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gerrit.openbmc.org / openbmc / bmcweb / e7d1a1cfd59ed69cd11d1db76e2ae4a9a8771407
commite7d1a1cfd59ed69cd11d1db76e2ae4a9a8771407[log] [tgz]
authorEd Tanous <ed@tanous.net>Mon Sep 28 09:36:35 2020 -0700
committerEd Tanous <ed@tanous.net>Tue Sep 29 21:56:23 2020 +0000
tree6ca5197b77e42bfcfa0607567fcdd5a988a9bf3e
parent2c70f8004afdc27bd42968b8bf7480f2e534974c [diff]
Remove Server header from responses

The HTTP Server header allows potential attackers to fingerprint the BMC
much easier than they could otherwise, as the bmc essentially reports
its name to requests.

From section 7.4.2 of RFC7231:
"An origin server MAY generate a Server field in its responses."

This patchset moves bmcwebs position that it will not publish the server
field, as it does not contain useful data for the client.

It should be noted, it looks like OpenSSL was using the server name for
its connection ID.  It's not clear this is correct, or desired, but I've
inlined the old value (to avoid changing behavior).  Also, it was
missing a return code check, so I added it.

Tested:
Will verify in the webui (TBD)

Signed-off-by: Ed Tanous <ed@tanous.net>
Change-Id: Ieee6f15d8299e76517952514ff196008a563b63c
2 files changed
tree: 6ca5197b77e42bfcfa0607567fcdd5a988a9bf3e
  1. cmake/
  2. http/
  3. include/
  4. redfish-core/
  5. scripts/
  6. src/
  7. static/
  8. .clang-format
  9. .dockerignore
  10. .gitignore
  11. bmcweb.service.in
  12. bmcweb.socket
  13. build_x86.sh
  14. build_x86_docker.sh
  15. cmake-format.json
  16. CMakeLists.txt
  17. CMakeLists.txt.in
  18. COMMON_ERRORS.md
  19. config.h.in
  20. DEVELOPING.md
  21. Dockerfile
  22. Dockerfile.base
  23. JenkinsFile
  24. LICENCE
  25. MAINTAINERS
  26. pam-webserver
  27. README.md
  28. Redfish.md
README.md

OpenBMC webserver

This component attempts to be a "do everything" embedded webserver for openbmc.

Capabilities

At this time, the webserver implements a few interfaces:

  • Authentication middleware that supports cookie and token based authentication, as well as CSRF prevention backed by linux PAM authentication credentials.
  • An (incomplete) attempt at replicating phosphor-dbus-rest interfaces in C++. Right now, a few of the endpoint definitions work as expected, but there is still a lot of work to be done. The portions of the interface that are functional are designed to work correctly for phosphor-webui, but may not yet be complete.
  • Replication of the rest-dbus backend interfaces to allow bmc debug to logged in users.
  • An initial attempt at a read-only redfish interface. Currently the redfish interface targets ServiceRoot, SessionService, AccountService, Roles, and ManagersService. Some functionality here has been shimmed to make development possible. For example, there exists only a single user role.
  • SSL key generation at runtime. See the configuration section for details.
  • Static file hosting. Currently, static files are hosted from the fixed location at /usr/share/www. This is intended to allow loose coupling with yocto projects, and allow overriding static files at build time.
  • Dbus-monitor over websocket. A generic endpoint that allows UIs to open a websocket and register for notification of events to avoid polling in single page applications. (this interface may be modified in the future due to security concerns.

Configuration

BMCWeb is configured by setting -D flags that correspond to options in bmcweb/CMakeLists.txt and then compiling. For example, cmake -DBMCWEB_ENABLE_KVM=NO ... followed by make. The option names become C++ preprocessor symbols that control which code is compiled into the program.

When BMCWeb starts running, it reads persistent configuration data (such as UUID and session data) from a local file. If this is not usable, it generates a new configuration.

When BMCWeb SSL support is enabled and a usable certificate is not found, it will generate a self-sign a certificate before launching the server. The keys are generated by the secp384r1 algorithm. The certificate

  • is issued by C=US, O=OpenBMC, CN=testhost,
  • is valid for 10 years,
  • has a random serial number, and
  • is signed using the SHA-256 algorithm.