diff --git a/library/x509_create.c b/library/x509_create.c
new file mode 100644
index 0000000..839b5df
--- /dev/null
+++ b/library/x509_create.c
@@ -0,0 +1,563 @@
+/*
+ *  X.509 base functions for creating certificates / CSRs
+ *
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+#include "common.h"
+
+#if defined(MBEDTLS_X509_CREATE_C)
+
+#include "x509_internal.h"
+#include "mbedtls/asn1write.h"
+#include "mbedtls/error.h"
+#include "mbedtls/oid.h"
+
+#include <string.h>
+
+#include "mbedtls/platform.h"
+
+#include "mbedtls/asn1.h"
+
+/* Structure linking OIDs for X.509 DN AttributeTypes to their
+ * string representations and default string encodings used by Mbed TLS. */
+typedef struct {
+    const char *name; /* String representation of AttributeType, e.g.
+                       * "CN" or "emailAddress". */
+    size_t name_len; /* Length of 'name', without trailing 0 byte. */
+    const char *oid; /* String representation of OID of AttributeType,
+                      * as per RFC 5280, Appendix A.1. encoded as per
+                      * X.690 */
+    int default_tag; /* The default character encoding used for the
+                      * given attribute type, e.g.
+                      * MBEDTLS_ASN1_UTF8_STRING for UTF-8. */
+} x509_attr_descriptor_t;
+
+#define ADD_STRLEN(s)     s, sizeof(s) - 1
+
+/* X.509 DN attributes from RFC 5280, Appendix A.1. */
+static const x509_attr_descriptor_t x509_attrs[] =
+{
+    { ADD_STRLEN("CN"),
+      MBEDTLS_OID_AT_CN, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("commonName"),
+      MBEDTLS_OID_AT_CN, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("C"),
+      MBEDTLS_OID_AT_COUNTRY, MBEDTLS_ASN1_PRINTABLE_STRING },
+    { ADD_STRLEN("countryName"),
+      MBEDTLS_OID_AT_COUNTRY, MBEDTLS_ASN1_PRINTABLE_STRING },
+    { ADD_STRLEN("O"),
+      MBEDTLS_OID_AT_ORGANIZATION, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("organizationName"),
+      MBEDTLS_OID_AT_ORGANIZATION, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("L"),
+      MBEDTLS_OID_AT_LOCALITY, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("locality"),
+      MBEDTLS_OID_AT_LOCALITY, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("R"),
+      MBEDTLS_OID_PKCS9_EMAIL, MBEDTLS_ASN1_IA5_STRING },
+    { ADD_STRLEN("OU"),
+      MBEDTLS_OID_AT_ORG_UNIT, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("organizationalUnitName"),
+      MBEDTLS_OID_AT_ORG_UNIT, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("ST"),
+      MBEDTLS_OID_AT_STATE, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("stateOrProvinceName"),
+      MBEDTLS_OID_AT_STATE, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("emailAddress"),
+      MBEDTLS_OID_PKCS9_EMAIL, MBEDTLS_ASN1_IA5_STRING },
+    { ADD_STRLEN("serialNumber"),
+      MBEDTLS_OID_AT_SERIAL_NUMBER, MBEDTLS_ASN1_PRINTABLE_STRING },
+    { ADD_STRLEN("postalAddress"),
+      MBEDTLS_OID_AT_POSTAL_ADDRESS, MBEDTLS_ASN1_PRINTABLE_STRING },
+    { ADD_STRLEN("postalCode"),
+      MBEDTLS_OID_AT_POSTAL_CODE, MBEDTLS_ASN1_PRINTABLE_STRING },
+    { ADD_STRLEN("dnQualifier"),
+      MBEDTLS_OID_AT_DN_QUALIFIER, MBEDTLS_ASN1_PRINTABLE_STRING },
+    { ADD_STRLEN("title"),
+      MBEDTLS_OID_AT_TITLE, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("surName"),
+      MBEDTLS_OID_AT_SUR_NAME, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("SN"),
+      MBEDTLS_OID_AT_SUR_NAME, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("givenName"),
