gecko-dev/security/nss/lib/pkcs7/secmime.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.
 */

/*
 * Stuff specific to S/MIME policy and interoperability.
 * Depends on PKCS7, but there should be no dependency the other way around.
 *
 * $Id: secmime.c,v 1.2 2002/12/12 06:05:36 nelsonb%netscape.com Exp $
 */

#include "secmime.h"
#include "secoid.h"
#include "pk11func.h"
#include "ciferfam.h"	/* for CIPHER_FAMILY symbols */
#include "secasn1.h"
#include "secitem.h"
#include "cert.h"
#include "key.h"
#include "secerr.h"

typedef struct smime_cipher_map_struct {
    unsigned long cipher;
    SECOidTag algtag;
    SECItem *parms;
} smime_cipher_map;

/*
 * These are macros because I think some subsequent parameters,
 * like those for RC5, will want to use them, too, separately.
 */
#define SMIME_DER_INTVAL_16	SEC_ASN1_INTEGER, 0x01, 0x10
#define SMIME_DER_INTVAL_40	SEC_ASN1_INTEGER, 0x01, 0x28
#define SMIME_DER_INTVAL_64	SEC_ASN1_INTEGER, 0x01, 0x40
#define SMIME_DER_INTVAL_128	SEC_ASN1_INTEGER, 0x02, 0x00, 0x80

#ifdef SMIME_DOES_RC5	/* will be needed; quiet unused warning for now */
static unsigned char smime_int16[] = { SMIME_DER_INTVAL_16 };
#endif
static unsigned char smime_int40[] = { SMIME_DER_INTVAL_40 };
static unsigned char smime_int64[] = { SMIME_DER_INTVAL_64 };
static unsigned char smime_int128[] = { SMIME_DER_INTVAL_128 };

static SECItem smime_rc2p40 = { siBuffer, smime_int40, sizeof(smime_int40) };
static SECItem smime_rc2p64 = { siBuffer, smime_int64, sizeof(smime_int64) };
static SECItem smime_rc2p128 = { siBuffer, smime_int128, sizeof(smime_int128) };

static smime_cipher_map smime_cipher_maps[] = {
    { SMIME_RC2_CBC_40,		SEC_OID_RC2_CBC,	&smime_rc2p40 },
    { SMIME_RC2_CBC_64,		SEC_OID_RC2_CBC,	&smime_rc2p64 },
    { SMIME_RC2_CBC_128,	SEC_OID_RC2_CBC,	&smime_rc2p128 },
#ifdef SMIME_DOES_RC5
    { SMIME_RC5PAD_64_16_40,	SEC_OID_RC5_CBC_PAD,	&smime_rc5p40 },
    { SMIME_RC5PAD_64_16_64,	SEC_OID_RC5_CBC_PAD,	&smime_rc5p64 },
    { SMIME_RC5PAD_64_16_128,	SEC_OID_RC5_CBC_PAD,	&smime_rc5p128 },
#endif
    { SMIME_DES_CBC_56,		SEC_OID_DES_CBC,	NULL },
    { SMIME_DES_EDE3_168,	SEC_OID_DES_EDE3_CBC,	NULL },
    { SMIME_FORTEZZA,		SEC_OID_FORTEZZA_SKIPJACK, NULL}
};

/*
 * Note, the following value really just needs to be an upper bound
 * on the ciphers.
 */
static const int smime_symmetric_count = sizeof(smime_cipher_maps)
					 / sizeof(smime_cipher_map);

static unsigned long *smime_prefs, *smime_newprefs;
static int smime_current_pref_index = 0;
static PRBool smime_prefs_complete = PR_FALSE;
static PRBool smime_prefs_changed = PR_TRUE;

static unsigned long smime_policy_bits = 0;


static int
smime_mapi_by_cipher (unsigned long cipher)
{
    int i;

    for (i = 0; i < smime_symmetric_count; i++) {
	if (smime_cipher_maps[i].cipher == cipher)
	    break;
    }

