GT 5.0.4: GSI C Admin Guide

Introduction

This guide contains advanced configuration information for system administrators working with GSI C. It provides references to information on procedures typically performed by system administrators, including installation, configuring, deploying, and testing the installation.

[Important]Important

The security tools are installed as part of the Globus Toolkit installation process. For instructions on basic installation of the Globus Toolkit, see the Installing GT 5.0.4.

Authentication in the Globus Toolkit is based on X.509 certificates. This document describes the configuration steps required to:

  • determine whether or not to trust certificates issued by a particular Certificate Authority (CA),
  • provide appropriate default values for use by the grid-cert-request command, which is used to generate certificates,
  • request service certificates, used by services to authenticate themselves to users, and
  • specify identity mapping information.

Chapter 1. Configuring Certificates

This section describes the configuration steps required to:

  • determine whether or not to trust certificates issued by a particular Certificate Authority (CA),
  • provide appropriate default values for use by the grid-cert-request command, which is used to generate certificates,
  • request service certificates, used by services to authenticate themselves to users, and
  • specify identity mapping information.

In general, Globus tools will look for a configuration file in a user-specific location first, and in a system-wide location if no user-specific file was found. The configuration commands described here may be run by administrators to create system-wide defaults and by individuals to override those defaults.

1. Configuring Globus to Trust a Particular Certificate Authority

1.1. Trusted certificates directory

The Globus tools will trust certificates issued by a CA if (and only if) it can find information about the CA in the trusted certificates directory.

The trusted certificates directory is located as described below and exists either on a per-machine or on a per-installation basis.

X509_CERT_DIR is the environment variable used to specify the path to the trusted certificates directory. This directory contains information about which CAs are trusted (including the CA certificates themselves) and, in some cases, configuration information used by grid-cert-request to formulate certificate requests. The location of the trusted certificates directory is looked for in the following order:

  1. value of the X509_CERT_DIR environment variable
  2. $HOME/.globus/certificates
  3. /etc/grid-security/certificates exists
  4. $GLOBUS_LOCATION/share/certificates

1.2. Trusted certificates files

The following two files must exist in the directory for each trusted CA:

Table 1.1. CA files

cert_hash.0The trusted CA Certificate.
cert_hash.signing_policyA configuration file defining the distinguished names of certificates signed by the CA.

Non-WS Globus components will honor a certificate only if:

  • its CA certificate exists (with the appropriate name) in the TRUSTED_CA directory, and
  • the certificate's distinguished name matches the pattern described in the signing policy file.

1.3. Hash of the CA certificate

The cert_hash that appears in the file names above is the hash of the CA certificate, which can be found by running the command:

$GLOBUS_LOCATION/bin/openssl x509 -hash -noout < ca_certificate

1.4. Creating a signing policy by hand

Some CAs provide tools to install their CA certificates and signing policy files into the trusted certificates directory. You can, however, create a signing policy file by hand; the signing policy file has the following format:

access_id_CA X509 'CA Distinguished Name'
pos_rights globus CA:sign
cond_subjects globus '"Distinguished Name Pattern"'

In the above, the CA Distinguished Name is the subject name of the CA certificate, and the Distinguished Name Pattern is a string used to match the distinguished names of certificates granted by the CA.

Some very simple wildcard matching is done: if the Distinguished Name Pattern ends with a '*', then any distinguished name that matches the part of the CA subject name before the '*' is considered a match.

Note: the cond_subjects line may contain a space-separated list of distinguished name patterns.

1.5. Repository of CAs

A repository of CA certificates that are widely used in academic and research settings can be found here.

2. Configuring Globus to Create Appropriate Certificate Requests

The grid-cert-request command, which is used to create certificates, uses the following configuration files:

Table 1.2. Certificate request configuration files

globus-user-ssl.confDefines the distinguished name to use for a user's certificate request. The format is described here.
globus-host-ssl.confDefines the distinguished name for a host (or service) certificate request. The format is described here.
grid-security.confA base configuration file that contains the name and email address for the CA.
directionsAn optional file that may contain directions on using the CA.

