I am going to have a look into this. Thanks for the instructions on how to reproduce. Might get a while to reply, please bear with me.
Thanks, Antonio
From: Edward Yang via TF-M tf-m@lists.trustedfirmware.org Sent: Thursday, March 23, 2023 01:36 To: tf-m@lists.trustedfirmware.org Subject: [TF-M] Please help check the failure of PSA_ALG_HKDF_EXPAND operation test
Hi experts,
Recently we're testing the HKDF-EXPAND interface with TF-M v1.7.0 on stm32l562e_dk platform.
But the HKDF-EXPAND output didn't match the expected OKM.
The test vector is as below:
ALG : PSA_ALG_HKDF_EXPAND(PSA_ALG_SHA_256), "info" : decode_hex("f0f1f2f3f4f5f6f7f8f9"), "L" : 42, "PRK" : "077709362c2e32df0ddc3f0dc47bba6390b6c73bb50f9c3122ec844ad7c2b3e5" "OKM" : "3cb25f25faacd57a90434f64d0362f2a2d2d0a90cf1a5a4c5db02d56ecc4c5bf34007208d5b887185865"
The corresponding code is as follow：
int8_t okm[42]={0}; uint8_t info[] = {0xf0,0xf1,0xf2,0xf3,0xf4,0xf5,0xf6,0xf7,0xf8,0xf9}; uint8_t ikm[]= { 0x7,0x77,0x9,0x36,0x2c,0x2e,0x32,0xdf, 0xd,0xdc,0x3f,0xd,0xc4,0x7b,0xba,0x63, 0x90,0xb6,0xc7,0x3b,0xb5,0xf,0x9c,0x31, 0x22,0xec,0x84,0x4a,0xd7,0xc2,0xb3,0xe5 };
status = psa_key_derivation_setup(&operation, PSA_ALG_HKDF_EXPAND(PSA_ALG_SHA_256));
status = psa_key_derivation_input_bytes(&operation, PSA_KEY_DERIVATION_INPUT_SECRET, ikm, sizeof(ikm)); status = psa_key_derivation_input_bytes(&operation, PSA_KEY_DERIVATION_INPUT_INFO, info, sizeof(info)); status = psa_key_derivation_output_bytes( &operation, okm, sizeof(okm) );
The actual output okm is : 5a 1c ea 2d 24 ee 79 c5 bf ce 27 7b ... be b 3b 2e 19 18 77 ae, which didn't match the OKM of above test vector.
Have we misused the HKDF-EXPAND operation?
Best Regards, Poppy Wu 吴偏偏