crypto/cryptosoft: Add support for PBKDF2

[PruteanuVlad]

Summary

This adds support for PBKDF2 (SHA1 and SHA256) while leveraging the existing infrastructure for HMAC.
I tried to take advantage of the existing HMAC code as much as possible.
Test app has been added in this PR: apache/nuttx-apps#3437

Modified files:

boards/xtensa/esp32/esp32-devkitc/configs/crypto/defconfig - enables the test app
crypto/cryptodev.c - treats the new PBKDF2 cases and handles new struct field
crypto/cryptosoft.c - handles the actual algorithm implementation
include/crypto/cryptodev.h - new defines for pbkdf2

Impact

This allows users to derive keys using PBKDF2.

##Testing

Development was done using ESP32 DevkitC.
Building was done on Ubuntu 24.04 VM.
For testing, I ran the PBKDF2 test from the PR mentioned above.

nsh> pbkdf2
hmac PBKDF2 SHA1 success
hmac PBKDF2 SHA1 success
hmac PBKDF2 SHA1 success
hmac PBKDF2 SHA1 success
hmac PBKDF2 SHA1 success
hmac PBKDF2 SHA1 success
hmac PBKDF2 SHA256 success
hmac PBKDF2 SHA256 success
hmac PBKDF2 SHA256 success
hmac PBKDF2 SHA256 success
hmac PBKDF2 SHA256 success
hmac PBKDF2 SHA256 success

[ThePassionate]

Hi, thanks for adding PBKDF2 support — this is a useful addition to the crypto stack! I have a few suggestions below, mostly around cleanup.

1. swcr_freesession: missing PBKDF2 — memory leak

   swcr_freesession() does not handle CRYPTO_PBKDF2_HMAC_SHA1 / CRYPTO_PBKDF2_HMAC_SHA256. These algorithms go through the authcommon path in swcr_newsession(), which allocates both sw_ictx and sw_octx. Without corresponding cases in swcr_freesession(), neither buffer is freed on session teardown — this is a memory leak.

2. targetlen added to struct crypt_op but never referenced

[simbit18]

Hi @PruteanuVlad please fix

====================================================================================
Configuration/Tool: sim/crypto
2026-03-25 22:54:34
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cryptosoft.c: In function 'swcr_process':
Error: cryptosoft.c:2057:13: error: implicit declaration of function 'swcr_pbkdf2' [-Werror=implicit-function-declaration]
 2057 |             swcr_pbkdf2(crp, crd, sw, crp->crp_buf);
      |             ^~~~~~~~~~~
cryptosoft.c: In function 'swcr_pbkdf2':
Error: cryptosoft.c:2119:21: error: pointer targets in assignment from 'uint8_t *' {aka 'unsigned char *'} to 'caddr_t' {aka 'char *'} differ in signedness [-Werror=pointer-sign]
 2119 |   crp_dummy.crp_mac = macbuf;
      |                     ^
Error: cryptosoft.c:2126:48: error: implicit declaration of function 'htonl' [-Werror=implicit-function-declaration]
 2126 |       *(uint32_t *)(saltblk + crp->crp_ilen) = htonl(blocknum);
      |                                                ^~~~~
cc1: all warnings being treated as errors
make[1]: *** [Makefile:98: cryptosoft.o] Error 1
make[1]: Target 'libcrypto.a' not remade because of errors.
make: *** [tools/LibTargets.mk:95: crypto/libcrypto.a] Error 2
make: Target 'all' not remade because of errors.
/github/workspace/sources/nuttx/tools/testbuild.sh: line 385: /github/workspace/sources/nuttx/../nuttx/nuttx.manifest: No such file or directory
  [1/1] Normalize sim/crypto
====================================================================================

[acassis]

@PruteanuVlad please update the Documentation to include this algorithm as supported

[PruteanuVlad]

Thanks for the review 😄
I went through a few revisions so there were some missed leftovers, but I cleaned it up now.