Squashed 'lib/mbedtls/external/mbedtls/' content from commit 2ca6c285a0dd

git-subtree-dir: lib/mbedtls/external/mbedtls
git-subtree-split: 2ca6c285a0dd3f33982dd57299012dacab1ff206

1 files changed, 1776 insertions, 0 deletions

diff --git a/library/x509.c b/library/x509.c
new file mode 100644
index 00000000000..f97fb44589e
--- /dev/null
+++ b/library/x509.c
@@ -0,0 +1,1776 @@
+/*
+ *  X.509 common functions for parsing and verification
+ *
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+/*
+ *  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
+ */
+
+#include "common.h"
+
+#if defined(MBEDTLS_X509_USE_C)
+
+#include "x509_internal.h"
+#include "mbedtls/asn1.h"
+#include "mbedtls/error.h"
+#include "mbedtls/oid.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#if defined(MBEDTLS_PEM_PARSE_C)
+#include "mbedtls/pem.h"
+#endif
+
+#include "mbedtls/asn1write.h"
+
+#include "mbedtls/platform.h"
+
+#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)                                     \
+    do {                                                \
+        if ((ret = (code)) != 0) {                      \
+            return ret;                                 \
+        }                                               \
+    } while (0)
+
+#define CHECK_RANGE(min, max, val)                      \
+    do {                                                \
+        if ((val) < (min) || (val) > (max)) {           \
+            return ret;                                 \
+        }                                               \
+    } while (0)
+
+/*
+ *  CertificateSerialNumber  ::=  INTEGER
+ */
+int mbedtls_x509_get_serial(unsigned char **p, const unsigned char *end,
+                            mbedtls_x509_buf *serial)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    if ((end - *p) < 1) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(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_ERROR_ADD(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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    if ((ret = mbedtls_asn1_get_alg_null(p, end, alg)) != 0) {
+        return MBEDTLS_ERROR_ADD(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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    if ((ret = mbedtls_asn1_get_alg(p, end, alg, params)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG, ret);
+    }
+
+    return 0;
+}
+
+/*
+ * Convert md type to string
+ */
+#if !defined(MBEDTLS_X509_REMOVE_INFO) && defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT)
+
+static inline const char *md_type_to_string(mbedtls_md_type_t md_alg)
+{
+    switch (md_alg) {
+#if defined(MBEDTLS_MD_CAN_MD5)
+        case MBEDTLS_MD_MD5:
+            return "MD5";
+#endif
+#if defined(MBEDTLS_MD_CAN_SHA1)
+        case MBEDTLS_MD_SHA1:
+            return "SHA1";
+#endif
+#if defined(MBEDTLS_MD_CAN_SHA224)
+        case MBEDTLS_MD_SHA224:
+            return "SHA224";
+#endif
+#if defined(MBEDTLS_MD_CAN_SHA256)
+        case MBEDTLS_MD_SHA256:
+            return "SHA256";
+#endif
+#if defined(MBEDTLS_MD_CAN_SHA384)
+        case MBEDTLS_MD_SHA384:
+            return "SHA384";
+#endif
+#if defined(MBEDTLS_MD_CAN_SHA512)
+        case MBEDTLS_MD_SHA512:
+            return "SHA512";
+#endif
+#if defined(MBEDTLS_MD_CAN_RIPEMD160)
+        case MBEDTLS_MD_RIPEMD160:
+            return "RIPEMD160";
+#endif
+        case MBEDTLS_MD_NONE:
+            return NULL;
+        default:
+            return NULL;
+    }
+}
+
+#endif /* !defined(MBEDTLS_X509_REMOVE_INFO) && defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT) */
+
+#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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG,
+                                 MBEDTLS_ERR_ASN1_UNEXPECTED_TAG);
+    }
+
+    p = alg->p;
+    end = p + alg->len;
+
+    if (p >= end) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(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_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG, ret);
+    }
+
+    if (p != end) {
+        return MBEDTLS_ERROR_ADD(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. Enforce 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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    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_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG, ret);
+        }
+
+        if (p != end2) {
+            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG,
+                                     MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+        }
+    } else if (ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG,
+                                     MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+        }
+    } else if (ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG, ret);
+        }
+
+        if (p != end2) {
+            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG,
+                                     MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+        }
+    } else if (ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG, ret);
+        }
+
+        if (p != end2) {
+            return MBEDTLS_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_ALG, ret);
+    }
+
+    if (p != end) {
+        return MBEDTLS_ERROR_ADD(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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_NAME, ret);
+    }
+
+    end = *p + len;
+
+    if ((end - *p) < 1) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_NAME, ret);
+    }
+
+    oid->p = *p;
+    *p += oid->len;
+
+    if ((end - *p) < 1) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_NAME, ret);
+    }
+
+    val->p = *p;
+    *p += val->len;
+
+    if (*p != end) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_NAME,
+                                 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+    }
+
+    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().
+ *
+ * On success, this function may allocate a linked list starting at cur->next
+ * that must later be free'd by the caller using mbedtls_free(). In error
+ * cases, this function frees all allocated memory internally and the caller
+ * has no freeing responsibilities.
