examples/edhoc-rs-no_std: wire up psa

kaspar030 commented 1 year ago

This PR wires up the PSA backend to examples/edhoc-rs-no_std. (it's #28 rebased on main)

This is using a rust-psa-crypto fork, need to upstream needed no_std/baremetal patches. Also, the no_std fixes are hard-coded, so this breaks the psa std build

TODO:

[x] fix CI build (missing C cross compiler)
[x] clean up no_std patches to rust-psa-crypto
[x] fix linker error for baremetal target (missing free)
[x] fix missing entropy source in baremetal target
[x] fix linker error for baremetal target (missing calloc and strstr)
[x] build mbedtls with the static buffer allocator and initialize the allocator from Rust

kaspar030 commented 1 year ago

I fixed the free linker error. As expected, now mbedtls is missing an entropy source:

When doing cargo run --no-default-features --features psa in examples/edhoc-rs-no_std:

...
     Running `qemu-system-arm -cpu cortex-m3 -machine lm3s6965evb -nographic -semihosting-config enable=on,target=native -kernel /home/kaspar/src/edhoc-rs/target/thumbv7m-none-eabi/debug/edhoc-rs-no_std`
Timer with period zero, disabling
Hello, hacspec!
panicked at 'called `Result::unwrap()` on an `Err` value: InsufficientEntropy', crypto/edhoc-crypto-psa/src/lib.rs:16:24

Info on how to add a source for mbedtls in C is straight forward, but not so much going through rust-psa-crypto -> rust-psa-crypto-sys -> mbedtls. :(

malishav commented 1 year ago

Two commits pushed:

First one fixes the missing entropy source issue by:

defining our own mbedtls_hardware_poll function in psa crypto library, and
configuring mbedtls for crypto_baremetal build with MBEDTLS_ENTROPY_HARDWARE_ALT define, now in the baremetal branch on my fork of mbedtls.

The second commit adds a full handshake test which unfortunately fails to link with the following output:

 = note: rust-lld: warning: section type mismatch for .got
          >>> <internal>:(.got): SHT_PROGBITS
          >>> output section .got: SHT_NOBITS

          rust-lld: warning: section type mismatch for .got.plt
          >>> <internal>:(.got.plt): SHT_PROGBITS
          >>> output section .got: SHT_NOBITS

          rust-lld: warning: section type mismatch for .got
          >>> <internal>:(.got): SHT_PROGBITS
          >>> output section .got: SHT_NOBITS

          rust-lld: error: undefined symbol: calloc
          >>> referenced by platform.c
          >>>               platform.c.obj:(mbedtls_calloc_func) in archive /Users/malishav/Software/edhoc-rs/target/thumbv7m-none-eabi/debug/deps/libpsa_crypto_sys-a033baa857b1b4c9.rlib
          >>> did you mean: malloc
          >>> defined in: /Users/malishav/Software/edhoc-rs/target/thumbv7m-none-eabi/debug/deps/edhoc_rs_no_std-8b0cfcca31d2f4f7.8qrvu5iabanhtea.rcgu.o

          rust-lld: error: undefined symbol: strstr
          >>> referenced by pem.c:246 (/Users/malishav/.cargo/git/checkouts/rust-psa-crypto-e072e91dbdaa7d8f/efd8cf4/psa-crypto-sys/vendor/library/pem.c:246)
          >>>               pem.c.obj:(mbedtls_pem_read_buffer) in archive /Users/malishav/Software/edhoc-rs/target/thumbv7m-none-eabi/debug/deps/libpsa_crypto_sys-a033baa857b1b4c9.rlib
          >>> referenced by pem.c:251 (/Users/malishav/.cargo/git/checkouts/rust-psa-crypto-e072e91dbdaa7d8f/efd8cf4/psa-crypto-sys/vendor/library/pem.c:251)
          >>>               pem.c.obj:(mbedtls_pem_read_buffer) in archive /Users/malishav/Software/edhoc-rs/target/thumbv7m-none-eabi/debug/deps/libpsa_crypto_sys-a033baa857b1b4c9.rlib

          rust-lld: error: undefined symbol: mbedtls_psa_platform_get_builtin_key
          >>> referenced by psa_crypto_slot_management.c:295 (/Users/malishav/.cargo/git/checkouts/rust-psa-crypto-e072e91dbdaa7d8f/efd8cf4/psa-crypto-sys/vendor/library/psa_crypto_slot_management.c:295)
          >>>               psa_crypto_slot_management.c.obj:(psa_load_builtin_key_into_slot) in archive /Users/malishav/Software/edhoc-rs/target/thumbv7m-none-eabi/debug/deps/libpsa_crypto_sys-a033baa857b1b4c9.rlib

          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 74 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 268 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 462 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 476 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 490 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 534 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 578 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 628 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 678 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 708 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 738 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 768 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 798 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 828 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 858 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 888 bytes
          rust-lld: error: section '.text' will not fit in region 'FLASH': overflowed by 918 bytes
          rust-lld: error: too many errors emitted, stopping now (use --error-limit=0 to see all errors)

malishav commented 1 year ago

Hooray! I got the full handshake to work on thumbv7m-none-eabi target and the test passes when executed in the QEMU simulator using: cargo run --no-default-features --features psa --release!

Note the usage of the --release flag. Without it, the linker fails due to the lack of flash memory (the linker is configured with 256K limit for flash!?). However, when a similar example is built for CC2538 (changes in a separate branch), without the --release flag, things run smoothly in 512K.

To get this to work, I had to:

Change Rust's global memory allocator from static-alloc to embedded-alloc, and allocate 1024 Bytes for heap. With static-alloc no matter the size of the buffer I tried, panic is thrown as hacspec fails to allocate internal arrays.
Configure mbedtls to use the buffer allocator (MBEDTLS_MEMORY_BUFFER_ALLOC_C) and to call the appropriate C init function (mbedtls_memory_buffer_alloc_init) from Rust with an array of size 8192 Bytes.

malishav commented 1 year ago

@kaspar030 let me know if you see any showstopper to merging this PR, otherwise feel free to remove the Draft status so that we go ahead with the merge!

kaspar030 commented 1 year ago

Hooray! I got the full handshake to work on thumbv7m-none-eabi target and the test passes when executed in the QEMU simulator using: cargo run --no-default-features --features psa --release!

Awesome!

Without it, the linker fails due to the lack of flash memory (the linker is configured with 256K limit for flash!?).

Yup, the emulated board only has that much configured. IIUC that's hard-coded in the QEMU sources for that particular emulated SoC (lm3s6965evb). There's probably some other board with more flash.

I've tried to just do 'RUSTFLAGS=-Copt-level=s', but that hard-faults unfortunately.

malishav commented 1 year ago

Yep, there isn't much we can do about the memory footprint at this point as it is due to mbedtls and the hacspec dependencies. Proceeding with merge here

openwsn-berkeley / lakers

examples/edhoc-rs-no_std: wire up psa #31