gecko-dev/security/nss/lib/smime/cmscipher.c

/*
 * 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.
 */

/*
 * Encryption/decryption routines for CMS implementation, none of which are exported.
 *
 * $Id: cmscipher.c,v 1.4 2001/12/07 01:36:12 relyea%netscape.com Exp $
 */

#include "cmslocal.h"

#include "secoid.h"
#include "secitem.h"
#include "pk11func.h"
#include "secerr.h"
#include "secpkcs5.h"

/*
 * -------------------------------------------------------------------
 * Cipher stuff.
 */

typedef SECStatus (*nss_cms_cipher_function) (void *, unsigned char *, unsigned int *,
					unsigned int, const unsigned char *, unsigned int);
typedef SECStatus (*nss_cms_cipher_destroy) (void *, PRBool);

#define BLOCK_SIZE 4096

struct NSSCMSCipherContextStr {
    void *		cx;			/* PK11 cipher context */
    nss_cms_cipher_function doit;
    nss_cms_cipher_destroy destroy;
    PRBool		encrypt;		/* encrypt / decrypt switch */
    int			block_size;		/* block & pad sizes for cipher */
    int			pad_size;
    int			pending_count;		/* pending data (not yet en/decrypted */
    unsigned char	pending_buf[BLOCK_SIZE];/* because of blocking */
};

/*
 * NSS_CMSCipherContext_StartDecrypt - create a cipher context to do decryption
 * based on the given bulk * encryption key and algorithm identifier (which may include an iv).
 *
 * XXX Once both are working, it might be nice to combine this and the
 * function below (for starting up encryption) into one routine, and just
 * have two simple cover functions which call it. 
 */
NSSCMSCipherContext *
NSS_CMSCipherContext_StartDecrypt(PK11SymKey *key, SECAlgorithmID *algid)
{
    NSSCMSCipherContext *cc;
    void *ciphercx;
    CK_MECHANISM_TYPE mechanism;
    SECItem *param;
    PK11SlotInfo *slot;
    SECOidTag algtag;

    algtag = SECOID_GetAlgorithmTag(algid);

    /* set param and mechanism */
    if (SEC_PKCS5IsAlgorithmPBEAlg(algid)) {
	CK_MECHANISM pbeMech, cryptoMech;
	SECItem *pbeParams;
	SEC_PKCS5KeyAndPassword *keyPwd;

	PORT_Memset(&pbeMech, 0, sizeof(CK_MECHANISM));
	PORT_Memset(&cryptoMech, 0, sizeof(CK_MECHANISM));

	/* HACK ALERT!
	 * in this case, key is not actually a PK11SymKey *, but a SEC_PKCS5KeyAndPassword *
	 */
	keyPwd = (SEC_PKCS5KeyAndPassword *)key;
	key = keyPwd->key;

	/* find correct PK11 mechanism and parameters to initialize pbeMech */
	pbeMech.mechanism = PK11_AlgtagToMechanism(algtag);
	pbeParams = PK11_ParamFromAlgid(algid);
	if (!pbeParams)
	    return NULL;
	pbeMech.pParameter = pbeParams->data;
	pbeMech.ulParameterLen = pbeParams->len;

	/* now map pbeMech to cryptoMech */
	if (PK11_MapPBEMechanismToCryptoMechanism(&pbeMech, &cryptoMech, keyPwd->pwitem,
						  PR_FALSE) != CKR_OK) { 
	    SECITEM_ZfreeItem(pbeParams, PR_TRUE);
	    return NULL;
	}
	SECITEM_ZfreeItem(pbeParams, PR_TRUE);