+ */
+int mbedtls_x509_get_name(unsigned char **p, const unsigned char *end,
+                          mbedtls_x509_name *cur)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t set_len;
+    const unsigned char *end_set;
+    mbedtls_x509_name *head = cur;
+
+    /* 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) {
+            ret = MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_NAME, ret);
+            goto error;
+        }
+
+        end_set  = *p + set_len;
+
+        while (1) {
+            if ((ret = x509_get_attr_type_value(p, end_set, cur)) != 0) {
+                goto error;
+            }
+
+            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) {
+                ret = MBEDTLS_ERR_X509_ALLOC_FAILED;
+                goto error;
+            }
+
+            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) {
+            ret = MBEDTLS_ERR_X509_ALLOC_FAILED;
+            goto error;
+        }
+
+        cur = cur->next;
+    }
+
+error:
+    /* Skip the first element as we did not allocate it */
+    mbedtls_asn1_free_named_data_list_shallow(head->next);
+    head->next = NULL;
+
+    return ret;
+}
+
+static int x509_date_is_valid(const mbedtls_x509_time *t)
+{
+    unsigned int month_days;
+    unsigned int year;
+    switch (t->mon) {
+        case 1: case 3: case 5: case 7: case 8: case 10: case 12:
+            month_days = 31;
+            break;
+        case 4: case 6: case 9: case 11:
+            month_days = 30;
+            break;
+        case 2:
+            year = (unsigned int) t->year;
+            month_days = ((year & 3) || (!(year % 100)
+                                         && (year % 400)))
+                          ? 28 : 29;
+            break;
+        default:
+            return MBEDTLS_ERR_X509_INVALID_DATE;
+    }
+
+    if ((unsigned int) (t->day - 1) >= month_days ||      /* (1 - days in month) */
+        /* (unsigned int) (t->mon - 1) >= 12 || */  /* (1 - 12) checked above */
+        (unsigned int) t->year > 9999 ||         /* (0 - 9999) */
+        (unsigned int) t->hour > 23 ||           /* (0 - 23) */
+        (unsigned int) t->min  > 59 ||           /* (0 - 59) */
+        (unsigned int) t->sec  > 59) {           /* (0 - 59) */
+        return MBEDTLS_ERR_X509_INVALID_DATE;
+    }
+
+    return 0;
+}
+
+static int x509_parse2_int(const unsigned char *p)
+{
+    uint32_t d1 = p[0] - '0';
+    uint32_t d2 = p[1] - '0';
+    return (d1 < 10 && d2 < 10) ? (int) (d1 * 10 + d2) : -1;
+}
+
+/*
+ * Parse an ASN1_UTC_TIME (yearlen=2) or ASN1_GENERALIZED_TIME (yearlen=4)
+ * field.
+ */
+static int x509_parse_time(const unsigned char *p, mbedtls_x509_time *tm,
+                           size_t yearlen)
+{
+    int x;
+
+    /*
+     * Parse year, month, day, hour, minute, second
+     */
+    tm->year = x509_parse2_int(p);
+    if (tm->year < 0) {
+        return MBEDTLS_ERR_X509_INVALID_DATE;
+    }
+
+    if (4 == yearlen) {
+        x = tm->year * 100;
+        p += 2;
+        tm->year = x509_parse2_int(p);
+        if (tm->year < 0) {
+            return MBEDTLS_ERR_X509_INVALID_DATE;
+        }
+    } else {
+        x = (tm->year < 50) ? 2000 : 1900;
+    }
+    tm->year += x;
+
+    tm->mon  = x509_parse2_int(p + 2);
+    tm->day  = x509_parse2_int(p + 4);
+    tm->hour = x509_parse2_int(p + 6);
+    tm->min  = x509_parse2_int(p + 8);
+    tm->sec  = x509_parse2_int(p + 10);
+
+    return x509_date_is_valid(tm);
+}
+
+/*
+ *  Time ::= CHOICE {
+ *       utcTime        UTCTime,
+ *       generalTime    GeneralizedTime }
+ */
+int mbedtls_x509_get_time(unsigned char **p, const unsigned char *end,
+                          mbedtls_x509_time *tm)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len, year_len;
+    unsigned char tag;
+
+    if ((end - *p) < 1) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_DATE,
+                                 MBEDTLS_ERR_ASN1_UNEXPECTED_TAG);
+    }
+
+    (*p)++;
+    ret = mbedtls_asn1_get_len(p, end, &len);
+
+    if (ret != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_DATE, ret);
+    }
+
+    /* len is 12 or 14 depending on year_len, plus optional trailing 'Z' */
+    if (len != year_len + 10 &&
+        !(len == year_len + 11 && (*p)[(len - 1)] == 'Z')) {
+        return MBEDTLS_ERR_X509_INVALID_DATE;
+    }
+
+    (*p) += len;
+    return x509_parse_time(*p - len, tm, year_len);
+}
+
+int mbedtls_x509_get_sig(unsigned char **p, const unsigned char *end, mbedtls_x509_buf *sig)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len;
+    int tag_type;
+
+    if ((end - *p) < 1) {
+        return MBEDTLS_ERROR_ADD(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_ERROR_ADD(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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    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_ERROR_ADD(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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len;
+
+    /* Extension structure use EXPLICIT tagging. That is, the actual
+     * `Extensions` structure is wrapped by a tag-length pair using
+     * the respective context-specific tag. */
+    ret = mbedtls_asn1_get_tag(p, end, &ext->len,
+                               MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | tag);
+    if (ret != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    ext->tag = MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | tag;
