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/*
* The contents of this file are subject to the Mozilla Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is the Netscape security libraries.
*
* The Initial Developer of the Original Code is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1994-2000 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the
* terms of the GNU General Public License Version 2 or later (the
* "GPL"), in which case the provisions of the GPL are applicable
* instead of those above. If you wish to allow use of your
* version of this file only under the terms of the GPL and not to
* allow others to use your version of this file under the MPL,
* indicate your decision by deleting the provisions above and
* replace them with the notice and other provisions required by
* the GPL. If you do not delete the provisions above, a recipient
* may use your version of this file under either the MPL or the
* GPL.
*/
#include "secasn1.h"
#include "secitem.h"
#include "prerr.h"
#ifndef DSA_SUBPRIME_LEN
#define DSA_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;
unsigned int cntDst = dest->len;
unsigned char c;
/* skip any leading zeros. */
while (cntSrc && !(c = *pSrc)) {
pSrc++;
cntSrc--;
}
if (!cntSrc) {
*pDst = 0;
dest->len = 1;
return;
}
if (c & 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" DSA signature, 20 bytes of r followed by 20 bytes of s.
** dest is the signature DER encoded. ?
*/
SECStatus
DSAU_EncodeDerSig(SECItem *dest, SECItem *src)
{
SECItem * item;
SECItem srcItem;
DSA_ASN1Signature sig;
unsigned char signedR[DSA_SUBPRIME_LEN + 1];
unsigned char signedS[DSA_SUBPRIME_LEN + 1];
PORT_Memset(&sig, 0, sizeof(sig));
PORT_Assert(src->len == 2 * DSA_SUBPRIME_LEN);
if (src->len != 2 * DSA_SUBPRIME_LEN) {
PORT_SetError( PR_INVALID_ARGUMENT_ERROR );
return SECFailure;
}
/* 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.data = signedR;
sig.r.len = sizeof signedR;
sig.s.data = signedS;
sig.s.len = sizeof signedR;
srcItem.data = src->data;
srcItem.len = DSA_SUBPRIME_LEN;
DSAU_ConvertUnsignedToSigned(&sig.r, &srcItem);
srcItem.data += DSA_SUBPRIME_LEN;
DSAU_ConvertUnsignedToSigned(&sig.s, &srcItem);
item = SEC_ASN1EncodeItem(NULL, dest, &sig, DSA_SignatureTemplate);
if (item == NULL)
return SECFailure;
/* XXX leak item? */
return SECSuccess;
}
/* src is a DER-encoded DSA signature.
** Returns a newly-allocated SECItem structure, pointing at a newly allocated
** buffer containing the "raw" DSA signature, which is 20 bytes of r,
** followed by 20 bytes of s.
*/
SECItem *
DSAU_DecodeDerSig(SECItem *item)
{
SECItem * result = NULL;
SECStatus status;
DSA_ASN1Signature sig;
SECItem dst;
PORT_Memset(&sig, 0, sizeof(sig));
result = PORT_ZNew(SECItem);
if (result == NULL)
goto loser;
result->len = 2 * DSA_SUBPRIME_LEN;
result->data = (unsigned char*)PORT_Alloc(2 * DSA_SUBPRIME_LEN);
if (result->data == NULL)
goto loser;
status = SEC_ASN1DecodeItem(NULL, &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 = DSA_SUBPRIME_LEN;
status = DSAU_ConvertSignedToFixedUnsigned(&dst, &sig.r);
if (status != SECSuccess)
goto loser;
dst.data += DSA_SUBPRIME_LEN;
status = DSAU_ConvertSignedToFixedUnsigned(&dst, &sig.s);
if (status != SECSuccess)
goto loser;
done:
if (sig.r.data != NULL)
PORT_Free(sig.r.data);
if (sig.s.data != NULL)
PORT_Free(sig.s.data);
return result;
loser:
if (result != NULL) {
SECITEM_FreeItem(result, PR_TRUE);
result = NULL;
}
goto done;
}
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