	/* and use it to initialize param & mechanism */
	if ((param = (SECItem *)PORT_ZAlloc(sizeof(SECItem))) == NULL)
	     return NULL;

	param->data = (unsigned char *)cryptoMech.pParameter;
	param->len = cryptoMech.ulParameterLen;
	mechanism = cryptoMech.mechanism;
    } else {
	mechanism = PK11_AlgtagToMechanism(algtag);
	if ((param = PK11_ParamFromAlgid(algid)) == NULL)
	    return NULL;
    }

    cc = (NSSCMSCipherContext *)PORT_ZAlloc(sizeof(NSSCMSCipherContext));
    if (cc == NULL) {
	SECITEM_FreeItem(param,PR_TRUE);
	return NULL;
    }

    /* figure out pad and block sizes */
    cc->pad_size = PK11_GetBlockSize(mechanism, param);
    slot = PK11_GetSlotFromKey(key);
    cc->block_size = PK11_IsHW(slot) ? BLOCK_SIZE : cc->pad_size;
    PK11_FreeSlot(slot);

    /* create PK11 cipher context */
    ciphercx = PK11_CreateContextBySymKey(mechanism, CKA_DECRYPT, key, param);
    SECITEM_FreeItem(param, PR_TRUE);
    if (ciphercx == NULL) {
	PORT_Free (cc);
	return NULL;
    }

    cc->cx = ciphercx;
    cc->doit =  (nss_cms_cipher_function) PK11_CipherOp;
    cc->destroy = (nss_cms_cipher_destroy) PK11_DestroyContext;
    cc->encrypt = PR_FALSE;
    cc->pending_count = 0;

    return cc;
}

/*
 * NSS_CMSCipherContext_StartEncrypt - create a cipher object to do encryption,
 * based on the given bulk encryption key and algorithm tag.  Fill in the algorithm
 * identifier (which may include an iv) appropriately.
 *
 * XXX Once both are working, it might be nice to combine this and the
 * function above (for starting up decryption) into one routine, and just
 * have two simple cover functions which call it. 
 */
NSSCMSCipherContext *
NSS_CMSCipherContext_StartEncrypt(PRArenaPool *poolp, PK11SymKey *key, SECAlgorithmID *algid)
{
    NSSCMSCipherContext *cc;
    void *ciphercx;
    SECItem *param;
    SECStatus rv;
    CK_MECHANISM_TYPE mechanism;
    PK11SlotInfo *slot;
    PRBool needToEncodeAlgid = PR_FALSE;
    SECOidTag algtag = SECOID_GetAlgorithmTag(algid);

    /* set param and mechanism */
    if (SEC_PKCS5IsAlgorithmPBEAlg(algid)) {
	CK_MECHANISM pbeMech, cryptoMech;
	SECItem *pbeParams;
	SEC_PKCS5KeyAndPassword *keyPwd;

	PORT_Memset(&pbeMech, 0, sizeof(CK_MECHANISM));
	PORT_Memset(&cryptoMech, 0, sizeof(CK_MECHANISM));

	/* HACK ALERT!
	 * in this case, key is not actually a PK11SymKey *, but a SEC_PKCS5KeyAndPassword *
	 */
	keyPwd = (SEC_PKCS5KeyAndPassword *)key;
	key = keyPwd->key;

	/* find correct PK11 mechanism and parameters to initialize pbeMech */
	pbeMech.mechanism = PK11_AlgtagToMechanism(algtag);
	pbeParams = PK11_ParamFromAlgid(algid);
	if (!pbeParams)
	    return NULL;
	pbeMech.pParameter = pbeParams->data;
	pbeMech.ulParameterLen = pbeParams->len;

	/* now map pbeMech to cryptoMech */
	if (PK11_MapPBEMechanismToCryptoMechanism(&pbeMech, &cryptoMech, keyPwd->pwitem,
						  PR_FALSE) != CKR_OK) { 
	    SECITEM_ZfreeItem(pbeParams, PR_TRUE);
	    return NULL;
	}
	SECITEM_ZfreeItem(pbeParams, PR_TRUE);

