Hacking NSS

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Using NSS from Pluto

use lsw_nss_error*() to report errors

It includes both the error symbol name and the error message (the former is really useful when reading the code^D^D^D^D documentation when tracking down why the error was returned).

Building Libreswan using custom NSS RPMs

Building NSS RPMs on the guest

Here, we use the build machine (it has lots of memory and network access) and the 9p mounted directory /pool (aka $(KVM_POOLDIR), but /testing and /root should also work). Just remember that any changes to build aren't permanent, we'll get to that later.

Prepare the machine (xmlto is hacked so that it doesn't try to preserve permissions when copying files within the 9p file system):

$ ./kvm sh build
build# dnf install -y fedpkg
build# dnf builddep -y nss
build# sed -i -e 's/ -p / /' \
   /usr/share/xmlto/format/docbook/man \

Get the sources (drop --branch f32 if trying to build rawhide):

build# cd /pool
build# cat /etc/fedora-release
Fedora release 32 (Thirty Two)
build# fedpkg clone --branch f32 --anonymous nss
build# cd nss

hack nss.specso that it has a unique suffix, and check result:

build# sed -i -e '/global baserelease/ s/$/lsw/' nss.spec
build# sed -i -e '/global nspr_release/ s/$/lsw/' nss.spec
build# fedpkg verrel

if fedpkg verrel fails more hacks may be required

hobble running tests during the build (optional):

build# sed -i -e 's/bcond_without tests/bcond_with tests/' nss.spec

finally build:

build# fedpkg local --without tests:


build# fedpkg prep --without tests
build# fedpkg compile --short-circuit --without tests

the RPMs are under x86_64.

Building NSS RPMs on the host

Hmm, something goes here!

fedpkg mock-config
fedpkg mockbuild

Installing the NSS RPMs (and making them stick)

The NSS RPMs can either be installed manually on build (which means they only stick around until ./kvm uninstall), or they can be made more permenant by installing them into the base domain.

To install the RPMs on the base domain, add the following lines to Makefile.inc.local:

# Prepend the directory containing the RPMs, include /
KVM_NSS_RPMDIR = /pool/nss/x86_64/
KVM_NSPR_RPMDIR = /pool/nss/x86_64/
# Append the actual RPM version
KVM_NSS_VERSION = -3.71.0-1lsw.fc32.x86_64.rpm
KVM_NSPR_VERSION = -4.32.0-3lsw.fc32.x86_64.rpm

and then upgrade the base domain:

$ ./kvm upgrade
 Upgrading        : nss-util-3.63.0-1_lsw.fc32.x86_64                     1/20 

finally, confirm:

$ ./kvm install
$ ./kvm sh east
east# rpm -q nss

If needed, the the customized domains can be reverted. In Makefile.inc.local, comment out the lines added above, and then run:

$ ./kvm downgrade
$ ./kvm upgrade
 Installing       : nss-util-3.63.0-1.fc32.x86_64                       13/330 

Distributing Custom NSS RPMs

Tar up both the .rpm and .srpm files into a single archive and make that available. That way, who ever downloads the archive always gets the source code.

Building a Newer Version Of NSS

Typically this isn't needed as Fedora will back-port the latest release of NSS to all supported releases, and even when the release isn't up-to-date, the code hasn't changed much so patches still work.

However, here are some notes on the problems encountered when building fedpkg co rawhide on f32:

crypto-policies was too old

  • the dependency can be broken by editing the Requires: line, however ...
  • the test ikev2-x509-ecdsa-01 fails on east with:
SEC_ERROR_CERT_SIGNATURE_ALGORITHM_DISABLED: The certificate was signed using a signature algorithm that is disabled because it is not secure.
  • a fix is force the upgrade of crypto-policies and crypto-policies-scripts, however ...
  • this breaks SSH, which breaks any test using SSH as an endpoint

Building Libreswan using a scratch NSS+NSPR build

Building NSS+NSPR From Scratch

Prepare the machine:

$ ./kvm sh build
build# #
build# dnf install -y gcc-c++ perl-interpreter    # aka dnf builddep -y nss
build# dnf install -y hg python gyp ninja-build   # used by build scripts
build# sed -i -e 's/ -p / /' \
   /usr/share/xmlto/format/docbook/man \
  • xmlto is hacked so that it doesn't try to preserve permissions when copying files within the 9p file system
any build in / will be lost the next time the domain is rebuilt
  • the dependencies can be automated by adding KVM_UPGRADE_PACKAGES += ... to Makefile.inc.local
  • this doesn't solve the problem with xmlto

Download and build using Building NSS as a guide:

build# cd /source
build# hg clone https://hg.mozilla.org/projects/nspr
build# hg clone https://hg.mozilla.org/projects/nss
build# ./nss/build.sh -cc # clean without building
build# ./nss/build.sh --enable-libpkix --enable-fips

testing (for comparison, NSS build farm):

build# HOST=localhost DOMSUF=localdomain USE_64=1 nss/tests/all.sh

however, of most interest is PKIX:

( cd nss/tests/cert/ ; USE_64=1 NSS_ENABLE_PKIX_VERIFY=1 DOMSUF=localdomain TESTDIR=/tmp/nss-test-results ./cert.sh )
  • need to point TESTDIR at something local as cat >>EOF breaks with 9p

Linking with libreswan

finally, to link nss against the build, add the following to Makefile.inc.local (how correct is this?):

KVM_NSS_CFLAGS = -I/source/nspr/Debug/dist/include/nspr -I/source/dist/public/nss
KVM_NSS_LDFLAGS = -L/source/dist/Debug/lib/ -Wl,-rpath,/source/dist/Debug/lib/ -lnss3

and then build as per normal:

$ ./kvm install

and confirm it worked:

$ ./kvm sh build
build# ldd /usr/local/libexec/ipsec/pluto  # should show above path

Debugging NSS

NSS_ENABLE_PKIX_VERIFY=1 LD_LIBRARY_PATH=$(cd ../dist/Debug/lib && pwd) gdb --args $(cd ../dist/Debug/bin && pwd)/certutil -V -n PasswordCert -u S -d ../tests_results/security/build.1/dbpass
(gdb) break PKIX_Shutdown
(gdb) break cert_VerifyCertChainPkix