diff --git a/include/polarssl/x509write.h b/include/polarssl/x509write.h
index 0e443ee..8600b42 100644
--- a/include/polarssl/x509write.h
+++ b/include/polarssl/x509write.h
@@ -84,6 +84,31 @@
 }
 x509_csr;
 
+#define X509_CRT_VERSION_1              0
+#define X509_CRT_VERSION_2              1
+#define X509_CRT_VERSION_3              2
+
+#define X509_RFC5280_MAX_SERIAL_LEN 32
+#define X509_RFC5280_UTC_TIME_LEN   15
+
+/**
+ * Container for writing a certificate (CRT)
+ */
+typedef struct _x509write_cert
+{
+    int version;
+    mpi serial;
+    rsa_context *subject_key;
+    rsa_context *issuer_key;
+    x509_req_name *subject;
+    x509_req_name *issuer;
+    md_type_t md_alg;
+    char not_before[X509_RFC5280_UTC_TIME_LEN + 1];
+    char not_after[X509_RFC5280_UTC_TIME_LEN + 1];
+    asn1_named_data *extensions;
+}
+x509write_cert;
+
 /* \} addtogroup x509_module */
 
 /**
@@ -170,6 +195,125 @@
 void x509write_csr_free( x509_csr *ctx );
 
 /**
+ * \brief           Initialize a CRT writing context
+ *
+ * \param ctx       CRT context to initialize
+ */
+void x509write_crt_init( x509write_cert *ctx );
+
+/**
+ * \brief           Set the verion for a Certificate
+ *                  Default: X509_CRT_VERSION_3
+ *
+ * \param ctx       CRT context to use
+ * \param version   version to set (X509_CRT_VERSION_1, X509_CRT_VERSION_2 or
+ *                                  X509_CRT_VERSION_3)
+ */
+void x509write_crt_set_version( x509write_cert *ctx, int version );
+
+/**
+ * \brief           Set the serial number for a Certificate.
+ *
+ * \param ctx       CRT context to use
+ * \param serial    serial number to set
+ *
+ * \return          0 if successful
+ */
+int x509write_crt_set_serial( x509write_cert *ctx, const mpi *serial );
+
+/**
+ * \brief           Set the validity period for a Certificate
+ *                  Timestamps should be in string format for UTC timezone
+ *                  i.e. "YYYYMMDDhhmmss"
+ *                  e.g. "20131231235959" for December 31st 2013
+ *                       at 23:59:59
+ *
+ * \param ctx       CRT context to use
+ * \param not_before    not_before timestamp
+ * \param not_after     not_after timestamp
+ *
+ * \return          0 if timestamp was parsed successfully, or
+ *                  a specific error code
+ */
+int x509write_crt_set_validity( x509write_cert *ctx, char *not_before,
+                                char *not_after );
+
+/**
+ * \brief           Set the issuer name for a Certificate
+ *                  Issuer names should contain a comma-separated list
+ *                  of OID types and values:
+ *                  e.g. "C=NL,O=Offspark,CN=PolarSSL CA"
+ *
+ * \param ctx           CRT context to use
+ * \param issuer_name   issuer name to set
+ *
+ * \return          0 if issuer name was parsed successfully, or
+ *                  a specific error code
+ */
+int x509write_crt_set_issuer_name( x509write_cert *ctx, char *issuer_name );
+
+/**
+ * \brief           Set the subject name for a Certificate
+ *                  Subject names should contain a comma-separated list
+ *                  of OID types and values:
+ *                  e.g. "C=NL,O=Offspark,CN=PolarSSL Server 1"
+ *
+ * \param ctx           CRT context to use
+ * \param subject_name  subject name to set
+ *
+ * \return          0 if subject name was parsed successfully, or
+ *                  a specific error code
+ */
+int x509write_crt_set_subject_name( x509write_cert *ctx, char *subject_name );
+
+/**
+ * \brief           Set the subject public key for the certificate
+ *
+ * \param ctx       CRT context to use
+ * \param rsa       RSA public key to include
+ */
+void x509write_crt_set_subject_key( x509write_cert *ctx, rsa_context *rsa );
+
+/**
+ * \brief           Set the issuer key used for signing the certificate
+ *
+ * \param ctx       CRT context to use
+ * \param rsa       RSA key to sign with
+ */
+void x509write_crt_set_issuer_key( x509write_cert *ctx, rsa_context *rsa );
+
+/**
+ * \brief           Set the MD algorithm to use for the signature
+ *                  (e.g. POLARSSL_MD_SHA1)
+ *
+ * \param ctx       CRT context to use
+ * \param md_ald    MD algorithm to use
+ */
+void x509write_crt_set_md_alg( x509write_cert *ctx, md_type_t md_alg );
+
+/**
+ * \brief           Free the contents of a CRT write context
+ *
+ * \param ctx       CRT context to free
+ */
+void x509write_crt_free( x509write_cert *ctx );
+
+/**
+ * \brief           Write a built up certificate to a X509 DER structure
+ *                  Note: data is written at the end of the buffer! Use the
+ *                        return value to determine where you should start
+ *                        using the buffer
+ *
+ * \param crt       certificate to write away
+ * \param buf       buffer to write to
+ * \param size      size of the buffer
+ *
+ * \return          length of data written if successful, or a specific
+ *                  error code
+ */
+int x509write_crt_der( x509write_cert *ctx, unsigned char *buf, size_t size );
+
+/**
  * \brief           Write a RSA public key to a PKCS#1 DER structure
  *                  Note: data is written at the end of the buffer! Use the
  *                        return value to determine where you should start
@@ -217,6 +361,17 @@
 