	/* and use it to initialize param & mechanism */
	if ((param = (SECItem *)PORT_ZAlloc(sizeof(SECItem))) == NULL)
	    return NULL;

	param->data = (unsigned char *)cryptoMech.pParameter;
	param->len = cryptoMech.ulParameterLen;
	mechanism = cryptoMech.mechanism;
    } else {
	mechanism = PK11_AlgtagToMechanism(algtag);
	if ((param = PK11_GenerateNewParam(mechanism, key)) == NULL)
	    return NULL;
	needToEncodeAlgid = PR_TRUE;
    }

    cc = (NSSCMSCipherContext *)PORT_ZAlloc(sizeof(NSSCMSCipherContext));
    if (cc == NULL)
	return NULL;

    /* now find pad and block sizes for our mechanism */
    cc->pad_size = PK11_GetBlockSize(mechanism,param);
    slot = PK11_GetSlotFromKey(key);
    cc->block_size = PK11_IsHW(slot) ? BLOCK_SIZE : cc->pad_size;
    PK11_FreeSlot(slot);

    /* and here we go, creating a PK11 cipher context */
    ciphercx = PK11_CreateContextBySymKey(mechanism, CKA_ENCRYPT, key, param);
    if (ciphercx == NULL) {
	PORT_Free(cc);
	cc = NULL;
	goto loser;
    }

    /*
     * These are placed after the CreateContextBySymKey() because some
     * mechanisms have to generate their IVs from their card (i.e. FORTEZZA).
     * Don't move it from here.
     * XXX is that right? the purpose of this is to get the correct algid
     *     containing the IVs etc. for encoding. this means we need to set this up
     *     BEFORE encoding the algid in the contentInfo, right?
     */
    if (needToEncodeAlgid) {
	rv = PK11_ParamToAlgid(algtag, param, poolp, algid);
	if(rv != SECSuccess) {
	    PORT_Free(cc);
	    cc = NULL;
	    goto loser;
	}
    }

    cc->cx = ciphercx;
    cc->doit = (nss_cms_cipher_function)PK11_CipherOp;
    cc->destroy = (nss_cms_cipher_destroy)PK11_DestroyContext;
    cc->encrypt = PR_TRUE;
    cc->pending_count = 0;

loser:
    SECITEM_FreeItem(param, PR_TRUE);

    return cc;
}

void
NSS_CMSCipherContext_Destroy(NSSCMSCipherContext *cc)
{
    PORT_Assert(cc != NULL);
    if (cc == NULL)
	return;
    (*cc->destroy)(cc->cx, PR_TRUE);
    PORT_Free(cc);
}

/*
 * NSS_CMSCipherContext_DecryptLength - find the output length of the next call to decrypt.
 *
 * cc - the cipher context
 * input_len - number of bytes used as input
 * final - true if this is the final chunk of data
 *
 * Result can be used to perform memory allocations.  Note that the amount
 * is exactly accurate only when not doing a block cipher or when final
 * is false, otherwise it is an upper bound on the amount because until
 * we see the data we do not know how many padding bytes there are
 * (always between 1 and bsize).
 *
 * Note that this can return zero, which does not mean that the decrypt
 * operation can be skipped!  (It simply means that there are not enough
 * bytes to make up an entire block; the bytes will be reserved until
 * there are enough to encrypt/decrypt at least one block.)  However,
 * if zero is returned it *does* mean that no output buffer need be
 * passed in to the subsequent decrypt operation, as no output bytes
 * will be stored.
 */
unsigned int
NSS_CMSCipherContext_DecryptLength(NSSCMSCipherContext *cc, unsigned int input_len, PRBool final)
{
    int blocks, block_size;

    PORT_Assert (! cc->encrypt);

    block_size = cc->block_size;

    /*
     * If this is not a block cipher, then we always have the same
     * number of output bytes as we had input bytes.
     */
    if (block_size == 0)
	return input_len;

