- Improved X509 certificate parsing to include extended certificate fields, such as Key Usage

ChangeLog

@@ -11,6 +11,8 @@ Note: Most of these features have been donated by Fox-IT
    * Added reading of DHM context from memory and file
    * Added verification callback on certificate chain
      verification to allow external blacklisting.
+   * Improved X509 certificate parsing to include extended
+     certificate fields, including Key Usage.
 
 = Version 0.14.0 released on 2010-08-16
 Features

include/polarssl/x509.h

@@ -144,13 +144,132 @@
 #define X509_ISSUER                  0x01
 #define X509_SUBJECT                 0x02
 
+/** Returns the size of the binary string, without the trailing \0 */
+#define OID_SIZE(x) (sizeof(x) - 1)
+
 #define OID_X520                "\x55\x04"
-#define OID_CN                  "\x55\x04\x03"
+#define OID_CN                  OID_X520 "\x03"
+
 #define OID_PKCS1               "\x2A\x86\x48\x86\xF7\x0D\x01\x01"
-#define OID_PKCS1_RSA           "\x2A\x86\x48\x86\xF7\x0D\x01\x01\x01"
+#define OID_PKCS1_RSA           OID_PKCS1 "\x01"
-#define OID_PKCS1_RSA_SHA       "\x2A\x86\x48\x86\xF7\x0D\x01\x01\x05"
+#define OID_PKCS1_RSA_SHA       OID_PKCS1 "\x05"
+
 #define OID_PKCS9               "\x2A\x86\x48\x86\xF7\x0D\x01\x09"
-#define OID_PKCS9_EMAIL         "\x2A\x86\x48\x86\xF7\x0D\x01\x09\x01"
+#define OID_PKCS9_EMAIL         OID_PKCS9 "\x01"
+
+/** ISO arc for standard certificate and CRL extensions */
+#define OID_ID_CE               "\x55\x1D" /**< id-ce OBJECT IDENTIFIER  ::=  {joint-iso-ccitt(2) ds(5) 29} */
+
+/**
+ * Private Internet Extensions
+ * { iso(1) identified-organization(3) dod(6) internet(1)
+ *                      security(5) mechanisms(5) pkix(7) }
+ */
+#define OID_PKIX                "\x2B\x06\x01\x05\x05\x07"
+
+/*
+ * OIDs for standard certificate extensions
+ */
+#define OID_AUTHORITY_KEY_IDENTIFIER    OID_ID_CE "\x23" /**< id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::=  { id-ce 35 } */
+#define OID_SUBJECT_KEY_IDENTIFIER      OID_ID_CE "\x0E" /**< id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::=  { id-ce 14 } */
+#define OID_KEY_USAGE                   OID_ID_CE "\x0F" /**< id-ce-keyUsage OBJECT IDENTIFIER ::=  { id-ce 15 } */
+#define OID_CERTIFICATE_POLICIES        OID_ID_CE "\x20" /**< id-ce-certificatePolicies OBJECT IDENTIFIER ::=  { id-ce 32 } */
+#define OID_POLICY_MAPPINGS             OID_ID_CE "\x21" /**< id-ce-policyMappings OBJECT IDENTIFIER ::=  { id-ce 33 } */
+#define OID_SUBJECT_ALT_NAME            OID_ID_CE "\x11" /**< id-ce-subjectAltName OBJECT IDENTIFIER ::=  { id-ce 17 } */
+#define OID_ISSUER_ALT_NAME             OID_ID_CE "\x12" /**< id-ce-issuerAltName OBJECT IDENTIFIER ::=  { id-ce 18 } */
+#define OID_SUBJECT_DIRECTORY_ATTRS     OID_ID_CE "\x09" /**< id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::=  { id-ce 9 } */
+#define OID_BASIC_CONSTRAINTS           OID_ID_CE "\x13" /**< id-ce-basicConstraints OBJECT IDENTIFIER ::=  { id-ce 19 } */
+#define OID_NAME_CONSTRAINTS            OID_ID_CE "\x1E" /**< id-ce-nameConstraints OBJECT IDENTIFIER ::=  { id-ce 30 } */
+#define OID_POLICY_CONSTRAINTS          OID_ID_CE "\x24" /**< id-ce-policyConstraints OBJECT IDENTIFIER ::=  { id-ce 36 } */
+#define OID_EXTENDED_KEY_USAGE          OID_ID_CE "\x25" /**< id-ce-extKeyUsage OBJECT IDENTIFIER ::= { id-ce 37 } */
+#define OID_CRL_DISTRIBUTION_POINTS     OID_ID_CE "\x1F" /**< id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::=  { id-ce 31 } */
+#define OID_INIHIBIT_ANYPOLICY          OID_ID_CE "\x36" /**< id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::=  { id-ce 54 } */
+#define OID_FRESHEST_CRL                OID_ID_CE "\x2E" /**< id-ce-freshestCRL OBJECT IDENTIFIER ::=  { id-ce 46 } */
+
+/*
+ * X.509 v3 Key Usage Extension flags
+ */
+#define KU_DIGITAL_SIGNATURE            (0x80)  /* bit 0 */
+#define KU_NON_REPUDIATION              (0x40)  /* bit 1 */
+#define KU_KEY_ENCIPHERMENT             (0x20)  /* bit 2 */