 #if defined(POLARSSL_BASE64_C)
 /**
+ * \brief           Write a built up certificate to a X509 PEM string
+ *
+ * \param crt       certificate to write away
+ * \param buf       buffer to write to
+ * \param size      size of the buffer
+ *
+ * \return          0 successful, or a specific error code
+ */
+int x509write_crt_pem( x509write_cert *ctx, unsigned char *buf, size_t size );
+
+/**
  * \brief           Write a RSA public key to a PKCS#1 PEM string
  *
  * \param rsa       RSA to write away
diff --git a/library/x509write.c b/library/x509write.c
index 7e04e12..1428c67 100644
--- a/library/x509write.c
+++ b/library/x509write.c
@@ -45,55 +45,19 @@
 #define polarssl_free       free
 #endif
 
-void x509write_csr_init( x509_csr *ctx )
-{
-    memset( ctx, 0, sizeof(x509_csr) );
-}
-
-void x509write_csr_free( x509_csr *ctx )
-{
-    x509_req_name *cur;
-    asn1_named_data *cur_ext;
-
-    while( ( cur = ctx->subject ) != NULL )
-    {
-        ctx->subject = cur->next;
-        polarssl_free( cur );
-    }
-
-    while( ( cur_ext = ctx->extensions ) != NULL )
-    {
-        ctx->extensions = cur_ext->next;
-        asn1_free_named_data( cur_ext );
-        polarssl_free( cur_ext );
-    }
-
-    memset( ctx, 0, sizeof(x509_csr) );
-}
-
-void x509write_csr_set_md_alg( x509_csr *ctx, md_type_t md_alg )
-{
-    ctx->md_alg = md_alg;
-}
-
-void x509write_csr_set_rsa_key( x509_csr *ctx, rsa_context *rsa )
-{
-    ctx->rsa = rsa;
-}
-
-int x509write_csr_set_subject_name( x509_csr *ctx, char *subject_name )
+static int x509write_string_to_names( x509_req_name **head, char *name )
 {
     int ret = 0;
-    char *s = subject_name, *c = s;
+    char *s = name, *c = s;
     char *end = s + strlen( s );
     char *oid = NULL;
     int in_tag = 1;
     x509_req_name *cur;
 
-    while( ctx->subject )
+    while( *head != NULL )
     {
-        cur = ctx->subject;
-        ctx->subject = ctx->subject->next;
+        cur = *head;
+        *head = cur->next;
         polarssl_free( cur );
     }
 
@@ -143,8 +107,8 @@
 
             memset( cur, 0, sizeof(x509_req_name) );
 
-            cur->next = ctx->subject;
-            ctx->subject = cur;
+            cur->next = *head;
+            *head = cur;
 
             strncpy( cur->oid, oid, strlen( oid ) );
             strncpy( cur->name, s, c - s );
@@ -160,6 +124,47 @@
     return( ret );
 }
 
+void x509write_csr_init( x509_csr *ctx )
+{
+    memset( ctx, 0, sizeof(x509_csr) );
+}
+
+void x509write_csr_free( x509_csr *ctx )
+{
+    x509_req_name *cur;
+    asn1_named_data *cur_ext;
+
+    while( ( cur = ctx->subject ) != NULL )
+    {
+        ctx->subject = cur->next;
+        polarssl_free( cur );
+    }
+
+    while( ( cur_ext = ctx->extensions ) != NULL )
+    {
+        ctx->extensions = cur_ext->next;
+        asn1_free_named_data( cur_ext );
+        polarssl_free( cur_ext );
+    }
+
+    memset( ctx, 0, sizeof(x509_csr) );
+}
+
+void x509write_csr_set_md_alg( x509_csr *ctx, md_type_t md_alg )
+{
+    ctx->md_alg = md_alg;
+}
+
+void x509write_csr_set_rsa_key( x509_csr *ctx, rsa_context *rsa )
+{
+    ctx->rsa = rsa;
+}
+
+int x509write_csr_set_subject_name( x509_csr *ctx, char *subject_name )
+{
+    return x509write_string_to_names( &ctx->subject, subject_name );
+}
+
 int x509write_csr_set_extension( x509_csr *ctx,
                                  const char *oid, size_t oid_len,
                                  const unsigned char *val, size_t val_len )
@@ -257,6 +262,94 @@
     return( 0 );
 }
 