Many CAs provide tools to install configuration files with the following names in the Trusted Certificates directory:

  • globus-user-ssl.conf.cert_hash

  • globus-host-ssl.conf.cert_hash

  • grid_security.conf.cert_hash

  • directions.cert_hash

2.1. Creating a certificate request for a specific CA

The command:

grid-cert-request -ca cert_hash

will create a certificate request based on the specified CA's configuration files.

2.2. Listing available CAs

The command:

grid-cert-request -ca

will list the available CAs and let the user choose which one to create a request for.

2.3. Specifying a default CA for certificate requests

The default CA is the CA that will be used for certificate requests if grid-cert-request is invoked without the -ca flag.

You can specify a default CA by invoking the grid-default-ca command (follow the link for examples of using the command).

2.4. directions file

The directions file may contain specific directions on how to use the CA. There are three types of printed messages:

  • REQUEST HEADER, printed to a certificate request file,
  • USER INSTRUCTIONS, printed on the screen when one requests a user certificate,
  • NONUSER INSTRUCTIONS, printed on the screen when one requests a certificate for a service.

Each message is delimited from others with lines ----- BEGIN message type TEXT ----- and ----- END message type TEXT -----. For example, the directions file would contain the following lines:

----- BEGIN REQUEST HEADER TEXT -----
This is a Certificate Request file

It should be mailed to ${GSI_CA_EMAIL_ADDR}
----- END REQUEST HEADER TEXT -----

If this file does not exist, the default messages are printed.

3. Requesting Service Certificates

Different CAs use different mechanisms for issuing end-user certificates; some use mechanisms that are entirely web-based, while others require you to generate a certificate request and send it to the CA. If you need to create a certificate request for a service certificate, you can do so by running:

grid-cert-request -host hostname -service service_name

where hostname is the fully-qualified name of the host on which the service will be running, and service_name is the name of the service. This will create the following three files:

Table 1.3. Certificate request files

GRID_SECURITY/service_name/service_namecert.pemAn empty file. When you receive your actual service certificate from your CA, you should place it in this file.
GRID_SECURITY/service_name/service_namecert_request.pemThe certificate request, which you should send to your CA.
GRID_SECURITY/service_name/service_namekey.pemThe private key associated with your certificate request, encrypted with the pass phrase that you entered when prompted by grid-cert-request.

The grid-cert-request command recognizes several other useful options; you can list these with:

grid-cert-request -help

4. Configuring Credential Mappings

Several Globus services map certificates to local unix usernames to be used with unix services. The default implementation uses a gridmap file to map the distinguished name of the identity of the client's certificate to a local login name. Administrators can modify the contents of the gridmap file to control what certificate identities are allowed to access Globus services, as well as configure, via an environment variable, what gridmap file a particular service uses.

In addition to the identity-based mapping done via the gridmap file, administrators can configure Globus services to to use arbitrary mapping functions. These may use other criteria, such as SAML assertions, to map a certificate to a local account, or may map certificates to temporary accounts. Administrators can install different mapping implementations and configure services to use them by creating appropriate configuration files and setting environment variables.

4.1. Configuring Identity Mappings Using gridmap Files

Gridmap files contain a database of entries mapping distinguished names to local user names. These may be manipulated by using the following tools.

4.1.1. Adding an entry to a gridmap file

To add an entry to the gridmap file, run:

$GLOBUS_LOCATION/sbin/grid-mapfile-add-entry \
        -dn "Distinguished Name" \
        -ln local_name

4.1.2. Deleting an entry from a gridmap file

To delete an entry from the gridmap file, run:

$GLOBUS_LOCATION/sbin/grid-mapfile-delete-entry \
        -dn "Distinguished Name" \
        -ln local_name

4.1.3. Checking consistency of a gridmap file

To check the consistency of the gridmap file, run

$GLOBUS_LOCATION/sbin/grid-mapfile-check-consistency

4.1.4. Configuring per-service gridmap files

To configure a service to use a particular gridmap file, set the GRIDMAP variable in the service's environment to the path of the gridmap file. In this way, you can grant different access rights to different certificate identities on a per-service basis by setting the GRIDMAP variable in different service environments.

