diff --git a/library/x509.c b/library/x509.c
new file mode 100644
index 0000000..3f8e290
--- /dev/null
+++ b/library/x509.c
@@ -0,0 +1,1062 @@
+/*
+ *  X.509 common functions for parsing and verification
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+/*
+ *  The ITU-T X.509 standard defines a certificate format for PKI.
+ *
+ *  http://www.ietf.org/rfc/rfc5280.txt (Certificates and CRLs)
+ *  http://www.ietf.org/rfc/rfc3279.txt (Alg IDs for CRLs)
+ *  http://www.ietf.org/rfc/rfc2986.txt (CSRs, aka PKCS#10)
+ *
+ *  http://www.itu.int/ITU-T/studygroups/com17/languages/X.680-0207.pdf
+ *  http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_X509_USE_C)
+
+#include "mbedtls/x509.h"
+#include "mbedtls/asn1.h"
+#include "mbedtls/oid.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#if defined(MBEDTLS_PEM_PARSE_C)
+#include "mbedtls/pem.h"
+#endif
+
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdio.h>
+#include <stdlib.h>
+#define mbedtls_free      free
+#define mbedtls_calloc    calloc
+#define mbedtls_printf    printf
+#define mbedtls_snprintf  snprintf
+#endif
+
+#if defined(MBEDTLS_HAVE_TIME)
+#include "mbedtls/platform_time.h"
+#endif
+#if defined(MBEDTLS_HAVE_TIME_DATE)
+#include "mbedtls/platform_util.h"
+#include <time.h>
+#endif
+
+#define CHECK(code) if( ( ret = code ) != 0 ){ return( ret ); }
+#define CHECK_RANGE(min, max, val) if( val < min || val > max ){ return( ret ); }
+
+/*
+ *  CertificateSerialNumber  ::=  INTEGER
+ */
+int mbedtls_x509_get_serial( unsigned char **p, const unsigned char *end,
+                     mbedtls_x509_buf *serial )
+{
+    int ret;
+
+    if( ( end - *p ) < 1 )
+        return( MBEDTLS_ERR_X509_INVALID_SERIAL +
+                MBEDTLS_ERR_ASN1_OUT_OF_DATA );
+
+    if( **p != ( MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_PRIMITIVE | 2 ) &&
+        **p !=   MBEDTLS_ASN1_INTEGER )
+        return( MBEDTLS_ERR_X509_INVALID_SERIAL +
+                MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
+
+    serial->tag = *(*p)++;
+
+    if( ( ret = mbedtls_asn1_get_len( p, end, &serial->len ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_SERIAL + ret );
+
+    serial->p = *p;
+    *p += serial->len;
+
+    return( 0 );
+}
+
+/* Get an algorithm identifier without parameters (eg for signatures)
+ *
+ *  AlgorithmIdentifier  ::=  SEQUENCE  {
+ *       algorithm               OBJECT IDENTIFIER,
+ *       parameters              ANY DEFINED BY algorithm OPTIONAL  }
+ */
+int mbedtls_x509_get_alg_null( unsigned char **p, const unsigned char *end,
+                       mbedtls_x509_buf *alg )
+{
+    int ret;
+
+    if( ( ret = mbedtls_asn1_get_alg_null( p, end, alg ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    return( 0 );
+}
+
+/*
+ * Parse an algorithm identifier with (optional) parameters
+ */
+int mbedtls_x509_get_alg( unsigned char **p, const unsigned char *end,
+                  mbedtls_x509_buf *alg, mbedtls_x509_buf *params )
+{
+    int ret;
+
+    if( ( ret = mbedtls_asn1_get_alg( p, end, alg, params ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT)
+/*
+ * HashAlgorithm ::= AlgorithmIdentifier
+ *
+ * AlgorithmIdentifier  ::=  SEQUENCE  {
+ *      algorithm               OBJECT IDENTIFIER,
+ *      parameters              ANY DEFINED BY algorithm OPTIONAL  }
+ *
+ * For HashAlgorithm, parameters MUST be NULL or absent.