+    ext->p   = *p;
+    end      = *p + ext->len;
+
+    /*
+     * Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension
+     */
+    if ((ret = mbedtls_asn1_get_tag(p, end, &len,
+                                    MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    if (end != *p + len) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+    }
+
+    return 0;
+}
+
+static char nibble_to_hex_digit(int i)
+{
+    return (i < 10) ? (i + '0') : (i - 10 + 'A');
+}
+
+/*
+ * 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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t i, j, n, asn1_len_size, asn1_tag_size, asn1_tag_len_buf_start;
+    /* 6 is enough as our asn1 write functions only write one byte for the tag and at most five bytes for the length*/
+    unsigned char asn1_tag_len_buf[6];
+    unsigned char *asn1_len_p;
+    unsigned char c, merge = 0;
+    const mbedtls_x509_name *name;
+    const char *short_name = NULL;
+    char lowbits, highbits;
+    char s[MBEDTLS_X509_MAX_DN_NAME_SIZE], *p;
+    int print_hexstring;
+
+    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;
+        }
+
+        print_hexstring = (name->val.tag != MBEDTLS_ASN1_UTF8_STRING) &&
+                          (name->val.tag != MBEDTLS_ASN1_PRINTABLE_STRING) &&
+                          (name->val.tag != MBEDTLS_ASN1_IA5_STRING);
+
+        if ((ret = mbedtls_oid_get_attr_short_name(&name->oid, &short_name)) == 0) {
+            ret = mbedtls_snprintf(p, n, "%s=", short_name);
+        } else {
+            if ((ret = mbedtls_oid_get_numeric_string(p, n, &name->oid)) > 0) {
+                n -= ret;
+                p += ret;
+                ret = mbedtls_snprintf(p, n, "=");
+                print_hexstring = 1;
+            } else if (ret == MBEDTLS_ERR_OID_BUF_TOO_SMALL) {
+                return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+            } else {
+                ret = mbedtls_snprintf(p, n, "\?\?=");
+            }
+        }
+        MBEDTLS_X509_SAFE_SNPRINTF;
+
+        if (print_hexstring) {
+            s[0] = '#';
+
+            asn1_len_p = asn1_tag_len_buf + sizeof(asn1_tag_len_buf);
+            if ((ret = mbedtls_asn1_write_len(&asn1_len_p, asn1_tag_len_buf, name->val.len)) < 0) {
+                return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+            }
+            asn1_len_size = ret;
+            if ((ret = mbedtls_asn1_write_tag(&asn1_len_p, asn1_tag_len_buf, name->val.tag)) < 0) {
+                return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+            }
+            asn1_tag_size = ret;
+            asn1_tag_len_buf_start = sizeof(asn1_tag_len_buf) - asn1_len_size - asn1_tag_size;
+            for (i = 0, j = 1; i < asn1_len_size + asn1_tag_size; i++) {
+                if (j + 1 >= sizeof(s) - 1) {
+                    return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+                }
+                c = asn1_tag_len_buf[asn1_tag_len_buf_start+i];
+                lowbits = (c & 0x0F);
+                highbits = c >> 4;
+                s[j++] = nibble_to_hex_digit(highbits);
+                s[j++] = nibble_to_hex_digit(lowbits);
+            }
+            for (i = 0; i < name->val.len; i++) {
+                if (j + 1 >= sizeof(s) - 1) {
+                    return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+                }
+                c = name->val.p[i];
+                lowbits = (c & 0x0F);
+                highbits = c >> 4;
+                s[j++] = nibble_to_hex_digit(highbits);
+                s[j++] = nibble_to_hex_digit(lowbits);
+            }
+        } else {
+            for (i = 0, j = 0; i < name->val.len; i++, j++) {
+                if (j >= sizeof(s) - 1) {
+                    return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+                }
+
+                c = name->val.p[i];
+                // Special characters requiring escaping, RFC 4514 Section 2.4
+                if (c == '\0') {
+                    return MBEDTLS_ERR_X509_INVALID_NAME;
+                } else {
+                    if (strchr(",=+<>;\"\\", c) ||
+                        ((i == 0) && strchr("# ", c)) ||
+                        ((i == name->val.len-1) && (c == ' '))) {
+                        if (j + 1 >= sizeof(s) - 1) {
+                            return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+                        }
+                        s[j++] = '\\';
+                    }
+                }
+                if (c < 32 || c >= 127) {
+                    if (j + 3 >= sizeof(s) - 1) {
+                        return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+                    }
+                    s[j++] = '\\';
+                    lowbits = (c & 0x0F);
+                    highbits = c >> 4;
+                    s[j++] = nibble_to_hex_digit(highbits);
+                    s[j] = nibble_to_hex_digit(lowbits);
+                } else {
+                    s[j] = c;
+                }
+            }
+        }
+        s[j] = '\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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    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);
+}
+
+#if !defined(MBEDTLS_X509_REMOVE_INFO)
+/*
