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https://github.com/RIOT-OS/RIOT.git
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sys/net/credman: add key loading functions
This allows to load private and public keys encoded in DER format.
This commit is contained in:
Leandro Lanzieri
parent
b6dee72161
commit
9980aa35b3
@ -21,6 +21,7 @@ PSEUDOMODULES += cortexm_fpu
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PSEUDOMODULES += cortexm_svc
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PSEUDOMODULES += cpp
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PSEUDOMODULES += cpu_check_address
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PSEUDOMODULES += credman_load
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PSEUDOMODULES += dbgpin
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PSEUDOMODULES += devfs_%
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PSEUDOMODULES += dhcpv6_%
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@ -699,6 +699,10 @@ ifneq (,$(filter sock_dtls, $(USEMODULE)))
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USEMODULE += sock_udp
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endif
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ifneq (,$(filter credman_load, $(USEMODULE)))
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USEPKG += tiny-asn1
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endif
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ifneq (,$(filter suit,$(USEMODULE)))
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USEPKG += nanocbor
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USEPKG += libcose
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@ -29,6 +29,7 @@
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#include <unistd.h>
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#include <stdint.h>
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#include "kernel_defines.h"
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#ifdef __cplusplus
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extern "C" {
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@ -45,6 +46,13 @@ extern "C" {
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#ifndef CONFIG_CREDMAN_MAX_CREDENTIALS
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#define CONFIG_CREDMAN_MAX_CREDENTIALS (2)
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#endif
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/**
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* @brief Maximum number of ASN.1 objects when decoding keys.
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*/
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#ifndef CONFIG_CREDMAN_MAX_ASN1_OBJ
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#define CONFIG_CREDMAN_MAX_ASN1_OBJ (8)
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#endif
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/** @} */
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/**
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@ -185,6 +193,76 @@ void credman_delete(credman_tag_t tag, credman_type_t type);
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*/
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int credman_get_used_count(void);
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#if IS_USED(MODULE_CREDMAN_LOAD) || DOXYGEN
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/**
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* @brief Load a public key from a buffer, as a `SubjectPublicKeyInfo` sequence, according to
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* RFC5280. The key should be encoded in DER format.
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*
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* @pre `buf != NULL && out != NULL`.
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*
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* @note To use this functionality include the module `credman_load`. Credman only supports ECDSA
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* for now, so [RFC5480](https://tools.ietf.org/html/rfc5480) applies.
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*
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* @experimental This API is considered experimental and will probably change without notice!
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*
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* @see https://tools.ietf.org/html/rfc5280#section-4.1
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*
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* @param[in] buf Buffer holding the encoded public key
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* @param[in] buf_len Length of @p buf
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* @param[out] out ECDSA public key to populate
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*
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* @retval CREDMAN_OK on success
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* @retval CREDMAN_INVALID if the key is not valid
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*/
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int credman_load_public_key(const void *buf, size_t buf_len, ecdsa_public_key_t *out);
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/**
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* @brief Load a private key from a buffer, as a `OneAsymmetricKey` sequence, according to RFC5958.
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* This is compatible with the previous version PKCS#8 (defined in RFC5208). If the optional
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* respective public key is present, it will be loaded as well. The key should be encoded in
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* DER format.
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*
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* @pre `buf != NULL && cred != NULL`
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*
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* @note To use this functionality include the module `credman_load`. Credman only supports ECDSA
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* for now.
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*
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* @experimental This API is considered experimental and will probably change without notice!
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*
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* @see https://tools.ietf.org/html/rfc5958#section-2
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*
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* @param[in] buf Buffer holding the encoded private key
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* @param[in] buf_len Length of @p buf
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* @param[out] cred Credential to populate
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*
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* @retval CREDMAN_OK on success
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* @retval CREDMAN_INVALID if the key is not valid
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*/
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int credman_load_private_key(const void *buf, size_t buf_len, credman_credential_t *cred);
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/**
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* @brief Load an ECC private key from a buffer, as an `ECPrivateKey` sequence, according to RFC5915.
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* If the optional respective public key is present, it will be loaded as well. The key
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* should be encoded in DER format.
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*
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* @pre `buf != NULL && cred != NULL`
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*
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* @note To use this functionality include the module `credman_load`.