+#define KU_DATA_ENCIPHERMENT            (0x10)  /* bit 3 */
+#define KU_KEY_AGREEMENT                (0x08)  /* bit 4 */
+#define KU_KEY_CERT_SIGN                (0x04)  /* bit 5 */
+#define KU_CRL_SIGN                     (0x02)  /* bit 6 */
+
+/*
+ * X.509 v3 Extended key usage OIDs
+ */
+#define OID_ANY_EXTENDED_KEY_USAGE      OID_EXTENDED_KEY_USAGE "\x00" /**< anyExtendedKeyUsage OBJECT IDENTIFIER ::= { id-ce-extKeyUsage 0 } */
+
+#define OID_KP                          OID_PKIX "\x03" /**< id-kp OBJECT IDENTIFIER ::= { id-pkix 3 } */
+#define OID_SERVER_AUTH                 OID_KP "\x01" /**< id-kp-serverAuth OBJECT IDENTIFIER ::= { id-kp 1 } */
+#define OID_CLIENT_AUTH                 OID_KP "\x02" /**< id-kp-clientAuth OBJECT IDENTIFIER ::= { id-kp 2 } */
+#define OID_CODE_SIGNING                OID_KP "\x03" /**< id-kp-codeSigning OBJECT IDENTIFIER ::= { id-kp 3 } */
+#define OID_EMAIL_PROTECTION            OID_KP "\x04" /**< id-kp-emailProtection OBJECT IDENTIFIER ::= { id-kp 4 } */
+#define OID_TIME_STAMPING               OID_KP "\x08" /**< id-kp-timeStamping OBJECT IDENTIFIER ::= { id-kp 8 } */
+#define OID_OCSP_SIGNING                OID_KP "\x09" /**< id-kp-OCSPSigning OBJECT IDENTIFIER ::= { id-kp 9 } */
+
+#define STRING_SERVER_AUTH              "TLS Web Server Authentication"
+#define STRING_CLIENT_AUTH              "TLS Web Client Authentication"
+#define STRING_CODE_SIGNING             "Code Signing"
+#define STRING_EMAIL_PROTECTION         "E-mail Protection"
+#define STRING_TIME_STAMPING            "Time Stamping"
+#define STRING_OCSP_SIGNING             "OCSP Signing"
+
+/*
+ * OIDs for CRL extensions
+ */
+#define OID_PRIVATE_KEY_USAGE_PERIOD    OID_ID_CE "\x10"
+#define OID_CRL_NUMBER                  OID_ID_CE "\x14" /**< id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 } */
+
+/*
+ * Netscape certificate extensions
+ */
+#define OID_NETSCAPE                "\x60\x86\x48\x01\x86\xF8\x42" /**< Netscape OID */
+#define OID_NS_CERT                 OID_NETSCAPE "\x01"
+#define OID_NS_CERT_TYPE            OID_NS_CERT  "\x01"
+#define OID_NS_BASE_URL             OID_NS_CERT  "\x02"
+#define OID_NS_REVOCATION_URL       OID_NS_CERT  "\x03"
+#define OID_NS_CA_REVOCATION_URL    OID_NS_CERT  "\x04"
+#define OID_NS_RENEWAL_URL          OID_NS_CERT  "\x07"
+#define OID_NS_CA_POLICY_URL        OID_NS_CERT  "\x08"
+#define OID_NS_SSL_SERVER_NAME      OID_NS_CERT  "\x0C"
+#define OID_NS_COMMENT              OID_NS_CERT  "\x0D"
+#define OID_NS_DATA_TYPE            OID_NETSCAPE "\x02"
+#define OID_NS_CERT_SEQUENCE        OID_NS_DATA_TYPE "\x05"
+
+/*
+ * Netscape certificate types
+ * (http://www.mozilla.org/projects/security/pki/nss/tech-notes/tn3.html)
+ */
+
+#define NS_CERT_TYPE_SSL_CLIENT         (0x80)  /* bit 0 */
+#define NS_CERT_TYPE_SSL_SERVER         (0x40)  /* bit 1 */
+#define NS_CERT_TYPE_EMAIL              (0x20)  /* bit 2 */
+#define NS_CERT_TYPE_OBJECT_SIGNING     (0x10)  /* bit 3 */
+#define NS_CERT_TYPE_RESERVED           (0x08)  /* bit 4 */
+#define NS_CERT_TYPE_SSL_CA             (0x04)  /* bit 5 */
+#define NS_CERT_TYPE_EMAIL_CA           (0x02)  /* bit 6 */
+#define NS_CERT_TYPE_OBJECT_SIGNING_CA  (0x01)  /* bit 7 */
+
+#define EXT_AUTHORITY_KEY_IDENTIFIER    (1 << 0)
+#define EXT_SUBJECT_KEY_IDENTIFIER      (1 << 1)
+#define EXT_KEY_USAGE                   (1 << 2)
+#define EXT_CERTIFICATE_POLICIES        (1 << 3)
+#define EXT_POLICY_MAPPINGS             (1 << 4)
+#define EXT_SUBJECT_ALT_NAME            (1 << 5)
+#define EXT_ISSUER_ALT_NAME             (1 << 6)
+#define EXT_SUBJECT_DIRECTORY_ATTRS     (1 << 7)
+#define EXT_BASIC_CONSTRAINTS           (1 << 8)
+#define EXT_NAME_CONSTRAINTS            (1 << 9)
+#define EXT_POLICY_CONSTRAINTS          (1 << 10)
+#define EXT_EXTENDED_KEY_USAGE          (1 << 11)
+#define EXT_CRL_DISTRIBUTION_POINTS     (1 << 12)
+#define EXT_INIHIBIT_ANYPOLICY          (1 << 13)
+#define EXT_FRESHEST_CRL                (1 << 14)
+
+#define EXT_NS_CERT_TYPE                (1 << 16)
 