You can use tools described above to operate on different gridmap files by either setting the GRIDMAP environment variable prior to invoking them, or by using the -mapfile command-line option.

For reference, the GSI C code looks for the gridmap in these locations:

Table 1.4. Gridmap File Location Algorithm

Locationnotes

GRIDMAP environment variable

/etc/grid-security/grid-mapfile

Only for services running as root.

HOME.gridmap

Only for services not running as root.

4.1.5. Gridmap formats

A gridmap line of the form:

"Distinguished Name" local_name

maps the distinguished name Distinguished Name to the local name local_name.

A gridmap line of the form:

"Distinguished Name" local_name1,local_name2

maps Distinguished Name to both local_name1 and local_name2; any number of local user names may occur in the comma-separated local name list.

For more detailed information about the gridmap file see the file description and grammars on dev.globus.org.

4.2. Configuring Alternate Credential Mappings

To use an alternative credential mapping, you create a gsi-authz.conf file containing information about how the mapping functions are called from the authorization library.

To configure a per-service authorization configuration file, set the GSI_AUTHZ_CONF variable to the path to the configuration file in the environment of the service.

For reference, the GSI C code looks for the authorization configuration file in these locations (in the given order):

Table 1.5. Authorization Configuration File Locations

Location

GSI_AUTHZ_CONF environment variable

/etc/grid-security/gsi-authz.conf

GLOBUS_LOCATION/etc/gsi-authz.conf

HOME/.gsi-authz.conf

4.2.1. Callout File Format

The authorization file defines a set of callouts, one per line. Each callout is defined by an abstract type, library, and symbol separated by whitespace. Comments begin with the # character and continue to the end of line.

Table 1.6. Authorization Configuration File Locations

FieldMeaning

abstract type

Type of the callout: globus_mapping is used for credential mapping callouts

library

Path to the shared object containing the callout implementation. The library name may be a literal filename, or a partial filename to which the compilation flavor of the service is appended to the filename before its extension.

symbol

The exported symbol containing the entry point to the callout implementation.

Here is a sample gsi-authz.conf file that configures a globus_mapping callout to use the globus_gridmap_callout function in the /usr/local/globus/lib/libglobus_gridmap_callout_gcc32dbg shared object:

# abstract-type     library                                            symbol

globus_mapping      /opt/globus/lib/libglobus_gridmap_callout_gcc32dbg globus_gridmap_callout

5. GSI File Permissions Requirements

Chapter 2. Testing

There is no content available at this time.

Chapter 3. Security Considerations

1. Security considerations for GSI C

  • During host authorization, the toolkit treats host names of the form "hostname-ANYTHING.edu" as equivalent to "hostname.edu". This means that if a service was set up to do host authorization and hence accept the certificate "hostname.edu", it would also accept certificates with DNs "hostname-ANYTHING.edu".

    The feature is in place to allow a multi-homed host following a "hostname-interface" naming convention, to have a single host certificate. For example, host "grid.test.edu" would also accept the likes of "grid-1.test.edu" or "grid-foo.test.edu".

    [Note]Note

    The string ANYTHING matches only the name of the host and not domain components. This means that "hostname.edu" will not match "hostname-foo.sub.edu", but will match "host-foo.edu".

    [Note]Note

    If a host was set up to accept "hostname-1.edu", it will not accept "hostname-ANYTHING.edu" but will accept "hostname.edu". That is, only one of the names being compared may contain the hyphen character in the host name.

    A bug has been opened to see if this feature needs to be modified.