+void x509write_crt_init( x509write_cert *ctx )
+{
+    memset( ctx, 0, sizeof(x509write_cert) );
+
+    mpi_init( &ctx->serial );
+    ctx->version = X509_CRT_VERSION_3;
+}
+
+void x509write_crt_free( x509write_cert *ctx )
+{
+    x509_req_name *cur;
+    asn1_named_data *cur_ext;
+
+    mpi_free( &ctx->serial );
+
+    while( ( cur = ctx->subject ) != NULL )
+    {
+        ctx->subject = cur->next;
+        polarssl_free( cur );
+    }
+
+    while( ( cur = ctx->issuer ) != NULL )
+    {
+        ctx->issuer = cur->next;
+        polarssl_free( cur );
+    }
+
+    while( ( cur_ext = ctx->extensions ) != NULL )
+    {
+        ctx->extensions = cur_ext->next;
+        asn1_free_named_data( cur_ext );
+        polarssl_free( cur_ext );
+    }
+
+    memset( ctx, 0, sizeof(x509_csr) );
+}
+
+void x509write_crt_set_md_alg( x509write_cert *ctx, md_type_t md_alg )
+{
+    ctx->md_alg = md_alg;
+}
+
+void x509write_crt_set_subject_key( x509write_cert *ctx, rsa_context *rsa )
+{
+    ctx->subject_key = rsa;
+}
+
+void x509write_crt_set_issuer_key( x509write_cert *ctx, rsa_context *rsa )
+{
+    ctx->issuer_key = rsa;
+}
+
+int x509write_crt_set_subject_name( x509write_cert *ctx, char *subject_name )
+{
+    return x509write_string_to_names( &ctx->subject, subject_name );
+}
+
+int x509write_crt_set_issuer_name( x509write_cert *ctx, char *issuer_name )
+{
+    return x509write_string_to_names( &ctx->issuer, issuer_name );
+}
+
+int x509write_crt_set_serial( x509write_cert *ctx, const mpi *serial )
+{
+    int ret;
+
+    if( ( ret = mpi_copy( &ctx->serial, serial ) ) != 0 )
+        return( ret );
+
+    return( 0 );
+}
+
+int x509write_crt_set_validity( x509write_cert *ctx, char *not_before,
+                                char *not_after )
+{
+    if( strlen(not_before) != X509_RFC5280_UTC_TIME_LEN - 1 ||
+        strlen(not_after)  != X509_RFC5280_UTC_TIME_LEN - 1 )
+    {
+        return( POLARSSL_ERR_X509WRITE_BAD_INPUT_DATA );
+    }
+    strncpy( ctx->not_before, not_before, X509_RFC5280_UTC_TIME_LEN );
+    strncpy( ctx->not_after , not_after , X509_RFC5280_UTC_TIME_LEN );
+    ctx->not_before[X509_RFC5280_UTC_TIME_LEN - 1] = 'Z';
+    ctx->not_after[X509_RFC5280_UTC_TIME_LEN - 1] = 'Z';
+
+    return( 0 );
+}
+
 int x509write_pubkey_der( rsa_context *rsa, unsigned char *buf, size_t size )
 {
     int ret;
@@ -344,6 +437,18 @@
     return( len );
 }
 
+/*
+ *  RelativeDistinguishedName ::=
+ *    SET OF AttributeTypeAndValue
+ *
+ *  AttributeTypeAndValue ::= SEQUENCE {
+ *    type     AttributeType,
+ *    value    AttributeValue }
+ *
+ *  AttributeType ::= OBJECT IDENTIFIER
+ *
+ *  AttributeValue ::= ANY DEFINED BY AttributeType
+ */
 static int x509_write_name( unsigned char **p, unsigned char *start, char *oid,
                             char *name )
 {
@@ -376,6 +481,25 @@
     return( len );
 }
 
+static int x509_write_names( unsigned char **p, unsigned char *start,
+                             x509_req_name *first )
+{
+    int ret;
+    size_t len = 0;
+    x509_req_name *cur = first;
+
+    while( cur != NULL )
+    {
+        ASN1_CHK_ADD( len, x509_write_name( p, start, cur->oid, cur->name ) );
+        cur = cur->next;
+    }
+
+    ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+
+    return( len );
+}
+
 static int x509_write_sig( unsigned char **p, unsigned char *start,
                            const char *oid, unsigned char *sig, size_t size )
 {
@@ -402,6 +526,21 @@
     return( len );
 }
 