+ * 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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    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;
+
+        pss_opts = (const mbedtls_pk_rsassa_pss_options *) sig_opts;
+
+        const char *name = md_type_to_string(md_alg);
+        const char *mgf_name = md_type_to_string(pss_opts->mgf1_hash_id);
+
+        ret = mbedtls_snprintf(p, n, " (%s, MGF1-%s, 0x%02X)",
+                               name ? name : "???",
+                               mgf_name ? mgf_name : "???",
+                               (unsigned int) 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);
+}
+#endif /* MBEDTLS_X509_REMOVE_INFO */
+
+/*
+ * 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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    ret = mbedtls_snprintf(p, n, "%s key size", name);
+    MBEDTLS_X509_SAFE_SNPRINTF;
+
+    return 0;
+}
+
+int mbedtls_x509_time_cmp(const mbedtls_x509_time *t1,
+                          const mbedtls_x509_time *t2)
+{
+    int x;
+
+    x = (((t1->year << 9) | (t1->mon << 5) | (t1->day)) -
+         ((t2->year << 9) | (t2->mon << 5) | (t2->day)));
+    if (x != 0) {
+        return x;
+    }
+
+    x = (((t1->hour << 12) | (t1->min << 6) | (t1->sec)) -
+         ((t2->hour << 12) | (t2->min << 6) | (t2->sec)));
+    return x;
+}
+
+#if defined(MBEDTLS_HAVE_TIME_DATE)
+int mbedtls_x509_time_gmtime(mbedtls_time_t tt, mbedtls_x509_time *now)
+{
+    struct tm tm;
+
+    if (mbedtls_platform_gmtime_r(&tt, &tm) == NULL) {
+        return -1;
+    }
+
+    now->year = tm.tm_year + 1900;
+    now->mon  = tm.tm_mon  + 1;
+    now->day  = tm.tm_mday;
+    now->hour = tm.tm_hour;
+    now->min  = tm.tm_min;
+    now->sec  = tm.tm_sec;
+    return 0;
+}
+
+static int x509_get_current_time(mbedtls_x509_time *now)
+{
+    return mbedtls_x509_time_gmtime(mbedtls_time(NULL), now);
+}
+
+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 mbedtls_x509_time_cmp(to, &now) < 0;
+}
+
+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 mbedtls_x509_time_cmp(from, &now) > 0;
+}
+
+#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 */
+
+/* Common functions for parsing CRT and CSR. */
+#if defined(MBEDTLS_X509_CRT_PARSE_C) || defined(MBEDTLS_X509_CSR_PARSE_C)
+/*
+ * OtherName ::= SEQUENCE {
+ *      type-id    OBJECT IDENTIFIER,
+ *      value      [0] EXPLICIT ANY DEFINED BY type-id }
+ *
+ * HardwareModuleName ::= SEQUENCE {
+ *                           hwType OBJECT IDENTIFIER,
+ *                           hwSerialNum OCTET STRING }
+ *
+ * NOTE: we currently only parse and use otherName of type HwModuleName,
+ * as defined in RFC 4108.
+ */
+static int x509_get_other_name(const mbedtls_x509_buf *subject_alt_name,
+                               mbedtls_x509_san_other_name *other_name)
+{
+    int ret = 0;
+    size_t len;
+    unsigned char *p = subject_alt_name->p;
+    const unsigned char *end = p + subject_alt_name->len;
+    mbedtls_x509_buf cur_oid;
+
+    if ((subject_alt_name->tag &
+         (MBEDTLS_ASN1_TAG_CLASS_MASK | MBEDTLS_ASN1_TAG_VALUE_MASK)) !=
+        (MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_X509_SAN_OTHER_NAME)) {
+        /*
+         * The given subject alternative name is not of type "othername".
+         */
+        return MBEDTLS_ERR_X509_BAD_INPUT_DATA;
+    }
+
+    if ((ret = mbedtls_asn1_get_tag(&p, end, &len,
+                                    MBEDTLS_ASN1_OID)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    cur_oid.tag = MBEDTLS_ASN1_OID;
+    cur_oid.p = p;
+    cur_oid.len = len;
+
+    /*
+     * Only HwModuleName is currently supported.
+     */
+    if (MBEDTLS_OID_CMP(MBEDTLS_OID_ON_HW_MODULE_NAME, &cur_oid) != 0) {
+        return MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE;
+    }
+    other_name->type_id = cur_oid;
+
+    p += len;
+    if ((ret = mbedtls_asn1_get_tag(&p, end, &len,
+                                    MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_CONTEXT_SPECIFIC)) !=
+        0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    if (end != p + len) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+    }
+
+    if ((ret = mbedtls_asn1_get_tag(&p, end, &len,
+                                    MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    if (end != p + len) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+    }
+
+    if ((ret = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OID)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    other_name->value.hardware_module_name.oid.tag = MBEDTLS_ASN1_OID;
+    other_name->value.hardware_module_name.oid.p = p;
+    other_name->value.hardware_module_name.oid.len = len;
+
+    p += len;
+    if ((ret = mbedtls_asn1_get_tag(&p, end, &len,
+                                    MBEDTLS_ASN1_OCTET_STRING)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    other_name->value.hardware_module_name.val.tag = MBEDTLS_ASN1_OCTET_STRING;
+    other_name->value.hardware_module_name.val.p = p;
+    other_name->value.hardware_module_name.val.len = len;
+    p += len;
+    if (p != end) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+    }
+    return 0;
+}
+
+/* Check mbedtls_x509_get_subject_alt_name for detailed description.
+ *
+ * In some cases while parsing subject alternative names the sequence tag is optional
+ * (e.g. CertSerialNumber). This function is designed to handle such case.