 /** 
  * @addtogroup x509_module
@@ -172,6 +291,17 @@ typedef struct _x509_buf
 }
 x509_buf;
 
+/**
+ * Container for ASN1 bit strings.
+ */
+typedef struct _x509_bitstring
+{
+    int len;                    /**< ASN1 length, e.g. in octets. */
+    unsigned char unused_bits;  /**< Number of unused bits at the end of the string */
+    unsigned char *p;           /**< Raw ASN1 data for the bit string */
+}
+x509_bitstring;
+
 /**
  * Container for ASN1 named information objects. 
  * It allows for Relative Distinguished Names (e.g. cn=polarssl,ou=code,etc.).
@@ -184,6 +314,16 @@ typedef struct _x509_name
 }
 x509_name;
 
+/**
+ * Container for a sequence of ASN.1 items
+ */
+typedef struct _x509_sequence
+{
+    x509_buf buf;                   /**< Buffer containing the given ASN.1 item. */
+    struct _x509_sequence *next;    /**< The next entry in the sequence. */
+}
+x509_sequence;
+
 /** Container for date and time (precision in seconds). */
 typedef struct _x509_time
 {
@@ -220,9 +360,16 @@ typedef struct _x509_cert
     x509_buf subject_id;        /**< Optional X.509 v2/v3 subject unique identifier. */
     x509_buf v3_ext;            /**< Optional X.509 v3 extensions. Only Basic Contraints are supported at this time. */
 
+    int ext_types;              /**< Bit string containing detected and parsed extensions */
     int ca_istrue;              /**< Optional Basic Constraint extension value: 1 if this certificate belongs to a CA, 0 otherwise. */
     int max_pathlen;            /**< Optional Basic Constraint extension value: The maximum path length to the root certificate. */
 
