/*
 * Copyright (C) 1997-2000 Sensus Consulting Ltd.
 * Matt Newman <matt@sensus.org>
 * Copyright (C) 2023 Brian O'Hagan
 */
#include <tcl.h>
#include <stdio.h>
#include <openssl/bio.h>
#include <openssl/sha.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <openssl/asn1.h>
#include "tlsInt.h"

/*
 *  Ensure these are not macros - known to be defined on Win32
 */
#ifdef min
#undef min
#endif

#ifdef max
#undef max
#endif

static int min(int a, int b)
{
    return (a < b) ? a : b;
}

static int max(int a, int b)
{
    return (a > b) ? a : b;
}

/*
 * Binary string to hex string
 */
int String_to_Hex(char* input, int len, char *output, int max) {
    int count = 0;

    for (int i = 0; i < len && count < max - 1; i++, count += 2) {
	sprintf(output + count, "%02X", input[i] & 0xff);
    }
    output[count] = 0;
    return count;
}

/*
 *------------------------------------------------------*
 *
 *	Tls_NewX509Obj --
 *
 *	------------------------------------------------*
 *	Converts a X509 certificate into a Tcl_Obj
 *	------------------------------------------------*
 *
 *	Side effects:
 *		None
 *
 *	Result:
 *		A Tcl List Object representing the provided
 *		X509 certificate.
 *
 *------------------------------------------------------*
 */

#define CERT_STR_SIZE 32768

Tcl_Obj*
Tls_NewX509Obj(Tcl_Interp *interp, X509 *cert) {
    Tcl_Obj *certPtr = Tcl_NewListObj(0, NULL);
    BIO *bio;
    int nid, pknid, bits, num_of_exts, len;
    uint32_t xflags;
    char subject[BUFSIZ];
    char issuer[BUFSIZ];
    char serial[BUFSIZ];
    char notBefore[BUFSIZ];
    char notAfter[BUFSIZ];
    char buffer[BUFSIZ];
    char certStr[CERT_STR_SIZE];
    unsigned char md[EVP_MAX_MD_SIZE];
    STACK_OF(GENERAL_NAME) *san;
    STACK_OF(DIST_POINT) *crl;
    STACK_OF(OPENSSL_STRING) *ocsp;

    certStr[0]   = 0;
    subject[0]   = 0;
    issuer[0]    = 0;
    serial[0]    = 0;
    notBefore[0] = 0;
    notAfter[0]  = 0;
    if ((bio = BIO_new(BIO_s_mem())) != NULL) {
	int n;
	unsigned long flags = XN_FLAG_RFC2253 | ASN1_STRFLGS_UTF8_CONVERT;
	flags &= ~ASN1_STRFLGS_ESC_MSB;

	/* Get subject name */
	if (X509_NAME_print_ex(bio, X509_get_subject_name(cert), 0, flags) > 0) {
	    n = BIO_read(bio, subject, min(BIO_pending(bio), BUFSIZ - 1));
	    subject[max(n, 0)] = 0;
	    (void)BIO_flush(bio);
	}

	/* Get issuer name */
	if (X509_NAME_print_ex(bio, X509_get_issuer_name(cert), 0, flags) > 0) {
	    n = BIO_read(bio, issuer, min(BIO_pending(bio), BUFSIZ - 1));
	    issuer[max(n, 0)] = 0;
	    (void)BIO_flush(bio);
	}

	/* Get serial number */
	if (i2a_ASN1_INTEGER(bio, X509_get0_serialNumber(cert)) > 0) {
	    n = BIO_read(bio, serial, min(BIO_pending(bio), BUFSIZ - 1));
	    serial[max(n, 0)] = 0;
	    (void)BIO_flush(bio);
	}

        /* Get certificate */
        if (PEM_write_bio_X509(bio, cert)) {
            char *certStr_p = certStr;
            int certStr_len = 0;
            while (1) {
                int toRead = min(BIO_pending(bio), CERT_STR_SIZE - certStr_len - 1);
                toRead = min(toRead, BUFSIZ);
                if (toRead == 0) {
                    break;
                }
                dprintf("Reading %i bytes from the certificate...", toRead);
                n = BIO_read(bio, certStr_p, toRead);
                if (n <= 0) {
                    break;
                }
                certStr_len += n;
                certStr_p   += n;
            }
            *certStr_p = '\0';
            (void)BIO_flush(bio);
        }

	/* Get all cert info */
	if (X509_print_ex(bio, cert, flags, 0)) {
	    char all[65536];
	    n = BIO_read(bio, all, min(BIO_pending(bio), 65535));
	    all[max(n, 0)] = 0;
	    (void)BIO_flush(bio);
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("all", -1));
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(all, n));
	}