+ */
+int mbedtls_x509_get_subject_alt_name_ext(unsigned char **p,
+                                          const unsigned char *end,
+                                          mbedtls_x509_sequence *subject_alt_name)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t tag_len;
+    mbedtls_asn1_sequence *cur = subject_alt_name;
+
+    while (*p < end) {
+        mbedtls_x509_subject_alternative_name tmp_san_name;
+        mbedtls_x509_buf tmp_san_buf;
+        memset(&tmp_san_name, 0, sizeof(tmp_san_name));
+
+        tmp_san_buf.tag = **p;
+        (*p)++;
+
+        if ((ret = mbedtls_asn1_get_len(p, end, &tag_len)) != 0) {
+            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+        }
+
+        tmp_san_buf.p = *p;
+        tmp_san_buf.len = tag_len;
+
+        if ((tmp_san_buf.tag & MBEDTLS_ASN1_TAG_CLASS_MASK) !=
+            MBEDTLS_ASN1_CONTEXT_SPECIFIC) {
+            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                     MBEDTLS_ERR_ASN1_UNEXPECTED_TAG);
+        }
+
+        /*
+         * Check that the SAN is structured correctly by parsing it.
+         * The SAN structure is discarded afterwards.
+         */
+        ret = mbedtls_x509_parse_subject_alt_name(&tmp_san_buf, &tmp_san_name);
+        /*
+         * In case the extension is malformed, return an error,
+         * and clear the allocated sequences.
+         */
+        if (ret != 0 && ret != MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE) {
+            mbedtls_asn1_sequence_free(subject_alt_name->next);
+            subject_alt_name->next = NULL;
+            return ret;
+        }
+
+        mbedtls_x509_free_subject_alt_name(&tmp_san_name);
+        /* Allocate and assign next pointer */
+        if (cur->buf.p != NULL) {
+            if (cur->next != NULL) {
+                return MBEDTLS_ERR_X509_INVALID_EXTENSIONS;
+            }
+
+            cur->next = mbedtls_calloc(1, sizeof(mbedtls_asn1_sequence));
+
+            if (cur->next == NULL) {
+                return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                         MBEDTLS_ERR_ASN1_ALLOC_FAILED);
+            }
+
+            cur = cur->next;
+        }
+
+        cur->buf = tmp_san_buf;
+        *p += tmp_san_buf.len;
+    }
+
+    /* Set final sequence entry's next pointer to NULL */
+    cur->next = NULL;
+
+    if (*p != end) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+    }
+
+    return 0;
+}
+
+/*
+ * SubjectAltName ::= GeneralNames
+ *
+ * GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName
+ *
+ * GeneralName ::= CHOICE {
+ *      otherName                       [0]     OtherName,
+ *      rfc822Name                      [1]     IA5String,
+ *      dNSName                         [2]     IA5String,
+ *      x400Address                     [3]     ORAddress,
+ *      directoryName                   [4]     Name,
+ *      ediPartyName                    [5]     EDIPartyName,
+ *      uniformResourceIdentifier       [6]     IA5String,
+ *      iPAddress                       [7]     OCTET STRING,
+ *      registeredID                    [8]     OBJECT IDENTIFIER }
+ *
+ * OtherName ::= SEQUENCE {
+ *      type-id    OBJECT IDENTIFIER,
+ *      value      [0] EXPLICIT ANY DEFINED BY type-id }
+ *
+ * EDIPartyName ::= SEQUENCE {
+ *      nameAssigner            [0]     DirectoryString OPTIONAL,
+ *      partyName               [1]     DirectoryString }
+ *
+ * We list all types, but use the following GeneralName types from RFC 5280:
+ * "dnsName", "uniformResourceIdentifier" and "hardware_module_name"
+ * of type "otherName", as defined in RFC 4108.