+    unsigned char key_usage;    /**< Optional key usage extension value: See the values below */
+
+    x509_sequence ext_key_usage; /**< Optional list of extended key usage OIDs. */
+
+    unsigned char ns_cert_type; /**< Optional Netscape certificate type extension value: See the values below */
+
     x509_buf sig_oid2;          /**< Signature algorithm. Must match sig_oid1. */
     x509_buf sig;               /**< Signature: hash of the tbs part signed with the private key. */
     int sig_alg;                /**< Internal representation of the signature algorithm, e.g. SIG_RSA_MD2 */
@@ -476,6 +623,28 @@ int x509parse_cert_info( char *buf, size_t size, const char *prefix,
 int x509parse_crl_info( char *buf, size_t size, const char *prefix,
                         const x509_crl *crl );
 
+/**
+ * \brief          Give an known OID, return its descriptive string.
+ *
+ * \param oid      buffer containing the oid
+ *
+ * \return         Return a string if the OID is known,
+ *                 or NULL otherwise.
+ */
+const char *x509_oid_get_description( x509_buf *oid );
+
+/*
+ * \brief          Give an OID, return a string version of its OID number.
+ *
+ * \param buf      Buffer to write to
+ * \param size     Maximum size of buffer
+ * \param oid      Buffer containing the OID
+ *
+ * \return         The amount of data written to the buffer, or -1 in
+ *                 case of an error.
+ */
+int x509_oid_get_numeric_string( char *buf, size_t size, x509_buf *oid );
+
 /**
  * \brief          Check a given x509_time against the system time and check
  *                 if it is valid.
@@ -521,6 +690,17 @@ int x509parse_verify( x509_cert *crt,
                       int (*f_vrfy)(void *, x509_cert *, int, int),
                       void *p_vrfy );
 
+/**
+ * \brief          Verify the certificate signature
+ *
+ * \param crt      a certificate to be verified
+ * \param crl      the CRL to verify against
+ *
+ * \return         1 if the certificate is revoked, 0 otherwise
+ *
+ */
+int x509parse_revoked( const x509_cert *crt, const x509_crl *crl );
+
 /** @} name Functions to verify a certificate */
 
 

library/x509parse.c

@@ -170,6 +170,89 @@ static int asn1_get_mpi( unsigned char **p,
     return( ret );
 }
 
+static int asn1_get_bitstring( unsigned char **p, const unsigned char *end,
+        x509_bitstring *bs)
+{
+    int ret;
+
+    /* Certificate type is a single byte bitstring */
+    if( ( ret = asn1_get_tag( p, end, &bs->len, ASN1_BIT_STRING ) ) != 0 )
+        return( ret );
+
+    /* Check length, subtract one for actual bit string length */
+    if ( bs->len < 1 )
+        return( POLARSSL_ERR_ASN1_OUT_OF_DATA );
+    bs->len -= 1;
+
+    /* Get number of unused bits, ensure unused bits <= 7 */
+    bs->unused_bits = **p;
+    if( bs->unused_bits > 7 )
+        return( POLARSSL_ERR_ASN1_INVALID_LENGTH );
+    (*p)++;
+
+    /* Get actual bitstring */
+    bs->p = *p;
+    *p += bs->len;
+
+    if( *p != end )
+        return( POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
+
+    return 0;
+}
+
+
+/*
+ *  Parses and splits an ASN.1 "SEQUENCE OF <tag>"
+ */
+static int asn1_get_sequence_of( unsigned char **p,
+                          const unsigned char *end,
+                          x509_sequence *cur,
+                          int tag)
+{
+    int ret, len;
+    x509_buf *buf;
+
+    /* Get main sequence tag */
+    if( ( ret = asn1_get_tag( p, end, &len,
+            ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
+        return( ret );
+
+    if( *p + len != end )
+        return( POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
+
+    while( *p < end )
+    {
+        buf = &(cur->buf);
+        buf->tag = **p;
+
+        if( ( ret = asn1_get_tag( p, end, &buf->len, tag ) ) != 0 )
+            return( ret );
+
+        buf->p = *p;
+        *p += buf->len;
+
+        /* Allocate and assign next pointer */
+        if (*p < end)
+        {
+            cur->next = (x509_sequence *) malloc(
+                 sizeof( x509_sequence ) );
+
+            if( cur->next == NULL )
+                return( 1 );
+
+            cur = cur->next;
+        }
+    }
+
+    /* Set final sequence entry's next pointer to NULL */
+    cur->next = NULL;
+
+    if( *p != end )
+        return( POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
+
+    return( 0 );
+}
+
 /*
  *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
  */
@@ -524,6 +607,7 @@ static int x509_get_sig( unsigned char **p,
     if( ( ret = asn1_get_tag( p, end, &len, ASN1_BIT_STRING ) ) != 0 )
         return( POLARSSL_ERR_X509_CERT_INVALID_SIGNATURE | ret );
 