	/* Get Validity - Not Before */
	if (ASN1_TIME_print(bio, X509_get0_notBefore(cert))) {
	    n = BIO_read(bio, notBefore, min(BIO_pending(bio), BUFSIZ - 1));
	    notBefore[max(n, 0)] = 0;
	    (void)BIO_flush(bio);
	}

	/* Get Validity - Not After */
	if (ASN1_TIME_print(bio, X509_get0_notAfter(cert))) {
	    n = BIO_read(bio, notAfter, min(BIO_pending(bio), BUFSIZ - 1));
	    notAfter[max(n, 0)] = 0;
	    (void)BIO_flush(bio);
	}

	BIO_free(bio);
    }

    /* Version of the encoded certificate */
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("version", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewLongObj(X509_get_version(cert)+1));

    /* Signature algorithm used by the CA to sign the certificate. Must match signatureAlgorithm. */
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("signature", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(OBJ_nid2ln(X509_get_signature_nid(cert)),-1));

    /* SHA1 Fingerprint of cert - DER representation */
    X509_digest(cert, EVP_sha1(), md, &len);
    len = String_to_Hex(md, len, buffer, BUFSIZ);
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("sha1_hash", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(buffer, len));

    /* SHA256 Fingerprint of cert - DER representation */
    X509_digest(cert, EVP_sha256(), md, &len);
    len = String_to_Hex(md, len, buffer, BUFSIZ);
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("sha256_hash", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(buffer, len));

    /* The subject identifies the entity associated with the public key stored in the subject public key field.  */
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("subject", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(subject, -1));

    /* The issuer identifies the entity that has signed and issued the certificate. */
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("issuer", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(issuer, -1));

    /* Certificate validity period is the time interval during which the CA
   warrants that it will maintain information about the status of the certificate. */
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("notBefore", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(notBefore, -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("notAfter", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(notAfter, -1));

    /* Unique number assigned by CA to certificate. */
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("serialNumber", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(serial, -1));

    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("certificate", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(certStr, -1));

    /* Information about the signature of certificate cert */
    /* Contains the public key and identify the algorithm with which the key is used */
    if (X509_get_signature_info(cert, &nid, &pknid, &bits, &xflags) == 1) {
	ASN1_BIT_STRING *key;

	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("signingDigest", -1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(OBJ_nid2ln(nid),-1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("publicKeyAlgorithm", -1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(OBJ_nid2ln(pknid),-1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("bits", -1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewIntObj(bits));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("extension_flags", -1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewIntObj(xflags));

	/* Public key - X509_get0_pubkey */
	key = X509_get0_pubkey_bitstr(cert);
	len = String_to_Hex(key->data, key->length, buffer, BUFSIZ);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("publicKey", -1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(buffer, len));

	/* Check if cert was issued by CA cert issuer or self signed */
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("self_signed", -1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewBooleanObj(X509_check_issued(cert, cert) == X509_V_OK));
    }

    /* Unique Ids -  The unique identifiers are present in the certificate to handle the
	possibility of reuse of subject and/or issuer names over time.*/
    {
	const ASN1_BIT_STRING *iuid, *suid;
        X509_get0_uids(cert, &iuid, &suid);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("issuerUniqueId", -1));
	if (iuid != NULL) {
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewByteArrayObj((char *)iuid->data, iuid->length));
	} else {
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("", -1));
	}

	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("subjectUniqueId", -1));
	if (suid != NULL) {
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewByteArrayObj((char *)suid->data, suid->length));
	} else {
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("", -1));
	}
    }

    /* Count of extensions */
    num_of_exts = X509_get_ext_count(cert);
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("num_extensions", -1));
    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewIntObj(num_of_exts));

    /* Get extension names */
    if (num_of_exts > 0) {
	Tcl_Obj *extsPtr = Tcl_NewListObj(0, NULL);
	const STACK_OF(X509_EXTENSION) *exts;
	exts = X509_get0_extensions(cert);

	for (int i=0; i < num_of_exts; i++) {
	    X509_EXTENSION *ex = sk_X509_EXTENSION_value(exts, i);
	    ASN1_OBJECT *obj = X509_EXTENSION_get_object(ex);
	    unsigned nid2 = OBJ_obj2nid(obj);
	    Tcl_ListObjAppendElement(interp, extsPtr, Tcl_NewStringObj(OBJ_nid2ln(nid2), -1));
	}
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("extensions", -1));
	Tcl_ListObjAppendElement(interp, certPtr, extsPtr);
    }