+ */
+int mbedtls_x509_get_subject_alt_name(unsigned char **p,
+                                      const unsigned char *end,
+                                      mbedtls_x509_sequence *subject_alt_name)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len;
+
+    /* Get main sequence tag */
+    if ((ret = mbedtls_asn1_get_tag(p, end, &len,
+                                    MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    if (*p + len != end) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH);
+    }
+
+    return mbedtls_x509_get_subject_alt_name_ext(p, end, subject_alt_name);
+}
+
+int mbedtls_x509_get_ns_cert_type(unsigned char **p,
+                                  const unsigned char *end,
+                                  unsigned char *ns_cert_type)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    mbedtls_x509_bitstring bs = { 0, 0, NULL };
+
+    if ((ret = mbedtls_asn1_get_bitstring(p, end, &bs)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    /* A bitstring with no flags set is still technically valid, as it will mean
+       that the certificate has no designated purpose at the time of creation. */
+    if (bs.len == 0) {
+        *ns_cert_type = 0;
+        return 0;
+    }
+
+    if (bs.len != 1) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
+                                 MBEDTLS_ERR_ASN1_INVALID_LENGTH);
+    }
+
+    /* Get actual bitstring */
+    *ns_cert_type = *bs.p;
+    return 0;
+}
+
+int mbedtls_x509_get_key_usage(unsigned char **p,
+                               const unsigned char *end,
+                               unsigned int *key_usage)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t i;
+    mbedtls_x509_bitstring bs = { 0, 0, NULL };
+
+    if ((ret = mbedtls_asn1_get_bitstring(p, end, &bs)) != 0) {
+        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
+    }
+
+    /* A bitstring with no flags set is still technically valid, as it will mean
+       that the certificate has no designated purpose at the time of creation. */
+    if (bs.len == 0) {
+        *key_usage = 0;
+        return 0;
+    }
+
+    /* Get actual bitstring */
+    *key_usage = 0;
+    for (i = 0; i < bs.len && i < sizeof(unsigned int); i++) {
+        *key_usage |= (unsigned int) bs.p[i] << (8*i);
+    }
+
+    return 0;
+}
+
+int mbedtls_x509_parse_subject_alt_name(const mbedtls_x509_buf *san_buf,
+                                        mbedtls_x509_subject_alternative_name *san)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    switch (san_buf->tag &
+            (MBEDTLS_ASN1_TAG_CLASS_MASK |
+             MBEDTLS_ASN1_TAG_VALUE_MASK)) {
+        /*
+         * otherName
+         */
+        case (MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_X509_SAN_OTHER_NAME):
+        {
+            mbedtls_x509_san_other_name other_name;
+
+            ret = x509_get_other_name(san_buf, &other_name);
+            if (ret != 0) {
+                return ret;
+            }
+
+            memset(san, 0, sizeof(mbedtls_x509_subject_alternative_name));
+            san->type = MBEDTLS_X509_SAN_OTHER_NAME;
+            memcpy(&san->san.other_name,
+                   &other_name, sizeof(other_name));
+
+        }
+        break;
+        /*
+         * uniformResourceIdentifier
+         */
+        case (MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_X509_SAN_UNIFORM_RESOURCE_IDENTIFIER):
+        {
+            memset(san, 0, sizeof(mbedtls_x509_subject_alternative_name));
+            san->type = MBEDTLS_X509_SAN_UNIFORM_RESOURCE_IDENTIFIER;
+
+            memcpy(&san->san.unstructured_name,
+                   san_buf, sizeof(*san_buf));
+
+        }
+        break;
+        /*
+         * dNSName
+         */
+        case (MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_X509_SAN_DNS_NAME):
+        {
+            memset(san, 0, sizeof(mbedtls_x509_subject_alternative_name));
+            san->type = MBEDTLS_X509_SAN_DNS_NAME;
+
+            memcpy(&san->san.unstructured_name,
+                   san_buf, sizeof(*san_buf));
+        }
+        break;
+        /*
+         * IP address
+         */
+        case (MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_X509_SAN_IP_ADDRESS):
+        {
+            memset(san, 0, sizeof(mbedtls_x509_subject_alternative_name));
+            san->type = MBEDTLS_X509_SAN_IP_ADDRESS;
+            // Only IPv6 (16 bytes) and IPv4 (4 bytes) types are supported
+            if (san_buf->len == 4 || san_buf->len == 16) {
+                memcpy(&san->san.unstructured_name,
+                       san_buf, sizeof(*san_buf));
+            } else {
+                return MBEDTLS_ERR_X509_BAD_INPUT_DATA;
+            }
+        }
+        break;
+        /*
+         * rfc822Name
+         */
+        case (MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_X509_SAN_RFC822_NAME):
+        {
+            memset(san, 0, sizeof(mbedtls_x509_subject_alternative_name));
+            san->type = MBEDTLS_X509_SAN_RFC822_NAME;
+            memcpy(&san->san.unstructured_name, san_buf, sizeof(*san_buf));
+        }
+        break;
+        /*
+         * directoryName
+         */
+        case (MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_X509_SAN_DIRECTORY_NAME):
+        {
+            size_t name_len;
+            unsigned char *p = san_buf->p;
+            memset(san, 0, sizeof(mbedtls_x509_subject_alternative_name));
+            san->type = MBEDTLS_X509_SAN_DIRECTORY_NAME;
+
+            ret = mbedtls_asn1_get_tag(&p, p + san_buf->len, &name_len,
+                                       MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE);
+
+            if (ret != 0) {
+                return ret;
+            }
+
+            if ((ret = mbedtls_x509_get_name(&p, p + name_len,
+                                             &san->san.directory_name)) != 0) {
+                return ret;
+            }
+        }
+        break;
+        /*
+         * Type not supported
+         */
+        default:
+            return MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE;
+    }
+    return 0;
+}
+
+void mbedtls_x509_free_subject_alt_name(mbedtls_x509_subject_alternative_name *san)
+{
+    if (san->type == MBEDTLS_X509_SAN_DIRECTORY_NAME) {
+        mbedtls_asn1_free_named_data_list_shallow(san->san.directory_name.next);
+    }
+}
+
+#if !defined(MBEDTLS_X509_REMOVE_INFO)
+int mbedtls_x509_info_subject_alt_name(char **buf, size_t *size,
+                                       const mbedtls_x509_sequence
+                                       *subject_alt_name,
+                                       const char *prefix)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t i;
+    size_t n = *size;
+    char *p = *buf;
+    const mbedtls_x509_sequence *cur = subject_alt_name;
