With this command we are finally updating data to the backing store
and cycling the write_count and each successful write. We also include
the write count in all response frames as the spec is a little unclear
but the example test code expected it.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
tools/vhost-user-rpmb/main.c | 111 +++++++++++++++++++++++++++++++++--
1 file changed, 105 insertions(+), 6 deletions(-)
diff --git a/tools/vhost-user-rpmb/main.c b/tools/vhost-user-rpmb/main.c
index 88747c50fa44..a17c3b4bcc4e 100644
--- a/tools/vhost-user-rpmb/main.c
+++ b/tools/vhost-user-rpmb/main.c
@@ -62,6 +62,7 @@ enum {
#define KiB (1UL << 10)
#define MAX_RPMB_SIZE (KiB * 128 * 256)
#define RPMB_KEY_MAC_SIZE 32
+#define RPMB_BLOCK_SIZE 256
/* RPMB Request Types */
#define VIRTIO_RPMB_REQ_PROGRAM_KEY 0x0001
@@ -100,7 +101,7 @@ struct virtio_rpmb_config {
struct virtio_rpmb_frame {
uint8_t stuff[196];
uint8_t key_mac[RPMB_KEY_MAC_SIZE];
- uint8_t data[256];
+ uint8_t data[RPMB_BLOCK_SIZE];
uint8_t nonce[16];
/* remaining fields are big-endian */
uint32_t write_counter;
@@ -124,6 +125,7 @@ typedef struct VuRpmb {
uint8_t last_nonce[16];
uint16_t last_result;
uint16_t last_reqresp;
+ uint16_t last_address;
uint32_t write_count;
} VuRpmb;
@@ -239,17 +241,30 @@ vrpmb_set_config(VuDev *dev, const uint8_t *data,
* which itself uses a 3 clause BSD chunk of code.
*/
+static const int rpmb_frame_dlen = (sizeof(struct virtio_rpmb_frame) -
+ offsetof(struct virtio_rpmb_frame, data));
+
static void vrpmb_update_mac_in_frame(VuRpmb *r, struct virtio_rpmb_frame *frm)
{
hmac_sha256_ctx ctx;
- static const int dlen = (sizeof(struct virtio_rpmb_frame) -
- offsetof(struct virtio_rpmb_frame, data));
hmac_sha256_init(&ctx, r->key, RPMB_KEY_MAC_SIZE);
- hmac_sha256_update(&ctx, frm->data, dlen);
+ hmac_sha256_update(&ctx, frm->data, rpmb_frame_dlen);
hmac_sha256_final(&ctx, &frm->key_mac[0], 32);
}
+static bool vrpmb_verify_mac_in_frame(VuRpmb *r, struct virtio_rpmb_frame *frm)
+{
+ hmac_sha256_ctx ctx;
+ uint8_t calculated_mac[RPMB_KEY_MAC_SIZE];
+
+ hmac_sha256_init(&ctx, r->key, RPMB_KEY_MAC_SIZE);
+ hmac_sha256_update(&ctx, frm->data, rpmb_frame_dlen);
+ hmac_sha256_final(&ctx, calculated_mac, RPMB_KEY_MAC_SIZE);
+
+ return memcmp(calculated_mac, frm->key_mac, RPMB_KEY_MAC_SIZE) == 0;
+}
+
/*
* Handlers for individual control messages
*/
@@ -324,6 +339,82 @@ vrpmb_handle_get_write_counter(VuDev *dev, struct virtio_rpmb_frame *frame)
return resp;
}
+/*
+ * vrpmb_handle_write:
+ *
+ * We will report the success/fail on receipt of
+ * VIRTIO_RPMB_REQ_RESULT_READ. Returns the number of extra frames
+ * processed in the request.
+ */
+static int vrpmb_handle_write(VuDev *dev, struct virtio_rpmb_frame *frame)
+{
+ VuRpmb *r = container_of(dev, VuRpmb, dev.parent);
+ int extra_frames = 0;
+ uint16_t block_count = be16toh(frame->block_count);
+ uint32_t write_counter = be32toh(frame->write_counter);
+ size_t offset;
+
+ r->last_reqresp = VIRTIO_RPMB_RESP_DATA_WRITE;
+ r->last_address = be16toh(frame->address);
+ offset = r->last_address * RPMB_BLOCK_SIZE;
+
+ /*
+ * Run the checks from:
+ * 5.12.6.1.3 Device Requirements: Device Operation: Data Write
+ */
+ if (!r->key) {
+ g_warning("no key programmed");
+ r->last_result = VIRTIO_RPMB_RES_NO_AUTH_KEY;
+ } else if (block_count == 0 ||
+ block_count > r->virtio_config.max_wr_cnt) {
+ r->last_result = VIRTIO_RPMB_RES_GENERAL_FAILURE;
+ } else if (false /* what does an expired write counter mean? */) {
+ r->last_result = VIRTIO_RPMB_RES_WRITE_COUNTER_EXPIRED;
+ } else if (offset > (r->virtio_config.capacity * (128 * KiB))) {
+ r->last_result = VIRTIO_RPMB_RES_ADDR_FAILURE;
+ } else if (!vrpmb_verify_mac_in_frame(r, frame)) {
+ r->last_result = VIRTIO_RPMB_RES_AUTH_FAILURE;
+ } else if (write_counter != r->write_count) {
+ r->last_result = VIRTIO_RPMB_RES_COUNT_FAILURE;
+ } else {
+ int i;
+ /* At this point we have a valid authenticated write request
+ * so the counter can incremented and we can attempt to
+ * update the backing device.