+static int x509_write_time( unsigned char **p, unsigned char *start,
+                            const char *time, size_t size )
+{
+    int ret;
+    size_t len = 0;
+
+    ASN1_CHK_ADD( len, asn1_write_raw_buffer( p, start,
+                                              (const unsigned char *) time,
+                                              size ) );
+    ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_GENERALIZED_TIME ) );
+
+    return( len );
+}
+
 int x509write_csr_der( x509_csr *ctx, unsigned char *buf, size_t size )
 {
     int ret;
@@ -410,9 +549,8 @@
     unsigned char hash[64];
     unsigned char sig[POLARSSL_MPI_MAX_SIZE];
     unsigned char tmp_buf[2048];
-    size_t sub_len = 0, pub_len = 0, sig_len = 0;
+    size_t pub_len = 0, sig_len = 0;
     size_t len = 0;
-    x509_req_name *cur = ctx->subject;
     asn1_named_data *cur_ext = ctx->extensions;
 
     c = tmp_buf + 2048 - 1;
@@ -482,16 +620,10 @@
     ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, pub_len ) );
     ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
 
-    while( cur != NULL )
-    {
-        ASN1_CHK_ADD( sub_len, x509_write_name( &c, tmp_buf, cur->oid, cur->name ) );
-
-        cur = cur->next;
-    }
-
-    len += sub_len;
-    ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, sub_len ) );
-    ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+    /*
+     *  Subject  ::=  Name
+     */
+    ASN1_CHK_ADD( len, x509_write_names( &c, tmp_buf, ctx->subject ) );
 
     /*
      *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
@@ -522,6 +654,123 @@
     return( len );
 }
 
+int x509write_crt_der( x509write_cert *ctx, unsigned char *buf, size_t size )
+{
+    int ret;
+    const char *sig_oid;
+    unsigned char *c, *c2;
+    unsigned char hash[64];
+    unsigned char sig[POLARSSL_MPI_MAX_SIZE];
+    unsigned char tmp_buf[2048];
+    size_t sub_len = 0, pub_len = 0, sig_len = 0;
+    size_t len = 0;
+    asn1_named_data *cur_ext = ctx->extensions;
+
+    c = tmp_buf + 2048 - 1;
+
+    // Generate correct OID
+    //
+    ret = oid_get_oid_by_sig_alg( POLARSSL_PK_RSA, ctx->md_alg, &sig_oid );
+    if( ret != 0 )
+        return( ret );
+
+
+    /*
+     *  SubjectPublicKeyInfo  ::=  SEQUENCE  {
+     *       algorithm            AlgorithmIdentifier,
+     *       subjectPublicKey     BIT STRING  }
+     */
+    ASN1_CHK_ADD( pub_len, asn1_write_mpi( &c, tmp_buf, &ctx->subject_key->E ) );
+    ASN1_CHK_ADD( pub_len, asn1_write_mpi( &c, tmp_buf, &ctx->subject_key->N ) );
+
+    ASN1_CHK_ADD( pub_len, asn1_write_len( &c, tmp_buf, pub_len ) );
+    ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+
+    if( c - tmp_buf < 1 )
+        return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
+
+    *--c = 0;
+    pub_len += 1;
+
+    ASN1_CHK_ADD( pub_len, asn1_write_len( &c, tmp_buf, pub_len ) );
+    ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, tmp_buf, ASN1_BIT_STRING ) );
+
+    ASN1_CHK_ADD( pub_len, asn1_write_algorithm_identifier( &c, tmp_buf, OID_PKCS1_RSA ) );
+
+    len += pub_len;
+    ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, pub_len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+
+    /*
+     *  Subject  ::=  Name
+     */
+    ASN1_CHK_ADD( len, x509_write_names( &c, tmp_buf, ctx->subject ) );
+
+    /*
+     *  Validity ::= SEQUENCE {
+     *       notBefore      Time,
+     *       notAfter       Time }
+     */
+    sub_len = 0;
+
+    ASN1_CHK_ADD( sub_len, x509_write_time( &c, tmp_buf, ctx->not_after,
+                                            X509_RFC5280_UTC_TIME_LEN ) );
+
+    ASN1_CHK_ADD( sub_len, x509_write_time( &c, tmp_buf, ctx->not_before,
+                                            X509_RFC5280_UTC_TIME_LEN ) );
+
+    len += sub_len;
+    ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, sub_len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+
+    /*
+     *  Issuer  ::=  Name
+     */
+    ASN1_CHK_ADD( len, x509_write_names( &c, tmp_buf, ctx->issuer ) );
+
+    /*
+     *  Signature   ::=  AlgorithmIdentifier
+     */
+    ASN1_CHK_ADD( len, asn1_write_algorithm_identifier( &c, tmp_buf,
+                                                        sig_oid ) );
+
+    /*
+     *  Serial   ::=  INTEGER
+     */
+    ASN1_CHK_ADD( len, asn1_write_mpi( &c, tmp_buf, &ctx->serial ) );
+
+    /*
+     *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
+     */
+    sub_len = 0;
+    ASN1_CHK_ADD( sub_len, asn1_write_int( &c, tmp_buf, ctx->version ) );
+    len += sub_len;
+    ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, sub_len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 0 ) );
+
+    ASN1_CHK_ADD( len, asn1_write_len( &c, tmp_buf, len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( &c, tmp_buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+
+    md( md_info_from_type( ctx->md_alg ), c, len, hash );
+
+    rsa_pkcs1_sign( ctx->issuer_key, NULL, NULL, RSA_PRIVATE, ctx->md_alg, 0, hash, sig );
+
+    c2 = buf + size - 1;
+    ASN1_CHK_ADD( sig_len, x509_write_sig( &c2, buf, sig_oid, sig, ctx->issuer_key->len ) );
+
+    c2 -= len;
+    memcpy( c2, c, len );
+
+    len += sig_len;
+    ASN1_CHK_ADD( len, asn1_write_len( &c2, buf, len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( &c2, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+
+    return( len );
+}
+
+#define PEM_BEGIN_CRT           "-----BEGIN CERTIFICATE-----\n"
+#define PEM_END_CRT             "-----END CERTIFICATE-----\n"
+
 #define PEM_BEGIN_CSR           "-----BEGIN CERTIFICATE REQUEST-----\n"
 #define PEM_END_CSR             "-----END CERTIFICATE REQUEST-----\n"
 