    /*
     * On the final call, we will always use up all of the pending
     * bytes plus all of the input bytes, *but*, there will be padding
     * at the end and we cannot predict how many bytes of padding we
     * will end up removing.  The amount given here is actually known
     * to be at least 1 byte too long (because we know we will have
     * at least 1 byte of padding), but seemed clearer/better to me.
     */
    if (final)
	return cc->pending_count + input_len;

    /*
     * Okay, this amount is exactly what we will output on the
     * next cipher operation.  We will always hang onto the last
     * 1 - block_size bytes for non-final operations.  That is,
     * we will do as many complete blocks as we can *except* the
     * last block (complete or partial).  (This is because until
     * we know we are at the end, we cannot know when to interpret
     * and removing the padding byte(s), which are guaranteed to
     * be there.)
     */
    blocks = (cc->pending_count + input_len - 1) / block_size;
    return blocks * block_size;
}

/*
 * NSS_CMSCipherContext_EncryptLength - find the output length of the next call to encrypt.
 *
 * cc - the cipher context
 * input_len - number of bytes used as input
 * final - true if this is the final chunk of data
 *
 * Result can be used to perform memory allocations.
 *
 * Note that this can return zero, which does not mean that the encrypt
 * operation can be skipped!  (It simply means that there are not enough
 * bytes to make up an entire block; the bytes will be reserved until
 * there are enough to encrypt/decrypt at least one block.)  However,
 * if zero is returned it *does* mean that no output buffer need be
 * passed in to the subsequent encrypt operation, as no output bytes
 * will be stored.
 */
unsigned int
NSS_CMSCipherContext_EncryptLength(NSSCMSCipherContext *cc, unsigned int input_len, PRBool final)
{
    int blocks, block_size;
    int pad_size;

    PORT_Assert (cc->encrypt);

    block_size = cc->block_size;
    pad_size = cc->pad_size;

    /*
     * If this is not a block cipher, then we always have the same
     * number of output bytes as we had input bytes.
     */
    if (block_size == 0)
	return input_len;

    /*
     * On the final call, we only send out what we need for
     * remaining bytes plus the padding.  (There is always padding,
     * so even if we have an exact number of blocks as input, we
     * will add another full block that is just padding.)
     */
    if (final) {
	if (pad_size == 0) {
    	    return cc->pending_count + input_len;
	} else {
    	    blocks = (cc->pending_count + input_len) / pad_size;
	    blocks++;
	    return blocks*pad_size;
	}
    }

    /*
     * Now, count the number of complete blocks of data we have.
     */
    blocks = (cc->pending_count + input_len) / block_size;


    return blocks * block_size;
}


/*
 * NSS_CMSCipherContext_Decrypt - do the decryption
 *
 * cc - the cipher context
 * output - buffer for decrypted result bytes
 * output_len_p - number of bytes in output
 * max_output_len - upper bound on bytes to put into output
 * input - pointer to input bytes
 * input_len - number of input bytes
 * final - true if this is the final chunk of data
 *
 * Decrypts a given length of input buffer (starting at "input" and
 * containing "input_len" bytes), placing the decrypted bytes in
 * "output" and storing the output length in "*output_len_p".
 * "cc" is the return value from NSS_CMSCipher_StartDecrypt.
 * When "final" is true, this is the last of the data to be decrypted.
 *
 * This is much more complicated than it sounds when the cipher is
 * a block-type, meaning that the decryption function will only
 * operate on whole blocks.  But our caller is operating stream-wise,
 * and can pass in any number of bytes.  So we need to keep track
 * of block boundaries.  We save excess bytes between calls in "cc".
 * We also need to determine which bytes are padding, and remove
 * them from the output.  We can only do this step when we know we
 * have the final block of data.  PKCS #7 specifies that the padding
 * used for a block cipher is a string of bytes, each of whose value is
 * the same as the length of the padding, and that all data is padded.
 * (Even data that starts out with an exact multiple of blocks gets
 * added to it another block, all of which is padding.)
 */ 
SECStatus
NSS_CMSCipherContext_Decrypt(NSSCMSCipherContext *cc, unsigned char *output,
		  unsigned int *output_len_p, unsigned int max_output_len,
		  const unsigned char *input, unsigned int input_len,
		  PRBool final)
{
    int blocks, bsize, pcount, padsize;
    unsigned int max_needed, ifraglen, ofraglen, output_len;
    unsigned char *pbuf;
    SECStatus rv;

