library/asn1parse.c - mirror/mbed-tls.git - TrustedFirmware Git Browser

 /*
  *  Generic ASN.1 parsing
  *
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
  */

 #include "common.h"

 #if defined(MBEDTLS_ASN1_PARSE_C) || defined(MBEDTLS_X509_CREATE_C) || \
     defined(MBEDTLS_PSA_UTIL_HAVE_ECDSA)

 #include "mbedtls/asn1.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"

 #include <string.h>

 #if defined(MBEDTLS_BIGNUM_C)
 #include "mbedtls/bignum.h"
 #endif

 #include "mbedtls/platform.h"

 /*
  * ASN.1 DER decoding routines
  */
 int mbedtls_asn1_get_len(unsigned char **p,
                          const unsigned char *end,
                          size_t *len)
 {
     if ((end - *p) < 1) {
         return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
     }

     if ((**p & 0x80) == 0) {
         *len = *(*p)++;
     } else {
         int n = (**p) & 0x7F;
         if (n == 0 || n > 4) {
             return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
         }
         if ((end - *p) <= n) {
             return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
         }
         *len = 0;
         (*p)++;
         while (n--) {
             *len = (*len << 8) | **p;
             (*p)++;
         }
     }

     if (*len > (size_t) (end - *p)) {
         return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
     }

     return 0;
 }

 int mbedtls_asn1_get_tag(unsigned char **p,
                          const unsigned char *end,
                          size_t *len, int tag)
 {
     if ((end - *p) < 1) {
         return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
     }

     if (**p != tag) {
         return MBEDTLS_ERR_ASN1_UNEXPECTED_TAG;
     }

     (*p)++;

     return mbedtls_asn1_get_len(p, end, len);
 }
 #endif /* MBEDTLS_ASN1_PARSE_C || MBEDTLS_X509_CREATE_C || MBEDTLS_PSA_UTIL_HAVE_ECDSA */

 #if defined(MBEDTLS_ASN1_PARSE_C)
 int mbedtls_asn1_get_bool(unsigned char **p,
                           const unsigned char *end,
                           int *val)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len;

     if ((ret = mbedtls_asn1_get_tag(p, end, &len, MBEDTLS_ASN1_BOOLEAN)) != 0) {
         return ret;
     }

     if (len != 1) {
         return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
     }

     *val = (**p != 0) ? 1 : 0;
     (*p)++;

     return 0;
 }

 static int asn1_get_tagged_int(unsigned char **p,
                                const unsigned char *end,
                                int tag, int *val)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len;

     if ((ret = mbedtls_asn1_get_tag(p, end, &len, tag)) != 0) {
         return ret;
     }

     /*
      * len==0 is malformed (0 must be represented as 020100 for INTEGER,
      * or 0A0100 for ENUMERATED tags
      */
     if (len == 0) {
         return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
     }
     /* This is a cryptography library. Reject negative integers. */
     if ((**p & 0x80) != 0) {
         return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
     }

     /* Skip leading zeros. */
     while (len > 0 && **p == 0) {
         ++(*p);
         --len;
     }

     /* Reject integers that don't fit in an int. This code assumes that
      * the int type has no padding bit. */
     if (len > sizeof(int)) {
         return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
     }
     if (len == sizeof(int) && (**p & 0x80) != 0) {
         return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
     }

     *val = 0;
     while (len-- > 0) {
         *val = (*val << 8) | **p;
         (*p)++;
     }

     return 0;
 }

 int mbedtls_asn1_get_int(unsigned char **p,
                          const unsigned char *end,
                          int *val)
 {
     return asn1_get_tagged_int(p, end, MBEDTLS_ASN1_INTEGER, val);
 }

 int mbedtls_asn1_get_enum(unsigned char **p,
                           const unsigned char *end,
                           int *val)
 {
     return asn1_get_tagged_int(p, end, MBEDTLS_ASN1_ENUMERATED, val);
 }