+      MBEDTLS_OID_AT_GIVEN_NAME, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("GN"),
+      MBEDTLS_OID_AT_GIVEN_NAME, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("initials"),
+      MBEDTLS_OID_AT_INITIALS, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("pseudonym"),
+      MBEDTLS_OID_AT_PSEUDONYM, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("generationQualifier"),
+      MBEDTLS_OID_AT_GENERATION_QUALIFIER, MBEDTLS_ASN1_UTF8_STRING },
+    { ADD_STRLEN("domainComponent"),
+      MBEDTLS_OID_DOMAIN_COMPONENT, MBEDTLS_ASN1_IA5_STRING },
+    { ADD_STRLEN("DC"),
+      MBEDTLS_OID_DOMAIN_COMPONENT,   MBEDTLS_ASN1_IA5_STRING },
+    { NULL, 0, NULL, MBEDTLS_ASN1_NULL }
+};
+
+static const x509_attr_descriptor_t *x509_attr_descr_from_name(const char *name, size_t name_len)
+{
+    const x509_attr_descriptor_t *cur;
+
+    for (cur = x509_attrs; cur->name != NULL; cur++) {
+        if (cur->name_len == name_len &&
+            strncmp(cur->name, name, name_len) == 0) {
+            break;
+        }
+    }
+
+    if (cur->name == NULL) {
+        return NULL;
+    }
+
+    return cur;
+}
+
+static int hex_to_int(char c)
+{
+    return ('0' <= c && c <= '9') ? (c - '0') :
+           ('a' <= c && c <= 'f') ? (c - 'a' + 10) :
+           ('A' <= c && c <= 'F') ? (c - 'A' + 10) : -1;
+}
+
+static int hexpair_to_int(const char *hexpair)
+{
+    int n1 = hex_to_int(*hexpair);
+    int n2 = hex_to_int(*(hexpair + 1));
+
+    if (n1 != -1 && n2 != -1) {
+        return (n1 << 4) | n2;
+    } else {
+        return -1;
+    }
+}
+
+static int parse_attribute_value_string(const char *s,
+                                        int len,
+                                        unsigned char *data,
+                                        size_t *data_len)
+{
+    const char *c;
+    const char *end = s + len;
+    unsigned char *d = data;
+    int n;
+
+    for (c = s; c < end; c++) {
+        if (*c == '\\') {
+            c++;
+
+            /* Check for valid escaped characters as per RFC 4514 Section 3 */
+            if (c + 1 < end && (n = hexpair_to_int(c)) != -1) {
+                if (n == 0) {
+                    return MBEDTLS_ERR_X509_INVALID_NAME;
+                }
+                *(d++) = n;
+                c++;
+            } else if (c < end && strchr(" ,=+<>#;\"\\", *c)) {
+                *(d++) = *c;
+            } else {
+                return MBEDTLS_ERR_X509_INVALID_NAME;
+            }
+        } else {
+            *(d++) = *c;
+        }
+
+        if (d - data == MBEDTLS_X509_MAX_DN_NAME_SIZE) {
+            return MBEDTLS_ERR_X509_INVALID_NAME;
+        }
+    }
+    *data_len = (size_t) (d - data);
+    return 0;
+}
+
+/** Parse a hexstring containing a DER-encoded string.
+ *
+ * \param s         A string of \p len bytes hexadecimal digits.
+ * \param len       Number of bytes to read from \p s.
+ * \param data      Output buffer of size \p data_size.
+ *                  On success, it contains the payload that's DER-encoded
+ *                  in the input (content without the tag and length).
+ *                  If the DER tag is a string tag, the payload is guaranteed
+ *                  not to contain null bytes.
+ * \param data_size Length of the \p data buffer.
+ * \param data_len  On success, the length of the parsed string.
+ *                  It is guaranteed to be less than
+ *                  #MBEDTLS_X509_MAX_DN_NAME_SIZE.
+ * \param tag       The ASN.1 tag that the payload in \p data is encoded in.
+ *
+ * \retval          0 on success.