    PORT_Assert (! cc->encrypt);

    /*
     * Check that we have enough room for the output.  Our caller should
     * already handle this; failure is really an internal error (i.e. bug).
     */
    max_needed = NSS_CMSCipherContext_DecryptLength(cc, input_len, final);
    PORT_Assert (max_output_len >= max_needed);
    if (max_output_len < max_needed) {
	/* PORT_SetError (XXX); */
	return SECFailure;
    }

    /*
     * hardware encryption does not like small decryption sizes here, so we
     * allow both blocking and padding.
     */
    bsize = cc->block_size;
    padsize = cc->pad_size;

    /*
     * When no blocking or padding work to do, we can simply call the
     * cipher function and we are done.
     */
    if (bsize == 0) {
	return (* cc->doit) (cc->cx, output, output_len_p, max_output_len,
			      input, input_len);
    }

    pcount = cc->pending_count;
    pbuf = cc->pending_buf;

    output_len = 0;

    if (pcount) {
	/*
	 * Try to fill in an entire block, starting with the bytes
	 * we already have saved away.
	 */
	while (input_len && pcount < bsize) {
	    pbuf[pcount++] = *input++;
	    input_len--;
	}
	/*
	 * If we have at most a whole block and this is not our last call,
	 * then we are done for now.  (We do not try to decrypt a lone
	 * single block because we cannot interpret the padding bytes
	 * until we know we are handling the very last block of all input.)
	 */
	if (input_len == 0 && !final) {
	    cc->pending_count = pcount;
	    if (output_len_p)
		*output_len_p = 0;
	    return SECSuccess;
	}
	/*
	 * Given the logic above, we expect to have a full block by now.
	 * If we do not, there is something wrong, either with our own
	 * logic or with (length of) the data given to us.
	 */
	PORT_Assert ((padsize == 0) || (pcount % padsize) == 0);
	if ((padsize != 0) && (pcount % padsize) != 0) {
	    PORT_Assert (final);	
	    PORT_SetError (SEC_ERROR_BAD_DATA);
	    return SECFailure;
	}
	/*
	 * Decrypt the block.
	 */
	rv = (*cc->doit)(cc->cx, output, &ofraglen, max_output_len,
			    pbuf, pcount);
	if (rv != SECSuccess)
	    return rv;

	/*
	 * For now anyway, all of our ciphers have the same number of
	 * bytes of output as they do input.  If this ever becomes untrue,
	 * then NSS_CMSCipherContext_DecryptLength needs to be made smarter!
	 */
	PORT_Assert(ofraglen == pcount);

	/*
	 * Account for the bytes now in output.
	 */
	max_output_len -= ofraglen;
	output_len += ofraglen;
	output += ofraglen;
    }

    /*
     * If this is our last call, we expect to have an exact number of
     * blocks left to be decrypted; we will decrypt them all.
     * 
     * If not our last call, we always save between 1 and bsize bytes
     * until next time.  (We must do this because we cannot be sure
     * that none of the decrypted bytes are padding bytes until we
     * have at least another whole block of data.  You cannot tell by
     * looking -- the data could be anything -- you can only tell by
     * context, knowing you are looking at the last block.)  We could
     * decrypt a whole block now but it is easier if we just treat it
     * the same way we treat partial block bytes.
     */
    if (final) {
	if (padsize) {
	    blocks = input_len / padsize;
	    ifraglen = blocks * padsize;
	} else ifraglen = input_len;
	PORT_Assert (ifraglen == input_len);