    In GT 5.0.4, it is possible to disable this behavior, by setting the enviornment variable GLOBUS_GSSAPI_NAME_COMPATIBILITY to STRICT_RFC2818.

Chapter 4. Debugging

Table of Contents

1. Logging

1. Logging

N/A

Chapter 5. Troubleshooting

For a list of common errors in GT, see Error Codes.

1. Credential Troubleshooting

1.1. Credential Errors

The following are some common problems that may cause clients or servers to report that credentials are invalid:

For a list of common errors in GT, see Error Codes.

Table 5.1. Credential Errors

Error CodeDefinitionPossible Solutions
Your proxy credential may have expiredYour proxy credential may have expired.Use grid-proxy-info to check whether the proxy credential has actually expired. If it has, generate a new proxy with grid-proxy-init.
The system clock on either the local or remote system is wrong.This may cause the server or client to conclude that a credential has expired.Check the system clocks on the local and remote system.
Your end-user certificate may have expiredYour end-user certificate may have expiredUse grid-cert-info to check your certificate's expiration date. If it has expired, follow your CA's procedures to get a new one.
The permissions may be wrong on your proxy fileIf the permissions on your proxy file are too lax (for example, if others can read your proxy file), Globus Toolkit clients will not use that file to authenticate.You can "fix" this problem by changing the permissions on the file or by destroying it (with grid-proxy-destroy) and creating a new one (with grid-proxy-init).

Important: However, it is still possible that someone else has made a copy of that file during the time that the permissions were wrong. In that case, they will be able to impersonate you until the proxy file expires or your permissions or end-user certificate are revoked, whichever happens first.

The permissions may be wrong on your private key fileIf the permissions on your end user certificate private key file are too lax (for example, if others can read the file), grid-proxy-init will refuse to create a proxy certificate.You can "fix" this by changing the permissions on the private key file.

Important: However, you will still have a much more serious problem: it is possible that someone has made a copy of your private key file. Although this file is encrypted, it is possible that someone will be able to decrypt the private key, at which point they will be able to impersonate you as long as your end user certificate is valid. You should contact your CA to have your end-user certificate revoked and get a new one.

The remote system may not trust your CAThe remote system may not trust your CAVerify that the remote system is configured to trust the CA that issued your end-entity certificate. See Installing GT 5.0.4 for details.
You may not trust the remote system's CAYou may not trust the remote system's CAVerify that your system is configured to trust the remote CA (or that your environment is set up to trust the remote CA). See Installing GT 5.0.4 for details.
There may be something wrong with the remote service's credentialsThere may be something wrong with the remote service's credentialsIt is sometimes difficult to distinguish between errors reported by the remote service regarding your credentials and errors reported by the client interface regarding the remote service's credentials. If you cannot find anything wrong with your credentials, check for the same conditions on the remote system (or ask a remote administrator to do so) .

1.2. Some tools to validate certificate setup

1.2.1. grid-cert-diagnostics

The grid-cert-diagnostics program checks prints diagnostics about the user's certificates, and host security environment.

% grid-cert-diagnostics -p

1.2.2. Check that the user certificate is valid

openssl verify -CApath /etc/grid-security/certificates
  -purpose sslclient ~/.globus/usercert.pem

1.2.3. Connect to the server using s_client

openssl s_client -ssl3 -cert ~/.globus/usercert.pem -key 
  ~/.globus/userkey.pem -CApath /etc/grid-security/certificates 
  -connect <host:port>

Here <host:port> denotes the server and port you connect to.

If it prints an error and puts you back at the command prompt, then it typically means that the server has closed the connection, i.e. that the server was not happy with the client's certificate and verification. Check the SSL log on the server.

If the command "hangs" then it has actually opened a telnet style (but secure) socket, and you can "talk" to the server.