    if (i == smime_symmetric_count)
	return -1;

    return i;
}


/*
 * this function locally records the user's preference
 */
SECStatus 
SECMIME_EnableCipher(long which, int on)
{
    unsigned long mask;

    if (smime_newprefs == NULL || smime_prefs_complete) {
	/*
	 * This is either the very first time, or we are starting over.
	 */
	smime_newprefs = (unsigned long*)PORT_ZAlloc (smime_symmetric_count
				      * sizeof(*smime_newprefs));
	if (smime_newprefs == NULL)
	    return SECFailure;
	smime_current_pref_index = 0;
	smime_prefs_complete = PR_FALSE;
    }

    mask = which & CIPHER_FAMILYID_MASK;
    if (mask == CIPHER_FAMILYID_MASK) {
    	/*
	 * This call signifies that all preferences have been set.
	 * Move "newprefs" over, after checking first whether or
	 * not the new ones are different from the old ones.
	 */
	if (smime_prefs != NULL) {
	    if (PORT_Memcmp (smime_prefs, smime_newprefs,
			     smime_symmetric_count * sizeof(*smime_prefs)) == 0)
		smime_prefs_changed = PR_FALSE;
	    else
		smime_prefs_changed = PR_TRUE;
	    PORT_Free (smime_prefs);
	}

	smime_prefs = smime_newprefs;
	smime_prefs_complete = PR_TRUE;
	return SECSuccess;
    }

    PORT_Assert (mask == CIPHER_FAMILYID_SMIME);
    if (mask != CIPHER_FAMILYID_SMIME) {
	/* XXX set an error! */
    	return SECFailure;
    }

    if (on) {
	PORT_Assert (smime_current_pref_index < smime_symmetric_count);
	if (smime_current_pref_index >= smime_symmetric_count) {
	    /* XXX set an error! */
	    return SECFailure;
	}

	smime_newprefs[smime_current_pref_index++] = which;
    }

    return SECSuccess;
}


/*
 * this function locally records the export policy
 */
SECStatus 
SECMIME_SetPolicy(long which, int on)
{
    unsigned long mask;

    PORT_Assert ((which & CIPHER_FAMILYID_MASK) == CIPHER_FAMILYID_SMIME);
    if ((which & CIPHER_FAMILYID_MASK) != CIPHER_FAMILYID_SMIME) {
	/* XXX set an error! */
    	return SECFailure;
    }

    which &= ~CIPHER_FAMILYID_MASK;

    PORT_Assert (which < 32);	/* bits in the long */
    if (which >= 32) {
	/* XXX set an error! */
    	return SECFailure;
    }

    mask = 1UL << which;

    if (on) {
    	smime_policy_bits |= mask;
    } else {
    	smime_policy_bits &= ~mask;
    }

    return SECSuccess;
}


/*
 * Based on the given algorithm (including its parameters, in some cases!)
 * and the given key (may or may not be inspected, depending on the
 * algorithm), find the appropriate policy algorithm specification
 * and return it.  If no match can be made, -1 is returned.
 */
static long
smime_policy_algorithm (SECAlgorithmID *algid, PK11SymKey *key)
{
    SECOidTag algtag;

    algtag = SECOID_GetAlgorithmTag (algid);
    switch (algtag) {
      case SEC_OID_RC2_CBC:
	{
	    unsigned int keylen_bits;

	    keylen_bits = PK11_GetKeyStrength (key, algid);
	    switch (keylen_bits) {
	      case 40:
		return SMIME_RC2_CBC_40;
	      case 64:
		return SMIME_RC2_CBC_64;
	      case 128:
		return SMIME_RC2_CBC_128;
	      default:
		break;
	    }
	}
	break;
      case SEC_OID_DES_CBC:
	return SMIME_DES_CBC_56;
      case SEC_OID_DES_EDE3_CBC:
	return SMIME_DES_EDE3_168;
      case SEC_OID_FORTEZZA_SKIPJACK:
	return SMIME_FORTEZZA;
#ifdef SMIME_DOES_RC5
      case SEC_OID_RC5_CBC_PAD:
	PORT_Assert (0);	/* XXX need to pull out parameters and match */
	break;
#endif
      default:
	break;
    }