@@ -571,6 +820,27 @@
     return( 0 );
 }
 
+int x509write_crt_pem( x509write_cert *crt, unsigned char *buf, size_t size )
+{
+    int ret;
+    unsigned char output_buf[4096];
+
+    if( ( ret = x509write_crt_der( crt, output_buf,
+                                   sizeof(output_buf) ) ) < 0 )
+    {
+        return( ret );
+    }
+
+    if( ( ret = x509write_pemify( PEM_BEGIN_CRT, PEM_END_CRT,
+                                  output_buf + sizeof(output_buf) - 1 - ret,
+                                  ret, buf, size ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    return( 0 );
+}
+
 int x509write_pubkey_pem( rsa_context *rsa, unsigned char *buf, size_t size )
 {
     int ret;
diff --git a/programs/.gitignore b/programs/.gitignore
index 2b7510f..b349cd4 100644
--- a/programs/.gitignore
+++ b/programs/.gitignore
@@ -40,3 +40,4 @@
 x509/cert_app
 x509/cert_req
 x509/crl_app
+x509/cert_write
diff --git a/programs/x509/CMakeLists.txt b/programs/x509/CMakeLists.txt
index d07cff8..8aaa4ac 100644
--- a/programs/x509/CMakeLists.txt
+++ b/programs/x509/CMakeLists.txt
@@ -19,6 +19,9 @@
 add_executable(cert_req cert_req.c)
 target_link_libraries(cert_req ${libs})
 