+ */
+ r->write_count++;
+ for (i = 0; i < block_count; i++) {
+ void *blk = r->flash_map + offset;
+ g_debug("%s: writing block %d", __func__, i);
+ if (mprotect(blk, RPMB_BLOCK_SIZE, PROT_WRITE) != 0) {
+ r->last_result = VIRTIO_RPMB_RES_WRITE_FAILURE;
+ break;
+ }
+ memcpy(blk, frame[i].data, RPMB_BLOCK_SIZE);
+ if (msync(blk, RPMB_BLOCK_SIZE, MS_SYNC) != 0) {
+ g_warning("%s: failed to sync update", __func__);
+ r->last_result = VIRTIO_RPMB_RES_WRITE_FAILURE;
+ break;
+ }
+ if (mprotect(blk, RPMB_BLOCK_SIZE, PROT_READ) != 0) {
+ g_warning("%s: failed to re-apply read protection", __func__);
+ r->last_result = VIRTIO_RPMB_RES_GENERAL_FAILURE;
+ break;
+ }
+ offset += RPMB_BLOCK_SIZE;
+ }
+ r->last_result = VIRTIO_RPMB_RES_OK;
+ extra_frames = i - 1;
+ }
+
+ g_info("%s: %s (%x, %d extra frames processed), write_count=%d", __func__,
+ r->last_result == VIRTIO_RPMB_RES_OK ? "successful":"failed",
+ r->last_result, extra_frames, r->write_count);
+
+ return extra_frames;
+}
+
+
/*
* Return the result of the last message. This is only valid if the
* previous message was VIRTIO_RPMB_REQ_PROGRAM_KEY or
@@ -339,10 +430,14 @@ static struct virtio_rpmb_frame * vrpmb_handle_result_read(VuDev *dev)
g_info("%s: for request:%x result:%x", __func__,
r->last_reqresp, r->last_result);
- if (r->last_reqresp == VIRTIO_RPMB_RESP_PROGRAM_KEY ||
- r->last_reqresp == VIRTIO_RPMB_REQ_DATA_WRITE) {
+ if (r->last_reqresp == VIRTIO_RPMB_RESP_PROGRAM_KEY) {
resp->result = htobe16(r->last_result);
resp->req_resp = htobe16(r->last_reqresp);
+ } else if (r->last_reqresp == VIRTIO_RPMB_RESP_DATA_WRITE) {
+ resp->result = htobe16(r->last_result);
+ resp->req_resp = htobe16(r->last_reqresp);
+ resp->write_counter = htobe32(r->write_count);
+ resp->address = htobe16(r->last_address);
} else {
resp->result = htobe16(VIRTIO_RPMB_RES_GENERAL_FAILURE);
}
@@ -445,6 +540,10 @@ vrpmb_handle_ctrl(VuDev *dev, int qidx)
__func__);
}
break;
+ case VIRTIO_RPMB_REQ_DATA_WRITE:
+ /* we can have multiple blocks handled */
+ n += vrpmb_handle_write(dev, f);
+ break;
default:
g_debug("un-handled request: %x", f->req_resp);
break;
--
2.20.1
On Fri, Sep 25, 2020 at 01:51:43PM +0100, Alex Bennée wrote:
> With this command we are finally updating data to the backing store
> and cycling the write_count and each successful write. We also include
> the write count in all response frames as the spec is a little unclear
> but the example test code expected it.
>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
> tools/vhost-user-rpmb/main.c | 111 +++++++++++++++++++++++++++++++++--
> 1 file changed, 105 insertions(+), 6 deletions(-)
>
> diff --git a/tools/vhost-user-rpmb/main.c b/tools/vhost-user-rpmb/main.c
> index 88747c50fa44..a17c3b4bcc4e 100644
> --- a/tools/vhost-user-rpmb/main.c
> +++ b/tools/vhost-user-rpmb/main.c
> @@ -62,6 +62,7 @@ enum {
> #define KiB (1UL << 10)
> #define MAX_RPMB_SIZE (KiB * 128 * 256)
> #define RPMB_KEY_MAC_SIZE 32
> +#define RPMB_BLOCK_SIZE 256
>
> /* RPMB Request Types */
> #define VIRTIO_RPMB_REQ_PROGRAM_KEY 0x0001
> @@ -100,7 +101,7 @@ struct virtio_rpmb_config {
> struct virtio_rpmb_frame {
> uint8_t stuff[196];
> uint8_t key_mac[RPMB_KEY_MAC_SIZE];
> - uint8_t data[256];
> + uint8_t data[RPMB_BLOCK_SIZE];
> uint8_t nonce[16];
> /* remaining fields are big-endian */
> uint32_t write_counter;
> @@ -124,6 +125,7 @@ typedef struct VuRpmb {
> uint8_t last_nonce[16];
> uint16_t last_result;
> uint16_t last_reqresp;
> + uint16_t last_address;
> uint32_t write_count;
> } VuRpmb;
>
> @@ -239,17 +241,30 @@ vrpmb_set_config(VuDev *dev, const uint8_t *data,
> * which itself uses a 3 clause BSD chunk of code.