    return -1;
}


static PRBool
smime_cipher_allowed (unsigned long which)
{
    unsigned long mask;

    which &= ~CIPHER_FAMILYID_MASK;
    PORT_Assert (which < 32);	/* bits per long (min) */
    if (which >= 32)
	return PR_FALSE;

    mask = 1UL << which;
    if ((mask & smime_policy_bits) == 0)
	return PR_FALSE;

    return PR_TRUE;
}


PRBool
SECMIME_DecryptionAllowed(SECAlgorithmID *algid, PK11SymKey *key)
{
    long which;

    which = smime_policy_algorithm (algid, key);
    if (which < 0)
	return PR_FALSE;

    return smime_cipher_allowed ((unsigned long)which);
}


/*
 * Does the current policy allow *any* S/MIME encryption (or decryption)?
 *
 * This tells whether or not *any* S/MIME encryption can be done,
 * according to policy.  Callers may use this to do nicer user interface
 * (say, greying out a checkbox so a user does not even try to encrypt
 * a message when they are not allowed to) or for any reason they want
 * to check whether S/MIME encryption (or decryption, for that matter)
 * may be done.
 *
 * It takes no arguments.  The return value is a simple boolean:
 *   PR_TRUE means encryption (or decryption) is *possible*
 *	(but may still fail due to other reasons, like because we cannot
 *	find all the necessary certs, etc.; PR_TRUE is *not* a guarantee)
 *   PR_FALSE means encryption (or decryption) is not permitted
 *
 * There are no errors from this routine.
 */
PRBool
SECMIME_EncryptionPossible (void)
{
    if (smime_policy_bits != 0)
	return PR_TRUE;

    return PR_FALSE;
}


/*
 * XXX Would like the "parameters" field to be a SECItem *, but the
 * encoder is having trouble with optional pointers to an ANY.  Maybe
 * once that is fixed, can change this back...
 */
typedef struct smime_capability_struct {
    unsigned long cipher;	/* local; not part of encoding */
    SECOidTag capIDTag;		/* local; not part of encoding */
    SECItem capabilityID;
    SECItem parameters;
} smime_capability;

static const SEC_ASN1Template smime_capability_template[] = {
    { SEC_ASN1_SEQUENCE,
	  0, NULL, sizeof(smime_capability) },
    { SEC_ASN1_OBJECT_ID,
	  offsetof(smime_capability,capabilityID), },
    { SEC_ASN1_OPTIONAL | SEC_ASN1_ANY,
	  offsetof(smime_capability,parameters), },
    { 0, }
};

static const SEC_ASN1Template smime_capabilities_template[] = {
    { SEC_ASN1_SEQUENCE_OF, 0, smime_capability_template }
};



static void
smime_fill_capability (smime_capability *cap)
{
    unsigned long cipher;
    SECOidTag algtag;
    int i;

    algtag = SECOID_FindOIDTag (&(cap->capabilityID));

    for (i = 0; i < smime_symmetric_count; i++) {
	if (smime_cipher_maps[i].algtag != algtag)
	    continue;
	/*
	 * XXX If SECITEM_CompareItem allowed NULLs as arguments (comparing
	 * 2 NULLs as equal and NULL and non-NULL as not equal), we could
	 * use that here instead of all of the following comparison code.
	 */
	if (cap->parameters.data != NULL) {
	    if (smime_cipher_maps[i].parms == NULL)
		continue;
	    if (cap->parameters.len != smime_cipher_maps[i].parms->len)
		continue;
	    if (PORT_Memcmp (cap->parameters.data,
			     smime_cipher_maps[i].parms->data,
			     cap->parameters.len) == 0)
		break;
	} else if (smime_cipher_maps[i].parms == NULL) {
	    break;
	}
    }