 #if defined(MBEDTLS_BIGNUM_C)
 int mbedtls_asn1_get_mpi(unsigned char **p,
                          const unsigned char *end,
                          mbedtls_mpi *X)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len;

     if ((ret = mbedtls_asn1_get_tag(p, end, &len, MBEDTLS_ASN1_INTEGER)) != 0) {
         return ret;
     }

     ret = mbedtls_mpi_read_binary(X, *p, len);

     *p += len;

     return ret;
 }
 #endif /* MBEDTLS_BIGNUM_C */

 int mbedtls_asn1_get_bitstring(unsigned char **p, const unsigned char *end,
                                mbedtls_asn1_bitstring *bs)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     /* Certificate type is a single byte bitstring */
     if ((ret = mbedtls_asn1_get_tag(p, end, &bs->len, MBEDTLS_ASN1_BIT_STRING)) != 0) {
         return ret;
     }

     /* Check length, subtract one for actual bit string length */
     if (bs->len < 1) {
         return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
     }
     bs->len -= 1;

     /* Get number of unused bits, ensure unused bits <= 7 */
     bs->unused_bits = **p;
     if (bs->unused_bits > 7) {
         return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
     }
     (*p)++;

     /* Get actual bitstring */
     bs->p = *p;
     *p += bs->len;

     if (*p != end) {
         return MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
     }

     return 0;
 }

 /*
  * Traverse an ASN.1 "SEQUENCE OF <tag>"
  * and call a callback for each entry found.
  */
 int mbedtls_asn1_traverse_sequence_of(
     unsigned char **p,
     const unsigned char *end,
     unsigned char tag_must_mask, unsigned char tag_must_val,
     unsigned char tag_may_mask, unsigned char tag_may_val,
     int (*cb)(void *ctx, int tag,
               unsigned char *start, size_t len),
     void *ctx)
 {
     int ret;
     size_t len;

     /* Get main sequence tag */
     if ((ret = mbedtls_asn1_get_tag(p, end, &len,
                                     MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
         return ret;
     }

     if (*p + len != end) {
         return MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
     }

     while (*p < end) {
         unsigned char const tag = *(*p)++;

         if ((tag & tag_must_mask) != tag_must_val) {
             return MBEDTLS_ERR_ASN1_UNEXPECTED_TAG;
         }

         if ((ret = mbedtls_asn1_get_len(p, end, &len)) != 0) {
             return ret;
         }

         if ((tag & tag_may_mask) == tag_may_val) {
             if (cb != NULL) {
                 ret = cb(ctx, tag, *p, len);
                 if (ret != 0) {
                     return ret;
                 }
             }
         }

         *p += len;
     }

     return 0;
 }

 /*
  * Get a bit string without unused bits
  */
 int mbedtls_asn1_get_bitstring_null(unsigned char **p, const unsigned char *end,
                                     size_t *len)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     if ((ret = mbedtls_asn1_get_tag(p, end, len, MBEDTLS_ASN1_BIT_STRING)) != 0) {
         return ret;
     }

     if (*len == 0) {
         return MBEDTLS_ERR_ASN1_INVALID_DATA;
     }
     --(*len);

     if (**p != 0) {
         return MBEDTLS_ERR_ASN1_INVALID_DATA;
     }
     ++(*p);

     return 0;
 }

 void mbedtls_asn1_sequence_free(mbedtls_asn1_sequence *seq)
 {
     while (seq != NULL) {
         mbedtls_asn1_sequence *next = seq->next;
         mbedtls_free(seq);
         seq = next;
     }
 }

 typedef struct {
     int tag;
     mbedtls_asn1_sequence *cur;
 } asn1_get_sequence_of_cb_ctx_t;

 static int asn1_get_sequence_of_cb(void *ctx,
                                    int tag,
                                    unsigned char *start,
                                    size_t len)
 {
     asn1_get_sequence_of_cb_ctx_t *cb_ctx =
         (asn1_get_sequence_of_cb_ctx_t *) ctx;
     mbedtls_asn1_sequence *cur =
         cb_ctx->cur;

     if (cur->buf.p != NULL) {
         cur->next =
             mbedtls_calloc(1, sizeof(mbedtls_asn1_sequence));

         if (cur->next == NULL) {
             return MBEDTLS_ERR_ASN1_ALLOC_FAILED;
         }