> */
>
> +static const int rpmb_frame_dlen = (sizeof(struct virtio_rpmb_frame) -
> + offsetof(struct virtio_rpmb_frame, data));
> +
> static void vrpmb_update_mac_in_frame(VuRpmb *r, struct virtio_rpmb_frame *frm)
> {
> hmac_sha256_ctx ctx;
> - static const int dlen = (sizeof(struct virtio_rpmb_frame) -
> - offsetof(struct virtio_rpmb_frame, data));
>
> hmac_sha256_init(&ctx, r->key, RPMB_KEY_MAC_SIZE);
> - hmac_sha256_update(&ctx, frm->data, dlen);
> + hmac_sha256_update(&ctx, frm->data, rpmb_frame_dlen);
> hmac_sha256_final(&ctx, &frm->key_mac[0], 32);
> }
>
> +static bool vrpmb_verify_mac_in_frame(VuRpmb *r, struct virtio_rpmb_frame *frm)
> +{
> + hmac_sha256_ctx ctx;
> + uint8_t calculated_mac[RPMB_KEY_MAC_SIZE];
> +
> + hmac_sha256_init(&ctx, r->key, RPMB_KEY_MAC_SIZE);
> + hmac_sha256_update(&ctx, frm->data, rpmb_frame_dlen);
> + hmac_sha256_final(&ctx, calculated_mac, RPMB_KEY_MAC_SIZE);
> +
> + return memcmp(calculated_mac, frm->key_mac, RPMB_KEY_MAC_SIZE) == 0;
>
I'd prefer using a constant time comparison function for this one
instead of memcmp (regardless if it's used for simulation or not) to
prevent eventual timing attacks.
> +}
> +
> /*
> * Handlers for individual control messages
> */
> @@ -324,6 +339,82 @@ vrpmb_handle_get_write_counter(VuDev *dev, struct virtio_rpmb_frame *frame)
> return resp;
> }
>
> +/*
> + * vrpmb_handle_write:
> + *
> + * We will report the success/fail on receipt of
> + * VIRTIO_RPMB_REQ_RESULT_READ. Returns the number of extra frames
> + * processed in the request.
> + */
> +static int vrpmb_handle_write(VuDev *dev, struct virtio_rpmb_frame *frame)
> +{
> + VuRpmb *r = container_of(dev, VuRpmb, dev.parent);
> + int extra_frames = 0;
> + uint16_t block_count = be16toh(frame->block_count);
> + uint32_t write_counter = be32toh(frame->write_counter);
> + size_t offset;
> +
> + r->last_reqresp = VIRTIO_RPMB_RESP_DATA_WRITE;
> + r->last_address = be16toh(frame->address);
> + offset = r->last_address * RPMB_BLOCK_SIZE;
> +
> + /*
> + * Run the checks from:
> + * 5.12.6.1.3 Device Requirements: Device Operation: Data Write
> + */
> + if (!r->key) {
> + g_warning("no key programmed");
> + r->last_result = VIRTIO_RPMB_RES_NO_AUTH_KEY;
> + } else if (block_count == 0 ||
> + block_count > r->virtio_config.max_wr_cnt) {
> + r->last_result = VIRTIO_RPMB_RES_GENERAL_FAILURE;
> + } else if (false /* what does an expired write counter mean? */) {
>
IIRC, the counter has room for a 32-bit value and the counter will never
wrap around. So once the counter have reached max for uint32_t, then
there is an additional bit set (permanently) in the operation result.
I.e., writes are no longer possible once that has happened. That is
probably what you're referring to here I suppose.
> + r->last_result = VIRTIO_RPMB_RES_WRITE_COUNTER_EXPIRED;
> + } else if (offset > (r->virtio_config.capacity * (128 * KiB))) {
> + r->last_result = VIRTIO_RPMB_RES_ADDR_FAILURE;
> + } else if (!vrpmb_verify_mac_in_frame(r, frame)) {
> + r->last_result = VIRTIO_RPMB_RES_AUTH_FAILURE;
> + } else if (write_counter != r->write_count) {
> + r->last_result = VIRTIO_RPMB_RES_COUNT_FAILURE;
> + } else {
> + int i;
> + /* At this point we have a valid authenticated write request
> + * so the counter can incremented and we can attempt to
> + * update the backing device.