-install(TARGETS cert_app crl_app cert_req
+add_executable(cert_write cert_write.c)
+target_link_libraries(cert_write ${libs})
+
+install(TARGETS cert_app crl_app cert_req cert_write
         DESTINATION "bin"
         PERMISSIONS OWNER_READ OWNER_WRITE OWNER_EXECUTE GROUP_READ GROUP_EXECUTE WORLD_READ WORLD_EXECUTE)
diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
new file mode 100644
index 0000000..59c49b2
--- /dev/null
+++ b/programs/x509/cert_write.c
@@ -0,0 +1,423 @@
+/*
+ *  Certificate generation and signing
+ *
+ *  Copyright (C) 2006-2013, Brainspark B.V.
+ *
+ *  This file is part of PolarSSL (http://www.polarssl.org)
+ *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
+ *
+ *  All rights reserved.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef _CRT_SECURE_NO_DEPRECATE
+#define _CRT_SECURE_NO_DEPRECATE 1
+#endif
+
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "polarssl/config.h"
+
+#include "polarssl/error.h"
+#include "polarssl/rsa.h"
+#include "polarssl/x509.h"
+#include "polarssl/base64.h"
+#include "polarssl/x509write.h"
+#include "polarssl/oid.h"
+
+#if !defined(POLARSSL_BIGNUM_C) || !defined(POLARSSL_RSA_C) ||         \
+    !defined(POLARSSL_X509_WRITE_C) || !defined(POLARSSL_FS_IO)
+int main( int argc, char *argv[] )
+{
+    ((void) argc);
+    ((void) argv);
+
+    printf("POLARSSL_BIGNUM_C and/or POLARSSL_RSA_C and/or "
+           "POLARSSL_X509_WRITE_C and/or POLARSSL_FS_IO not defined.\n");
+    return( 0 );
+}
+#else
+
+#define DFL_SUBJECT_KEY         "subject.key"
+#define DFL_ISSUER_KEY          "ca.key"
+#define DFL_SUBJECT_PWD         ""
+#define DFL_ISSUER_PWD          ""
+#define DFL_OUTPUT_FILENAME     "cert.crt"
+#define DFL_SUBJECT_NAME        "CN=Cert,O=PolarSSL,C=NL"
+#define DFL_ISSUER_NAME         "CN=CA,O=PolarSSL,C=NL"
+#define DFL_NOT_BEFORE          "20010101000000"
+#define DFL_NOT_AFTER           "20301231235959"
+#define DFL_SERIAL              "1"
+#define DFL_KEY_USAGE           0
+#define DFL_NS_CERT_TYPE        0
+
+/*
+ * global options
+ */
+struct options
+{
+    char *subject_key;          /* filename of the subject key file     */
+    char *issuer_key;           /* filename of the issuer key file      */
+    char *subject_pwd;          /* password for the subject key file    */
+    char *issuer_pwd;           /* password for the issuer key file     */
+    char *output_file;          /* where to store the constructed key file  */
+    char *subject_name;         /* subject name for certificate         */
+    char *issuer_name;          /* issuer name for certificate          */
+    char *not_before;           /* validity period not before           */
+    char *not_after;            /* validity period not after            */
+    char *serial;               /* serial number string                 */
+    unsigned char key_usage;    /* key usage flags                      */
+    unsigned char ns_cert_type; /* NS cert type                         */
+} opt;
+
+int write_certificate( x509write_cert *crt, char *output_file )
+{
+    int ret;
+    FILE *f;
+    unsigned char output_buf[4096];
+    size_t len = 0;
+
+    memset( output_buf, 0, 4096 );
+    if( ( ret = x509write_crt_pem( crt, output_buf, 4096 ) ) < 0 )
+        return( ret );
+
+    len = strlen( (char *) output_buf );
+
+    if( ( f = fopen( output_file, "w" ) ) == NULL )
+        return( -1 );
+
+    if( fwrite( output_buf, 1, len, f ) != len )
+        return( -1 );
+
+    fclose(f);
+
+    return( 0 );
+}
+
+#define USAGE \
+    "\n usage: cert_write param=<>...\n"                \
+    "\n acceptable parameters:\n"                       \
+    "    subject_key=%%s      default: subject.key\n"   \
+    "    subject_pwd=%%s      default: (empty)\n"       \
+    "    issuer_key=%%s       default: ca.key\n"        \
+    "    issuer_pwd=%%s       default: (empty)\n"       \
+    "    output_file=%%s      default: cert.crt\n"      \
+    "    subject_name=%%s     default: CN=Cert,O=PolarSSL,C=NL\n"   \
+    "    issuer_name=%%s      default: CN=CA,O=PolarSSL,C=NL\n"     \
+    "    serial=%%s           default: 1\n"             \
+    "    not_before=%%s       default: 20010101000000\n"\
+    "    not_after=%%s        default: 20301231235959\n"\
+    "    key_usage=%%s        default: (empty)\n"       \
+    "                        Comma-separated-list of values:\n"     \
+    "                          digital_signature\n"     \
+    "                          non_repudiation\n"       \
+    "                          key_encipherment\n"      \
+    "                          data_encipherment\n"     \