         cur = cur->next;
     }

     cur->buf.p = start;
     cur->buf.len = len;
     cur->buf.tag = tag;

     cb_ctx->cur = cur;
     return 0;
 }

 /*
  *  Parses and splits an ASN.1 "SEQUENCE OF <tag>"
  */
 int mbedtls_asn1_get_sequence_of(unsigned char **p,
                                  const unsigned char *end,
                                  mbedtls_asn1_sequence *cur,
                                  int tag)
 {
     asn1_get_sequence_of_cb_ctx_t cb_ctx = { tag, cur };
     memset(cur, 0, sizeof(mbedtls_asn1_sequence));
     return mbedtls_asn1_traverse_sequence_of(
         p, end, 0xFF, tag, 0, 0,
         asn1_get_sequence_of_cb, &cb_ctx);
 }

 int mbedtls_asn1_get_alg(unsigned char **p,
                          const unsigned char *end,
                          mbedtls_asn1_buf *alg, mbedtls_asn1_buf *params)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len;

     if ((ret = mbedtls_asn1_get_tag(p, end, &len,
                                     MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
         return ret;
     }

     if ((end - *p) < 1) {
         return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
     }

     alg->tag = **p;
     end = *p + len;

     if ((ret = mbedtls_asn1_get_tag(p, end, &alg->len, MBEDTLS_ASN1_OID)) != 0) {
         return ret;
     }

     alg->p = *p;
     *p += alg->len;

     if (*p == end) {
         mbedtls_platform_zeroize(params, sizeof(mbedtls_asn1_buf));
         return 0;
     }

     params->tag = **p;
     (*p)++;

     if ((ret = mbedtls_asn1_get_len(p, end, &params->len)) != 0) {
         return ret;
     }

     params->p = *p;
     *p += params->len;

     if (*p != end) {
         return MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
     }

     return 0;
 }

 int mbedtls_asn1_get_alg_null(unsigned char **p,
                               const unsigned char *end,
                               mbedtls_asn1_buf *alg)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     mbedtls_asn1_buf params;

     memset(&params, 0, sizeof(mbedtls_asn1_buf));

     if ((ret = mbedtls_asn1_get_alg(p, end, alg, &params)) != 0) {
         return ret;
     }

     if ((params.tag != MBEDTLS_ASN1_NULL && params.tag != 0) || params.len != 0) {
         return MBEDTLS_ERR_ASN1_INVALID_DATA;
     }

     return 0;
 }

 #if !defined(MBEDTLS_DEPRECATED_REMOVED)
 void mbedtls_asn1_free_named_data(mbedtls_asn1_named_data *cur)
 {
     if (cur == NULL) {
         return;
     }

     mbedtls_free(cur->oid.p);
     mbedtls_free(cur->val.p);

     mbedtls_platform_zeroize(cur, sizeof(mbedtls_asn1_named_data));
 }
 #endif /* MBEDTLS_DEPRECATED_REMOVED */

 void mbedtls_asn1_free_named_data_list(mbedtls_asn1_named_data **head)
 {
     mbedtls_asn1_named_data *cur;

     while ((cur = *head) != NULL) {
         *head = cur->next;
         mbedtls_free(cur->oid.p);
         mbedtls_free(cur->val.p);
         mbedtls_free(cur);
     }
 }

 void mbedtls_asn1_free_named_data_list_shallow(mbedtls_asn1_named_data *name)
 {
     for (mbedtls_asn1_named_data *next; name != NULL; name = next) {
         next = name->next;
         mbedtls_free(name);
     }
 }

 const mbedtls_asn1_named_data *mbedtls_asn1_find_named_data(const mbedtls_asn1_named_data *list,
                                                             const char *oid, size_t len)
 {
     while (list != NULL) {
         if (list->oid.len == len &&
             memcmp(list->oid.p, oid, len) == 0) {
             break;
         }

         list = list->next;
     }

     return list;
 }

 #endif /* MBEDTLS_ASN1_PARSE_C */
	/*
	* Generic ASN.1 parsing
	*
	* Copyright The Mbed TLS Contributors
	* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
	*/

	#include "common.h"