    /* Certificate Alias as UTF-8 string */
    {
	unsigned char *bstring;
	len = 0;
	bstring = X509_alias_get0(cert, &len);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("alias", -1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj((char *)bstring, len));
    }

    /* Get Subject Key id, Authority Key id. The Authority Key Identifier (AKI) of a
	certificate should be the Subject Key Identifier (SKI) of its signer (the CA). */
    {
	/* Identifies certificates that contain a particular public key */
	ASN1_OCTET_STRING *astring;
	/* X509_keyid_get0 */
	astring = X509_get0_subject_key_id(cert);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("subjectKeyIdentifier", -1));
	if (astring != NULL) {
	    len = String_to_Hex((char *)ASN1_STRING_get0_data(astring), ASN1_STRING_length(astring), buffer, BUFSIZ);
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(buffer, len));
	} else {
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("", -1));
	}

	/* Identifies the public key corresponding to the private key used to sign a certificate */
	astring = X509_get0_authority_key_id(cert);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("authorityKeyIdentifier", -1));
	if (astring != NULL) {
	    len = String_to_Hex((char *)ASN1_STRING_get0_data(astring), ASN1_STRING_length(astring), buffer, BUFSIZ);
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(buffer, len));
	} else {
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("", -1));
	}
	
	/*  const GENERAL_NAMES *X509_get0_authority_issuer(cert);
	const ASN1_INTEGER *X509_get0_authority_serial(cert); */
    }
 
    /* Signature algorithm and value */
    /* The signatureAlgorithm field contains the identifier for the cryptographic algorithm
	used by the CA to sign this certificate. The signatureValue field contains a digital
	signature computed upon the ASN.1 DER encoded tbsCertificate. */
    {
	const X509_ALGOR *sig_alg;
	const ASN1_BIT_STRING *sig;
	int sig_nid;

	X509_get0_signature(&sig, &sig_alg, cert);
	/* sig_nid = X509_get_signature_nid(cert) */
	sig_nid = OBJ_obj2nid(sig_alg->algorithm);

	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("signatureAlgorithm", -1));
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(OBJ_nid2ln(sig_nid),-1));

	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("signatureValue", -1));
	if (sig_nid != NID_undef) {
	    len = String_to_Hex(sig->data, sig->length, buffer, BUFSIZ);
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj(buffer, len));
	} else {
	    Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("", -1));
	}
    }

    /* Key usage extension defines the purpose (e.g., encipherment, signature, certificate
	signing) of the key contained in the certificate. */
    {
	Tcl_Obj *purpPtr = Tcl_NewListObj(0, NULL);
	for (int j = 0; j < X509_PURPOSE_get_count(); j++) {
	    X509_PURPOSE *ptmp = X509_PURPOSE_get0(j);
	    Tcl_Obj *tmpPtr = Tcl_NewListObj(0, NULL);

	    for (int i = 0; i < 2; i++) {
		int idret = X509_check_purpose(cert, X509_PURPOSE_get_id(ptmp), i);
		Tcl_ListObjAppendElement(interp, tmpPtr, Tcl_NewStringObj(i ? "CA" : "nonCA", -1));
		Tcl_ListObjAppendElement(interp, tmpPtr, Tcl_NewStringObj(idret ? "Yes" : "No", -1));
	    }
	    Tcl_ListObjAppendElement(interp, purpPtr, Tcl_NewStringObj(X509_PURPOSE_get0_name(ptmp), -1));
	    Tcl_ListObjAppendElement(interp, purpPtr, tmpPtr);
	}
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("certificatePurpose", -1));
	Tcl_ListObjAppendElement(interp, certPtr, purpPtr);
    }

    /* Certificate Policies - indicates the issuing CA considers its issuerDomainPolicy
	equivalent to the subject CA's subjectDomainPolicy. */

    /* Subject Alternative Name (SAN) extension. Additional URLs, DNS name, or IP addresses
	bound to certificate. */
    san = X509_get_ext_d2i(cert, NID_subject_alt_name, NULL, NULL);
    if (san) {
	Tcl_Obj *namesPtr = Tcl_NewListObj(0, NULL);
	bio = BIO_new(BIO_s_mem());

	for (int i=0; i < sk_GENERAL_NAME_num(san); i++) {
	    const GENERAL_NAME *name = sk_GENERAL_NAME_value(san, i);

	    if (name && bio) {
		if (GENERAL_NAME_print(bio, name)) {
		    int n = BIO_read(bio, buffer, min(BIO_pending(bio), BUFSIZ));
		    buffer[max(n, 0)] = 0;
		    (void)BIO_flush(bio);
		    Tcl_ListObjAppendElement(interp, namesPtr, Tcl_NewStringObj(buffer, n));
		}
	    }
	}
	BIO_free(bio);
	sk_GENERAL_NAME_pop_free(san, GENERAL_NAME_free);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("subjectAltName", -1));
	Tcl_ListObjAppendElement(interp, certPtr, namesPtr);
    }