+
     if( --len < 1 || *(*p)++ != 0 )
         return( POLARSSL_ERR_X509_CERT_INVALID_SIGNATURE );
 
@@ -638,21 +722,132 @@ static int x509_get_crl_ext( unsigned char **p,
     return( 0 );
 }
 
+static int x509_get_basic_constraints( unsigned char **p,
+                                       const unsigned char *end,
+                                       int is_critical,
+                                       int *ca_istrue,
+                                       int *max_pathlen )
+{
+    int ret, len;
+
+    /*
+     * BasicConstraints ::= SEQUENCE {
+     *      cA                      BOOLEAN DEFAULT FALSE,
+     *      pathLenConstraint       INTEGER (0..MAX) OPTIONAL }
+     */
+    int is_cacert = 0; /* DEFAULT FALSE */
+    *max_pathlen = 0; /* endless */
+
+    if( ( ret = asn1_get_tag( p, end, &len,
+            ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+
+    if( *p == end )
+        return 0;
+
+    if( ( ret = asn1_get_bool( p, end, &is_cacert ) ) != 0 )
+    {
+        if( ret == POLARSSL_ERR_ASN1_UNEXPECTED_TAG )
+            ret = asn1_get_int( p, end, &is_cacert );
+
+        if( ret != 0 )
+            return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+
+        if( is_cacert != 0 )
+            is_cacert = 1;
+    }
+
+    if( *p == end )
+        return 0;
+
+    if( ( ret = asn1_get_int( p, end, max_pathlen ) ) != 0 )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+
+    if( *p != end )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
+                POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
+
+    (*max_pathlen)++;
+
+    *ca_istrue = is_critical & is_cacert;
+    return 0;
+}
+
+static int x509_get_ns_cert_type( unsigned char **p,
+                                       const unsigned char *end,
+                                       unsigned char *ns_cert_type)
+{
+    int ret;
+    x509_bitstring bs = {0};
+
+    if( ( ret = asn1_get_bitstring( p, end, &bs ) ) != 0 )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+
+    if( bs.len != 1 )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
+                POLARSSL_ERR_ASN1_INVALID_LENGTH );
+
+    /* Get actual bitstring */
+    *ns_cert_type = *bs.p;
+    return 0;
+}
+
+static int x509_get_key_usage( unsigned char **p,
+                               const unsigned char *end,
+                               unsigned char *key_usage)
+{
+    int ret;
+    x509_bitstring bs = {0};
+
+    if( ( ret = asn1_get_bitstring( p, end, &bs ) ) != 0 )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+
+    if( bs.len != 1 )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
+                POLARSSL_ERR_ASN1_INVALID_LENGTH );
+
+    /* Get actual bitstring */
+    *key_usage = *bs.p;
+    return 0;
+}
+
 /*
- * X.509 v3 extensions (only BasicConstraints are parsed)
+ * ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
+ *
+ * KeyPurposeId ::= OBJECT IDENTIFIER
+ */
+static int x509_get_ext_key_usage( unsigned char **p,
+                               const unsigned char *end,
+                               x509_sequence *ext_key_usage)
+{
+    int ret;
+
+    if( ( ret = asn1_get_sequence_of( p, end, ext_key_usage, ASN1_OID ) ) != 0 )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+
+    /* Sequence length must be >= 1 */
+    if( ext_key_usage->buf.p == NULL )
+        return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
+                POLARSSL_ERR_ASN1_INVALID_LENGTH );
+
+    return 0;
+}
+
+/*
+ * X.509 v3 extensions
+ *
+ * TODO: Perform all of the basic constraints tests required by the RFC
+ * TODO: Set values for undetected extensions to a sane default?
+ *
  */
 static int x509_get_crt_ext( unsigned char **p,
                              const unsigned char *end,
-                             x509_buf *ext,
+                             x509_cert *crt )
-                             int *ca_istrue,
-                             int *max_pathlen )
 {
     int ret, len;
-    int is_critical = 1;
-    int is_cacert   = 0;
     unsigned char *end_ext_data, *end_ext_octet;
 