	#if defined(MBEDTLS_ASN1_PARSE_C) \|\| defined(MBEDTLS_X509_CREATE_C) \|\| \
	defined(MBEDTLS_PSA_UTIL_HAVE_ECDSA)

	#include "mbedtls/asn1.h"
	#include "mbedtls/platform_util.h"
	#include "mbedtls/error.h"

	#include <string.h>

	#if defined(MBEDTLS_BIGNUM_C)
	#include "mbedtls/bignum.h"
	#endif

	#include "mbedtls/platform.h"

	/*
	* ASN.1 DER decoding routines
	*/
	int mbedtls_asn1_get_len(unsigned char **p,
	const unsigned char *end,
	size_t *len)
	{
	if ((end - *p) < 1) {
	return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
	}

	if ((**p & 0x80) == 0) {
	len = (*p)++;
	} else {
	int n = (**p) & 0x7F;
	if (n == 0 \|\| n > 4) {
	return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
	}
	if ((end - *p) <= n) {
	return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
	}
	*len = 0;
	(*p)++;
	while (n--) {
	len = (len << 8) \| **p;
	(*p)++;
	}
	}

	if (len > (size_t) (end - p)) {
	return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
	}

	return 0;
	}

	int mbedtls_asn1_get_tag(unsigned char **p,
	const unsigned char *end,
	size_t *len, int tag)
	{
	if ((end - *p) < 1) {
	return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
	}

	if (**p != tag) {
	return MBEDTLS_ERR_ASN1_UNEXPECTED_TAG;
	}

	(*p)++;

	return mbedtls_asn1_get_len(p, end, len);
	}
	#endif /* MBEDTLS_ASN1_PARSE_C \|\| MBEDTLS_X509_CREATE_C \|\| MBEDTLS_PSA_UTIL_HAVE_ECDSA */

	#if defined(MBEDTLS_ASN1_PARSE_C)
	int mbedtls_asn1_get_bool(unsigned char **p,
	const unsigned char *end,
	int *val)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t len;

	if ((ret = mbedtls_asn1_get_tag(p, end, &len, MBEDTLS_ASN1_BOOLEAN)) != 0) {
	return ret;
	}

	if (len != 1) {
	return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
	}

	val = (*p != 0) ? 1 : 0;
	(*p)++;

	return 0;
	}

	static int asn1_get_tagged_int(unsigned char **p,
	const unsigned char *end,
	int tag, int *val)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t len;

	if ((ret = mbedtls_asn1_get_tag(p, end, &len, tag)) != 0) {
	return ret;
	}

	/*
	* len==0 is malformed (0 must be represented as 020100 for INTEGER,
	* or 0A0100 for ENUMERATED tags
	*/
	if (len == 0) {
	return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
	}
	/* This is a cryptography library. Reject negative integers. */
	if ((**p & 0x80) != 0) {
	return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
	}

	/* Skip leading zeros. */
	while (len > 0 && **p == 0) {
	++(*p);
	--len;
	}

	/* Reject integers that don't fit in an int. This code assumes that
	* the int type has no padding bit. */
	if (len > sizeof(int)) {
	return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
	}
	if (len == sizeof(int) && (**p & 0x80) != 0) {
	return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
	}

	*val = 0;
	while (len-- > 0) {
	val = (val << 8) \| **p;
	(*p)++;
	}

	return 0;
	}

	int mbedtls_asn1_get_int(unsigned char **p,
	const unsigned char *end,
	int *val)
	{
	return asn1_get_tagged_int(p, end, MBEDTLS_ASN1_INTEGER, val);
	}

	int mbedtls_asn1_get_enum(unsigned char **p,
	const unsigned char *end,
	int *val)
	{
	return asn1_get_tagged_int(p, end, MBEDTLS_ASN1_ENUMERATED, val);
	}

	#if defined(MBEDTLS_BIGNUM_C)
	int mbedtls_asn1_get_mpi(unsigned char **p,
	const unsigned char *end,
	mbedtls_mpi *X)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t len;

	if ((ret = mbedtls_asn1_get_tag(p, end, &len, MBEDTLS_ASN1_INTEGER)) != 0) {
	return ret;
	}

	ret = mbedtls_mpi_read_binary(X, *p, len);

