/*
* Key Derivation Function (KDF) Module
*
* Provides commands to derive keys.
*
* Copyright (C) 2023 Brian O'Hagan
*
*/
#include "tlsInt.h"
#include "tclOpts.h"
#include <openssl/evp.h>
#include <openssl/kdf.h>
/*******************************************************************/
/*
* Get cipher
*/
EVP_CIPHER *Util_GetCipher(Tcl_Interp *interp, char *name, int exist) {
EVP_CIPHER *cipher = NULL;
if (name != NULL) {
cipher = EVP_get_cipherbyname(name);
if (cipher == NULL) {
Tcl_AppendResult(interp, "Invalid cipher: \"", name, "\"", NULL);
}
} else if (exist) {
Tcl_AppendResult(interp, "No cipher specified", NULL);
}
return cipher;
}
/*
* Get message digest
*/
EVP_MD *Util_GetDigest(Tcl_Interp *interp, char *name, int exist) {
EVP_MD *md = NULL;
if (name != NULL) {
md = EVP_get_digestbyname(name);
if (md == NULL) {
Tcl_AppendResult(interp, "Invalid digest: \"", name, "\"", NULL);
}
} else if (exist) {
Tcl_AppendResult(interp, "No digest specified", NULL);
}
return md;
}
/*******************************************************************/
/* Options for KDF commands */
static const char *command_opts [] = {
"-cipher", "-digest", "-hash", "-info", "-iterations", "-key", "-length", "-password",
"-salt", "-size", "-N", "-n", "-r", "-p", NULL};
enum _command_opts {
_opt_cipher, _opt_digest, _opt_hash, _opt_info, _opt_iter, _opt_key, _opt_length,
_opt_password, _opt_salt, _opt_size, _opt_N, _opt_n, _opt_r, _opt_p
};
/*
*-------------------------------------------------------------------
*
* KDF_PBKDF2 --
*
* PKCS5_PBKDF2_HMAC key derivation function (KDF) specified by PKCS #5.
* KDFs include PBKDF2 from RFC 2898/8018 and Scrypt from RFC 7914.
*
* Returns:
* TCL_OK or TCL_ERROR
*
* Side effects:
* Sets result to a list of key and iv values, or an error message
*
*-------------------------------------------------------------------
*/
static int KDF_PBKDF2(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
int pass_len = 0, salt_len = 0, fn;
int iklen, ivlen, iter = 1;
unsigned char *password = NULL, *salt = NULL;
const EVP_MD *md = NULL;
const EVP_CIPHER *cipher = NULL;
int buf_len = (EVP_MAX_KEY_LENGTH + EVP_MAX_IV_LENGTH)*4, dk_len = buf_len;
unsigned char tmpkeyiv[(EVP_MAX_KEY_LENGTH + EVP_MAX_IV_LENGTH)*4];
char *cipherName = NULL, *digestName = NULL;
dprintf("Called");
/* Clear errors */
Tcl_ResetResult(interp);
ERR_clear_error();
/* Validate arg count */
if (objc < 3 || objc > 11) {
Tcl_WrongNumArgs(interp, 1, objv, "[-cipher cipher | -size length] -digest digest ?-iterations count? ?-password string? ?-salt string?");
return TCL_ERROR;
}
/* Init buffers */
memset(tmpkeyiv, 0, buf_len);
/* Get options */
for (int idx = 1; idx < objc; idx++) {
/* Get option */
if (Tcl_GetIndexFromObj(interp, objv[idx], command_opts, "option", 0, &fn) != TCL_OK) {
return TCL_ERROR;
}
/* Validate arg has a value */
if (++idx >= objc) {
Tcl_AppendResult(interp, "No value for option \"", command_opts[fn], "\"", (char *) NULL);
return TCL_ERROR;
}
switch(fn) {
case _opt_cipher:
GET_OPT_STRING(objv[idx], cipherName, NULL);
break;
case _opt_digest:
case _opt_hash:
GET_OPT_STRING(objv[idx], digestName, NULL);
break;
case _opt_iter:
GET_OPT_INT(objv[idx], &iter);
break;
case _opt_key:
case _opt_password:
GET_OPT_BYTE_ARRAY(objv[idx], password, &pass_len);
break;
case _opt_salt:
GET_OPT_BYTE_ARRAY(objv[idx], salt, &salt_len);
break;
case _opt_length:
case _opt_size:
GET_OPT_INT(objv[idx], &dk_len);
break;
}
}
/* Validate options */
if (cipherName != NULL && (cipher = Util_GetCipher(interp, cipherName, 0)) == NULL) {
return TCL_ERROR;
}
if ((md = Util_GetDigest(interp, digestName, TRUE)) == NULL) {
return TCL_ERROR;
}
if (iter < 1) {
Tcl_SetObjResult(interp, Tcl_ObjPrintf("Invalid iterations count %d: must be > 0", iter));
return TCL_ERROR;
}
if (dk_len < 1 || dk_len > buf_len) {
Tcl_SetObjResult(interp, Tcl_ObjPrintf("Invalid derived key length %d: must be 0 < size <= %d", dk_len, buf_len));
return TCL_ERROR;
}
/* Set output type sizes */
if (cipher == NULL) {
if (dk_len > buf_len) dk_len = buf_len;
iklen = dk_len;
ivlen = 0;
} else {
iklen = EVP_CIPHER_key_length(cipher);
ivlen = EVP_CIPHER_iv_length(cipher);
dk_len = iklen+ivlen;
}
/* Derive key */
if (!PKCS5_PBKDF2_HMAC(password, pass_len, salt, salt_len, iter, md, dk_len, tmpkeyiv)) {
Tcl_AppendResult(interp, "Key derivation failed: ", REASON(), NULL);
return TCL_ERROR;
}
/* Set result to key and iv */
if (cipher == NULL) {
Tcl_SetObjResult(interp, Tcl_NewByteArrayObj(tmpkeyiv, dk_len));
} else {
Tcl_Obj *resultObj = Tcl_NewListObj(0, NULL);
LAPPEND_BARRAY(interp, resultObj, "key", tmpkeyiv, iklen);
LAPPEND_BARRAY(interp, resultObj, "iv", tmpkeyiv+iklen, ivlen);
Tcl_SetObjResult(interp, resultObj);
}
/* Clear data */
memset(tmpkeyiv, 0, buf_len);
return TCL_OK;
}
/*
*-------------------------------------------------------------------
*
* KDF_HKDF --
*
* HMAC-based Extract-and-Expand Key Derivation Function (HKDF).
