diff --git a/library/x509_create.c b/library/x509_create.c
index 839b5df..e428461 100644
--- a/library/x509_create.c
+++ b/library/x509_create.c
@@ -278,6 +278,135 @@
     return MBEDTLS_ERR_X509_INVALID_NAME;
 }
 
+#if defined(MBEDTLS_OID_C)
+
+/* Return the OID for the given x.y.z.... style numeric string  */
+int mbedtls_oid_from_numeric_string(mbedtls_asn1_buf *oid,
+                                    const char *oid_str, size_t size)
+{
+    int ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
+    const char *str_ptr = oid_str;
+    const char *str_bound = oid_str + size;
+    unsigned int val = 0;
+    unsigned int component1, component2;
+    size_t encoded_len;
+    unsigned char *resized_mem;
+
+    /* Count the number of dots to get a worst-case allocation size. */
+    size_t num_dots = 0;
+    for (size_t i = 0; i < size; i++) {
+        if (oid_str[i] == '.') {
+            num_dots++;
+        }
+    }
+    /* Allocate maximum possible required memory:
+     * There are (num_dots + 1) integer components, but the first 2 share the
+     * same subidentifier, so we only need num_dots subidentifiers maximum. */
+    if (num_dots == 0 || (num_dots > MBEDTLS_OID_MAX_COMPONENTS - 1)) {
+        return MBEDTLS_ERR_ASN1_INVALID_DATA;
+    }
+    /* Each byte can store 7 bits, calculate number of bytes for a
+     * subidentifier:
+     *
+     * bytes = ceil(subidentifer_size * 8 / 7)
+     */
+    size_t bytes_per_subidentifier = (((sizeof(unsigned int) * 8) - 1) / 7)
+                                     + 1;
+    size_t max_possible_bytes = num_dots * bytes_per_subidentifier;
+    oid->p = mbedtls_calloc(max_possible_bytes, 1);
+    if (oid->p == NULL) {
+        return MBEDTLS_ERR_ASN1_ALLOC_FAILED;
+    }
+    unsigned char *out_ptr = oid->p;
+    unsigned char *out_bound = oid->p + max_possible_bytes;
+
+    ret = oid_parse_number(&component1, &str_ptr, str_bound);
+    if (ret != 0) {
+        goto error;
+    }
+    if (component1 > 2) {
+        /* First component can't be > 2 */
+        ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
+        goto error;
+    }
+    if (str_ptr >= str_bound || *str_ptr != '.') {
+        ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
+        goto error;
+    }
+    str_ptr++;
+
+    ret = oid_parse_number(&component2, &str_ptr, str_bound);
+    if (ret != 0) {
+        goto error;
+    }
+    if ((component1 < 2) && (component2 > 39)) {
+        /* Root nodes 0 and 1 may have up to 40 children, numbered 0-39 */
+        ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
+        goto error;
+    }
+    if (str_ptr < str_bound) {
+        if (*str_ptr == '.') {
+            str_ptr++;
+        } else {
+            ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
+            goto error;
+        }
+    }
+
+    if (component2 > (UINT_MAX - (component1 * 40))) {
+        ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
+        goto error;
+    }
+    ret = oid_subidentifier_encode_into(&out_ptr, out_bound,
+                                        (component1 * 40) + component2);
+    if (ret != 0) {
+        goto error;
+    }
+
+    while (str_ptr < str_bound) {
+        ret = oid_parse_number(&val, &str_ptr, str_bound);
+        if (ret != 0) {
+            goto error;
+        }
+        if (str_ptr < str_bound) {
+            if (*str_ptr == '.') {
+                str_ptr++;
+            } else {
+                ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
+                goto error;
+            }
+        }
+
+        ret = oid_subidentifier_encode_into(&out_ptr, out_bound, val);
+        if (ret != 0) {
+            goto error;
+        }
+    }
+
+    encoded_len = (size_t) (out_ptr - oid->p);
+    resized_mem = mbedtls_calloc(encoded_len, 1);
+    if (resized_mem == NULL) {
+        ret = MBEDTLS_ERR_ASN1_ALLOC_FAILED;
+        goto error;
+    }
+    memcpy(resized_mem, oid->p, encoded_len);
+    mbedtls_free(oid->p);
+    oid->p = resized_mem;
+    oid->len = encoded_len;
+
+    oid->tag = MBEDTLS_ASN1_OID;
+
+    return 0;
+
+error:
+    mbedtls_free(oid->p);
+    oid->p = NULL;
+    oid->len = 0;
+    return ret;
+}
+
+#endif /* MBEDTLS_OID_C */
+
 int mbedtls_x509_string_to_names(mbedtls_asn1_named_data **head, const char *name)
 {
     int ret = MBEDTLS_ERR_X509_INVALID_NAME;