    if (i == smime_symmetric_count)
	cipher = 0;
    else
	cipher = smime_cipher_maps[i].cipher;

    cap->cipher = cipher;
    cap->capIDTag = algtag;
}


static long
smime_choose_cipher (CERTCertificate *scert, CERTCertificate **rcerts)
{
    PRArenaPool *poolp;
    long chosen_cipher;
    int *cipher_abilities;
    int *cipher_votes;
    int strong_mapi;
    int rcount, mapi, max, i;
	PRBool isFortezza = PK11_FortezzaHasKEA(scert);

    if (smime_policy_bits == 0) {
	PORT_SetError (SEC_ERROR_BAD_EXPORT_ALGORITHM);
	return -1;
    }

    chosen_cipher = SMIME_RC2_CBC_40;		/* the default, LCD */

    poolp = PORT_NewArena (1024);		/* XXX what is right value? */
    if (poolp == NULL)
	goto done;

    cipher_abilities = (int*)PORT_ArenaZAlloc (poolp,
					 smime_symmetric_count * sizeof(int));
    if (cipher_abilities == NULL)
	goto done;

    cipher_votes = (int*)PORT_ArenaZAlloc (poolp,
				     smime_symmetric_count * sizeof(int));
    if (cipher_votes == NULL)
	goto done;

    /*
     * XXX Should have a #define somewhere which specifies default
     * strong cipher.  (Or better, a way to configure, which would
     * take Fortezza into account as well.)
     */

    /* If the user has the Fortezza preference turned on, make
     *  that the strong cipher. Otherwise, use triple-DES. */
    strong_mapi = -1;
    if (isFortezza) {
	for(i=0;i < smime_current_pref_index && strong_mapi < 0;i++)
	{
	    if (smime_prefs[i] == SMIME_FORTEZZA)
		strong_mapi = smime_mapi_by_cipher(SMIME_FORTEZZA);
	}
    }

    if (strong_mapi == -1)
	strong_mapi = smime_mapi_by_cipher (SMIME_DES_EDE3_168);

    PORT_Assert (strong_mapi >= 0);

    for (rcount = 0; rcerts[rcount] != NULL; rcount++) {
	SECItem *profile;
	smime_capability **caps;
	int capi, pref;
	SECStatus dstat;

	pref = smime_symmetric_count;
	profile = CERT_FindSMimeProfile (rcerts[rcount]);
	if (profile != NULL && profile->data != NULL && profile->len > 0) {
	    caps = NULL;
	    dstat = SEC_ASN1DecodeItem (poolp, &caps,
					smime_capabilities_template,
					profile);
	    if (dstat == SECSuccess && caps != NULL) {
		for (capi = 0; caps[capi] != NULL; capi++) {
		    smime_fill_capability (caps[capi]);
		    mapi = smime_mapi_by_cipher (caps[capi]->cipher);
		    if (mapi >= 0) {
			cipher_abilities[mapi]++;
			cipher_votes[mapi] += pref;
			--pref;
		    }
		}
	    }
	} else {
	    SECKEYPublicKey *key;
	    unsigned int pklen_bits;

	    /*
	     * XXX This is probably only good for RSA keys.  What I would
	     * really like is a function to just say;  Is the public key in
	     * this cert an export-length key?  Then I would not have to
	     * know things like the value 512, or the kind of key, or what
	     * a subjectPublicKeyInfo is, etc.
	     */
	    key = CERT_ExtractPublicKey (rcerts[rcount]);
	    if (key != NULL) {
		pklen_bits = SECKEY_PublicKeyStrength (key) * 8;
		SECKEY_DestroyPublicKey (key);

