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inconsistency DC state recovery
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@z4yx
z4yx committed Aug 28, 2023
1 parent 7ddce05 commit a13b736
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Showing 2 changed files with 86 additions and 12 deletions.
9 changes: 8 additions & 1 deletion applets/ctap/ctap-internal.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@
#define KH_KEY_ATTR 0x04
#define HE_KEY_ATTR 0x05
#define DC_FILE "ctap_dc"
#define DC_NUMBERS_ATTR 0x00
#define DC_GENERAL_ATTR 0x00
#define DC_META_FILE "ctap_dm"
#define LB_FILE "ctap_lb"
#define LB_FILE_TMP "ctap_lbt"
Expand Down Expand Up @@ -246,6 +246,13 @@ typedef struct {
uint8_t cred_blob[MAX_CRED_BLOB_LENGTH];
} __packed CTAP_discoverable_credential;

typedef struct {
uint8_t numbers;
uint8_t index; // enough when MAX_DC_NUM == 64
uint8_t pending_add: 1;
uint8_t pending_delete: 1;
} __packed CTAP_dc_general_attr;

typedef struct {
uint8_t rp_id_hash[SHA256_DIGEST_LENGTH];
uint8_t rp_id[MAX_STORED_RPID_LENGTH];
Expand Down
89 changes: 78 additions & 11 deletions applets/ctap/ctap.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,7 @@ uint8_t ctap_install(uint8_t reset) {
}
uint8_t kh_key[KH_KEY_SIZE] = {0};
if (write_file(DC_FILE, NULL, 0, 0, 1) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
if (write_attr(DC_FILE, DC_NUMBERS_ATTR, kh_key, 1) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
if (write_attr(DC_FILE, DC_GENERAL_ATTR, kh_key, sizeof(CTAP_dc_general_attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
if (write_file(DC_META_FILE, NULL, 0, 0, 1) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
if (write_file(CTAP_CERT_FILE, NULL, 0, 0, 0) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
if (write_attr(CTAP_CERT_FILE, SIGN_CTR_ATTR, kh_key, 4) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
Expand Down Expand Up @@ -159,6 +159,52 @@ static void build_ed25519_cose_key(uint8_t *data) {
data[9] = 0x20;
}

int ctap_consistency_check(void) {
CTAP_dc_general_attr attr;
if (read_attr(DC_FILE, DC_GENERAL_ATTR, &attr, sizeof(attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
if (attr.pending_add || attr.pending_delete) {
DBG_MSG("Rolling back credential operations\n");
if (get_file_size(DC_FILE) >= ((int) attr.index + 1) * (int) sizeof(CTAP_discoverable_credential)) {
CTAP_discoverable_credential dc;
if (read_file(DC_FILE, &dc, attr.index * (int) sizeof(CTAP_discoverable_credential),
sizeof(CTAP_discoverable_credential)) < 0)
return CTAP2_ERR_UNHANDLED_REQUEST;
if (!dc.deleted) {
// delete the credential that had been written
DBG_MSG("Delete cred at %hhu\n", attr.index);
dc.deleted = 1;

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@dangfan

dangfan Aug 29, 2023

Member

dc.deleted = true might be used here.
if (write_file(DC_FILE, &dc, attr.index * (int) sizeof(CTAP_discoverable_credential),
sizeof(CTAP_discoverable_credential), 0) < 0)
return CTAP2_ERR_UNHANDLED_REQUEST;
}
}
// delete the meta then
int nr_rp = get_file_size(DC_META_FILE);
if (nr_rp < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
nr_rp /= sizeof(CTAP_rp_meta);
for (int i = 0; i < nr_rp; ++i) {
CTAP_rp_meta meta;
int size = read_file(DC_META_FILE, &meta, i * (int) sizeof(CTAP_rp_meta), sizeof(CTAP_rp_meta));
if (size < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
if ((meta.slots & (1ull << attr.index)) != 0) {
DBG_MSG("Orig slot bitmap: 0x%llx\n", meta.slots);
meta.slots &= ~(1ull << attr.index);
DBG_MSG("New slot bitmap: 0x%llx\n", meta.slots);
size = write_file(DC_META_FILE, &meta, i * (int) sizeof(CTAP_rp_meta), sizeof(CTAP_rp_meta), 0);
if (size < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
break;
}
}
if (attr.pending_delete)
attr.numbers--;

attr.pending_add = 0;
attr.pending_delete = 0;
if (write_attr(DC_FILE, DC_GENERAL_ATTR, &attr, sizeof(attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
}
return 0;
}

uint8_t ctap_make_auth_data(uint8_t *rp_id_hash, uint8_t *buf, uint8_t flags, const uint8_t *extension,
uint8_t extension_size, size_t *len, int32_t alg_type, bool dc, uint8_t cred_protect) {
// See https://www.w3.org/TR/webauthn/#sec-authenticator-data
Expand Down Expand Up @@ -235,6 +281,9 @@ static uint8_t ctap_make_credential(CborEncoder *encoder, uint8_t *params, size_
int ret = parse_make_credential(&parser, &mc, params, len);
CHECK_PARSER_RET(ret);

ret = ctap_consistency_check();
CHECK_PARSER_RET(ret);

// 1. If authenticator supports clientPin features and the platform sends a zero length pin_uv_auth_param
if ((mc.parsed_params & PARAM_PIN_UV_AUTH_PARAM) && mc.pin_uv_auth_param_len == 0) {
// a. Request evidence of user interaction in an authenticator-specific way (e.g., flash the LED light).
Expand Down Expand Up @@ -539,13 +588,15 @@ static uint8_t ctap_make_credential(CborEncoder *encoder, uint8_t *params, size_
memcpy(dc.cred_blob, mc.ext_cred_blob, mc.ext_cred_blob_len);
}
dc.deleted = false;

