/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "cryptohi.h"

#include "secasn1.h"

#include "secitem.h"

#include "prerr.h"

#ifndef DSA1_SUBPRIME_LEN

#define DSA1_SUBPRIME_LEN 20 /* bytes */

#endif

typedef struct {

    SECItem r;

    SECItem s;

} DSA_ASN1Signature;

const SEC_ASN1Template DSA_SignatureTemplate[] = {

    { SEC_ASN1_SEQUENCE, 0, NULL, sizeof(DSA_ASN1Signature) },

    { SEC_ASN1_INTEGER, offsetof(DSA_ASN1Signature, r) },

    { SEC_ASN1_INTEGER, offsetof(DSA_ASN1Signature, s) },

    { 0 }

};

/* Input is variable length multi-byte integer, MSB first (big endian).

** Most signficant bit of first byte is NOT treated as a sign bit.

** May be one or more leading bytes of zeros.

** Output is variable length multi-byte integer, MSB first (big endian).

** Most significant bit of first byte will be zero (positive sign bit)

** No more than one leading zero byte.

** Caller supplies dest buffer, and assures that it is long enough,

** e.g. at least one byte longer that src's buffer.

*/

void

DSAU_ConvertUnsignedToSigned(SECItem *dest, SECItem *src)

{

    unsigned char *pSrc = src->data;

    unsigned char *pDst = dest->data;

    unsigned int cntSrc = src->len;

    /* skip any leading zeros. */

    while (cntSrc && !(*pSrc)) {

        pSrc++;

        cntSrc--;

    }

    if (!cntSrc) {

        *pDst = 0;

        dest->len = 1;

        return;

    }

    if (*pSrc & 0x80)

        *pDst++ = 0;

    PORT_Memcpy(pDst, pSrc, cntSrc);

    dest->len = (pDst - dest->data) + cntSrc;

}

/*

** src is a buffer holding a signed variable length integer.

** dest is a buffer which will be filled with an unsigned integer,

** MSB first (big endian) with leading zeros, so that the last byte

** of src will be the LSB of the integer.  The result will be exactly

** the length specified by the caller in dest->len.

** src can be shorter than dest.  src can be longer than dst, but only

** if the extra leading bytes are zeros.

*/

SECStatus

DSAU_ConvertSignedToFixedUnsigned(SECItem *dest, SECItem *src)

{

    unsigned char *pSrc = src->data;

    unsigned char *pDst = dest->data;

    unsigned int cntSrc = src->len;

    unsigned int cntDst = dest->len;

    int zCount = cntDst - cntSrc;

    if (zCount > 0) {

        PORT_Memset(pDst, 0, zCount);

        PORT_Memcpy(pDst + zCount, pSrc, cntSrc);

        return SECSuccess;

    }

    if (zCount <= 0) {

        /* Source is longer than destination.  Check for leading zeros. */

        while (zCount++ < 0) {

            if (*pSrc++ != 0)

                goto loser;

        }

    }

    PORT_Memcpy(pDst, pSrc, cntDst);

    return SECSuccess;

loser:

    PORT_SetError(PR_INVALID_ARGUMENT_ERROR);

    return SECFailure;

}

/* src is a "raw" ECDSA or DSA signature, the first half contains r

 * and the second half contains s. dest is the DER encoded signature.

 */

static SECStatus

common_EncodeDerSig(SECItem *dest, SECItem *src)

{

    SECItem *item;

    SECItem srcItem;

    DSA_ASN1Signature sig;

    unsigned char *signedR;

    unsigned char *signedS;

    unsigned int len;

    /* Allocate memory with room for an extra byte that

     * may be required if the top bit in the first byte

     * is already set.

     */

    len = src->len / 2;

    signedR = (unsigned char *)PORT_Alloc(len + 1);

    if (!signedR)

        return SECFailure;

    signedS = (unsigned char *)PORT_ZAlloc(len + 1);

    if (!signedS) {

        if (signedR)

            PORT_Free(signedR);

        return SECFailure;

    }

    PORT_Memset(&sig, 0, sizeof(sig));

    /* Must convert r and s from "unsigned" integers to "signed" integers.