+ */
+static int x509_get_hash_alg( const mbedtls_x509_buf *alg, mbedtls_md_type_t *md_alg )
+{
+    int ret;
+    unsigned char *p;
+    const unsigned char *end;
+    mbedtls_x509_buf md_oid;
+    size_t len;
+
+    /* Make sure we got a SEQUENCE and setup bounds */
+    if( alg->tag != ( MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) )
+        return( MBEDTLS_ERR_X509_INVALID_ALG +
+                MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
+
+    p = (unsigned char *) alg->p;
+    end = p + alg->len;
+
+    if( p >= end )
+        return( MBEDTLS_ERR_X509_INVALID_ALG +
+                MBEDTLS_ERR_ASN1_OUT_OF_DATA );
+
+    /* Parse md_oid */
+    md_oid.tag = *p;
+
+    if( ( ret = mbedtls_asn1_get_tag( &p, end, &md_oid.len, MBEDTLS_ASN1_OID ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    md_oid.p = p;
+    p += md_oid.len;
+
+    /* Get md_alg from md_oid */
+    if( ( ret = mbedtls_oid_get_md_alg( &md_oid, md_alg ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    /* Make sure params is absent of NULL */
+    if( p == end )
+        return( 0 );
+
+    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len, MBEDTLS_ASN1_NULL ) ) != 0 || len != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    if( p != end )
+        return( MBEDTLS_ERR_X509_INVALID_ALG +
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+
+    return( 0 );
+}
+
+/*
+ *    RSASSA-PSS-params  ::=  SEQUENCE  {
+ *       hashAlgorithm     [0] HashAlgorithm DEFAULT sha1Identifier,
+ *       maskGenAlgorithm  [1] MaskGenAlgorithm DEFAULT mgf1SHA1Identifier,
+ *       saltLength        [2] INTEGER DEFAULT 20,
+ *       trailerField      [3] INTEGER DEFAULT 1  }
+ *    -- Note that the tags in this Sequence are explicit.
+ *
+ * RFC 4055 (which defines use of RSASSA-PSS in PKIX) states that the value
+ * of trailerField MUST be 1, and PKCS#1 v2.2 doesn't even define any other
+ * option. Enfore this at parsing time.
+ */
+int mbedtls_x509_get_rsassa_pss_params( const mbedtls_x509_buf *params,
+                                mbedtls_md_type_t *md_alg, mbedtls_md_type_t *mgf_md,
+                                int *salt_len )
+{
+    int ret;
+    unsigned char *p;
+    const unsigned char *end, *end2;
+    size_t len;
+    mbedtls_x509_buf alg_id, alg_params;
+
+    /* First set everything to defaults */
+    *md_alg = MBEDTLS_MD_SHA1;
+    *mgf_md = MBEDTLS_MD_SHA1;
+    *salt_len = 20;
+
+    /* Make sure params is a SEQUENCE and setup bounds */
+    if( params->tag != ( MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) )
+        return( MBEDTLS_ERR_X509_INVALID_ALG +
+                MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
+
+    p = (unsigned char *) params->p;
+    end = p + params->len;
+
+    if( p == end )
+        return( 0 );
+
+    /*
+     * HashAlgorithm
+     */
+    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
+                    MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 0 ) ) == 0 )
+    {
+        end2 = p + len;
+
+        /* HashAlgorithm ::= AlgorithmIdentifier (without parameters) */
+        if( ( ret = mbedtls_x509_get_alg_null( &p, end2, &alg_id ) ) != 0 )
+            return( ret );
+
+        if( ( ret = mbedtls_oid_get_md_alg( &alg_id, md_alg ) ) != 0 )
+            return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+        if( p != end2 )
+            return( MBEDTLS_ERR_X509_INVALID_ALG +
+                    MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+    }
+    else if( ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    if( p == end )
+        return( 0 );
+
+    /*
+     * MaskGenAlgorithm
+     */
+    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
+                    MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 1 ) ) == 0 )
+    {
+        end2 = p + len;
+
+        /* MaskGenAlgorithm ::= AlgorithmIdentifier (params = HashAlgorithm) */
+        if( ( ret = mbedtls_x509_get_alg( &p, end2, &alg_id, &alg_params ) ) != 0 )
+            return( ret );
+
+        /* Only MFG1 is recognised for now */
+        if( MBEDTLS_OID_CMP( MBEDTLS_OID_MGF1, &alg_id ) != 0 )
+            return( MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE +
+                    MBEDTLS_ERR_OID_NOT_FOUND );
+
+        /* Parse HashAlgorithm */