> + */
> + r->write_count++;
> + for (i = 0; i < block_count; i++) {
> + void *blk = r->flash_map + offset;
> + g_debug("%s: writing block %d", __func__, i);
> + if (mprotect(blk, RPMB_BLOCK_SIZE, PROT_WRITE) != 0) {
> + r->last_result = VIRTIO_RPMB_RES_WRITE_FAILURE;
> + break;
> + }
> + memcpy(blk, frame[i].data, RPMB_BLOCK_SIZE);
> + if (msync(blk, RPMB_BLOCK_SIZE, MS_SYNC) != 0) {
> + g_warning("%s: failed to sync update", __func__);
> + r->last_result = VIRTIO_RPMB_RES_WRITE_FAILURE;
> + break;
> + }
> + if (mprotect(blk, RPMB_BLOCK_SIZE, PROT_READ) != 0) {
> + g_warning("%s: failed to re-apply read protection", __func__);
> + r->last_result = VIRTIO_RPMB_RES_GENERAL_FAILURE;
> + break;
> + }
> + offset += RPMB_BLOCK_SIZE;
> + }
> + r->last_result = VIRTIO_RPMB_RES_OK;
> + extra_frames = i - 1;
> + }
> +
> + g_info("%s: %s (%x, %d extra frames processed), write_count=%d", __func__,
> + r->last_result == VIRTIO_RPMB_RES_OK ? "successful":"failed",
> + r->last_result, extra_frames, r->write_count);
> +
> + return extra_frames;
> +}
> +
> +
> /*
> * Return the result of the last message. This is only valid if the
> * previous message was VIRTIO_RPMB_REQ_PROGRAM_KEY or
> @@ -339,10 +430,14 @@ static struct virtio_rpmb_frame * vrpmb_handle_result_read(VuDev *dev)
> g_info("%s: for request:%x result:%x", __func__,
> r->last_reqresp, r->last_result);
>
> - if (r->last_reqresp == VIRTIO_RPMB_RESP_PROGRAM_KEY ||
> - r->last_reqresp == VIRTIO_RPMB_REQ_DATA_WRITE) {
> + if (r->last_reqresp == VIRTIO_RPMB_RESP_PROGRAM_KEY) {
> resp->result = htobe16(r->last_result);
> resp->req_resp = htobe16(r->last_reqresp);
> + } else if (r->last_reqresp == VIRTIO_RPMB_RESP_DATA_WRITE) {
> + resp->result = htobe16(r->last_result);
> + resp->req_resp = htobe16(r->last_reqresp);
> + resp->write_counter = htobe32(r->write_count);
> + resp->address = htobe16(r->last_address);
> } else {
> resp->result = htobe16(VIRTIO_RPMB_RES_GENERAL_FAILURE);
> }
> @@ -445,6 +540,10 @@ vrpmb_handle_ctrl(VuDev *dev, int qidx)
> __func__);
> }
> break;
> + case VIRTIO_RPMB_REQ_DATA_WRITE:
> + /* we can have multiple blocks handled */
> + n += vrpmb_handle_write(dev, f);
> + break;
> default:
> g_debug("un-handled request: %x", f->req_resp);
> break;
> --
> 2.20.1
>
--
Regards,
Joakim
Joakim Bech <joakim.bech@linaro.org> writes:
> On Fri, Sep 25, 2020 at 01:51:43PM +0100, Alex Bennée wrote:
>> With this command we are finally updating data to the backing store
>> and cycling the write_count and each successful write. We also include
>> the write count in all response frames as the spec is a little unclear
>> but the example test code expected it.
>>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> ---
>> tools/vhost-user-rpmb/main.c | 111 +++++++++++++++++++++++++++++++++--
>> 1 file changed, 105 insertions(+), 6 deletions(-)
>>
>> diff --git a/tools/vhost-user-rpmb/main.c b/tools/vhost-user-rpmb/main.c
>> index 88747c50fa44..a17c3b4bcc4e 100644
>> --- a/tools/vhost-user-rpmb/main.c
>> +++ b/tools/vhost-user-rpmb/main.c
>> @@ -62,6 +62,7 @@ enum {
>> #define KiB (1UL << 10)
>> #define MAX_RPMB_SIZE (KiB * 128 * 256)
>> #define RPMB_KEY_MAC_SIZE 32
>> +#define RPMB_BLOCK_SIZE 256
>>
>> /* RPMB Request Types */
>> #define VIRTIO_RPMB_REQ_PROGRAM_KEY 0x0001
>> @@ -100,7 +101,7 @@ struct virtio_rpmb_config {
>> struct virtio_rpmb_frame {
>> uint8_t stuff[196];
>> uint8_t key_mac[RPMB_KEY_MAC_SIZE];
>> - uint8_t data[256];
>> + uint8_t data[RPMB_BLOCK_SIZE];
>> uint8_t nonce[16];
>> /* remaining fields are big-endian */
>> uint32_t write_counter;
>> @@ -124,6 +125,7 @@ typedef struct VuRpmb {
>> uint8_t last_nonce[16];
>> uint16_t last_result;
>> uint16_t last_reqresp;
>> + uint16_t last_address;
>> uint32_t write_count;
>> } VuRpmb;
>>
>> @@ -239,17 +241,30 @@ vrpmb_set_config(VuDev *dev, const uint8_t *data,
>> * which itself uses a 3 clause BSD chunk of code.
