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[edn/cryptolib] Adapt the crypto lib to the new sw_cmd_sts register
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This commit aligns the crypto library to the new behavior of the EDN's
sw_cmd_sts register. This commit is similar to the previous commit for
the dif's.

Signed-off-by: Hakim Filali <[email protected]>
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Hakim Filali committed Jan 18, 2024
1 parent 567946f commit 0293f15
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Showing 2 changed files with 112 additions and 30 deletions.
117 changes: 87 additions & 30 deletions sw/device/lib/crypto/drivers/entropy.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -308,14 +308,15 @@ static status_t csrng_fsm_idle_wait(void) {
return OTCRYPTO_RECOV_ERR;
}

// Write a CSRNG command to a register. That register can be the SW interface
// Write a CSRNG command to a register. That register can be the SW interface
// of CSRNG, in which case the `check_completion` argument should be `true`.
// That register can alternatively be one of EDN's that holds commands that EDN
// passes to CSRNG, in which case the `check_completion` argument must be
// `false`.
// passes to CSRNG. In this case, the check_completion register should only be
// true for non-generate commands issued to the SW register.
OT_WARN_UNUSED_RESULT
static status_t csrng_send_app_cmd(uint32_t reg_address,
static status_t csrng_send_app_cmd(uint32_t base_address,
entropy_csrng_cmd_t cmd,
entropy_csrng_send_app_cmd_type_t cmd_type,
bool check_completion) {
enum {
// This is to maintain full compliance with NIST SP 800-90A, which requires
Expand All @@ -328,13 +329,41 @@ static status_t csrng_send_app_cmd(uint32_t reg_address,
}

HARDENED_TRY(csrng_fsm_idle_wait());

uint32_t cmd_reg;
uint32_t sts_reg;
uint32_t rdy_bit;
uint32_t reg;
bool cmd_ready;
do {
reg = abs_mmio_read32(kBaseCsrng + CSRNG_SW_CMD_STS_REG_OFFSET);
cmd_ready = bitfield_bit32_read(reg, CSRNG_SW_CMD_STS_CMD_RDY_BIT);
} while (!cmd_ready);
bool ready;

switch (cmd_type) {
case kEntropyCsrngSendAppCmdTypeCsrng:
cmd_reg = base_address + CSRNG_CMD_REQ_REG_OFFSET;
sts_reg = base_address + CSRNG_SW_CMD_STS_REG_OFFSET;
rdy_bit = CSRNG_SW_CMD_STS_CMD_RDY_BIT;
break;
case kEntropyCsrngSendAppCmdTypeEdnSw:
cmd_reg = base_address + EDN_SW_CMD_REQ_REG_OFFSET;
sts_reg = base_address + EDN_SW_CMD_STS_REG_OFFSET;
rdy_bit = EDN_SW_CMD_STS_CMD_RDY_BIT;
break;
case kEntropyCsrngSendAppCmdTypeEdnGen:
cmd_reg = base_address + EDN_GENERATE_CMD_REG_OFFSET;
break;
case kEntropyCsrngSendAppCmdTypeEdnRes:
cmd_reg = base_address + EDN_RESEED_CMD_REG_OFFSET;
break;
default:
return INVALID_ARGUMENT();
}

if ((cmd_type == kEntropyCsrngSendAppCmdTypeCsrng) ||
(cmd_type == kEntropyCsrngSendAppCmdTypeEdnSw)) {
// Wait for the status register to be ready to accept the next command.
do {
reg = abs_mmio_read32(sts_reg);
ready = bitfield_bit32_read(reg, rdy_bit);
} while (!ready);
}

#define ENTROPY_CMD(m, i) ((bitfield_field32_t){.mask = m, .index = i})
// The application command header is not specified as a register in the
Expand All @@ -361,12 +390,13 @@ static status_t csrng_send_app_cmd(uint32_t reg_address,
return OTCRYPTO_RECOV_ERR;
}

if (check_completion) {
if (check_completion && (cmd_type == kEntropyCsrngSendAppCmdTypeCsrng)) {
// Clear the `cs_cmd_req_done` bit, which is asserted whenever a command
// request is completed, because that bit will be used below to determine if
// this command request is completed.
// this command request is completed. EDN automatically clears the
// acknowledgement bit upon writing the command.
reg = bitfield_bit32_write(0, CSRNG_INTR_STATE_CS_CMD_REQ_DONE_BIT, true);
abs_mmio_write32(kBaseCsrng + CSRNG_INTR_STATE_REG_OFFSET, reg);
abs_mmio_write32(base_address + CSRNG_INTR_STATE_REG_OFFSET, reg);
}