+    mbedtls_x509_subject_alternative_name san;
+    int parse_ret;
+
+    while (cur != NULL) {
+        memset(&san, 0, sizeof(san));
+        parse_ret = mbedtls_x509_parse_subject_alt_name(&cur->buf, &san);
+        if (parse_ret != 0) {
+            if (parse_ret == MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE) {
+                ret = mbedtls_snprintf(p, n, "\n%s    <unsupported>", prefix);
+                MBEDTLS_X509_SAFE_SNPRINTF;
+            } else {
+                ret = mbedtls_snprintf(p, n, "\n%s    <malformed>", prefix);
+                MBEDTLS_X509_SAFE_SNPRINTF;
+            }
+            cur = cur->next;
+            continue;
+        }
+
+        switch (san.type) {
+            /*
+             * otherName
+             */
+            case MBEDTLS_X509_SAN_OTHER_NAME:
+            {
+                mbedtls_x509_san_other_name *other_name = &san.san.other_name;
+
+                ret = mbedtls_snprintf(p, n, "\n%s    otherName :", prefix);
+                MBEDTLS_X509_SAFE_SNPRINTF;
+
+                if (MBEDTLS_OID_CMP(MBEDTLS_OID_ON_HW_MODULE_NAME,
+                                    &other_name->type_id) == 0) {
+                    ret = mbedtls_snprintf(p, n, "\n%s        hardware module name :", prefix);
+                    MBEDTLS_X509_SAFE_SNPRINTF;
+                    ret =
+                        mbedtls_snprintf(p, n, "\n%s            hardware type          : ", prefix);
+                    MBEDTLS_X509_SAFE_SNPRINTF;
+
+                    ret = mbedtls_oid_get_numeric_string(p,
+                                                         n,
+                                                         &other_name->value.hardware_module_name.oid);
+                    MBEDTLS_X509_SAFE_SNPRINTF;
+
+                    ret =
+                        mbedtls_snprintf(p, n, "\n%s            hardware serial number : ", prefix);
+                    MBEDTLS_X509_SAFE_SNPRINTF;
+
+                    for (i = 0; i < other_name->value.hardware_module_name.val.len; i++) {
+                        ret = mbedtls_snprintf(p,
+                                               n,
+                                               "%02X",
+                                               other_name->value.hardware_module_name.val.p[i]);
+                        MBEDTLS_X509_SAFE_SNPRINTF;
+                    }
+                }/* MBEDTLS_OID_ON_HW_MODULE_NAME */
+            }
+            break;
+            /*
+             * uniformResourceIdentifier
+             */
+            case MBEDTLS_X509_SAN_UNIFORM_RESOURCE_IDENTIFIER:
+            {
+                ret = mbedtls_snprintf(p, n, "\n%s    uniformResourceIdentifier : ", prefix);
+                MBEDTLS_X509_SAFE_SNPRINTF;
+                if (san.san.unstructured_name.len >= n) {
+                    if (n > 0) {
+                        *p = '\0';
+                    }
+                    return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+                }
+
+                memcpy(p, san.san.unstructured_name.p, san.san.unstructured_name.len);
+                p += san.san.unstructured_name.len;
+                n -= san.san.unstructured_name.len;
+            }
+            break;
+            /*
+             * dNSName
+             * RFC822 Name
+             */
+            case MBEDTLS_X509_SAN_DNS_NAME:
+            case MBEDTLS_X509_SAN_RFC822_NAME:
+            {
+                const char *dns_name = "dNSName";
+                const char *rfc822_name = "rfc822Name";
+
+                ret = mbedtls_snprintf(p, n,
+                                       "\n%s    %s : ",
+                                       prefix,
+                                       san.type ==
+                                       MBEDTLS_X509_SAN_DNS_NAME ? dns_name : rfc822_name);
+                MBEDTLS_X509_SAFE_SNPRINTF;
+                if (san.san.unstructured_name.len >= n) {
+                    if (n > 0) {
+                        *p = '\0';
+                    }
+                    return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+                }
+
+                memcpy(p, san.san.unstructured_name.p, san.san.unstructured_name.len);
+                p += san.san.unstructured_name.len;
+                n -= san.san.unstructured_name.len;
+            }
+            break;
+            /*
+             * iPAddress
+             */
+            case MBEDTLS_X509_SAN_IP_ADDRESS:
+            {
+                ret = mbedtls_snprintf(p, n, "\n%s    %s : ",
+                                       prefix, "iPAddress");
+                MBEDTLS_X509_SAFE_SNPRINTF;
+                if (san.san.unstructured_name.len >= n) {
+                    if (n > 0) {
+                        *p = '\0';
+                    }
+                    return MBEDTLS_ERR_X509_BUFFER_TOO_SMALL;
+                }
+
+                unsigned char *ip = san.san.unstructured_name.p;
+                // Only IPv6 (16 bytes) and IPv4 (4 bytes) types are supported
+                if (san.san.unstructured_name.len == 4) {
+                    ret = mbedtls_snprintf(p, n, "%u.%u.%u.%u", ip[0], ip[1], ip[2], ip[3]);
+                    MBEDTLS_X509_SAFE_SNPRINTF;
+                } else if (san.san.unstructured_name.len == 16) {
+                    ret = mbedtls_snprintf(p, n,
+                                           "%X%X:%X%X:%X%X:%X%X:%X%X:%X%X:%X%X:%X%X",
+                                           ip[0], ip[1], ip[2], ip[3], ip[4], ip[5], ip[6],
+                                           ip[7], ip[8], ip[9], ip[10], ip[11], ip[12], ip[13],
+                                           ip[14], ip[15]);
+                    MBEDTLS_X509_SAFE_SNPRINTF;
+                } else {
+                    if (n > 0) {
+                        *p = '\0';
+                    }
+                    return MBEDTLS_ERR_X509_BAD_INPUT_DATA;
+                }
+            }
+            break;
+            /*
+             * directoryName
+             */
+            case MBEDTLS_X509_SAN_DIRECTORY_NAME:
+            {
+                ret = mbedtls_snprintf(p, n, "\n%s    directoryName : ", prefix);
+                if (ret < 0 || (size_t) ret >= n) {
+                    mbedtls_x509_free_subject_alt_name(&san);
+                }
+
+                MBEDTLS_X509_SAFE_SNPRINTF;
+                ret = mbedtls_x509_dn_gets(p, n, &san.san.directory_name);
+
+                if (ret < 0) {
+                    mbedtls_x509_free_subject_alt_name(&san);
+                    if (n > 0) {
+                        *p = '\0';
+                    }
+                    return ret;
+                }
+
+                p += ret;
+                n -= ret;
+            }
+            break;
+            /*
+             * Type not supported, skip item.