>> */
>>
>> +static const int rpmb_frame_dlen = (sizeof(struct virtio_rpmb_frame) -
>> + offsetof(struct virtio_rpmb_frame, data));
>> +
>> static void vrpmb_update_mac_in_frame(VuRpmb *r, struct virtio_rpmb_frame *frm)
>> {
>> hmac_sha256_ctx ctx;
>> - static const int dlen = (sizeof(struct virtio_rpmb_frame) -
>> - offsetof(struct virtio_rpmb_frame, data));
>>
>> hmac_sha256_init(&ctx, r->key, RPMB_KEY_MAC_SIZE);
>> - hmac_sha256_update(&ctx, frm->data, dlen);
>> + hmac_sha256_update(&ctx, frm->data, rpmb_frame_dlen);
>> hmac_sha256_final(&ctx, &frm->key_mac[0], 32);
>> }
>>
>> +static bool vrpmb_verify_mac_in_frame(VuRpmb *r, struct virtio_rpmb_frame *frm)
>> +{
>> + hmac_sha256_ctx ctx;
>> + uint8_t calculated_mac[RPMB_KEY_MAC_SIZE];
>> +
>> + hmac_sha256_init(&ctx, r->key, RPMB_KEY_MAC_SIZE);
>> + hmac_sha256_update(&ctx, frm->data, rpmb_frame_dlen);
>> + hmac_sha256_final(&ctx, calculated_mac, RPMB_KEY_MAC_SIZE);
>> +
>> + return memcmp(calculated_mac, frm->key_mac, RPMB_KEY_MAC_SIZE) == 0;
>>
> I'd prefer using a constant time comparison function for this one
> instead of memcmp (regardless if it's used for simulation or not) to
> prevent eventual timing attacks.
Could you recommend such a function for this?
>
>> +}
>> +
>> /*
>> * Handlers for individual control messages
>> */
>> @@ -324,6 +339,82 @@ vrpmb_handle_get_write_counter(VuDev *dev, struct virtio_rpmb_frame *frame)
>> return resp;
>> }
>>
>> +/*
>> + * vrpmb_handle_write:
>> + *
>> + * We will report the success/fail on receipt of
>> + * VIRTIO_RPMB_REQ_RESULT_READ. Returns the number of extra frames
>> + * processed in the request.
>> + */
>> +static int vrpmb_handle_write(VuDev *dev, struct virtio_rpmb_frame *frame)
>> +{
>> + VuRpmb *r = container_of(dev, VuRpmb, dev.parent);
>> + int extra_frames = 0;
>> + uint16_t block_count = be16toh(frame->block_count);
>> + uint32_t write_counter = be32toh(frame->write_counter);
>> + size_t offset;
>> +
>> + r->last_reqresp = VIRTIO_RPMB_RESP_DATA_WRITE;
>> + r->last_address = be16toh(frame->address);
>> + offset = r->last_address * RPMB_BLOCK_SIZE;
>> +
>> + /*
>> + * Run the checks from:
>> + * 5.12.6.1.3 Device Requirements: Device Operation: Data Write
>> + */
>> + if (!r->key) {
>> + g_warning("no key programmed");
>> + r->last_result = VIRTIO_RPMB_RES_NO_AUTH_KEY;
>> + } else if (block_count == 0 ||
>> + block_count > r->virtio_config.max_wr_cnt) {
>> + r->last_result = VIRTIO_RPMB_RES_GENERAL_FAILURE;
>> + } else if (false /* what does an expired write counter mean? */) {
>>
> IIRC, the counter has room for a 32-bit value and the counter will never
> wrap around. So once the counter have reached max for uint32_t, then
> there is an additional bit set (permanently) in the operation result.
> I.e., writes are no longer possible once that has happened. That is
> probably what you're referring to here I suppose.
That would make sense. I'll see if I can make the spec language a bit
clearer as well.
>
>> + r->last_result = VIRTIO_RPMB_RES_WRITE_COUNTER_EXPIRED;
>> + } else if (offset > (r->virtio_config.capacity * (128 * KiB))) {
>> + r->last_result = VIRTIO_RPMB_RES_ADDR_FAILURE;
>> + } else if (!vrpmb_verify_mac_in_frame(r, frame)) {
>> + r->last_result = VIRTIO_RPMB_RES_AUTH_FAILURE;
>> + } else if (write_counter != r->write_count) {
>> + r->last_result = VIRTIO_RPMB_RES_COUNT_FAILURE;
>> + } else {
>> + int i;
>> + /* At this point we have a valid authenticated write request
>> + * so the counter can incremented and we can attempt to
>> + * update the backing device.