		if (pklen_bits > 512) {
		    cipher_abilities[strong_mapi]++;
		    cipher_votes[strong_mapi] += pref;
		}
	    }
	}
	if (profile != NULL)
	    SECITEM_FreeItem (profile, PR_TRUE);
    }

    max = 0;
    for (mapi = 0; mapi < smime_symmetric_count; mapi++) {
	if (cipher_abilities[mapi] != rcount)
	    continue;
	if (! smime_cipher_allowed (smime_cipher_maps[mapi].cipher))
	    continue;
	if (!isFortezza  && (smime_cipher_maps[mapi].cipher == SMIME_FORTEZZA))
		continue;
	if (cipher_votes[mapi] > max) {
	    chosen_cipher = smime_cipher_maps[mapi].cipher;
	    max = cipher_votes[mapi];
	} /* XXX else if a tie, let scert break it? */
    }

done:
    if (poolp != NULL)
	PORT_FreeArena (poolp, PR_FALSE);

    return chosen_cipher;
}


/*
 * XXX This is a hack for now to satisfy our current interface.
 * Eventually, with more parameters needing to be specified, just
 * looking up the keysize is not going to be sufficient.
 */
static int
smime_keysize_by_cipher (unsigned long which)
{
    int keysize;

    switch (which) {
      case SMIME_RC2_CBC_40:
	keysize = 40;
	break;
      case SMIME_RC2_CBC_64:
	keysize = 64;
	break;
      case SMIME_RC2_CBC_128:
	keysize = 128;
	break;
#ifdef SMIME_DOES_RC5
      case SMIME_RC5PAD_64_16_40:
      case SMIME_RC5PAD_64_16_64:
      case SMIME_RC5PAD_64_16_128:
	/* XXX See comment above; keysize is not enough... */
	PORT_Assert (0);
	PORT_SetError (SEC_ERROR_INVALID_ALGORITHM);
	keysize = -1;
	break;
#endif
      case SMIME_DES_CBC_56:
      case SMIME_DES_EDE3_168:
      case SMIME_FORTEZZA:
	/*
	 * These are special; since the key size is fixed, we actually
	 * want to *avoid* specifying a key size.
	 */
	keysize = 0;
	break;
      default:
	keysize = -1;
	break;
    }

    return keysize;
}


/*
 * Start an S/MIME encrypting context.
 *
 * "scert" is the cert for the sender.  It will be checked for validity.
 * "rcerts" are the certs for the recipients.  They will also be checked.
 *
 * "certdb" is the cert database to use for verifying the certs.
 * It can be NULL if a default database is available (like in the client).
 *
 * This function already does all of the stuff specific to S/MIME protocol
 * and local policy; the return value just needs to be passed to
 * SEC_PKCS7Encode() or to SEC_PKCS7EncoderStart() to create the encoded data,
 * and finally to SEC_PKCS7DestroyContentInfo().
 *
 * An error results in a return value of NULL and an error set.
 * (Retrieve specific errors via PORT_GetError()/XP_GetError().)
 */
SEC_PKCS7ContentInfo *
SECMIME_CreateEncrypted(CERTCertificate *scert,
			CERTCertificate **rcerts,
			CERTCertDBHandle *certdb,
			SECKEYGetPasswordKey pwfn,
			void *pwfn_arg)
{
    SEC_PKCS7ContentInfo *cinfo;
    long cipher;
    SECOidTag encalg;
    int keysize;
    int mapi, rci;

    cipher = smime_choose_cipher (scert, rcerts);
    if (cipher < 0)
	return NULL;

    mapi = smime_mapi_by_cipher (cipher);
    if (mapi < 0)
	return NULL;