+ * \retval          #MBEDTLS_ERR_X509_INVALID_NAME if \p s does not contain
+ *                  a valid hexstring,
+ *                  or if the decoded hexstring is not valid DER,
+ *                  or if the payload does not fit in \p data,
+ *                  or if the payload is more than
+ *                  #MBEDTLS_X509_MAX_DN_NAME_SIZE bytes,
+ *                  of if \p *tag is an ASN.1 string tag and the payload
+ *                  contains a null byte.
+ * \retval          #MBEDTLS_ERR_X509_ALLOC_FAILED on low memory.
+ */
+static int parse_attribute_value_hex_der_encoded(const char *s,
+                                                 size_t len,
+                                                 unsigned char *data,
+                                                 size_t data_size,
+                                                 size_t *data_len,
+                                                 int *tag)
+{
+    /* Step 1: preliminary length checks. */
+    /* Each byte is encoded by exactly two hexadecimal digits. */
+    if (len % 2 != 0) {
+        /* Odd number of hex digits */
+        return MBEDTLS_ERR_X509_INVALID_NAME;
+    }
+    size_t const der_length = len / 2;
+    if (der_length > MBEDTLS_X509_MAX_DN_NAME_SIZE + 4) {
+        /* The payload would be more than MBEDTLS_X509_MAX_DN_NAME_SIZE
+         * (after subtracting the ASN.1 tag and length). Reject this early
+         * to avoid allocating a large intermediate buffer. */
+        return MBEDTLS_ERR_X509_INVALID_NAME;
+    }
+    if (der_length < 1) {
+        /* Avoid empty-buffer shenanigans. A valid DER encoding is never
+         * empty. */
+        return MBEDTLS_ERR_X509_INVALID_NAME;
+    }
+
+    /* Step 2: Decode the hex string into an intermediate buffer. */
+    unsigned char *der = mbedtls_calloc(1, der_length);
+    if (der == NULL) {
+        return MBEDTLS_ERR_X509_ALLOC_FAILED;
+    }
+    /* Beyond this point, der needs to be freed on exit. */
+    for (size_t i = 0; i < der_length; i++) {
+        int c = hexpair_to_int(s + 2 * i);
+        if (c < 0) {
+            goto error;
+        }
+        der[i] = c;
+    }
+
+    /* Step 3: decode the DER. */
+    /* We've checked that der_length >= 1 above. */
+    *tag = der[0];
+    {
+        unsigned char *p = der + 1;
+        if (mbedtls_asn1_get_len(&p, der + der_length, data_len) != 0) {
+            goto error;
+        }
+        /* Now p points to the first byte of the payload inside der,
+         * and *data_len is the length of the payload. */
+
+        /* Step 4: payload validation */
+        if (*data_len > MBEDTLS_X509_MAX_DN_NAME_SIZE) {
+            goto error;
+        }
+        /* Strings must not contain null bytes. */
+        if (MBEDTLS_ASN1_IS_STRING_TAG(*tag)) {
+            for (size_t i = 0; i < *data_len; i++) {
+                if (p[i] == 0) {
+                    goto error;
+                }
+            }
+        }
+
+        /* Step 5: output the payload. */
+        if (*data_len > data_size) {
+            goto error;
+        }
+        memcpy(data, p, *data_len);
+    }
+    mbedtls_free(der);
+
+    return 0;
+
+error:
+    mbedtls_free(der);
+    return MBEDTLS_ERR_X509_INVALID_NAME;
+}
+
+int mbedtls_x509_string_to_names(mbedtls_asn1_named_data **head, const char *name)
+{
+    int ret = MBEDTLS_ERR_X509_INVALID_NAME;
+    int parse_ret = 0;
+    const char *s = name, *c = s;
+    const char *end = s + strlen(s);
+    mbedtls_asn1_buf oid = { .p = NULL, .len = 0, .tag = MBEDTLS_ASN1_NULL };
+    const x509_attr_descriptor_t *attr_descr = NULL;
+    int in_attr_type = 1;
+    int tag;
+    int numericoid = 0;
+    unsigned char data[MBEDTLS_X509_MAX_DN_NAME_SIZE];
+    size_t data_len = 0;
+
+    /* Clear existing chain if present */
+    mbedtls_asn1_free_named_data_list(head);
+
+    while (c <= end) {
+        if (in_attr_type && *c == '=') {
+            if ((attr_descr = x509_attr_descr_from_name(s, (size_t) (c - s))) == NULL) {
+                if ((mbedtls_oid_from_numeric_string(&oid, s, (size_t) (c - s))) != 0) {
+                    return MBEDTLS_ERR_X509_INVALID_NAME;
+                } else {
+                    numericoid = 1;
+                }
+            } else {
+                oid.len = strlen(attr_descr->oid);