+             */
+            default:
+                ret = mbedtls_snprintf(p, n, "\n%s    <unsupported>", prefix);
+                MBEDTLS_X509_SAFE_SNPRINTF;
+                break;
+        }
+
+        /* So far memory is freed only in the case of directoryName
+         * parsing succeeding, as mbedtls_x509_get_name allocates memory. */
+        mbedtls_x509_free_subject_alt_name(&san);
+        cur = cur->next;
+    }
+
+    *p = '\0';
+
+    *size = n;
+    *buf = p;
+
+    return 0;
+}
+
+#define PRINT_ITEM(i)                                   \
+    do {                                                \
+        ret = mbedtls_snprintf(p, n, "%s" i, sep);      \
+        MBEDTLS_X509_SAFE_SNPRINTF;                     \
+        sep = ", ";                                     \
+    } while (0)
+
+#define CERT_TYPE(type, name)                           \
+    do {                                                \
+        if (ns_cert_type & (type)) {                    \
+            PRINT_ITEM(name);                           \
+        }                                               \
+    } while (0)
+
+int mbedtls_x509_info_cert_type(char **buf, size_t *size,
+                                unsigned char ns_cert_type)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t n = *size;
+    char *p = *buf;
+    const char *sep = "";
+
+    CERT_TYPE(MBEDTLS_X509_NS_CERT_TYPE_SSL_CLIENT,         "SSL Client");
+    CERT_TYPE(MBEDTLS_X509_NS_CERT_TYPE_SSL_SERVER,         "SSL Server");
+    CERT_TYPE(MBEDTLS_X509_NS_CERT_TYPE_EMAIL,              "Email");
+    CERT_TYPE(MBEDTLS_X509_NS_CERT_TYPE_OBJECT_SIGNING,     "Object Signing");
+    CERT_TYPE(MBEDTLS_X509_NS_CERT_TYPE_RESERVED,           "Reserved");
+    CERT_TYPE(MBEDTLS_X509_NS_CERT_TYPE_SSL_CA,             "SSL CA");
+    CERT_TYPE(MBEDTLS_X509_NS_CERT_TYPE_EMAIL_CA,           "Email CA");
+    CERT_TYPE(MBEDTLS_X509_NS_CERT_TYPE_OBJECT_SIGNING_CA,  "Object Signing CA");
+
+    *size = n;
+    *buf = p;
+
+    return 0;
+}
+
+#define KEY_USAGE(code, name)       \
+    do {                            \
+        if ((key_usage) & (code)) { \
+            PRINT_ITEM(name);       \
+        }                           \
+    } while (0)
+
+int mbedtls_x509_info_key_usage(char **buf, size_t *size,
+                                unsigned int key_usage)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t n = *size;
+    char *p = *buf;
+    const char *sep = "";
+
+    KEY_USAGE(MBEDTLS_X509_KU_DIGITAL_SIGNATURE,    "Digital Signature");
+    KEY_USAGE(MBEDTLS_X509_KU_NON_REPUDIATION,      "Non Repudiation");
+    KEY_USAGE(MBEDTLS_X509_KU_KEY_ENCIPHERMENT,     "Key Encipherment");
+    KEY_USAGE(MBEDTLS_X509_KU_DATA_ENCIPHERMENT,    "Data Encipherment");
+    KEY_USAGE(MBEDTLS_X509_KU_KEY_AGREEMENT,        "Key Agreement");
+    KEY_USAGE(MBEDTLS_X509_KU_KEY_CERT_SIGN,        "Key Cert Sign");
+    KEY_USAGE(MBEDTLS_X509_KU_CRL_SIGN,             "CRL Sign");
+    KEY_USAGE(MBEDTLS_X509_KU_ENCIPHER_ONLY,        "Encipher Only");
+    KEY_USAGE(MBEDTLS_X509_KU_DECIPHER_ONLY,        "Decipher Only");
+
+    *size = n;
+    *buf = p;
+
+    return 0;
+}
+#endif /* MBEDTLS_X509_REMOVE_INFO */
+#endif /* MBEDTLS_X509_CRT_PARSE_C || MBEDTLS_X509_CSR_PARSE_C */
+#endif /* MBEDTLS_X509_USE_C */