-    if( ( ret = x509_get_ext( p, end, ext ) ) != 0 )
+    if( ( ret = x509_get_ext( p, end, &crt->v3_ext ) ) != 0 )
     {
         if( ret == POLARSSL_ERR_ASN1_UNEXPECTED_TAG )
             return( 0 );
@@ -662,77 +857,107 @@ static int x509_get_crt_ext( unsigned char **p,
 
     while( *p < end )
     {
+        /*
+         * Extension  ::=  SEQUENCE  {
+         *      extnID      OBJECT IDENTIFIER,
+         *      critical    BOOLEAN DEFAULT FALSE,
+         *      extnValue   OCTET STRING  }
+         */
+        x509_buf extn_oid = {0, 0, NULL};
+        int is_critical = 0; /* DEFAULT FALSE */
+
         if( ( ret = asn1_get_tag( p, end, &len,
                 ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
             return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
 
         end_ext_data = *p + len;
 
-        if( memcmp( *p, "\x06\x03\x55\x1D\x13", 5 ) != 0 )
+        /* Get extension ID */
-        {
+        extn_oid.tag = **p;
-            *p += len;
-            continue;
-        }
 
-        *p += 5;
+        if( ( ret = asn1_get_tag( p, end, &extn_oid.len, ASN1_OID ) ) != 0 )
+            return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
 
+        extn_oid.p = *p;
+        *p += extn_oid.len;
+
+        if( ( end - *p ) < 1 )
+            return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
+                    POLARSSL_ERR_ASN1_OUT_OF_DATA );
+
+        /* Get optional critical */
         if( ( ret = asn1_get_bool( p, end_ext_data, &is_critical ) ) != 0 &&
             ( ret != POLARSSL_ERR_ASN1_UNEXPECTED_TAG ) )
             return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
 
+        /* Data should be octet string type */
         if( ( ret = asn1_get_tag( p, end_ext_data, &len,
                 ASN1_OCTET_STRING ) ) != 0 )
             return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
 
-        /*
-         * BasicConstraints ::= SEQUENCE {
-         *      cA                      BOOLEAN DEFAULT FALSE,
-         *      pathLenConstraint       INTEGER (0..MAX) OPTIONAL }
-         */
         end_ext_octet = *p + len;
 
         if( end_ext_octet != end_ext_data )
             return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
                     POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
 
-        if( ( ret = asn1_get_tag( p, end_ext_octet, &len,
+        /*
-                ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
+         * Detect supported extensions
-            return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+         */
-
+        if( ( OID_SIZE( OID_BASIC_CONSTRAINTS ) == extn_oid.len ) &&
-        if( *p == end_ext_octet )
+                memcmp( extn_oid.p, OID_BASIC_CONSTRAINTS, extn_oid.len ) == 0 )
-            continue;
-
-        if( ( ret = asn1_get_bool( p, end_ext_octet, &is_cacert ) ) != 0 )
         {
-            if( ret == POLARSSL_ERR_ASN1_UNEXPECTED_TAG )
+            /* Parse basic constraints */
-                ret = asn1_get_int( p, end_ext_octet, &is_cacert );
+            if( ( ret = x509_get_basic_constraints( p, end_ext_octet,
-
+                    is_critical, &crt->ca_istrue, &crt->max_pathlen ) ) != 0 )
-            if( ret != 0 )
+                return ( ret );
-                return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+            crt->ext_types |= EXT_BASIC_CONSTRAINTS;
-
-            if( is_cacert != 0 )
-                is_cacert  = 1;
         }
+        else if( ( OID_SIZE( OID_NS_CERT_TYPE ) == extn_oid.len ) &&
+                memcmp( extn_oid.p, OID_NS_CERT_TYPE, extn_oid.len ) == 0 )
+        {
+            /* Parse netscape certificate type */
+            if( ( ret = x509_get_ns_cert_type( p, end_ext_octet,
+                    &crt->ns_cert_type ) ) != 0 )
+                return ( ret );
+            crt->ext_types |= EXT_NS_CERT_TYPE;
+        }
+        else if( ( OID_SIZE( OID_KEY_USAGE ) == extn_oid.len ) &&
+                memcmp( extn_oid.p, OID_KEY_USAGE, extn_oid.len ) == 0 )
+        {
+            /* Parse key usage */
+            if( ( ret = x509_get_key_usage( p, end_ext_octet,
+                    &crt->key_usage ) ) != 0 )
+                return ( ret );
+            crt->ext_types |= EXT_KEY_USAGE;
+        }
+        else if( ( OID_SIZE( OID_EXTENDED_KEY_USAGE ) == extn_oid.len ) &&
+                memcmp( extn_oid.p, OID_EXTENDED_KEY_USAGE, extn_oid.len ) == 0 )
+        {
+            /* Parse extended key usage */
+            if( ( ret = x509_get_ext_key_usage( p, end_ext_octet,
+                    &crt->ext_key_usage ) ) != 0 )
+                return ( ret );
+            crt->ext_types |= EXT_EXTENDED_KEY_USAGE;
+        }
+        else
+        {
+            /* No parser found, skip extension */
+            *p = end_ext_octet;
 