+        if( ( ret = x509_get_hash_alg( &alg_params, mgf_md ) ) != 0 )
+            return( ret );
+
+        if( p != end2 )
+            return( MBEDTLS_ERR_X509_INVALID_ALG +
+                    MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+    }
+    else if( ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    if( p == end )
+        return( 0 );
+
+    /*
+     * salt_len
+     */
+    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
+                    MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 2 ) ) == 0 )
+    {
+        end2 = p + len;
+
+        if( ( ret = mbedtls_asn1_get_int( &p, end2, salt_len ) ) != 0 )
+            return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+        if( p != end2 )
+            return( MBEDTLS_ERR_X509_INVALID_ALG +
+                    MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+    }
+    else if( ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    if( p == end )
+        return( 0 );
+
+    /*
+     * trailer_field (if present, must be 1)
+     */
+    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
+                    MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 3 ) ) == 0 )
+    {
+        int trailer_field;
+
+        end2 = p + len;
+
+        if( ( ret = mbedtls_asn1_get_int( &p, end2, &trailer_field ) ) != 0 )
+            return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+        if( p != end2 )
+            return( MBEDTLS_ERR_X509_INVALID_ALG +
+                    MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+
+        if( trailer_field != 1 )
+            return( MBEDTLS_ERR_X509_INVALID_ALG );
+    }
+    else if( ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG )
+        return( MBEDTLS_ERR_X509_INVALID_ALG + ret );
+
+    if( p != end )
+        return( MBEDTLS_ERR_X509_INVALID_ALG +
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+
+    return( 0 );
+}
+#endif /* MBEDTLS_X509_RSASSA_PSS_SUPPORT */
+
+/*
+ *  AttributeTypeAndValue ::= SEQUENCE {
+ *    type     AttributeType,
+ *    value    AttributeValue }
+ *
+ *  AttributeType ::= OBJECT IDENTIFIER
+ *
+ *  AttributeValue ::= ANY DEFINED BY AttributeType
+ */
+static int x509_get_attr_type_value( unsigned char **p,
+                                     const unsigned char *end,
+                                     mbedtls_x509_name *cur )
+{
+    int ret;
+    size_t len;
+    mbedtls_x509_buf *oid;
+    mbedtls_x509_buf *val;
+
+    if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
+            MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_NAME + ret );
+
+    if( ( end - *p ) < 1 )
+        return( MBEDTLS_ERR_X509_INVALID_NAME +
+                MBEDTLS_ERR_ASN1_OUT_OF_DATA );
+
+    oid = &cur->oid;
+    oid->tag = **p;
+
+    if( ( ret = mbedtls_asn1_get_tag( p, end, &oid->len, MBEDTLS_ASN1_OID ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_NAME + ret );
+
+    oid->p = *p;
+    *p += oid->len;
+
+    if( ( end - *p ) < 1 )
+        return( MBEDTLS_ERR_X509_INVALID_NAME +
+                MBEDTLS_ERR_ASN1_OUT_OF_DATA );
+
+    if( **p != MBEDTLS_ASN1_BMP_STRING && **p != MBEDTLS_ASN1_UTF8_STRING      &&
+        **p != MBEDTLS_ASN1_T61_STRING && **p != MBEDTLS_ASN1_PRINTABLE_STRING &&
+        **p != MBEDTLS_ASN1_IA5_STRING && **p != MBEDTLS_ASN1_UNIVERSAL_STRING &&
+        **p != MBEDTLS_ASN1_BIT_STRING )
+        return( MBEDTLS_ERR_X509_INVALID_NAME +
+                MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
+
+    val = &cur->val;
+    val->tag = *(*p)++;
+
+    if( ( ret = mbedtls_asn1_get_len( p, end, &val->len ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_NAME + ret );
+
+    val->p = *p;
+    *p += val->len;
+
+    cur->next = NULL;
+
+    return( 0 );
+}
+
+/*
+ *  Name ::= CHOICE { -- only one possibility for now --
+ *       rdnSequence  RDNSequence }
+ *
+ *  RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
+ *
+ *  RelativeDistinguishedName ::=
+ *    SET OF AttributeTypeAndValue
+ *
+ *  AttributeTypeAndValue ::= SEQUENCE {
+ *    type     AttributeType,
+ *    value    AttributeValue }
+ *
+ *  AttributeType ::= OBJECT IDENTIFIER
+ *
+ *  AttributeValue ::= ANY DEFINED BY AttributeType
+ *
+ * The data structure is optimized for the common case where each RDN has only
+ * one element, which is represented as a list of AttributeTypeAndValue.