	*p += len;

	return ret;
	}
	#endif /* MBEDTLS_BIGNUM_C */

	int mbedtls_asn1_get_bitstring(unsigned char *p, const unsigned char end,
	mbedtls_asn1_bitstring *bs)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	/* Certificate type is a single byte bitstring */
	if ((ret = mbedtls_asn1_get_tag(p, end, &bs->len, MBEDTLS_ASN1_BIT_STRING)) != 0) {
	return ret;
	}

	/* Check length, subtract one for actual bit string length */
	if (bs->len < 1) {
	return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
	}
	bs->len -= 1;

	/* Get number of unused bits, ensure unused bits <= 7 */
	bs->unused_bits = **p;
	if (bs->unused_bits > 7) {
	return MBEDTLS_ERR_ASN1_INVALID_LENGTH;
	}
	(*p)++;

	/* Get actual bitstring */
	bs->p = *p;
	*p += bs->len;

	if (*p != end) {
	return MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
	}

	return 0;
	}

	/*
	* Traverse an ASN.1 "SEQUENCE OF <tag>"
	* and call a callback for each entry found.
	*/
	int mbedtls_asn1_traverse_sequence_of(
	unsigned char **p,
	const unsigned char *end,
	unsigned char tag_must_mask, unsigned char tag_must_val,
	unsigned char tag_may_mask, unsigned char tag_may_val,
	int (cb)(void ctx, int tag,
	unsigned char *start, size_t len),
	void *ctx)
	{
	int ret;
	size_t len;

	/* Get main sequence tag */
	if ((ret = mbedtls_asn1_get_tag(p, end, &len,
	MBEDTLS_ASN1_CONSTRUCTED \| MBEDTLS_ASN1_SEQUENCE)) != 0) {
	return ret;
	}

	if (*p + len != end) {
	return MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
	}

	while (*p < end) {
	unsigned char const tag = (p)++;

	if ((tag & tag_must_mask) != tag_must_val) {
	return MBEDTLS_ERR_ASN1_UNEXPECTED_TAG;
	}

	if ((ret = mbedtls_asn1_get_len(p, end, &len)) != 0) {
	return ret;
	}

	if ((tag & tag_may_mask) == tag_may_val) {
	if (cb != NULL) {
	ret = cb(ctx, tag, *p, len);
	if (ret != 0) {
	return ret;
	}
	}
	}

	*p += len;
	}

	return 0;
	}

	/*
	* Get a bit string without unused bits
	*/
	int mbedtls_asn1_get_bitstring_null(unsigned char *p, const unsigned char end,
	size_t *len)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	if ((ret = mbedtls_asn1_get_tag(p, end, len, MBEDTLS_ASN1_BIT_STRING)) != 0) {
	return ret;
	}

	if (*len == 0) {
	return MBEDTLS_ERR_ASN1_INVALID_DATA;
	}
	--(*len);

	if (**p != 0) {
	return MBEDTLS_ERR_ASN1_INVALID_DATA;
	}
	++(*p);

	return 0;
	}

	void mbedtls_asn1_sequence_free(mbedtls_asn1_sequence *seq)
	{
	while (seq != NULL) {
	mbedtls_asn1_sequence *next = seq->next;
	mbedtls_free(seq);
	seq = next;
	}
	}

	typedef struct {
	int tag;
	mbedtls_asn1_sequence *cur;
	} asn1_get_sequence_of_cb_ctx_t;

	static int asn1_get_sequence_of_cb(void *ctx,
	int tag,
	unsigned char *start,
	size_t len)
	{
	asn1_get_sequence_of_cb_ctx_t *cb_ctx =
	(asn1_get_sequence_of_cb_ctx_t *) ctx;
	mbedtls_asn1_sequence *cur =
	cb_ctx->cur;

	if (cur->buf.p != NULL) {
	cur->next =
	mbedtls_calloc(1, sizeof(mbedtls_asn1_sequence));