+                oid.p = mbedtls_calloc(1, oid.len);
+                memcpy(oid.p, attr_descr->oid, oid.len);
+                numericoid = 0;
+            }
+
+            s = c + 1;
+            in_attr_type = 0;
+        }
+
+        if (!in_attr_type && ((*c == ',' && *(c-1) != '\\') || c == end)) {
+            if (s == c) {
+                mbedtls_free(oid.p);
+                return MBEDTLS_ERR_X509_INVALID_NAME;
+            } else if (*s == '#') {
+                /* We know that c >= s (loop invariant) and c != s (in this
+                 * else branch), hence c - s - 1 >= 0. */
+                parse_ret = parse_attribute_value_hex_der_encoded(
+                    s + 1, (size_t) (c - s) - 1,
+                    data, sizeof(data), &data_len, &tag);
+                if (parse_ret != 0) {
+                    mbedtls_free(oid.p);
+                    return parse_ret;
+                }
+            } else {
+                if (numericoid) {
+                    mbedtls_free(oid.p);
+                    return MBEDTLS_ERR_X509_INVALID_NAME;
+                } else {
+                    if ((parse_ret =
+                             parse_attribute_value_string(s, (int) (c - s), data,
+                                                          &data_len)) != 0) {
+                        mbedtls_free(oid.p);
+                        return parse_ret;
+                    }
+                    tag = attr_descr->default_tag;
+                }
+            }
+
+            mbedtls_asn1_named_data *cur =
+                mbedtls_asn1_store_named_data(head, (char *) oid.p, oid.len,
+                                              (unsigned char *) data,
+                                              data_len);
+            mbedtls_free(oid.p);
+            oid.p = NULL;
+            if (cur == NULL) {
+                return MBEDTLS_ERR_X509_ALLOC_FAILED;
+            }
+
+            // set tagType
+            cur->val.tag = tag;
+
+            while (c < end && *(c + 1) == ' ') {
+                c++;
+            }
+
+            s = c + 1;
+            in_attr_type = 1;
+
+            /* Successfully parsed one name, update ret to success */
+            ret = 0;
+        }
+        c++;
+    }
+    if (oid.p != NULL) {
+        mbedtls_free(oid.p);
+    }
+    return ret;
+}
+
+/* The first byte of the value in the mbedtls_asn1_named_data structure is reserved
+ * to store the critical boolean for us
+ */
+int mbedtls_x509_set_extension(mbedtls_asn1_named_data **head, const char *oid, size_t oid_len,
+                               int critical, const unsigned char *val, size_t val_len)
+{
+    mbedtls_asn1_named_data *cur;
+
+    if (val_len > (SIZE_MAX  - 1)) {
+        return MBEDTLS_ERR_X509_BAD_INPUT_DATA;
+    }
+
+    if ((cur = mbedtls_asn1_store_named_data(head, oid, oid_len,
+                                             NULL, val_len + 1)) == NULL) {
+        return MBEDTLS_ERR_X509_ALLOC_FAILED;
+    }
+
+    cur->val.p[0] = critical;
+    memcpy(cur->val.p + 1, val, val_len);
+
+    return 0;
+}
+
+/*
+ *  RelativeDistinguishedName ::=
+ *    SET OF AttributeTypeAndValue
+ *
+ *  AttributeTypeAndValue ::= SEQUENCE {
+ *    type     AttributeType,
+ *    value    AttributeValue }
+ *
+ *  AttributeType ::= OBJECT IDENTIFIER
+ *
+ *  AttributeValue ::= ANY DEFINED BY AttributeType
+ */
+static int x509_write_name(unsigned char **p,
+                           unsigned char *start,
+                           mbedtls_asn1_named_data *cur_name)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len = 0;
+    const char *oid             = (const char *) cur_name->oid.p;
+    size_t oid_len              = cur_name->oid.len;
+    const unsigned char *name   = cur_name->val.p;
+    size_t name_len             = cur_name->val.len;
+
+    // Write correct string tag and value
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tagged_string(p, start,
+                                                               cur_name->val.tag,
+                                                               (const char *) name,
+                                                               name_len));
+    // Write OID
+    //
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_oid(p, start, oid,