>> + */
>> + r->write_count++;
>> + for (i = 0; i < block_count; i++) {
>> + void *blk = r->flash_map + offset;
>> + g_debug("%s: writing block %d", __func__, i);
>> + if (mprotect(blk, RPMB_BLOCK_SIZE, PROT_WRITE) != 0) {
>> + r->last_result = VIRTIO_RPMB_RES_WRITE_FAILURE;
>> + break;
>> + }
>> + memcpy(blk, frame[i].data, RPMB_BLOCK_SIZE);
>> + if (msync(blk, RPMB_BLOCK_SIZE, MS_SYNC) != 0) {
>> + g_warning("%s: failed to sync update", __func__);
>> + r->last_result = VIRTIO_RPMB_RES_WRITE_FAILURE;
>> + break;
>> + }
>> + if (mprotect(blk, RPMB_BLOCK_SIZE, PROT_READ) != 0) {
>> + g_warning("%s: failed to re-apply read protection", __func__);
>> + r->last_result = VIRTIO_RPMB_RES_GENERAL_FAILURE;
>> + break;
>> + }
>> + offset += RPMB_BLOCK_SIZE;
>> + }
>> + r->last_result = VIRTIO_RPMB_RES_OK;
>> + extra_frames = i - 1;
>> + }
>> +
>> + g_info("%s: %s (%x, %d extra frames processed), write_count=%d", __func__,
>> + r->last_result == VIRTIO_RPMB_RES_OK ? "successful":"failed",
>> + r->last_result, extra_frames, r->write_count);
>> +
>> + return extra_frames;
>> +}
>> +
>> +
>> /*
>> * Return the result of the last message. This is only valid if the
>> * previous message was VIRTIO_RPMB_REQ_PROGRAM_KEY or
>> @@ -339,10 +430,14 @@ static struct virtio_rpmb_frame * vrpmb_handle_result_read(VuDev *dev)
>> g_info("%s: for request:%x result:%x", __func__,
>> r->last_reqresp, r->last_result);
>>
>> - if (r->last_reqresp == VIRTIO_RPMB_RESP_PROGRAM_KEY ||
>> - r->last_reqresp == VIRTIO_RPMB_REQ_DATA_WRITE) {
>> + if (r->last_reqresp == VIRTIO_RPMB_RESP_PROGRAM_KEY) {
>> resp->result = htobe16(r->last_result);
>> resp->req_resp = htobe16(r->last_reqresp);
>> + } else if (r->last_reqresp == VIRTIO_RPMB_RESP_DATA_WRITE) {
>> + resp->result = htobe16(r->last_result);
>> + resp->req_resp = htobe16(r->last_reqresp);
>> + resp->write_counter = htobe32(r->write_count);
>> + resp->address = htobe16(r->last_address);
>> } else {
>> resp->result = htobe16(VIRTIO_RPMB_RES_GENERAL_FAILURE);
>> }
>> @@ -445,6 +540,10 @@ vrpmb_handle_ctrl(VuDev *dev, int qidx)
>> __func__);
>> }
>> break;
>> + case VIRTIO_RPMB_REQ_DATA_WRITE:
>> + /* we can have multiple blocks handled */
>> + n += vrpmb_handle_write(dev, f);
>> + break;
>> default:
>> g_debug("un-handled request: %x", f->req_resp);
>> break;
>> --
>> 2.20.1
>>
Thanks!
--
Alex Bennée
On Mon, Sep 28, 2020 at 03:56:19PM +0100, Alex Bennée wrote:
>
> Joakim Bech <joakim.bech@linaro.org> writes:
>
> > On Fri, Sep 25, 2020 at 01:51:43PM +0100, Alex Bennée wrote:
> >> With this command we are finally updating data to the backing store
> >> and cycling the write_count and each successful write. We also include
> >> the write count in all response frames as the spec is a little unclear
> >> but the example test code expected it.
