenSSH tunnel, a shell account for each > user should be set up on the database server. It is acceptable > for the shell program to be bogus (e.g., /bin/false), if the > tunnel is set up in to avoid launching a remote shell. > > On each client system the $HOME/.ssh/config file should contain > an additional line similiar to > > LocalForward 5555 psql.example.com:5432 "pgsql.example.com" strikes me as a better example hostname (I always think that psql == DB client, postgres/postmaster/pgsql == DB server). > Unfortunately, there are many potential drawbacks to SSL tunnels: I think you mean SSH tunnels. > *) the SSH implementation or protocol may be flawed. Serious problems > are discovered about once every 18- to 24- months. I'd be skeptical whether this weakness if specific to SSH -- there can be security holes in OpenSSL, the SSL protocol, the SSL implementation in PostgreSQL, etc. > *) the database server must provide shell accounts for all users > needing access. This can be a chore to maintain, esp. in if Remove the "in". > *) neither the front- or back-end can determine the level of > encryption provided by the SSH tunnel - or even whether an > SSH tunnel is in use. This prevents security-aware clients > from refusing any connection with unacceptly weak encryption. Spelling error. > Finally, the client library can have one or more trusted root > certificates compiled into it. This allows clients to verify > certificates without the need for local copies. To do this, > the source file src/interfaces/libpq/fe-ssl.c must be edited > and the database recompiled. "PostgreSQL" recompiled -- database versus RDBMS can be ambiguous. > Mutual authentication requires that servers and clients each > authenticate to the other. This protects the server from > false clients in addition to protecting the clients from false > servers. "false" in this context? Cheers, Neil -- Neil Conway <neilconway@rogers.com>