You should be able to scroll up and see the subject names of the server's verification chain:

depth=2 /DC=net/DC=ES/O=ESnet/OU=Certificate Authorities/CN=ESnet Root CA 1
verify return:1
depth=1 /DC=org/DC=DOEGrids/OU=Certificate Authorities/CN=DOEGrids CA 1
verify return:1
depth=0 /DC=org/DC=doegrids/OU=Services/CN=wiggum.mcs.anl.gov
verify return:1
    

In this case, there were no errors. Errors would give you an extra line next to the subject name of the certificate that caused the error.

1.2.4. Check that the server certificate is valid

Requires root login on server:

    openssl verify -CApath /etc/grid-security/certificates -purpose sslserver 
     /etc/grid-security/hostcert.pem

2. Grid map Troubleshooting

2.1. Grid map errors

The following are some common problems that may cause clients or servers to report that user are not authorized:

For a list of common errors in GT, see Error Codes.

Table 5.2. Gridmap Errors

Error CodeDefinitionPossible Solutions
The content of the grid map file does not conform to the expected formatThe content of the grid map file does not conform to the expected format Run grid-mapfile-check-consistency to make sure that your gridmap file conforms to the expected format.
The grid map file does not contain a entry for your DNThe grid map file does not contain a entry for your DN Use grid-mapfile-add-entry to add the relevant entry.

Glossary

C

Certificate Authority ( CA )

An entity that issues certificates.

CA Certificate

The CA's certificate. This certificate is used to verify signature on certificates issued by the CA. GSI typically stores a given CA certificate in /etc/grid-security/certificates/<hash>.0, where <hash> is the hash code of the CA identity.

CA Signing Policy

The CA signing policy is used to place constraints on the information you trust a given CA to bind to public keys. Specifically it constrains the identities a CA is trusted to assert in a certificate. In GSI the signing policy for a given CA can typically be found in /etc/grid-security/certificates/<hash>.signing_policy, where <hash> is the hash code of the CA identity.

E

End Entity Certificate (EEC)

A certificate belonging to a non-CA entity, e.g. you, me or the computer on your desk.

G

GAA configuration file

A file that configures the Generic Authorization and Access control GAA libraries. When using GSI, this file is typically found in /etc/grid-security/gsi-gaa.conf.

grid map file

A file containing entries mapping certificate subjects to local user names. This file can also serve as a access control list for GSI enabled services and is typically found in /etc/grid-security/grid-mapfile. For more information see the Gridmap section here.

GSI authorization callout configuration file

A file that configures authorization callouts to be used for mapping and authorization in GSI enabled services. When using GSI this file is typically found in /etc/grid-security/gsi-authz.conf.

H

host certificate

An EEC belonging to a host. When using GSI this certificate is typically stored in /etc/grid-security/hostcert.pem. For more information on possible host certificate locations see the GSI C Developer's Guide.

P

private key

The private part of a key pair. Depending on the type of certificate the key corresponds to it may typically be found in $HOME/.globus/userkey.pem (for user certificates), /etc/grid-security/hostkey.pem (for host certificates) or /etc/grid-security/<service>/<service>key.pem (for service certificates).

For more information on possible private key locations see this.

proxy credentials

The combination of a proxy certificate and its corresponding private key. GSI typically stores proxy credentials in /tmp/x509up_u<uid> , where <uid> is the user id of the proxy owner.

S

scheduler

Term used to describe a job scheduler mechanism to which GRAM interfaces. It is a networked system for submitting, controlling, and monitoring the workload of batch jobs in one or more computers. The jobs or tasks are scheduled for execution at a time chosen by the subsystem according to an available policy and availability of resources. Popular job schedulers include Portable Batch System (PBS), Platform LSF, and IBM LoadLeveler.

service certificate

A EEC for a specific service (e.g. FTP or LDAP). When using GSI this certificate is typically stored in /etc/grid-security/<service>/<service>cert.pem. For more information on possible service certificate locations, see this.

U

user certificate

A EEC belonging to a user. When using GSI, this certificate is typically stored in $HOME/.globus/usercert.pem. For more information on possible user certificate locations, see this.