+    "                          key_agreement\n"         \
+    "                          key_certificate_sign\n"  \
+    "                          crl_sign\n"              \
+    "    ns_cert_type=%%s     default: (empty)\n"       \
+    "                        Comma-separated-list of values:\n"     \
+    "                          ssl_client\n"            \
+    "                          ssl_server\n"            \
+    "                          email\n"                 \
+    "                          object_signing\n"        \
+    "                          ssl_ca\n"                \
+    "                          email_ca\n"              \
+    "                          object_signing_ca\n"     \
+    "\n"
+
+int main( int argc, char *argv[] )
+{
+    int ret = 0;
+    rsa_context issuer_rsa, subject_rsa;
+    char buf[1024];
+    int i, j, n;
+    char *p, *q, *r;
+    x509write_cert crt;
+    mpi serial;
+
+    /*
+     * Set to sane values
+     */
+    x509write_crt_init( &crt );
+    x509write_crt_set_md_alg( &crt, POLARSSL_MD_SHA1 );
+    rsa_init( &issuer_rsa, RSA_PKCS_V15, 0 );
+    rsa_init( &subject_rsa, RSA_PKCS_V15, 0 );
+    mpi_init( &serial );
+    memset( buf, 0, 1024 );
+
+    if( argc == 0 )
+    {
+    usage:
+        printf( USAGE );
+        ret = 1;
+        goto exit;
+    }
+
+    opt.subject_key         = DFL_SUBJECT_KEY;
+    opt.issuer_key          = DFL_ISSUER_KEY;
+    opt.subject_pwd         = DFL_SUBJECT_PWD;
+    opt.issuer_pwd          = DFL_ISSUER_PWD;
+    opt.output_file         = DFL_OUTPUT_FILENAME;
+    opt.subject_name        = DFL_SUBJECT_NAME;
+    opt.issuer_name         = DFL_ISSUER_NAME;
+    opt.not_before          = DFL_NOT_BEFORE;
+    opt.not_after           = DFL_NOT_AFTER;
+    opt.serial              = DFL_SERIAL;
+    opt.key_usage           = DFL_KEY_USAGE;
+    opt.ns_cert_type        = DFL_NS_CERT_TYPE;
+
+    for( i = 1; i < argc; i++ )
+    {
+
+        p = argv[i];
+        if( ( q = strchr( p, '=' ) ) == NULL )
+            goto usage;
+        *q++ = '\0';
+
+        n = strlen( p );
+        for( j = 0; j < n; j++ )
+        {
+            if( argv[i][j] >= 'A' && argv[i][j] <= 'Z' )
+                argv[i][j] |= 0x20;
+        }
+
+        if( strcmp( p, "subject_key" ) == 0 )
+            opt.subject_key = q;
+        else if( strcmp( p, "issuer_key" ) == 0 )
+            opt.issuer_key = q;
+        else if( strcmp( p, "subject_pwd" ) == 0 )
+            opt.subject_pwd = q;
+        else if( strcmp( p, "issuer_pwd" ) == 0 )
+            opt.issuer_pwd = q;
+        else if( strcmp( p, "output_file" ) == 0 )
+            opt.output_file = q;
+        else if( strcmp( p, "subject_name" ) == 0 )
+        {
+            opt.subject_name = q;
+        }
+        else if( strcmp( p, "issuer_name" ) == 0 )
+        {
+            opt.issuer_name = q;
+        }
+        else if( strcmp( p, "not_before" ) == 0 )
+        {
+            opt.not_before = q;
+        }
+        else if( strcmp( p, "not_after" ) == 0 )
+        {
+            opt.not_after = q;
+        }
+        else if( strcmp( p, "serial" ) == 0 )
+        {
+            opt.serial = q;
+        }
+        else if( strcmp( p, "key_usage" ) == 0 )
+        {
+            while( q != NULL )
+            {
+                if( ( r = strchr( q, ',' ) ) != NULL )
+                    *r++ = '\0';
+
+                if( strcmp( q, "digital_signature" ) == 0 )
+                    opt.key_usage |= KU_DIGITAL_SIGNATURE;
+                else if( strcmp( q, "non_repudiation" ) == 0 )
+                    opt.key_usage |= KU_NON_REPUDIATION;
+                else if( strcmp( q, "key_encipherment" ) == 0 )
+                    opt.key_usage |= KU_KEY_ENCIPHERMENT;
+                else if( strcmp( q, "data_encipherment" ) == 0 )
+                    opt.key_usage |= KU_DATA_ENCIPHERMENT;
+                else if( strcmp( q, "key_agreement" ) == 0 )
+                    opt.key_usage |= KU_KEY_AGREEMENT;
+                else if( strcmp( q, "key_cert_sign" ) == 0 )
+                    opt.key_usage |= KU_KEY_CERT_SIGN;
+                else if( strcmp( q, "crl_sign" ) == 0 )
+                    opt.key_usage |= KU_CRL_SIGN;
+                else
+                    goto usage;
+
+                q = r;
+            }
+        }
+        else if( strcmp( p, "ns_cert_type" ) == 0 )
+        {
+            while( q != NULL )
+            {
+                if( ( r = strchr( q, ',' ) ) != NULL )
+                    *r++ = '\0';
+
+                if( strcmp( q, "ssl_client" ) == 0 )