* See RFC 5869.
*
* Returns:
* TCL_OK or TCL_ERROR
*
* Side effects:
* Sets result to a key of specified length, or an error message
*
*-------------------------------------------------------------------
*/
static int KDF_HKDF(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
EVP_PKEY_CTX *pctx;
const EVP_MD *md = NULL;
unsigned char *salt = NULL, *key = NULL, *info = NULL, *out = NULL;
int salt_len = 0, key_len = 0, info_len = 0, dk_len = 1024, res = TCL_OK, fn;
char *digestName;
size_t out_len;
Tcl_Obj *resultObj;
dprintf("Called");
/* Clear errors */
Tcl_ResetResult(interp);
ERR_clear_error();
/* Validate arg count */
if (objc < 3 || objc > 11) {
Tcl_WrongNumArgs(interp, 1, objv, "-digest digest -key string ?-info string? ?-salt string? ?-size derived_length?");
return TCL_ERROR;
}
/* Get options */
for (int idx = 1; idx < objc; idx++) {
/* Get option */
if (Tcl_GetIndexFromObj(interp, objv[idx], command_opts, "option", 0, &fn) != TCL_OK) {
return TCL_ERROR;
}
/* Validate arg has a value */
if (++idx >= objc) {
Tcl_AppendResult(interp, "No value for option \"", command_opts[fn], "\"", (char *) NULL);
return TCL_ERROR;
}
switch(fn) {
case _opt_digest:
case _opt_hash:
GET_OPT_STRING(objv[idx], digestName, NULL);
break;
case _opt_info:
/* Max 1024/2048 */
GET_OPT_BYTE_ARRAY(objv[idx], info, &info_len);
break;
case _opt_key:
case _opt_password:
GET_OPT_BYTE_ARRAY(objv[idx], key, &key_len);
break;
case _opt_salt:
GET_OPT_BYTE_ARRAY(objv[idx], salt, &salt_len);
break;
case _opt_length:
case _opt_size:
GET_OPT_INT(objv[idx], &dk_len);
break;
}
}
/* Get digest */
if ((md = Util_GetDigest(interp, digestName, TRUE)) == NULL) {
goto error;
}
/* Create context */
pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
if (pctx == NULL) {
Tcl_AppendResult(interp, "Memory allocation error", (char *) NULL);
goto error;
}
if (EVP_PKEY_derive_init(pctx) < 1) {
Tcl_AppendResult(interp, "Initialize failed: ", REASON(), NULL);
goto error;
}
/* Set config parameters */
if (EVP_PKEY_CTX_set_hkdf_md(pctx, md) < 1) {
Tcl_AppendResult(interp, "Set digest failed: ", REASON(), NULL);
goto error;
}
if (EVP_PKEY_CTX_set1_hkdf_key(pctx, key, key_len) < 1) {
Tcl_AppendResult(interp, "Set key failed: ", REASON(), NULL);
goto error;
}
if (salt != NULL && EVP_PKEY_CTX_set1_hkdf_salt(pctx, salt, salt_len) < 1) {
Tcl_AppendResult(interp, "Set salt failed: ", REASON(), NULL);
goto error;
}
if (info != NULL && EVP_PKEY_CTX_add1_hkdf_info(pctx, info, info_len) < 1) {
Tcl_AppendResult(interp, "Set info failed: ", REASON(), NULL);
goto error;
}
/* Get buffer */
resultObj = Tcl_NewObj();
if ((out = Tcl_SetByteArrayLength(resultObj, dk_len)) == NULL) {
Tcl_AppendResult(interp, "Memory allocation error", (char *) NULL);
goto error;
}
out_len = (size_t) dk_len;
/* Derive key */
if (EVP_PKEY_derive(pctx, out, &out_len) > 0) {
/* Shrink buffer to actual size */
Tcl_SetByteArrayLength(resultObj, (int) out_len);
Tcl_SetObjResult(interp, resultObj);
goto done;
} else {
Tcl_AppendResult(interp, "Derive key failed: ", REASON(), NULL);
Tcl_DecrRefCount(resultObj);
}
error:
res = TCL_ERROR;
done:
if (pctx != NULL) {
EVP_PKEY_CTX_free(pctx);
}
return TCL_OK;
}
/*
*-------------------------------------------------------------------
*
* Tls_KeyCommands --
*
* Create key commands
*
* Returns:
* TCL_OK or TCL_ERROR
*
* Side effects:
* Creates commands
*
*-------------------------------------------------------------------
*/
int Tls_KeyCommands(Tcl_Interp *interp) {
Tcl_CreateObjCommand(interp, "tls::hkdf", KDF_HKDF, (ClientData) 0, (Tcl_CmdDeleteProc *) NULL);
Tcl_CreateObjCommand(interp, "tls::pbkdf2", KDF_PBKDF2, (ClientData) 0, (Tcl_CmdDeleteProc *) NULL);
return TCL_OK;
}
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