+ * For the general case we still use a flat list, but we mark elements of the
+ * same set so that they are "merged" together in the functions that consume
+ * this list, eg mbedtls_x509_dn_gets().
+ */
+int mbedtls_x509_get_name( unsigned char **p, const unsigned char *end,
+                   mbedtls_x509_name *cur )
+{
+    int ret;
+    size_t set_len;
+    const unsigned char *end_set;
+
+    /* don't use recursion, we'd risk stack overflow if not optimized */
+    while( 1 )
+    {
+        /*
+         * parse SET
+         */
+        if( ( ret = mbedtls_asn1_get_tag( p, end, &set_len,
+                MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SET ) ) != 0 )
+            return( MBEDTLS_ERR_X509_INVALID_NAME + ret );
+
+        end_set  = *p + set_len;
+
+        while( 1 )
+        {
+            if( ( ret = x509_get_attr_type_value( p, end_set, cur ) ) != 0 )
+                return( ret );
+
+            if( *p == end_set )
+                break;
+
+            /* Mark this item as being no the only one in a set */
+            cur->next_merged = 1;
+
+            cur->next = mbedtls_calloc( 1, sizeof( mbedtls_x509_name ) );
+
+            if( cur->next == NULL )
+                return( MBEDTLS_ERR_X509_ALLOC_FAILED );
+
+            cur = cur->next;
+        }
+
+        /*
+         * continue until end of SEQUENCE is reached
+         */
+        if( *p == end )
+            return( 0 );
+
+        cur->next = mbedtls_calloc( 1, sizeof( mbedtls_x509_name ) );
+
+        if( cur->next == NULL )
+            return( MBEDTLS_ERR_X509_ALLOC_FAILED );
+
+        cur = cur->next;
+    }
+}
+
+static int x509_parse_int( unsigned char **p, size_t n, int *res )
+{
+    *res = 0;
+
+    for( ; n > 0; --n )
+    {
+        if( ( **p < '0') || ( **p > '9' ) )
+            return ( MBEDTLS_ERR_X509_INVALID_DATE );
+
+        *res *= 10;
+        *res += ( *(*p)++ - '0' );
+    }
+
+    return( 0 );
+}
+
+static int x509_date_is_valid(const mbedtls_x509_time *t )
+{
+    int ret = MBEDTLS_ERR_X509_INVALID_DATE;
+    int month_len;
+
+    CHECK_RANGE( 0, 9999, t->year );
+    CHECK_RANGE( 0, 23,   t->hour );
+    CHECK_RANGE( 0, 59,   t->min  );
+    CHECK_RANGE( 0, 59,   t->sec  );
+
+    switch( t->mon )
+    {
+        case 1: case 3: case 5: case 7: case 8: case 10: case 12:
+            month_len = 31;
+            break;
+        case 4: case 6: case 9: case 11:
+            month_len = 30;
+            break;
+        case 2:
+            if( ( !( t->year % 4 ) && t->year % 100 ) ||
+                !( t->year % 400 ) )
+                month_len = 29;
+            else
+                month_len = 28;
+            break;
+        default:
+            return( ret );
+    }
+    CHECK_RANGE( 1, month_len, t->day );
+
+    return( 0 );
+}
+
+/*
+ * Parse an ASN1_UTC_TIME (yearlen=2) or ASN1_GENERALIZED_TIME (yearlen=4)
+ * field.