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*
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* @experimental This API is considered experimental and will probably change without notice!
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*
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* @see https://tools.ietf.org/html/rfc5915#section-3
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*
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* @param[in] buf Buffer holding the encoded private key
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* @param[in] buf_len Length of @p buf
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* @param[out] cred Credential to populate
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*
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* @retval CREDMAN_OK on success
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* @retval CREDMAN_INVALID if the key is not valid
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*/
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int credman_load_private_ecc_key(const void *buf, size_t buf_len, credman_credential_t *cred);
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#endif /* MODULE_CREDMAN_LOAD || DOXYGEN */
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#ifdef TEST_SUITES
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/**
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* @brief Empties the credential pool
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@ -20,4 +20,9 @@ config CREDMAN_MAX_CREDENTIALS
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Configure 'CONFIG_CREDMAN_MAX_CREDENTIALS', the maximum number of
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allowed credentials in the credential pool.
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config CREDMAN_MAX_ASN1_OBJ
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int "Maximum number of ASN.1 objects when decoding keys"
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default 8
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depends on USEMODULE_CREDMAN_LOAD
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endif # KCONFIG_USEMODULE_CREDMAN
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@ -18,15 +18,31 @@
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#include "net/credman.h"
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#include "mutex.h"
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#include "kernel_defines.h"
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#include <assert.h>
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#include <string.h>
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#include <inttypes.h>
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#define ENABLE_DEBUG 0
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#include "debug.h"
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static mutex_t _mutex = MUTEX_INIT;
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#if IS_USED(MODULE_CREDMAN_LOAD)
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#include "tiny-asn1.h"
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/* Context-specific tag in DER encoding
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* (see section 8.1.2.2 of ITU-T X.690 https://www.itu.int/rec/T-REC-X.690-200811-S) */
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#define ASN1_CONTEXT_TAG(v) (0xA0 | (v & 0x1F))
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/* ASN.1 representation of ecPublicKey - OID 1.2.840.10045.2.1
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* (see https://oidref.com/1.2.840.10045.2.1) */
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static const uint8_t ecPublicKey[] = { 0x2A, 0x86, 0x48, 0xCE, 0x3D, 0x02, 0x01 };
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static int _parse_ecc_point(const asn1_tree *key, const void **x, const void **y);
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#endif /* MODULE_CREDMAN_LOAD */
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static credman_credential_t credentials[CONFIG_CREDMAN_MAX_CREDENTIALS];
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static unsigned used = 0;
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@ -90,6 +106,269 @@ end:
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return ret;
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}
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#if IS_USED(MODULE_CREDMAN_LOAD)
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int credman_load_public_key(const void *buf, size_t buf_len, ecdsa_public_key_t *out)
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{
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asn1_tree objects[CONFIG_CREDMAN_MAX_ASN1_OBJ];
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asn1_tree pub_key;
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assert(buf);
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assert(out);
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int obj_count = der_object_count((uint8_t *)buf, buf_len);
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if (obj_count <= 0) {
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DEBUG("credman: could not calculate the number of elements within the key\n");
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return CREDMAN_INVALID;
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}
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if (obj_count > CONFIG_CREDMAN_MAX_ASN1_OBJ) {
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DEBUG("credman: not enough ASN.1 objects to decode key.\n");
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DEBUG("credman: current max is %d, and we need %d\n",
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CONFIG_CREDMAN_MAX_ASN1_OBJ, obj_count);
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return CREDMAN_INVALID;
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}
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int32_t res = der_decode((uint8_t *)buf, buf_len, &pub_key, objects, obj_count);
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if (res < 0) {
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DEBUG("credman: could not parse the key (%" PRId32 ")\n", res);
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return CREDMAN_INVALID;
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}
