Rust wrapper: add copy() to SHA256 and SHA384 via wc_Sha256Copy/wc_Sha384Copy

[MarkAtwood]

Summary

Implements the Clone trait for SHA256 and SHA384, backed by wc_Sha256Copy and wc_Sha384Copy respectively.

This allows mid-computation hash state to be cloned into an independent context in O(1), without re-hashing from scratch. The motivating use case is the rustls TLS provider, which needs to snapshot transcript hash state at multiple points during the handshake.

Changes

• wrapper/rust/wolfssl-wolfcrypt/src/sha.rs: implement Clone for SHA256 and SHA384 using MaybeUninit and the corresponding C copy functions via FFI. Panics on copy failure (should not occur under normal conditions).

Notes

• No public API breaking changes.
• No new dependencies.

[Copilot]

Pull request overview

This PR extends the Rust wolfssl-wolfcrypt SHA wrappers to support O(1) snapshotting of in-progress transcript hashes by adding copy() methods backed by wolfCrypt’s wc_Sha256Copy and wc_Sha384Copy.

Changes:

• Add SHA256::copy() implemented via wc_Sha256Copy.
• Add SHA384::copy() implemented via wc_Sha384Copy.

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[github-actions]

MemBrowse Memory Report

gcc-arm-cortex-m0plus

• FLASH: .text +680 B (+1.1%, 64,155 B / 262,144 B, total: 24% used)

gcc-arm-cortex-m3

• FLASH: .text +1,224 B (+1.0%, 122,481 B / 262,144 B, total: 47% used)

gcc-arm-cortex-m4

• FLASH: .rodata.CSWTCH.1 +4 B, .rodata.str1.1 +54 B, .rodata.wolfSSL_ERR_reason_error_string.str1.1 +88 B, .text +1,472 B (+0.8%, 200,320 B / 262,144 B, total: 76% used)

gcc-arm-cortex-m4-baremetal

• FLASH: .text +768 B (+1.2%, 66,827 B / 262,144 B, total: 25% used)

gcc-arm-cortex-m4-crypto-only

• FLASH: .rodata.CSWTCH.1 +4 B, .rodata.str1.1 +54 B, .text +960 B (+0.6%, 174,568 B / 262,144 B, total: 67% used)

gcc-arm-cortex-m4-dtls13

• FLASH: .text +1,344 B (+0.7%, 180,888 B / 1,048,576 B, total: 17% used)

gcc-arm-cortex-m4-min-ecc

• FLASH: .text +704 B (+1.2%, 61,741 B / 262,144 B, total: 24% used)

gcc-arm-cortex-m4-openssl-compat

• FLASH: .rodata +480 B, .text +4,416 B (+0.6%, 771,148 B / 1,048,576 B, total: 74% used)

gcc-arm-cortex-m4-pkcs7

• FLASH: .rodata.CSWTCH.1 +4 B, .rodata.str1.1 +54 B, .text +1,536 B (+0.8%, 212,588 B / 262,144 B, total: 81% used)

gcc-arm-cortex-m4-pq

• FLASH: .rodata +140 B, .text +2,112 B (+0.8%, 279,396 B / 1,048,576 B, total: 27% used)

gcc-arm-cortex-m4-rsa-only

• FLASH: .rodata +136 B, .text +2,240 B (+0.7%, 324,992 B / 1,048,576 B, total: 31% used)

gcc-arm-cortex-m4-sp-math

• FLASH: .text +704 B (+1.2%, 61,741 B / 262,144 B, total: 24% used)

gcc-arm-cortex-m4-tls12

• FLASH: .text +1,216 B (+1.0%, 123,213 B / 262,144 B, total: 47% used)

gcc-arm-cortex-m4-tls13

• FLASH: .rodata.CSWTCH.1 +4 B, .rodata.str1.1 +54 B, .rodata.wolfSSL_ERR_reason_error_string.str1.1 +88 B, .text +1,472 B (+0.7%, 236,082 B / 262,144 B, total: 90% used)

gcc-arm-cortex-m7

• FLASH: .rodata.CSWTCH.1 +4 B, .rodata.str1.1 +54 B, .rodata.wolfSSL_ERR_reason_error_string.str1.1 +88 B, .text +1,472 B (+0.8%, 200,320 B / 262,144 B, total: 76% used)

gcc-arm-cortex-m7-pq

• FLASH: .rodata +140 B, .text +2,048 B (+0.8%, 279,972 B / 1,048,576 B, total: 27% used)

gcc-arm-cortex-m7-tls13

• FLASH: .rodata.CSWTCH.1 +4 B, .rodata.str1.1 +54 B, .rodata.wolfSSL_ERR_reason_error_string.str1.1 +88 B, .text +1,536 B (+0.7%, 236,146 B / 262,144 B, total: 90% used)

linuxkm-pie

• Data: __patchable_function_entries +1,344 B (+5.6%, 25,552 B)

linuxkm-standard

• Data: __patchable_function_entries +2,296 B (+5.0%, 48,216 B)

stm32-sim-stm32h753

• FLASH: .text +1,968 B (+1.1%, 183,460 B / 2,097,152 B, total: 9% used)

[MarkAtwood]

All review feedback addressed in 71ce78c:

1. Uninitialized dst — now uses Self::new() to properly initialize before wc_Sha*Copy
2. &self unsoundness — changed to &mut self to model potential src mutation on MAXQ10XX
3. Tests — added test_sha256_copy and test_sha384_copy with independent expected digests

Ready for re-review.