+ */
+static int x509_parse_time( unsigned char **p, size_t len, size_t yearlen,
+                            mbedtls_x509_time *tm )
+{
+    int ret;
+
+    /*
+     * Minimum length is 10 or 12 depending on yearlen
+     */
+    if ( len < yearlen + 8 )
+        return ( MBEDTLS_ERR_X509_INVALID_DATE );
+    len -= yearlen + 8;
+
+    /*
+     * Parse year, month, day, hour, minute
+     */
+    CHECK( x509_parse_int( p, yearlen, &tm->year ) );
+    if ( 2 == yearlen )
+    {
+        if ( tm->year < 50 )
+            tm->year += 100;
+
+        tm->year += 1900;
+    }
+
+    CHECK( x509_parse_int( p, 2, &tm->mon ) );
+    CHECK( x509_parse_int( p, 2, &tm->day ) );
+    CHECK( x509_parse_int( p, 2, &tm->hour ) );
+    CHECK( x509_parse_int( p, 2, &tm->min ) );
+
+    /*
+     * Parse seconds if present
+     */
+    if ( len >= 2 )
+    {
+        CHECK( x509_parse_int( p, 2, &tm->sec ) );
+        len -= 2;
+    }
+    else
+        return ( MBEDTLS_ERR_X509_INVALID_DATE );
+
+    /*
+     * Parse trailing 'Z' if present
+     */
+    if ( 1 == len && 'Z' == **p )
+    {
+        (*p)++;
+        len--;
+    }
+
+    /*
+     * We should have parsed all characters at this point
+     */
+    if ( 0 != len )
+        return ( MBEDTLS_ERR_X509_INVALID_DATE );
+
+    CHECK( x509_date_is_valid( tm ) );
+
+    return ( 0 );
+}
+
+/*
+ *  Time ::= CHOICE {
+ *       utcTime        UTCTime,
+ *       generalTime    GeneralizedTime }
+ */
+int mbedtls_x509_get_time( unsigned char **p, const unsigned char *end,
+                           mbedtls_x509_time *tm )
+{
+    int ret;
+    size_t len, year_len;
+    unsigned char tag;
+
+    if( ( end - *p ) < 1 )
+        return( MBEDTLS_ERR_X509_INVALID_DATE +
+                MBEDTLS_ERR_ASN1_OUT_OF_DATA );
+
+    tag = **p;
+
+    if( tag == MBEDTLS_ASN1_UTC_TIME )
+        year_len = 2;
+    else if( tag == MBEDTLS_ASN1_GENERALIZED_TIME )
+        year_len = 4;
+    else
+        return( MBEDTLS_ERR_X509_INVALID_DATE +
+                MBEDTLS_ERR_ASN1_UNEXPECTED_TAG );
+
+    (*p)++;
+    ret = mbedtls_asn1_get_len( p, end, &len );
+
+    if( ret != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_DATE + ret );
+
+    return x509_parse_time( p, len, year_len, tm );
+}
+
+int mbedtls_x509_get_sig( unsigned char **p, const unsigned char *end, mbedtls_x509_buf *sig )
+{
+    int ret;
+    size_t len;
+    int tag_type;
+
+    if( ( end - *p ) < 1 )
+        return( MBEDTLS_ERR_X509_INVALID_SIGNATURE +
+                MBEDTLS_ERR_ASN1_OUT_OF_DATA );
+
+    tag_type = **p;
+
+    if( ( ret = mbedtls_asn1_get_bitstring_null( p, end, &len ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_SIGNATURE + ret );
+
+    sig->tag = tag_type;
+    sig->len = len;
+    sig->p = *p;
+
+    *p += len;
+
+    return( 0 );
+}
+
+/*
+ * Get signature algorithm from alg OID and optional parameters
+ */
+int mbedtls_x509_get_sig_alg( const mbedtls_x509_buf *sig_oid, const mbedtls_x509_buf *sig_params,
+                      mbedtls_md_type_t *md_alg, mbedtls_pk_type_t *pk_alg,
+                      void **sig_opts )
+{
+    int ret;
+
+    if( *sig_opts != NULL )
+        return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );
+
+    if( ( ret = mbedtls_oid_get_sig_alg( sig_oid, md_alg, pk_alg ) ) != 0 )
+        return( MBEDTLS_ERR_X509_UNKNOWN_SIG_ALG + ret );
+
+#if defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT)
+    if( *pk_alg == MBEDTLS_PK_RSASSA_PSS )
+    {
+        mbedtls_pk_rsassa_pss_options *pss_opts;
+
+        pss_opts = mbedtls_calloc( 1, sizeof( mbedtls_pk_rsassa_pss_options ) );
+        if( pss_opts == NULL )
+            return( MBEDTLS_ERR_X509_ALLOC_FAILED );
+
+        ret = mbedtls_x509_get_rsassa_pss_params( sig_params,
+                                          md_alg,
+                                          &pss_opts->mgf1_hash_id,
+                                          &pss_opts->expected_salt_len );
+        if( ret != 0 )
+        {
+            mbedtls_free( pss_opts );
+            return( ret );
+        }
+
+        *sig_opts = (void *) pss_opts;
+    }
+    else
+#endif /* MBEDTLS_X509_RSASSA_PSS_SUPPORT */
+    {
+        /* Make sure parameters are absent or NULL */
+        if( ( sig_params->tag != MBEDTLS_ASN1_NULL && sig_params->tag != 0 ) ||
+              sig_params->len != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_ALG );
+    }
+
+    return( 0 );
+}
+
+/*
+ * X.509 Extensions (No parsing of extensions, pointer should
+ * be either manually updated or extensions should be parsed!)