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/*
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* From https://tools.ietf.org/html/rfc5280#section-4.1
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*
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* SubjectPublicKeyInfo ::= SEQUENCE {
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* algorithm AlgorithmIdentifier,
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* subjectPublicKey BIT STRING }
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*
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* AlgorithmIdentifier ::= SEQUENCE {
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* algorithm OBJECT IDENTIFIER,
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* parameters ANY DEFINED BY algorithm OPTIONAL }
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*/
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/* the outer container is a 'SubjectPublicKeyInfo', which should be a SEQUENCE */
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if (pub_key.type != ASN1_TYPE_SEQUENCE) {
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DEBUG("credman: the public key information should be contained in an ASN.1 SEQUENCE\n");
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return CREDMAN_INVALID;
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}
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asn1_tree *algorithm_id = pub_key.child;
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asn1_tree *algorithm = algorithm_id->child;
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/* for now only ECDSA is supported by credman */
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/* the algorithm should be Elliptic Curve Public Key (OID 1.2.840.10045.2.1) */
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if (sizeof(ecPublicKey) != algorithm->length) {
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DEBUG("credman: wrong OID length for algorithm\n");
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return CREDMAN_INVALID;
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}
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if (memcmp(ecPublicKey, algorithm->data, sizeof(ecPublicKey)) != 0) {
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DEBUG("credman: wrong OID for algorithm. Expected 1.2.840.10045.2.1\n");
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return CREDMAN_INVALID;
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}
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return _parse_ecc_point(algorithm_id->next, &out->x, &out->y);
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}
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int credman_load_private_key(const void *buf, size_t buf_len, credman_credential_t *cred)
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{
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asn1_tree objects[CONFIG_CREDMAN_MAX_ASN1_OBJ];
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asn1_tree priv_key;
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assert(buf);
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assert(cred);
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int obj_count = der_object_count((uint8_t *)buf, buf_len);
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if (obj_count <= 0) {
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DEBUG("credman: could not calculate the number of elements within the key\n");
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return CREDMAN_INVALID;
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}
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if (obj_count > CONFIG_CREDMAN_MAX_ASN1_OBJ) {
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DEBUG("credman: not enough ASN.1 objects to decode key.\n");
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DEBUG("credman: current max is %d, and we need %d\n",
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CONFIG_CREDMAN_MAX_ASN1_OBJ, obj_count);
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return CREDMAN_INVALID;
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}
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if (der_decode((uint8_t *)buf, buf_len, &priv_key, objects, obj_count) < 0) {
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DEBUG("credman: could not parse the key\n");
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return CREDMAN_INVALID;
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}
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/*
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* From https://tools.ietf.org/html/rfc5958#section-2
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*
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* OneAsymmetricKey ::= SEQUENCE {
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* version Version,
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* privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
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* privateKey PrivateKey,
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* attributes [0] Attributes OPTIONAL,
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* ...,
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* [[2: publicKey [1] PublicKey OPTIONAL ]],
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* ...
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* }
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*
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* PrivateKeyAlgorithmIdentifier ::= AlgorithmIdentifier
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* { PUBLIC-KEY,
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* { PrivateKeyAlgorithms } }
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*
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* AlgorithmIdentifier ::= SEQUENCE {
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* algorithm OBJECT IDENTIFIER,
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* parameters ANY DEFINED BY algorithm OPTIONAL }
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*
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* PrivateKey ::= OCTET STRING
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* -- Content varies based on type of key. The
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* -- algorithm identifier dictates the format of
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* -- the key.