    /* Issuer Alternative Name */
    san = X509_get_ext_d2i(cert, NID_issuer_alt_name, NULL, NULL);
    if (san) {
	Tcl_Obj *namesPtr = Tcl_NewListObj(0, NULL);
	bio = BIO_new(BIO_s_mem());

	for (int i=0; i < sk_GENERAL_NAME_num(san); i++) {
	    const GENERAL_NAME *name = sk_GENERAL_NAME_value(san, i);

	    if (name && bio) {
		if (GENERAL_NAME_print(bio, name)) {
		    int n = BIO_read(bio, buffer, min(BIO_pending(bio), BUFSIZ));
		    buffer[max(n, 0)] = 0;
		    (void)BIO_flush(bio);
		    Tcl_ListObjAppendElement(interp, namesPtr, Tcl_NewStringObj(buffer, n));
		}
	    }
	}
	BIO_free(bio);
	sk_GENERAL_NAME_pop_free(san, GENERAL_NAME_free);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("issuerAltName", -1));
	Tcl_ListObjAppendElement(interp, certPtr, namesPtr);
    }

    /* Get the STACK of all crl distribution point entries for this certificate. */
    /* CRL_DIST_POINTS is typedef on STACK_OF(DIST_POINT). */
    crl = X509_get_ext_d2i(cert, NID_crl_distribution_points, NULL, NULL);
    if (crl) {
	Tcl_Obj *namesPtr = Tcl_NewListObj(0, NULL);

	for (int i=0; i < sk_DIST_POINT_num(crl); i++) {
	    DIST_POINT *dp = sk_DIST_POINT_value(crl, i);
	    DIST_POINT_NAME *distpoint = dp->distpoint;

	    if (distpoint->type == 0) {
		/* fullname GENERALIZEDNAME */
		for (int j = 0; j < sk_GENERAL_NAME_num(distpoint->name.fullname); j++) {
		    GENERAL_NAME *gen = sk_GENERAL_NAME_value(distpoint->name.fullname, j);
		    int type;
		    ASN1_STRING *uri = GENERAL_NAME_get0_value(gen, &type);
		    if (type == GEN_URI) {
			Tcl_ListObjAppendElement(interp, namesPtr,
			    Tcl_NewStringObj((char*)ASN1_STRING_get0_data(uri), ASN1_STRING_length(uri)));
		    }
		}
	    } else if (distpoint->type == 1) {
		/* relativename X509NAME */
		STACK_OF(X509_NAME_ENTRY) *sk_relname = distpoint->name.relativename;
		for (int j = 0; j < sk_X509_NAME_ENTRY_num(sk_relname); j++) {
		    X509_NAME_ENTRY *e = sk_X509_NAME_ENTRY_value(sk_relname, j);
		    ASN1_STRING *d = X509_NAME_ENTRY_get_data(e);
		    Tcl_ListObjAppendElement(interp, namesPtr, Tcl_NewStringObj((char*)ASN1_STRING_data(d), ASN1_STRING_length(d)));
		}
	    }
	}
	CRL_DIST_POINTS_free(crl);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("crlDistributionPoints", -1));
	Tcl_ListObjAppendElement(interp, certPtr, namesPtr);
    }

    /* Subject Directory Attributes */

    /* Basic Constraints - identifies whether the subject of the certificate is a CA and
	the maximum depth of valid certification paths that include this certificate. */

    /* Get OSCP URL */
    ocsp = X509_get1_ocsp(cert);
    if (ocsp) {
	Tcl_Obj *urlsPtr = Tcl_NewListObj(0, NULL);

	for (int i = 0; i < sk_OPENSSL_STRING_num(ocsp); i++) {
	    Tcl_ListObjAppendElement(interp, urlsPtr,
		Tcl_NewStringObj(sk_OPENSSL_STRING_value(ocsp, i), -1));
	}

	X509_email_free(ocsp);
	Tcl_ListObjAppendElement(interp, certPtr, Tcl_NewStringObj("ocsp", -1));
	Tcl_ListObjAppendElement(interp, certPtr, urlsPtr);
    }

    return certPtr;
}