-        if( *p == end_ext_octet )
+            if( is_critical )
-            continue;
+            {
-
+                /* Data is marked as critical: fail */
-        if( ( ret = asn1_get_int( p, end_ext_octet, max_pathlen ) ) != 0 )
+                return ( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
-            return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS | ret );
+                        POLARSSL_ERR_ASN1_UNEXPECTED_TAG );
-
+            }
-        if( *p != end_ext_octet )
+        }
-            return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
-                    POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
-
-        max_pathlen++;
     }
 
     if( *p != end )
         return( POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS |
                 POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
 
-    *ca_istrue = is_critical & is_cacert;
-
     return( 0 );
 }
 
@@ -783,7 +1008,8 @@ static int x509_get_entries( unsigned char **p,
         if( ( ret = x509_get_crl_ext( p, end, &cur_entry->entry_ext ) ) != 0 )
             return( ret );
 
-        if ( *p < end ) {
+        if ( *p < end )
+        {
             cur_entry->next = malloc( sizeof( x509_crl_entry ) );
             cur_entry = cur_entry->next;
             memset( cur_entry, 0, sizeof( x509_crl_entry ) );
@@ -1099,8 +1325,7 @@ int x509parse_crt( x509_cert *chain, const unsigned char *buf, int buflen )
 
     if( crt->version == 3 )
     {
-        ret = x509_get_crt_ext( &p, end, &crt->v3_ext,
+        ret = x509_get_crt_ext( &p, end, crt);
-                            &crt->ca_istrue, &crt->max_pathlen );
         if( ret != 0 )
         {
             x509_free( crt );
@@ -2006,7 +2231,8 @@ int x509parse_dn_gets( char *buf, size_t size, const x509_name *dn )
 
     while( name != NULL )
     {
-        if( name != dn ) {
+        if( name != dn )
+        {
             ret = snprintf( p, n, ", " );
             SAFE_SNPRINTF();
         }
@@ -2055,9 +2281,9 @@ int x509parse_dn_gets( char *buf, size_t size, const x509_name *dn )
         SAFE_SNPRINTF();
         }
         else
-    {
+        {
             ret = snprintf( p, n, "\?\?=" );
-        SAFE_SNPRINTF();
+            SAFE_SNPRINTF();
         }
 
         for( i = 0; i < name->val.len; i++ )
@@ -2156,6 +2382,76 @@ int x509parse_cert_info( char *buf, size_t size, const char *prefix,
     return( size - n );
 }
 