	if (ifraglen != input_len) {
	    PORT_SetError(SEC_ERROR_BAD_DATA);
	    return SECFailure;
	}
    } else {
	blocks = (input_len - 1) / bsize;
	ifraglen = blocks * bsize;
	PORT_Assert (ifraglen < input_len);

	pcount = input_len - ifraglen;
	PORT_Memcpy (pbuf, input + ifraglen, pcount);
	cc->pending_count = pcount;
    }

    if (ifraglen) {
	rv = (* cc->doit)(cc->cx, output, &ofraglen, max_output_len,
			    input, ifraglen);
	if (rv != SECSuccess)
	    return rv;

	/*
	 * For now anyway, all of our ciphers have the same number of
	 * bytes of output as they do input.  If this ever becomes untrue,
	 * then sec_PKCS7DecryptLength needs to be made smarter!
	 */
	PORT_Assert (ifraglen == ofraglen);
	if (ifraglen != ofraglen) {
	    PORT_SetError(SEC_ERROR_BAD_DATA);
	    return SECFailure;
	}

	output_len += ofraglen;
    } else {
	ofraglen = 0;
    }

    /*
     * If we just did our very last block, "remove" the padding by
     * adjusting the output length.
     */
    if (final && (padsize != 0)) {
	unsigned int padlen = *(output + ofraglen - 1);
	PORT_Assert (padlen > 0 && padlen <= padsize);
	if (padlen == 0 || padlen > padsize) {
	    PORT_SetError(SEC_ERROR_BAD_DATA);
	    return SECFailure;
	}
	output_len -= padlen;
    }

    PORT_Assert (output_len_p != NULL || output_len == 0);
    if (output_len_p != NULL)
	*output_len_p = output_len;

    return SECSuccess;
}

/*
 * NSS_CMSCipherContext_Encrypt - do the encryption
 *
 * cc - the cipher context
 * output - buffer for decrypted result bytes
 * output_len_p - number of bytes in output
 * max_output_len - upper bound on bytes to put into output
 * input - pointer to input bytes
 * input_len - number of input bytes
 * final - true if this is the final chunk of data
 *
 * Encrypts a given length of input buffer (starting at "input" and
 * containing "input_len" bytes), placing the encrypted bytes in
 * "output" and storing the output length in "*output_len_p".
 * "cc" is the return value from NSS_CMSCipher_StartEncrypt.
 * When "final" is true, this is the last of the data to be encrypted.
 *
 * This is much more complicated than it sounds when the cipher is
 * a block-type, meaning that the encryption function will only
 * operate on whole blocks.  But our caller is operating stream-wise,
 * and can pass in any number of bytes.  So we need to keep track
 * of block boundaries.  We save excess bytes between calls in "cc".
 * We also need to add padding bytes at the end.  PKCS #7 specifies
 * that the padding used for a block cipher is a string of bytes,
 * each of whose value is the same as the length of the padding,
 * and that all data is padded.  (Even data that starts out with
 * an exact multiple of blocks gets added to it another block,
 * all of which is padding.)
 *
 * XXX I would kind of like to combine this with the function above
 * which does decryption, since they have a lot in common.  But the
 * tricky parts about padding and filling blocks would be much
 * harder to read that way, so I left them separate.  At least for
 * now until it is clear that they are right.
 */ 
SECStatus
NSS_CMSCipherContext_Encrypt(NSSCMSCipherContext *cc, unsigned char *output,
		  unsigned int *output_len_p, unsigned int max_output_len,
		  const unsigned char *input, unsigned int input_len,
		  PRBool final)
{
    int blocks, bsize, padlen, pcount, padsize;
    unsigned int max_needed, ifraglen, ofraglen, output_len;
    unsigned char *pbuf;
    SECStatus rv;