+                                                     oid_len));
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start,
+                                                     MBEDTLS_ASN1_CONSTRUCTED |
+                                                     MBEDTLS_ASN1_SEQUENCE));
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start,
+                                                     MBEDTLS_ASN1_CONSTRUCTED |
+                                                     MBEDTLS_ASN1_SET));
+
+    return (int) len;
+}
+
+int mbedtls_x509_write_names(unsigned char **p, unsigned char *start,
+                             mbedtls_asn1_named_data *first)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len = 0;
+    mbedtls_asn1_named_data *cur = first;
+
+    while (cur != NULL) {
+        MBEDTLS_ASN1_CHK_ADD(len, x509_write_name(p, start, cur));
+        cur = cur->next;
+    }
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_CONSTRUCTED |
+                                                     MBEDTLS_ASN1_SEQUENCE));
+
+    return (int) len;
+}
+
+int mbedtls_x509_write_sig(unsigned char **p, unsigned char *start,
+                           const char *oid, size_t oid_len,
+                           unsigned char *sig, size_t size,
+                           mbedtls_pk_type_t pk_alg)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    int write_null_par;
+    size_t len = 0;
+
+    if (*p < start || (size_t) (*p - start) < size) {
+        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
+    }
+
+    len = size;
+    (*p) -= len;
+    memcpy(*p, sig, len);
+
+    if (*p - start < 1) {
+        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
+    }
+
+    *--(*p) = 0;
+    len += 1;
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_BIT_STRING));
+
+    // Write OID
+    //
+    if (pk_alg == MBEDTLS_PK_ECDSA) {
+        /*
+         * The AlgorithmIdentifier's parameters field must be absent for DSA/ECDSA signature
+         * algorithms, see https://www.rfc-editor.org/rfc/rfc5480#page-17 and
+         * https://www.rfc-editor.org/rfc/rfc5758#section-3.
+         */
+        write_null_par = 0;
+    } else {
+        write_null_par = 1;
+    }
+    MBEDTLS_ASN1_CHK_ADD(len,
+                         mbedtls_asn1_write_algorithm_identifier_ext(p, start, oid, oid_len,
+                                                                     0, write_null_par));
+
+    return (int) len;
+}
+
+static int x509_write_extension(unsigned char **p, unsigned char *start,
+                                mbedtls_asn1_named_data *ext)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len = 0;
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, ext->val.p + 1,
+                                                            ext->val.len - 1));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, ext->val.len - 1));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_OCTET_STRING));
+
+    if (ext->val.p[0] != 0) {
+        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_bool(p, start, 1));
+    }
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, ext->oid.p,
+                                                            ext->oid.len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, ext->oid.len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_OID));
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_CONSTRUCTED |
+                                                     MBEDTLS_ASN1_SEQUENCE));
+
+    return (int) len;
+}
+
+/*
+ * Extension  ::=  SEQUENCE  {
+ *     extnID      OBJECT IDENTIFIER,
+ *     critical    BOOLEAN DEFAULT FALSE,
+ *     extnValue   OCTET STRING
+ *                 -- contains the DER encoding of an ASN.1 value
+ *                 -- corresponding to the extension type identified
+ *                 -- by extnID
+ *     }
+ */
+int mbedtls_x509_write_extensions(unsigned char **p, unsigned char *start,
+                                  mbedtls_asn1_named_data *first)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len = 0;
+    mbedtls_asn1_named_data *cur_ext = first;
+
+    while (cur_ext != NULL) {
+        MBEDTLS_ASN1_CHK_ADD(len, x509_write_extension(p, start, cur_ext));
+        cur_ext = cur_ext->next;
+    }
+
+    return (int) len;
+}
+
+#endif /* MBEDTLS_X509_CREATE_C */