+                    opt.ns_cert_type |= NS_CERT_TYPE_SSL_CLIENT;
+                else if( strcmp( q, "ssl_server" ) == 0 )
+                    opt.ns_cert_type |= NS_CERT_TYPE_SSL_SERVER;
+                else if( strcmp( q, "email" ) == 0 )
+                    opt.ns_cert_type |= NS_CERT_TYPE_EMAIL;
+                else if( strcmp( q, "object_signing" ) == 0 )
+                    opt.ns_cert_type |= NS_CERT_TYPE_OBJECT_SIGNING;
+                else if( strcmp( q, "ssl_ca" ) == 0 )
+                    opt.ns_cert_type |= NS_CERT_TYPE_SSL_CA;
+                else if( strcmp( q, "email_ca" ) == 0 )
+                    opt.ns_cert_type |= NS_CERT_TYPE_EMAIL_CA;
+                else if( strcmp( q, "object_signing_ca" ) == 0 )
+                    opt.ns_cert_type |= NS_CERT_TYPE_OBJECT_SIGNING_CA;
+                else
+                    goto usage;
+
+                q = r;
+            }
+        }
+        else
+            goto usage;
+    }
+
+    // Parse serial to MPI
+    //
+    if( ( ret = mpi_read_string( &serial, 10, opt.serial ) ) != 0 )
+    {
+#ifdef POLARSSL_ERROR_C
+        error_strerror( ret, buf, 1024 );
+#endif
+        printf( " failed\n  !  mpi_read_string returned -0x%02x - %s\n\n", -ret, buf );
+        goto exit;
+    }
+
+/*
+    if( opt.key_usage )
+        x509write_csr_set_key_usage( &req, opt.key_usage );
+
+    if( opt.ns_cert_type )
+        x509write_csr_set_ns_cert_type( &req, opt.ns_cert_type );
+*/
+    /*
+     * 1.0. Check the names for validity
+     */
+    if( ( ret = x509write_crt_set_subject_name( &crt, opt.subject_name ) ) != 0 )
+    {
+#ifdef POLARSSL_ERROR_C
+        error_strerror( ret, buf, 1024 );
+#endif
+        printf( " failed\n  !  x509write_crt_set_subject_name returned -0x%02x - %s\n\n", -ret, buf );
+        goto exit;
+    }
+
+    if( ( ret = x509write_crt_set_issuer_name( &crt, opt.issuer_name ) ) != 0 )
+    {
+#ifdef POLARSSL_ERROR_C
+        error_strerror( ret, buf, 1024 );
+#endif
+        printf( " failed\n  !  x509write_crt_set_issuer_name returned -0x%02x - %s\n\n", -ret, buf );
+        goto exit;
+    }
+
+    /*
+     * 1.1. Load the keys
+     */
+    printf( "\n  . Loading the subject key ..." );
+    fflush( stdout );
+
+    ret = x509parse_keyfile_rsa( &subject_rsa, opt.subject_key, opt.subject_pwd );
+
+    if( ret != 0 )
+    {
+#ifdef POLARSSL_ERROR_C
+        error_strerror( ret, buf, 1024 );
+#endif
+        printf( " failed\n  !  x509parse_keyfile_rsa returned -0x%02x - %s\n\n", -ret, buf );
+        goto exit;
+    }
+
+    x509write_crt_set_subject_key( &crt, &subject_rsa );
+
+    printf( " ok\n" );
+
+    printf( "  . Loading the issuer key ..." );
+    fflush( stdout );
+
+    ret = x509parse_keyfile_rsa( &issuer_rsa, opt.issuer_key, opt.issuer_pwd );
+
+    if( ret != 0 )
+    {
+#ifdef POLARSSL_ERROR_C
+        error_strerror( ret, buf, 1024 );
+#endif
+        printf( " failed\n  !  x509parse_keyfile_rsa returned -x%02x - %s\n\n", -ret, buf );
+        goto exit;
+    }
+
+    x509write_crt_set_issuer_key( &crt, &issuer_rsa );
+
+    printf( " ok\n" );
+
+    printf( "  . Setting certificate values ..." );
+    fflush( stdout );
+
+    ret = x509write_crt_set_serial( &crt, &serial );
+    if( ret != 0 )
+    {
+#ifdef POLARSSL_ERROR_C
+        error_strerror( ret, buf, 1024 );
+#endif
+        printf( " failed\n  !  x509write_crt_set_serial returned -0x%02x - %s\n\n", -ret, buf );
+        goto exit;
+    }
+
+    ret = x509write_crt_set_validity( &crt, opt.not_before, opt.not_after );
+    if( ret != 0 )
+    {
+#ifdef POLARSSL_ERROR_C
+        error_strerror( ret, buf, 1024 );
+#endif
+        printf( " failed\n  !  x509write_crt_set_validity returned -0x%02x - %s\n\n", -ret, buf );
+        goto exit;
+    }
+
+    printf( " ok\n" );
+
+    /*
+     * 1.2. Writing the request
+     */
+    printf( "  . Writing the certificate..." );
+    fflush( stdout );
+
+    if( ( ret = write_certificate( &crt, opt.output_file ) ) != 0 )
+    {
+#ifdef POLARSSL_ERROR_C
+        error_strerror( ret, buf, 1024 );
+#endif
+        printf( " failed\n  !  write_certifcate -0x%02x - %s\n\n", -ret, buf );
+        goto exit;
+    }
+
+    printf( " ok\n" );
+
+exit:
+    x509write_crt_free( &crt );
+    rsa_free( &subject_rsa );
+    rsa_free( &issuer_rsa );
+    mpi_free( &serial );
+
+#if defined(_WIN32)
+    printf( "  + Press Enter to exit this program.\n" );
+    fflush( stdout ); getchar();
+#endif
+
+    return( ret );
+}
+#endif /* POLARSSL_BIGNUM_C && POLARSSL_RSA_C &&
+          POLARSSet_serial_X509_WRITE_C && POLARSSL_FS_IO */