	if (cur->next == NULL) {
	return MBEDTLS_ERR_ASN1_ALLOC_FAILED;
	}

	cur = cur->next;
	}

	cur->buf.p = start;
	cur->buf.len = len;
	cur->buf.tag = tag;

	cb_ctx->cur = cur;
	return 0;
	}

	/*
	* Parses and splits an ASN.1 "SEQUENCE OF <tag>"
	*/
	int mbedtls_asn1_get_sequence_of(unsigned char **p,
	const unsigned char *end,
	mbedtls_asn1_sequence *cur,
	int tag)
	{
	asn1_get_sequence_of_cb_ctx_t cb_ctx = { tag, cur };
	memset(cur, 0, sizeof(mbedtls_asn1_sequence));
	return mbedtls_asn1_traverse_sequence_of(
	p, end, 0xFF, tag, 0, 0,
	asn1_get_sequence_of_cb, &cb_ctx);
	}

	int mbedtls_asn1_get_alg(unsigned char **p,
	const unsigned char *end,
	mbedtls_asn1_buf alg, mbedtls_asn1_buf params)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t len;

	if ((ret = mbedtls_asn1_get_tag(p, end, &len,
	MBEDTLS_ASN1_CONSTRUCTED \| MBEDTLS_ASN1_SEQUENCE)) != 0) {
	return ret;
	}

	if ((end - *p) < 1) {
	return MBEDTLS_ERR_ASN1_OUT_OF_DATA;
	}

	alg->tag = **p;
	end = *p + len;

	if ((ret = mbedtls_asn1_get_tag(p, end, &alg->len, MBEDTLS_ASN1_OID)) != 0) {
	return ret;
	}

	alg->p = *p;
	*p += alg->len;

	if (*p == end) {
	mbedtls_platform_zeroize(params, sizeof(mbedtls_asn1_buf));
	return 0;
	}

	params->tag = **p;
	(*p)++;

	if ((ret = mbedtls_asn1_get_len(p, end, &params->len)) != 0) {
	return ret;
	}

	params->p = *p;
	*p += params->len;

	if (*p != end) {
	return MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
	}

	return 0;
	}

	int mbedtls_asn1_get_alg_null(unsigned char **p,
	const unsigned char *end,
	mbedtls_asn1_buf *alg)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	mbedtls_asn1_buf params;

	memset(&params, 0, sizeof(mbedtls_asn1_buf));

	if ((ret = mbedtls_asn1_get_alg(p, end, alg, &params)) != 0) {
	return ret;
	}

	if ((params.tag != MBEDTLS_ASN1_NULL && params.tag != 0) \|\| params.len != 0) {
	return MBEDTLS_ERR_ASN1_INVALID_DATA;
	}

	return 0;
	}

	#if !defined(MBEDTLS_DEPRECATED_REMOVED)
	void mbedtls_asn1_free_named_data(mbedtls_asn1_named_data *cur)
	{
	if (cur == NULL) {
	return;
	}

	mbedtls_free(cur->oid.p);
	mbedtls_free(cur->val.p);

	mbedtls_platform_zeroize(cur, sizeof(mbedtls_asn1_named_data));
	}
	#endif /* MBEDTLS_DEPRECATED_REMOVED */

	void mbedtls_asn1_free_named_data_list(mbedtls_asn1_named_data **head)
	{
	mbedtls_asn1_named_data *cur;

	while ((cur = *head) != NULL) {
	*head = cur->next;
	mbedtls_free(cur->oid.p);
	mbedtls_free(cur->val.p);
	mbedtls_free(cur);
	}
	}

	void mbedtls_asn1_free_named_data_list_shallow(mbedtls_asn1_named_data *name)
	{
	for (mbedtls_asn1_named_data *next; name != NULL; name = next) {
	next = name->next;
	mbedtls_free(name);
	}
	}

	const mbedtls_asn1_named_data mbedtls_asn1_find_named_data(const mbedtls_asn1_named_data list,
	const char *oid, size_t len)
	{
	while (list != NULL) {
	if (list->oid.len == len &&
	memcmp(list->oid.p, oid, len) == 0) {
	break;
	}

	list = list->next;
	}

	return list;
	}

	#endif /* MBEDTLS_ASN1_PARSE_C */