    ** If the high order bit of the first byte (MSB) is 1, then must

    ** prepend with leading zero.

    ** Must remove all but one leading zero byte from numbers.

    */

    sig.r.type = siUnsignedInteger;

    sig.r.data = signedR;

    sig.r.len = sizeof signedR;

    sig.s.type = siUnsignedInteger;

    sig.s.data = signedS;

    sig.s.len = sizeof signedR;

    srcItem.data = src->data;

    srcItem.len = len;

    DSAU_ConvertUnsignedToSigned(&sig.r, &srcItem);

    srcItem.data += len;

    DSAU_ConvertUnsignedToSigned(&sig.s, &srcItem);

    item = SEC_ASN1EncodeItem(NULL, dest, &sig, DSA_SignatureTemplate);

    if (signedR)

        PORT_Free(signedR);

    if (signedS)

        PORT_Free(signedS);

    if (item == NULL)

        return SECFailure;

    /* XXX leak item? */

    return SECSuccess;

}

/* src is a DER-encoded ECDSA or DSA signature.

** Returns a newly-allocated SECItem structure, pointing at a newly allocated

** buffer containing the "raw" signature, which is len bytes of r,

** followed by len bytes of s. For DSA, len is the length of q.

** For ECDSA, len depends on the key size used to create the signature.

*/

static SECItem *

common_DecodeDerSig(const SECItem *item, unsigned int len)

{

    SECItem *result = NULL;

    PORTCheapArenaPool arena;

    SECStatus status;

    DSA_ASN1Signature sig;

    SECItem dst;

    PORT_Memset(&sig, 0, sizeof(sig));

    /* Make enough room for r + s. */

    PORT_InitCheapArena(&arena, PR_MAX(2 * MAX_ECKEY_LEN, DSA_MAX_SIGNATURE_LEN));

    result = PORT_ZNew(SECItem);

    if (result == NULL)

        goto loser;

    result->len = 2 * len;

    result->data = (unsigned char *)PORT_Alloc(2 * len);

    if (result->data == NULL)

        goto loser;

    sig.r.type = siUnsignedInteger;

    sig.s.type = siUnsignedInteger;

    status = SEC_QuickDERDecodeItem(&arena.arena, &sig, DSA_SignatureTemplate, item);

    if (status != SECSuccess)

        goto loser;

    /* Convert sig.r and sig.s from variable  length signed integers to

    ** fixed length unsigned integers.

    */

    dst.data = result->data;

    dst.len = len;

    status = DSAU_ConvertSignedToFixedUnsigned(&dst, &sig.r);

    if (status != SECSuccess)

        goto loser;

    dst.data += len;

    status = DSAU_ConvertSignedToFixedUnsigned(&dst, &sig.s);

    if (status != SECSuccess)

        goto loser;

done:

    PORT_DestroyCheapArena(&arena);

    return result;

loser:

    if (result != NULL) {

        SECITEM_FreeItem(result, PR_TRUE);

        result = NULL;

    }

    goto done;

}

/* src is a "raw" DSA1 signature, 20 bytes of r followed by 20 bytes of s.

** dest is the signature DER encoded. ?

*/

SECStatus

DSAU_EncodeDerSig(SECItem *dest, SECItem *src)

{

    PORT_Assert(src->len == 2 * DSA1_SUBPRIME_LEN);

    if (src->len != 2 * DSA1_SUBPRIME_LEN) {

        PORT_SetError(PR_INVALID_ARGUMENT_ERROR);

        return SECFailure;

    }

    return common_EncodeDerSig(dest, src);

}

/* src is a "raw" DSA signature of length len (len/2 bytes of r followed

** by len/2 bytes of s). dest is the signature DER encoded.

*/

SECStatus

DSAU_EncodeDerSigWithLen(SECItem *dest, SECItem *src, unsigned int len)

{

    PORT_Assert((src->len == len) && (len % 2 == 0));

    if ((src->len != len) || (src->len % 2 != 0)) {

        PORT_SetError(PR_INVALID_ARGUMENT_ERROR);

        return SECFailure;

    }

    return common_EncodeDerSig(dest, src);

}

/* src is a DER-encoded DSA signature.

** Returns a newly-allocated SECItem structure, pointing at a newly allocated

** buffer containing the "raw" DSA1 signature, which is 20 bytes of r,

** followed by 20 bytes of s.

*/

SECItem *

DSAU_DecodeDerSig(const SECItem *item)

{

    return common_DecodeDerSig(item, DSA1_SUBPRIME_LEN);

}

/* src is a DER-encoded ECDSA signature.

** Returns a newly-allocated SECItem structure, pointing at a newly allocated

** buffer containing the "raw" ECDSA signature of length len containing

** r followed by s (both padded to take up exactly len/2 bytes).

*/

SECItem *

DSAU_DecodeDerSigToLen(const SECItem *item, unsigned int len)

{

    return common_DecodeDerSig(item, len / 2);

}