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*/
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/* the outer container is a 'OneAsymmetricKey', which should be a SEQUENCE */
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if (priv_key.type != ASN1_TYPE_SEQUENCE) {
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DEBUG("credman: the private key information should be contained in an ASN.1 SEQUENCE\n");
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return CREDMAN_INVALID;
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}
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/* point to version */
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asn1_tree *node = priv_key.child;
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if (!node || node->type != ASN1_TYPE_INTEGER) {
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DEBUG("credman: invalid private key version\n");
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return CREDMAN_INVALID;
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}
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/* point to privateKeyAlgorithm */
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node = node->next;
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if (!node || node->type != ASN1_TYPE_SEQUENCE || !node->length) {
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DEBUG("credman: invalid private key algorithm identifier\n");
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return CREDMAN_INVALID;
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}
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/* for now only ECDSA is supported by credman */
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/* the algorithm should be Elliptic Curve Public Key (OID 1.2.840.10045.2.1) */
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asn1_tree *algorithm = node->child;
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if (sizeof(ecPublicKey) != algorithm->length) {
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DEBUG("credman: wrong private key algorithm, only ecPublicKey is supported\n");
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return CREDMAN_INVALID;
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}
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if (memcmp(ecPublicKey, algorithm->data, sizeof(ecPublicKey)) != 0) {
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DEBUG("credman: wrong OID for algorithm. Expected 1.2.840.10045.2.1\n");
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return CREDMAN_INVALID;
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}
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/* point to privateKey */
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node = node->next;
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if (!node || node->type != ASN1_TYPE_OCTET_STRING || !node->data || !node->length) {
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DEBUG("credman: no private key found\n");
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return CREDMAN_INVALID;
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}
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return credman_load_private_ecc_key(node->data, node->length, cred);
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}
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int credman_load_private_ecc_key(const void *buf, size_t buf_len, credman_credential_t *cred)
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{
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asn1_tree objects[CONFIG_CREDMAN_MAX_ASN1_OBJ];
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asn1_tree priv_key;
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assert(buf);
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assert(cred);
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int obj_count = der_object_count((uint8_t *)buf, buf_len);
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if (obj_count <= 0) {
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DEBUG("credman: could not calculate the number of elements within the key\n");
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return CREDMAN_INVALID;
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}
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if (obj_count > CONFIG_CREDMAN_MAX_ASN1_OBJ) {
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DEBUG("credman: not enough ASN.1 objects to decode key.\n");
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DEBUG("credman: current max is %d, and we need %d\n",
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CONFIG_CREDMAN_MAX_ASN1_OBJ, obj_count);
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return CREDMAN_INVALID;
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}
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if (der_decode((uint8_t *)buf, buf_len, &priv_key, objects, obj_count) < 0) {
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DEBUG("credman: could not parse the key\n");
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return CREDMAN_INVALID;
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}
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/*
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* From https://tools.ietf.org/html/rfc5915#section-3
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*
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* ECPrivateKey ::= SEQUENCE {
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* version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
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* privateKey OCTET STRING,
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* parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
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* publicKey [1] BIT STRING OPTIONAL
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* }
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*/
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/* point to version, it SHALL be 1 */
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asn1_tree *node = priv_key.child;
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if (!node || node->type != ASN1_TYPE_INTEGER || node->data[0] != 0x01) {
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DEBUG("credman: invalid private key version\n");
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return CREDMAN_INVALID;
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}
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/* point to privateKey */
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node = node->next;
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if (!node || node->type != ASN1_TYPE_OCTET_STRING || !node->data || !node->length) {
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DEBUG("credman: invalid private key\n");
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return CREDMAN_INVALID;
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}
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cred->type = CREDMAN_TYPE_ECDSA;
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cred->params.ecdsa.public_key.x = NULL;
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cred->params.ecdsa.public_key.y = NULL;
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cred->params.ecdsa.private_key = node->data;
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/* try to find a publicKey by tag */
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while (node && node->type != ASN1_CONTEXT_TAG(1)) {
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node = node->next;
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}
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if (!node) {
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return CREDMAN_OK;
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}
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return _parse_ecc_point(node->child, &cred->params.ecdsa.public_key.x,
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&cred->params.ecdsa.public_key.y);
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}
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static int _parse_ecc_point(const asn1_tree *key, const void **x, const void **y)
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{
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if (!key || key->type != ASN1_TYPE_BIT_STRING) {
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DEBUG("credman: the key should be an ASN.1 BIT STRING\n");
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return CREDMAN_INVALID;
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}
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if (!key->length) {
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DEBUG("credman: the key is missing\n");
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return CREDMAN_INVALID;
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}
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/* SEC 1: Elliptic Curve Cryptography - Section 2.3.4 (https://www.secg.org/sec1-v2.pdf) */
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/* check for uncompressed key format */
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if (key->data[1] != 0x04) {
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DEBUG("credman: only uncompressed format is supported\n");
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return CREDMAN_INVALID;
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}
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size_t coords_len = (key->length - 2) / 2;
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uint8_t *_x = &key->data[2]; /* skip format specifier and unused bits */
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uint8_t *_y = &_x[coords_len];
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*x = _x;
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*y = _y;
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return CREDMAN_OK;
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}
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#endif /* MODULE_CREDMAN_LOAD */
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int credman_get(credman_credential_t *credential, credman_tag_t tag,
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credman_type_t type)
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{
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