> >>
> >> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> >> ---
> >> tools/vhost-user-rpmb/main.c | 111 +++++++++++++++++++++++++++++++++--
> >> 1 file changed, 105 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/tools/vhost-user-rpmb/main.c b/tools/vhost-user-rpmb/main.c
> >> index 88747c50fa44..a17c3b4bcc4e 100644
> >> --- a/tools/vhost-user-rpmb/main.c
> >> +++ b/tools/vhost-user-rpmb/main.c
> >> @@ -62,6 +62,7 @@ enum {
> >> #define KiB (1UL << 10)
> >> #define MAX_RPMB_SIZE (KiB * 128 * 256)
> >> #define RPMB_KEY_MAC_SIZE 32
> >> +#define RPMB_BLOCK_SIZE 256
> >>
> >> /* RPMB Request Types */
> >> #define VIRTIO_RPMB_REQ_PROGRAM_KEY 0x0001
> >> @@ -100,7 +101,7 @@ struct virtio_rpmb_config {
> >> struct virtio_rpmb_frame {
> >> uint8_t stuff[196];
> >> uint8_t key_mac[RPMB_KEY_MAC_SIZE];
> >> - uint8_t data[256];
> >> + uint8_t data[RPMB_BLOCK_SIZE];
> >> uint8_t nonce[16];
> >> /* remaining fields are big-endian */
> >> uint32_t write_counter;
> >> @@ -124,6 +125,7 @@ typedef struct VuRpmb {
> >> uint8_t last_nonce[16];
> >> uint16_t last_result;
> >> uint16_t last_reqresp;
> >> + uint16_t last_address;
> >> uint32_t write_count;
> >> } VuRpmb;
> >>
> >> @@ -239,17 +241,30 @@ vrpmb_set_config(VuDev *dev, const uint8_t *data,
> >> * which itself uses a 3 clause BSD chunk of code.
> >> */
> >>
> >> +static const int rpmb_frame_dlen = (sizeof(struct virtio_rpmb_frame) -
> >> + offsetof(struct virtio_rpmb_frame, data));
> >> +
> >> static void vrpmb_update_mac_in_frame(VuRpmb *r, struct virtio_rpmb_frame *frm)
> >> {
> >> hmac_sha256_ctx ctx;
> >> - static const int dlen = (sizeof(struct virtio_rpmb_frame) -
> >> - offsetof(struct virtio_rpmb_frame, data));
> >>
> >> hmac_sha256_init(&ctx, r->key, RPMB_KEY_MAC_SIZE);
> >> - hmac_sha256_update(&ctx, frm->data, dlen);
> >> + hmac_sha256_update(&ctx, frm->data, rpmb_frame_dlen);
> >> hmac_sha256_final(&ctx, &frm->key_mac[0], 32);
> >> }
> >>
> >> +static bool vrpmb_verify_mac_in_frame(VuRpmb *r, struct virtio_rpmb_frame *frm)
> >> +{
> >> + hmac_sha256_ctx ctx;
> >> + uint8_t calculated_mac[RPMB_KEY_MAC_SIZE];
> >> +
> >> + hmac_sha256_init(&ctx, r->key, RPMB_KEY_MAC_SIZE);
> >> + hmac_sha256_update(&ctx, frm->data, rpmb_frame_dlen);
> >> + hmac_sha256_final(&ctx, calculated_mac, RPMB_KEY_MAC_SIZE);
> >> +
> >> + return memcmp(calculated_mac, frm->key_mac, RPMB_KEY_MAC_SIZE) == 0;
> >>
> > I'd prefer using a constant time comparison function for this one
> > instead of memcmp (regardless if it's used for simulation or not) to
> > prevent eventual timing attacks.
>
> Could you recommend such a function for this?
>
Here is such an implementation:
https://github.com/OP-TEE/optee_os/blob/master/lib/libutils/ext/consttime_memcmp.c
However, cross check the license so it's OK to use. If not there are
similar implementations out there under other licenses.
> >
> >> +}
> >> +
> >> /*
> >> * Handlers for individual control messages
> >> */
> >> @@ -324,6 +339,82 @@ vrpmb_handle_get_write_counter(VuDev *dev, struct virtio_rpmb_frame *frame)
> >> return resp;
> >> }
> >>
> >> +/*
> >> + * vrpmb_handle_write:
> >> + *
> >> + * We will report the success/fail on receipt of
> >> + * VIRTIO_RPMB_REQ_RESULT_READ. Returns the number of extra frames
> >> + * processed in the request.
> >> + */
> >> +static int vrpmb_handle_write(VuDev *dev, struct virtio_rpmb_frame *frame)
> >> +{
> >> + VuRpmb *r = container_of(dev, VuRpmb, dev.parent);
> >> + int extra_frames = 0;
> >> + uint16_t block_count = be16toh(frame->block_count);
> >> + uint32_t write_counter = be32toh(frame->write_counter);
> >> + size_t offset;
> >> +
> >> + r->last_reqresp = VIRTIO_RPMB_RESP_DATA_WRITE;
> >> + r->last_address = be16toh(frame->address);
> >> + offset = r->last_address * RPMB_BLOCK_SIZE;
> >> +
> >> + /*
> >> + * Run the checks from:
> >> + * 5.12.6.1.3 Device Requirements: Device Operation: Data Write
> >> + */
> >> + if (!r->key) {
> >> + g_warning("no key programmed");
> >> + r->last_result = VIRTIO_RPMB_RES_NO_AUTH_KEY;
> >> + } else if (block_count == 0 ||
> >> + block_count > r->virtio_config.max_wr_cnt) {
> >> + r->last_result = VIRTIO_RPMB_RES_GENERAL_FAILURE;
> >> + } else if (false /* what does an expired write counter mean? */) {
> >>
> > IIRC, the counter has room for a 32-bit value and the counter will never
> > wrap around. So once the counter have reached max for uint32_t, then
> > there is an additional bit set (permanently) in the operation result.