CTAP_dc_general_attr attr;
if (read_attr(DC_FILE, DC_GENERAL_ATTR, &attr, sizeof(attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
attr.pending_add = 1;
attr.index = (uint8_t)pos;
if (write_attr(DC_FILE, DC_GENERAL_ATTR, &attr, sizeof(attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
if (write_file(DC_FILE, &dc, pos * (int) sizeof(CTAP_discoverable_credential),
sizeof(CTAP_discoverable_credential), 0) < 0)
return CTAP2_ERR_UNHANDLED_REQUEST;
uint8_t numbers;
if (read_attr(DC_FILE, DC_NUMBERS_ATTR, &numbers, sizeof(numbers)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
++numbers;
if (write_attr(DC_FILE, DC_NUMBERS_ATTR, &numbers, sizeof(numbers)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;

// Process metadata
size = get_file_size(DC_META_FILE);
Expand Down Expand Up @@ -578,6 +629,9 @@ static uint8_t ctap_make_credential(CborEncoder *encoder, uint8_t *params, size_
if (write_file(DC_META_FILE, &meta, meta_pos * (int) sizeof(CTAP_rp_meta),
sizeof(CTAP_rp_meta), 0) < 0)
return CTAP2_ERR_UNHANDLED_REQUEST;
attr.pending_add = 0;
++attr.numbers;
if (write_attr(DC_FILE, DC_GENERAL_ATTR, &attr, sizeof(attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
}

// 18. Otherwise, if the "rk" option is false: the authenticator MUST create a non-discoverable credential.
Expand Down Expand Up @@ -667,6 +721,8 @@ static uint8_t ctap_get_assertion(CborEncoder *encoder, uint8_t *params, size_t

if (!in_get_next_assertion) {
credential_counter = 0;
ret = ctap_consistency_check();
CHECK_PARSER_RET(ret);
} else {
// GET_NEXT_ASSERTION
// 1. If authenticator does not remember any authenticatorGetAssertion parameters, return CTAP2_ERR_NOT_ALLOWED.
Expand Down Expand Up @@ -1507,16 +1563,17 @@ static uint8_t ctap_credential_management(CborEncoder *encoder, const uint8_t *p
CTAP_credential_management cm;
int ret = parse_credential_management(&parser, &cm, params, len);
CHECK_PARSER_RET(ret);
ret = ctap_consistency_check();
CHECK_PARSER_RET(ret);

static int idx, n_rp; // for rp enumeration
static uint64_t slots; // for credential enumeration
int size, counter;
CborEncoder map, sub_map;
uint8_t numbers;
uint8_t numbers = 0;
CTAP_rp_meta meta;
CTAP_discoverable_credential dc;
bool include_numbers;
if (read_attr(DC_FILE, DC_NUMBERS_ATTR, &numbers, sizeof(numbers)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;

if (cm.sub_command == CM_CMD_GET_CREDS_METADATA ||
cm.sub_command == CM_CMD_ENUMERATE_RPS_BEGIN ||
Expand All @@ -1525,6 +1582,10 @@ static uint8_t ctap_credential_management(CborEncoder *encoder, const uint8_t *p
cm.sub_command == CM_CMD_UPDATE_USER_INFORMATION) {
last_cm_cmd = cm.sub_command;
uint8_t *buf = (uint8_t *) &dc; // buffer reuse
_Static_assert(sizeof(CTAP_dc_general_attr) < sizeof(dc), "CTAP_dc_general_attr buffer overflow");
if (read_attr(DC_FILE, DC_GENERAL_ATTR, buf, sizeof(CTAP_dc_general_attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
numbers = ((CTAP_dc_general_attr*)buf)->numbers;

buf[0] = cm.sub_command;
if (cm.param_len + 1 > sizeof(dc)) return CTAP1_ERR_INVALID_LENGTH;
if (cm.param_len > 0) memcpy(&buf[1], cm.sub_command_params_ptr, cm.param_len);
Expand Down Expand Up @@ -1764,17 +1825,20 @@ static uint8_t ctap_credential_management(CborEncoder *encoder, const uint8_t *p
}
}
if (idx == numbers) return CTAP2_ERR_NO_CREDENTIALS;
// TODO: how to achieve the consistency?

CTAP_dc_general_attr attr;
if (read_attr(DC_FILE, DC_GENERAL_ATTR, &attr, sizeof(attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
attr.index = (uint8_t)idx;
attr.pending_delete = 1;
if (write_attr(DC_FILE, DC_GENERAL_ATTR, &attr, sizeof(attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;

// delete dc first
dc.deleted = true;
if (write_file(DC_FILE, &dc, idx * (int) sizeof(CTAP_discoverable_credential),
sizeof(CTAP_discoverable_credential),
0) < 0)
return CTAP2_ERR_UNHANDLED_REQUEST;
DBG_MSG("Slot %d deleted\n", idx);
if (read_attr(DC_FILE, DC_NUMBERS_ATTR, &numbers, sizeof(numbers)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
--numbers;
if (write_attr(DC_FILE, DC_NUMBERS_ATTR, &numbers, sizeof(numbers)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
// delete the meta then
size = get_file_size(DC_META_FILE);
if (size < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
Expand All @@ -1791,6 +1855,9 @@ static uint8_t ctap_credential_management(CborEncoder *encoder, const uint8_t *p
break;
}
}
attr.numbers--;
attr.pending_delete = 0;
if (write_attr(DC_FILE, DC_GENERAL_ATTR, &attr, sizeof(attr)) < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
break;

case CM_CMD_UPDATE_USER_INFORMATION:
Expand Down

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