    PORT_Assert (cc->encrypt);

    /*
     * Check that we have enough room for the output.  Our caller should
     * already handle this; failure is really an internal error (i.e. bug).
     */
    max_needed = NSS_CMSCipherContext_EncryptLength (cc, input_len, final);
    PORT_Assert (max_output_len >= max_needed);
    if (max_output_len < max_needed) {
	/* PORT_SetError (XXX); */
	return SECFailure;
    }

    bsize = cc->block_size;
    padsize = cc->pad_size;

    /*
     * When no blocking and padding work to do, we can simply call the
     * cipher function and we are done.
     */
    if (bsize == 0) {
	return (*cc->doit)(cc->cx, output, output_len_p, max_output_len,
			      input, input_len);
    }

    pcount = cc->pending_count;
    pbuf = cc->pending_buf;

    output_len = 0;

    if (pcount) {
	/*
	 * Try to fill in an entire block, starting with the bytes
	 * we already have saved away.
	 */
	while (input_len && pcount < bsize) {
	    pbuf[pcount++] = *input++;
	    input_len--;
	}
	/*
	 * If we do not have a full block and we know we will be
	 * called again, then we are done for now.
	 */
	if (pcount < bsize && !final) {
	    cc->pending_count = pcount;
	    if (output_len_p != NULL)
		*output_len_p = 0;
	    return SECSuccess;
	}
	/*
	 * If we have a whole block available, encrypt it.
	 */
	if ((padsize == 0) || (pcount % padsize) == 0) {
	    rv = (* cc->doit) (cc->cx, output, &ofraglen, max_output_len,
				pbuf, pcount);
	    if (rv != SECSuccess)
		return rv;

	    /*
	     * For now anyway, all of our ciphers have the same number of
	     * bytes of output as they do input.  If this ever becomes untrue,
	     * then sec_PKCS7EncryptLength needs to be made smarter!
	     */
	    PORT_Assert (ofraglen == pcount);

	    /*
	     * Account for the bytes now in output.
	     */
	    max_output_len -= ofraglen;
	    output_len += ofraglen;
	    output += ofraglen;

	    pcount = 0;
	}
    }

    if (input_len) {
	PORT_Assert (pcount == 0);

	blocks = input_len / bsize;
	ifraglen = blocks * bsize;

	if (ifraglen) {
	    rv = (* cc->doit) (cc->cx, output, &ofraglen, max_output_len,
				input, ifraglen);
	    if (rv != SECSuccess)
		return rv;

	    /*
	     * For now anyway, all of our ciphers have the same number of
	     * bytes of output as they do input.  If this ever becomes untrue,
	     * then sec_PKCS7EncryptLength needs to be made smarter!
	     */
	    PORT_Assert (ifraglen == ofraglen);

	    max_output_len -= ofraglen;
	    output_len += ofraglen;
	    output += ofraglen;
	}

	pcount = input_len - ifraglen;
	PORT_Assert (pcount < bsize);
	if (pcount)
	    PORT_Memcpy (pbuf, input + ifraglen, pcount);
    }

    if (final) {
	padlen = padsize - (pcount % padsize);
	PORT_Memset (pbuf + pcount, padlen, padlen);
	rv = (* cc->doit) (cc->cx, output, &ofraglen, max_output_len,
			    pbuf, pcount+padlen);
	if (rv != SECSuccess)
	    return rv;

	/*
	 * For now anyway, all of our ciphers have the same number of
	 * bytes of output as they do input.  If this ever becomes untrue,
	 * then sec_PKCS7EncryptLength needs to be made smarter!
	 */
	PORT_Assert (ofraglen == (pcount+padlen));
	output_len += ofraglen;
    } else {
	cc->pending_count = pcount;
    }

    PORT_Assert (output_len_p != NULL || output_len == 0);
    if (output_len_p != NULL)
	*output_len_p = output_len;

    return SECSuccess;
}