[PATCH 0/5] net: lwip: root certificates

[Jerome Forissier <jerome.forissier@linaro.org>]

This series adds support for HTTP server authentication using root (CA)
certificates.

As a first step, the wget command is extended to support a sub-command:
cacert <addr> <size>. The memory region shall contain the CA
certificates. With this, it is possible to load the certificates from
storage or get them from the network for example, which is convenient
for testing at least. The Kconfig symbol for this feature is
WGET_CACERT=y.

Then new Kconfig symbols are added to support providing the certificates
at build time, as a DER or PEM encoded X509 collection:
WGET_BUILTIN_CACERT=y and WGET_BUILTIN_CACERT_PATH=<some path>.
Note that PEM support requires MBEDTLS_LIB_X509_PEM=y (for the cacert
command as well as for the builtin way).

Here is a complete example (showing only the relevant output from the
various commands):

 make qemu_arm64_lwip_defconfig
 wget https://curl.se/ca/cacert.pem
 echo CONFIG_WGET_BUILTIN_CACERT=y >>.config
 echo CONFIG_WGET_BUILTIN_CACERT_PATH=cacert.pem >>.config
 make olddefconfig
 make -j$(nproc) CROSS_COMPILE="ccache aarch64-linux-gnu-"
 qemu-system-aarch64 -M virt -nographic -cpu max \
        -object rng-random,id=rng0,filename=/dev/urandom \
        -device virtio-rng-pci,rng=rng0 -bios u-boot.bin
 => dhcp
 # HTTPS transfer using the builtin CA certificates
 => wget https://www.google.com/
 18724 bytes transferred in 15 ms (1.2 MiB/s)
 # Disable certificate validation
 => wget cacert 0 0
 # Unsafe HTTPS transfer
 => wget https://www.google.com/
 WARNING: no CA certificates, HTTPS connections not authenticated
 16570 bytes transferred in 15 ms (1.1 MiB/s)
 # Dowload and apply CA certificates from the net
 => wget https://curl.se/ca/cacert.pem
 WARNING: no CA certificates, HTTPS connections not authenticated
 ##
 233263 bytes transferred in 61 ms (3.6 MiB/s)
 => wget cacert $fileaddr $filesize
 # Now HTTPS is authenticated against the new CA
 => wget https://www.google.com/
 18743 bytes transferred in 14 ms (1.3 MiB/s)
 # Drop the certificates again...
 => wget cacert 0 0
 # Check that transfer is not secure
 => wget https://www.google.com/
 WARNING: no CA certificates, HTTPS connections not authenticated
 # Restore the builtin CA
 => wget cacert builtin
 # No more WARNING
 => wget https://www.google.com/
 18738 bytes transferred in 15 ms (1.2 MiB/s)

Jerome Forissier (5):
  net: lwip: extend wget to support CA (root) certificates
  lwip: tls: enforce checking of server certificates based on CA
    availability
  lwip: tls: warn when no CA exists amd log certificate validation
    errors
  net: lwip: add support for built-in root certificates
  configs: qemu_arm64_lwip_defconfig: enable WGET_CACERT and
    MBEDTLS_LIB_X509_PEM

 cmd/Kconfig                                   | 29 ++++++
 cmd/net-lwip.c                                | 19 +++-
 configs/qemu_arm64_lwip_defconfig             |  2 +
 .../src/apps/altcp_tls/altcp_tls_mbedtls.c    |  9 +-
 .../lwip/apps/altcp_tls_mbedtls_opts.h        |  6 --
 lib/mbedtls/Makefile                          |  3 +
 lib/mbedtls/mbedtls_def_config.h              |  5 ++
 net/lwip/Makefile                             |  6 ++
 net/lwip/wget.c                               | 90 ++++++++++++++++++-
 9 files changed, 158 insertions(+), 11 deletions(-)

-- 
2.43.0