+ */
+int mbedtls_x509_get_ext( unsigned char **p, const unsigned char *end,
+                  mbedtls_x509_buf *ext, int tag )
+{
+    int ret;
+    size_t len;
+
+    if( *p == end )
+        return( 0 );
+
+    ext->tag = **p;
+
+    if( ( ret = mbedtls_asn1_get_tag( p, end, &ext->len,
+            MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | tag ) ) != 0 )
+        return( ret );
+
+    ext->p = *p;
+    end = *p + ext->len;
+
+    /*
+     * Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension
+     *
+     * Extension  ::=  SEQUENCE  {
+     *      extnID      OBJECT IDENTIFIER,
+     *      critical    BOOLEAN DEFAULT FALSE,
+     *      extnValue   OCTET STRING  }
+     */
+    if( ( ret = mbedtls_asn1_get_tag( p, end, &len,
+            MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
+        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
+
+    if( end != *p + len )
+        return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
+                MBEDTLS_ERR_ASN1_LENGTH_MISMATCH );
+
+    return( 0 );
+}
+
+/*
+ * Store the name in printable form into buf; no more
+ * than size characters will be written
+ */
+int mbedtls_x509_dn_gets( char *buf, size_t size, const mbedtls_x509_name *dn )
+{
+    int ret;
+    size_t i, n;
+    unsigned char c, merge = 0;
+    const mbedtls_x509_name *name;
+    const char *short_name = NULL;
+    char s[MBEDTLS_X509_MAX_DN_NAME_SIZE], *p;
+
+    memset( s, 0, sizeof( s ) );
+
+    name = dn;
+    p = buf;
+    n = size;
+
+    while( name != NULL )
+    {
+        if( !name->oid.p )
+        {
+            name = name->next;
+            continue;
+        }
+
+        if( name != dn )
+        {
+            ret = mbedtls_snprintf( p, n, merge ? " + " : ", " );
+            MBEDTLS_X509_SAFE_SNPRINTF;
+        }
+
+        ret = mbedtls_oid_get_attr_short_name( &name->oid, &short_name );
+
+        if( ret == 0 )
+            ret = mbedtls_snprintf( p, n, "%s=", short_name );
+        else
+            ret = mbedtls_snprintf( p, n, "\?\?=" );
+        MBEDTLS_X509_SAFE_SNPRINTF;
+
+        for( i = 0; i < name->val.len; i++ )
+        {
+            if( i >= sizeof( s ) - 1 )
+                break;
+
+            c = name->val.p[i];
+            if( c < 32 || c == 127 || ( c > 128 && c < 160 ) )
+                 s[i] = '?';
+            else s[i] = c;
+        }
+        s[i] = '\0';
+        ret = mbedtls_snprintf( p, n, "%s", s );
+        MBEDTLS_X509_SAFE_SNPRINTF;
+
+        merge = name->next_merged;
+        name = name->next;
+    }
+
+    return( (int) ( size - n ) );
+}
+
+/*
+ * Store the serial in printable form into buf; no more
+ * than size characters will be written