+/* Compare a given OID string with an OID x509_buf * */
+#define OID_CMP(oid_str, oid_buf) \
+        ( ( OID_SIZE(oid_str) == (oid_buf)->len ) && \
+                memcmp( (oid_str), (oid_buf)->p, (oid_buf)->len) == 0)
+
+/*
+ * Return an informational string describing the given OID
+ */
+const char *x509_oid_get_description( x509_buf *oid )
+{
+    if ( oid == NULL )
+        return ( NULL );
+    
+    else if( OID_CMP( OID_SERVER_AUTH, oid ) )
+        return( STRING_SERVER_AUTH );
+    
+    else if( OID_CMP( OID_CLIENT_AUTH, oid ) )
+        return( STRING_CLIENT_AUTH );
+    
+    else if( OID_CMP( OID_CODE_SIGNING, oid ) )
+        return( STRING_CODE_SIGNING );
+    
+    else if( OID_CMP( OID_EMAIL_PROTECTION, oid ) )
+        return( STRING_EMAIL_PROTECTION );
+    
+    else if( OID_CMP( OID_TIME_STAMPING, oid ) )
+        return( STRING_TIME_STAMPING );
+
+    else if( OID_CMP( OID_OCSP_SIGNING, oid ) )
+        return( STRING_OCSP_SIGNING );
+
+    return( NULL );
+}
+
+/* Return the x.y.z.... style numeric string for the given OID */
+int x509_oid_get_numeric_string( char *buf, size_t size, x509_buf *oid )
+{
+    int ret, n, i;
+    unsigned int value;
+    char *p;
+
+    p = buf;
+    n = size;
+
+    /* First byte contains first two dots */
+    if( oid->len > 0 )
+    {
+        ret = snprintf( p, n, "%d.%d", oid->p[0]/40, oid->p[0]%40 );
+        SAFE_SNPRINTF();
+    }
+
+    /* TODO: value can overflow in value. */
+    value = 0;
+    for( i=1; i < oid->len; i++ )
+    {
+        value <<= 7;
+        value += oid->p[i] & 0x7F;
+
+        if( !( oid->p[i] & 0x80 ) )
+        {
+            /* Last byte */
+            ret = snprintf( p, n, ".%d", value );
+            SAFE_SNPRINTF();
+            value = 0;
+        }
+    }
+
+    return( size - n );
+}
+
 /*
  * Return an informational string about the CRL.
  */
@@ -2207,7 +2503,8 @@ int x509parse_crl_info( char *buf, size_t size, const char *prefix,
         nr = ( entry->serial.len <= 32 )
             ? entry->serial.len  : 32;
 
-        for( i = 0; i < nr; i++ ) {
+        for( i = 0; i < nr; i++ )
+        {
             ret = snprintf( p, n, "%02X%s",
                     entry->serial.p[i], ( i < nr - 1 ) ? ":" : "" );
             SAFE_SNPRINTF();
@@ -2402,7 +2699,8 @@ int x509parse_verify( x509_cert *crt,
             verify_ok = 0;
 
         /* crt is verified to be a child of the parent cur, call verify callback */
-        if( NULL != f_vrfy ) {
+        if( NULL != f_vrfy )
+        {
             if ( f_vrfy( p_vrfy, crt, pathlen-1, verify_ok ) != 0 )
                 return( POLARSSL_ERR_X509_CERT_VERIFY_FAILED );
         } else if ( verify_ok == 0 ) {
@@ -2509,7 +2807,8 @@ int x509parse_verify( x509_cert *crt,
 
 
     /* Verification succeeded, call callback on top cert */
-    if( NULL != f_vrfy ) {
+    if( NULL != f_vrfy )
+    {
         if ( f_vrfy(p_vrfy, crt, pathlen - 1, 1) != 0 )
             return( POLARSSL_ERR_X509_CERT_VERIFY_FAILED );
     }
@@ -2526,6 +2825,8 @@ void x509_free( x509_cert *crt )
     x509_cert *cert_prv;
     x509_name *name_cur;
     x509_name *name_prv;
+    x509_sequence *seq_cur;
+    x509_sequence *seq_prv;
 
     if( crt == NULL )
         return;
@@ -2552,6 +2853,15 @@ void x509_free( x509_cert *crt )
             free( name_prv );
         }
 
+        seq_cur = cert_cur->ext_key_usage.next;
+        while( seq_cur != NULL )
+        {
+            seq_prv = seq_cur;
+            seq_cur = seq_cur->next;
+            memset( seq_prv, 0, sizeof( x509_sequence ) );
+            free( seq_prv );
+        }
+
         if( cert_cur->raw.p != NULL )
         {
             memset( cert_cur->raw.p, 0, cert_cur->raw.len );