> > I.e., writes are no longer possible once that has happened. That is
> > probably what you're referring to here I suppose.
>
> That would make sense. I'll see if I can make the spec language a bit
> clearer as well.
>
> >
> >> + r->last_result = VIRTIO_RPMB_RES_WRITE_COUNTER_EXPIRED;
> >> + } else if (offset > (r->virtio_config.capacity * (128 * KiB))) {
> >> + r->last_result = VIRTIO_RPMB_RES_ADDR_FAILURE;
> >> + } else if (!vrpmb_verify_mac_in_frame(r, frame)) {
> >> + r->last_result = VIRTIO_RPMB_RES_AUTH_FAILURE;
> >> + } else if (write_counter != r->write_count) {
> >> + r->last_result = VIRTIO_RPMB_RES_COUNT_FAILURE;
> >> + } else {
> >> + int i;
> >> + /* At this point we have a valid authenticated write request
> >> + * so the counter can incremented and we can attempt to
> >> + * update the backing device.
> >> + */
> >> + r->write_count++;
> >> + for (i = 0; i < block_count; i++) {
> >> + void *blk = r->flash_map + offset;
> >> + g_debug("%s: writing block %d", __func__, i);
> >> + if (mprotect(blk, RPMB_BLOCK_SIZE, PROT_WRITE) != 0) {
> >> + r->last_result = VIRTIO_RPMB_RES_WRITE_FAILURE;
> >> + break;
> >> + }
> >> + memcpy(blk, frame[i].data, RPMB_BLOCK_SIZE);
> >> + if (msync(blk, RPMB_BLOCK_SIZE, MS_SYNC) != 0) {
> >> + g_warning("%s: failed to sync update", __func__);
> >> + r->last_result = VIRTIO_RPMB_RES_WRITE_FAILURE;
> >> + break;
> >> + }
> >> + if (mprotect(blk, RPMB_BLOCK_SIZE, PROT_READ) != 0) {
> >> + g_warning("%s: failed to re-apply read protection", __func__);
> >> + r->last_result = VIRTIO_RPMB_RES_GENERAL_FAILURE;
> >> + break;
> >> + }
> >> + offset += RPMB_BLOCK_SIZE;
> >> + }
> >> + r->last_result = VIRTIO_RPMB_RES_OK;
> >> + extra_frames = i - 1;
> >> + }
> >> +
> >> + g_info("%s: %s (%x, %d extra frames processed), write_count=%d", __func__,
> >> + r->last_result == VIRTIO_RPMB_RES_OK ? "successful":"failed",
> >> + r->last_result, extra_frames, r->write_count);
> >> +
> >> + return extra_frames;
> >> +}
> >> +
> >> +
> >> /*
> >> * Return the result of the last message. This is only valid if the
> >> * previous message was VIRTIO_RPMB_REQ_PROGRAM_KEY or
> >> @@ -339,10 +430,14 @@ static struct virtio_rpmb_frame * vrpmb_handle_result_read(VuDev *dev)
> >> g_info("%s: for request:%x result:%x", __func__,
> >> r->last_reqresp, r->last_result);
> >>
> >> - if (r->last_reqresp == VIRTIO_RPMB_RESP_PROGRAM_KEY ||
> >> - r->last_reqresp == VIRTIO_RPMB_REQ_DATA_WRITE) {
> >> + if (r->last_reqresp == VIRTIO_RPMB_RESP_PROGRAM_KEY) {
> >> resp->result = htobe16(r->last_result);
> >> resp->req_resp = htobe16(r->last_reqresp);
> >> + } else if (r->last_reqresp == VIRTIO_RPMB_RESP_DATA_WRITE) {
> >> + resp->result = htobe16(r->last_result);
> >> + resp->req_resp = htobe16(r->last_reqresp);
> >> + resp->write_counter = htobe32(r->write_count);
> >> + resp->address = htobe16(r->last_address);
> >> } else {
> >> resp->result = htobe16(VIRTIO_RPMB_RES_GENERAL_FAILURE);
> >> }
> >> @@ -445,6 +540,10 @@ vrpmb_handle_ctrl(VuDev *dev, int qidx)
> >> __func__);
> >> }
> >> break;
> >> + case VIRTIO_RPMB_REQ_DATA_WRITE:
> >> + /* we can have multiple blocks handled */
> >> + n += vrpmb_handle_write(dev, f);
> >> + break;
> >> default:
> >> g_debug("un-handled request: %x", f->req_resp);
> >> break;
> >> --
> >> 2.20.1
> >>
>
> Thanks!
>
> --
> Alex Bennée
--
Regards,
Joakim
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