+ */
+int mbedtls_x509_serial_gets( char *buf, size_t size, const mbedtls_x509_buf *serial )
+{
+    int ret;
+    size_t i, n, nr;
+    char *p;
+
+    p = buf;
+    n = size;
+
+    nr = ( serial->len <= 32 )
+        ? serial->len  : 28;
+
+    for( i = 0; i < nr; i++ )
+    {
+        if( i == 0 && nr > 1 && serial->p[i] == 0x0 )
+            continue;
+
+        ret = mbedtls_snprintf( p, n, "%02X%s",
+                serial->p[i], ( i < nr - 1 ) ? ":" : "" );
+        MBEDTLS_X509_SAFE_SNPRINTF;
+    }
+
+    if( nr != serial->len )
+    {
+        ret = mbedtls_snprintf( p, n, "...." );
+        MBEDTLS_X509_SAFE_SNPRINTF;
+    }
+
+    return( (int) ( size - n ) );
+}
+
+/*
+ * Helper for writing signature algorithms
+ */
+int mbedtls_x509_sig_alg_gets( char *buf, size_t size, const mbedtls_x509_buf *sig_oid,
+                       mbedtls_pk_type_t pk_alg, mbedtls_md_type_t md_alg,
+                       const void *sig_opts )
+{
+    int ret;
+    char *p = buf;
+    size_t n = size;
+    const char *desc = NULL;
+
+    ret = mbedtls_oid_get_sig_alg_desc( sig_oid, &desc );
+    if( ret != 0 )
+        ret = mbedtls_snprintf( p, n, "???"  );
+    else
+        ret = mbedtls_snprintf( p, n, "%s", desc );
+    MBEDTLS_X509_SAFE_SNPRINTF;
+
+#if defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT)
+    if( pk_alg == MBEDTLS_PK_RSASSA_PSS )
+    {
+        const mbedtls_pk_rsassa_pss_options *pss_opts;
+        const mbedtls_md_info_t *md_info, *mgf_md_info;
+
+        pss_opts = (const mbedtls_pk_rsassa_pss_options *) sig_opts;
+
+        md_info = mbedtls_md_info_from_type( md_alg );
+        mgf_md_info = mbedtls_md_info_from_type( pss_opts->mgf1_hash_id );
+
+        ret = mbedtls_snprintf( p, n, " (%s, MGF1-%s, 0x%02X)",
+                              md_info ? mbedtls_md_get_name( md_info ) : "???",
+                              mgf_md_info ? mbedtls_md_get_name( mgf_md_info ) : "???",
+                              pss_opts->expected_salt_len );
+        MBEDTLS_X509_SAFE_SNPRINTF;
+    }
+#else
+    ((void) pk_alg);
+    ((void) md_alg);
+    ((void) sig_opts);
+#endif /* MBEDTLS_X509_RSASSA_PSS_SUPPORT */
+
+    return( (int)( size - n ) );
+}
+
+/*
+ * Helper for writing "RSA key size", "EC key size", etc
+ */
+int mbedtls_x509_key_size_helper( char *buf, size_t buf_size, const char *name )
+{
+    char *p = buf;
+    size_t n = buf_size;
+    int ret;
+
+    ret = mbedtls_snprintf( p, n, "%s key size", name );
+    MBEDTLS_X509_SAFE_SNPRINTF;
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_HAVE_TIME_DATE)
+/*
+ * Set the time structure to the current time.
+ * Return 0 on success, non-zero on failure.