// Build and write application command header.
Expand All @@ -378,13 +408,21 @@ static status_t csrng_send_app_cmd(uint32_t reg_address,
reg = bitfield_field32_write(reg, kAppCmdFieldFlag0, kMultiBitBool4True);
}

abs_mmio_write32(reg_address, reg);
abs_mmio_write32(cmd_reg, reg);

for (size_t i = 0; i < cmd_len; ++i) {
abs_mmio_write32(reg_address, cmd.seed_material->data[i]);
// If the command is issued to the SW register of the EDN, the reg ready
// bit needs to be polled before writing each word of additional data.
if (cmd_type == kEntropyCsrngSendAppCmdTypeEdnSw) {
do {
reg = abs_mmio_read32(base_address + EDN_SW_CMD_STS_REG_OFFSET);
ready = bitfield_bit32_read(reg, EDN_SW_CMD_STS_CMD_REG_RDY_BIT);
} while (!ready);
}
abs_mmio_write32(cmd_reg, cmd.seed_material->data[i]);
}

if (check_completion) {
if (check_completion && (cmd_type == kEntropyCsrngSendAppCmdTypeCsrng)) {
if (cmd.id == kEntropyDrbgOpGenerate) {
// The Generate command is complete only after all entropy bits have been
// consumed. Thus poll the register that indicates if entropy bits are
Expand All @@ -409,6 +447,22 @@ static status_t csrng_send_app_cmd(uint32_t reg_address,
}
}

if (check_completion && (cmd_type == kEntropyCsrngSendAppCmdTypeEdnSw)) {
// Acknowledgements for generate commands are only sent after all the
// entropy is consumed. Thus the acknowledgement bit shall only be polled
// for non-generate commands.
if (cmd.id != kEntropyDrbgOpGenerate) {
do {
reg = abs_mmio_read32(sts_reg);
} while (!bitfield_bit32_read(reg, EDN_SW_CMD_STS_CMD_ACK_BIT));

// Check the "status" bit, which will be 1 only if there was an error.
if (bitfield_bit32_read(reg, EDN_SW_CMD_STS_CMD_STS_BIT)) {
return OTCRYPTO_RECOV_ERR;
}
}
}

return OTCRYPTO_OK;
}

Expand Down Expand Up @@ -474,11 +528,10 @@ static status_t edn_ready_block(uint32_t edn_address) {
*/
OT_WARN_UNUSED_RESULT
static status_t edn_configure(const edn_config_t *config) {
HARDENED_TRY(csrng_send_app_cmd(
config->base_address + EDN_RESEED_CMD_REG_OFFSET, config->reseed, false));
HARDENED_TRY(
csrng_send_app_cmd(config->base_address + EDN_GENERATE_CMD_REG_OFFSET,
config->generate, false));
HARDENED_TRY(csrng_send_app_cmd(config->base_address, config->reseed,
kEntropyCsrngSendAppCmdTypeEdnRes, false));
HARDENED_TRY(csrng_send_app_cmd(config->base_address, config->generate,
kEntropyCsrngSendAppCmdTypeEdnGen, false));
abs_mmio_write32(
config->base_address + EDN_MAX_NUM_REQS_BETWEEN_RESEEDS_REG_OFFSET,
config->reseed_interval);
Expand All @@ -490,10 +543,9 @@ static status_t edn_configure(const edn_config_t *config) {
abs_mmio_write32(config->base_address + EDN_CTRL_REG_OFFSET, reg);

HARDENED_TRY(edn_ready_block(config->base_address));
HARDENED_TRY(
csrng_send_app_cmd(config->base_address + EDN_SW_CMD_REQ_REG_OFFSET,
config->instantiate, false));
return edn_ready_block(config->base_address);
HARDENED_TRY(csrng_send_app_cmd(config->base_address, config->instantiate,
kEntropyCsrngSendAppCmdTypeEdnSw, true));
return OTCRYPTO_OK;
}