+ */
+static int x509_get_current_time( mbedtls_x509_time *now )
+{
+    struct tm *lt, tm_buf;
+    mbedtls_time_t tt;
+    int ret = 0;
+
+    tt = mbedtls_time( NULL );
+    lt = mbedtls_platform_gmtime_r( &tt, &tm_buf );
+
+    if( lt == NULL )
+        ret = -1;
+    else
+    {
+        now->year = lt->tm_year + 1900;
+        now->mon  = lt->tm_mon  + 1;
+        now->day  = lt->tm_mday;
+        now->hour = lt->tm_hour;
+        now->min  = lt->tm_min;
+        now->sec  = lt->tm_sec;
+    }
+
+    return( ret );
+}
+
+/*
+ * Return 0 if before <= after, 1 otherwise
+ */
+static int x509_check_time( const mbedtls_x509_time *before, const mbedtls_x509_time *after )
+{
+    if( before->year  > after->year )
+        return( 1 );
+
+    if( before->year == after->year &&
+        before->mon   > after->mon )
+        return( 1 );
+
+    if( before->year == after->year &&
+        before->mon  == after->mon  &&
+        before->day   > after->day )
+        return( 1 );
+
+    if( before->year == after->year &&
+        before->mon  == after->mon  &&
+        before->day  == after->day  &&
+        before->hour  > after->hour )
+        return( 1 );
+
+    if( before->year == after->year &&
+        before->mon  == after->mon  &&
+        before->day  == after->day  &&
+        before->hour == after->hour &&
+        before->min   > after->min  )
+        return( 1 );
+
+    if( before->year == after->year &&
+        before->mon  == after->mon  &&
+        before->day  == after->day  &&
+        before->hour == after->hour &&
+        before->min  == after->min  &&
+        before->sec   > after->sec  )
+        return( 1 );
+
+    return( 0 );
+}
+
+int mbedtls_x509_time_is_past( const mbedtls_x509_time *to )
+{
+    mbedtls_x509_time now;
+
+    if( x509_get_current_time( &now ) != 0 )
+        return( 1 );
+
+    return( x509_check_time( &now, to ) );
+}
+
+int mbedtls_x509_time_is_future( const mbedtls_x509_time *from )
+{
+    mbedtls_x509_time now;
+
+    if( x509_get_current_time( &now ) != 0 )
+        return( 1 );
+
+    return( x509_check_time( from, &now ) );
+}
+
+#else  /* MBEDTLS_HAVE_TIME_DATE */
+
+int mbedtls_x509_time_is_past( const mbedtls_x509_time *to )
+{
+    ((void) to);
+    return( 0 );
+}
+
+int mbedtls_x509_time_is_future( const mbedtls_x509_time *from )
+{
+    ((void) from);
+    return( 0 );
+}
+#endif /* MBEDTLS_HAVE_TIME_DATE */
+
+#if defined(MBEDTLS_SELF_TEST)
+
+#include "mbedtls/x509_crt.h"
+#include "mbedtls/certs.h"
+
+/*
+ * Checkup routine
+ */
+int mbedtls_x509_self_test( int verbose )
+{
+    int ret = 0;
+#if defined(MBEDTLS_CERTS_C) && defined(MBEDTLS_SHA256_C)
+    uint32_t flags;
+    mbedtls_x509_crt cacert;
+    mbedtls_x509_crt clicert;
+
+    if( verbose != 0 )
+        mbedtls_printf( "  X.509 certificate load: " );
+
+    mbedtls_x509_crt_init( &cacert );
+    mbedtls_x509_crt_init( &clicert );
+
+    ret = mbedtls_x509_crt_parse( &clicert, (const unsigned char *) mbedtls_test_cli_crt,
+                           mbedtls_test_cli_crt_len );
+    if( ret != 0 )
+    {
+        if( verbose != 0 )
+            mbedtls_printf( "failed\n" );
+
+        goto cleanup;
+    }
+
+    ret = mbedtls_x509_crt_parse( &cacert, (const unsigned char *) mbedtls_test_ca_crt,
+                          mbedtls_test_ca_crt_len );
+    if( ret != 0 )
+    {
+        if( verbose != 0 )
+            mbedtls_printf( "failed\n" );
+
+        goto cleanup;
+    }
+
+    if( verbose != 0 )
+        mbedtls_printf( "passed\n  X.509 signature verify: ");
+
+    ret = mbedtls_x509_crt_verify( &clicert, &cacert, NULL, NULL, &flags, NULL, NULL );
+    if( ret != 0 )
+    {
+        if( verbose != 0 )
+            mbedtls_printf( "failed\n" );
+
+        goto cleanup;
+    }
+
+    if( verbose != 0 )
+        mbedtls_printf( "passed\n\n");
+
+cleanup:
+    mbedtls_x509_crt_free( &cacert  );
+    mbedtls_x509_crt_free( &clicert );
+#else
+    ((void) verbose);
+#endif /* MBEDTLS_CERTS_C && MBEDTLS_SHA1_C */
+    return( ret );
+}
+
+#endif /* MBEDTLS_SELF_TEST */
+
+#endif /* MBEDTLS_X509_USE_C */