/**
Expand Down Expand Up @@ -806,35 +858,38 @@ status_t entropy_complex_check(void) {
status_t entropy_csrng_instantiate(
hardened_bool_t disable_trng_input,
const entropy_seed_material_t *seed_material) {
return csrng_send_app_cmd(kBaseCsrng + CSRNG_CMD_REQ_REG_OFFSET,
return csrng_send_app_cmd(kBaseCsrng,
(entropy_csrng_cmd_t){
.id = kEntropyDrbgOpInstantiate,
.disable_trng_input = disable_trng_input,
.seed_material = seed_material,
.generate_len = 0,
},
kEntropyCsrngSendAppCmdTypeCsrng,
true);
}

status_t entropy_csrng_reseed(hardened_bool_t disable_trng_input,
const entropy_seed_material_t *seed_material) {
return csrng_send_app_cmd(kBaseCsrng + CSRNG_CMD_REQ_REG_OFFSET,
return csrng_send_app_cmd(kBaseCsrng,
(entropy_csrng_cmd_t){
.id = kEntropyDrbgOpReseed,
.disable_trng_input = disable_trng_input,
.seed_material = seed_material,
.generate_len = 0,
},
kEntropyCsrngSendAppCmdTypeCsrng,
true);
}

status_t entropy_csrng_update(const entropy_seed_material_t *seed_material) {
return csrng_send_app_cmd(kBaseCsrng + CSRNG_CMD_REQ_REG_OFFSET,
return csrng_send_app_cmd(kBaseCsrng,
(entropy_csrng_cmd_t){
.id = kEntropyDrbgOpUpdate,
.seed_material = seed_material,
.generate_len = 0,
},
kEntropyCsrngSendAppCmdTypeCsrng,
true);
}

Expand All @@ -843,12 +898,13 @@ status_t entropy_csrng_generate_start(
// Round up the number of 128bit blocks. Aligning with respect to uint32_t.
// TODO(#6112): Consider using a canonical reference for alignment operations.
const uint32_t num_128bit_blocks = ceil_div(len, 4);
return csrng_send_app_cmd(kBaseCsrng + CSRNG_CMD_REQ_REG_OFFSET,
return csrng_send_app_cmd(kBaseCsrng,
(entropy_csrng_cmd_t){
.id = kEntropyDrbgOpGenerate,
.seed_material = seed_material,
.generate_len = num_128bit_blocks,
},
kEntropyCsrngSendAppCmdTypeCsrng,
true);
}

Expand Down Expand Up @@ -898,11 +954,12 @@ status_t entropy_csrng_generate(const entropy_seed_material_t *seed_material,
}

status_t entropy_csrng_uninstantiate(void) {
return csrng_send_app_cmd(kBaseCsrng + CSRNG_CMD_REQ_REG_OFFSET,
return csrng_send_app_cmd(kBaseCsrng,
(entropy_csrng_cmd_t){
.id = kEntropyDrbgOpUninstantiate,
.seed_material = NULL,
.generate_len = 0,
},
kEntropyCsrngSendAppCmdTypeCsrng,
true);
}
25 changes: 25 additions & 0 deletions sw/device/lib/crypto/drivers/entropy.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,31 @@ typedef struct entropy_seed_material {
uint32_t data[kEntropySeedWords];
} entropy_seed_material_t;

/**
* This enum type contains all the different command types for
* csrng_send_app_cmd().
*/
typedef enum entropy_csrng_send_app_cmd_type {
/**
* Command issued directly to CSRNG.
*/
kEntropyCsrngSendAppCmdTypeCsrng,
/**
* Command issued to CSRNG via the SW_CMD_REQ register of the EDN.
*/
kEntropyCsrngSendAppCmdTypeEdnSw,
/**
* Command issued to CSRNG via the GENERATE_CMD register of the EDN.
* This type of command will be used in the auto mode of the EDN.
*/
kEntropyCsrngSendAppCmdTypeEdnGen,
/**
* Command issued to CSRNG via the RESEED_CMD register of the EDN.
* This type of command will be used in the auto mode of the EDN.
*/
kEntropyCsrngSendAppCmdTypeEdnRes,
} entropy_csrng_send_app_cmd_type_t;

/**
* Constant empty seed material for the entropy complex.
*
Expand Down

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