    /*
     * XXX This is stretching it -- CreateEnvelopedData should probably
     * take a cipher itself of some sort, because we cannot know what the
     * future will bring in terms of parameters for each type of algorithm.
     * For example, just an algorithm and keysize is *not* sufficient to
     * fully specify the usage of RC5 (which also needs to know rounds and
     * block size).  Work this out into a better API!
     */
    encalg = smime_cipher_maps[mapi].algtag;
    keysize = smime_keysize_by_cipher (cipher);
    if (keysize < 0)
	return NULL;

    cinfo = SEC_PKCS7CreateEnvelopedData (scert, certUsageEmailRecipient,
					  certdb, encalg, keysize,
					  pwfn, pwfn_arg);
    if (cinfo == NULL)
	return NULL;

    for (rci = 0; rcerts[rci] != NULL; rci++) {
	if (rcerts[rci] == scert)
	    continue;
	if (SEC_PKCS7AddRecipient (cinfo, rcerts[rci], certUsageEmailRecipient,
				   NULL) != SECSuccess) {
	    SEC_PKCS7DestroyContentInfo (cinfo);
	    return NULL;
	}
    }

    return cinfo;
}


static smime_capability **smime_capabilities;
static SECItem *smime_encoded_caps;
static PRBool lastUsedFortezza;


static SECStatus
smime_init_caps (PRBool isFortezza)
{
    smime_capability *cap;
    smime_cipher_map *map;
    SECOidData *oiddata;
    SECStatus rv;
    int i, capIndex;

    if (smime_encoded_caps != NULL 
	&& (! smime_prefs_changed) 
	&& lastUsedFortezza == isFortezza)
	return SECSuccess;

    if (smime_encoded_caps != NULL) {
	SECITEM_FreeItem (smime_encoded_caps, PR_TRUE);
	smime_encoded_caps = NULL;
    }

    if (smime_capabilities == NULL) {
	smime_capabilities = (smime_capability**)PORT_ZAlloc (
					  (smime_symmetric_count + 1)
					  * sizeof(smime_capability *));
	if (smime_capabilities == NULL)
	    return SECFailure;
    }

    rv = SECFailure;

    /* 
       The process of creating the encoded PKCS7 cipher capability list
       involves two basic steps: 

       (a) Convert our internal representation of cipher preferences 
           (smime_prefs) into an array containing cipher OIDs and 
	   parameter data (smime_capabilities). This step is
	   performed here.

       (b) Encode, using ASN.1, the cipher information in 
           smime_capabilities, leaving the encoded result in 
	   smime_encoded_caps.

       (In the process of performing (a), Lisa put in some optimizations
       which allow us to avoid needlessly re-populating elements in 
       smime_capabilities as we walk through smime_prefs.)

       We want to use separate loop variables for smime_prefs and
       smime_capabilities because in the case where the Skipjack cipher 
       is turned on in the prefs, but where we don't want to include 
       Skipjack in the encoded capabilities (presumably due to using a 
       non-fortezza cert when sending a message), we want to avoid creating
       an empty element in smime_capabilities. This would otherwise cause 
       the encoding step to produce an empty set, since Skipjack happens 
       to be the first cipher in smime_prefs, if it is turned on.
    */
    for (i = 0, capIndex = 0; i < smime_current_pref_index; i++, capIndex++) {
	int mapi;

	/* Get the next cipher preference in smime_prefs. */
	mapi = smime_mapi_by_cipher (smime_prefs[i]);
	if (mapi < 0)
	    break;

	/* Find the corresponding entry in the cipher map. */
	PORT_Assert (mapi < smime_symmetric_count);
	map = &(smime_cipher_maps[mapi]);

	/* If we're using a non-Fortezza cert, only advertise non-Fortezza
	   capabilities. (We advertise all capabilities if we have a 
	   Fortezza cert.) */
	if ((!isFortezza) && (map->cipher == SMIME_FORTEZZA))
	{
	    capIndex--; /* we want to visit the same caps index entry next time */
	    continue;
	}

	/*
	 * Convert the next preference found in smime_prefs into an
	 * smime_capability.
	 */

	cap = smime_capabilities[capIndex];
	if (cap == NULL) {
	    cap = (smime_capability*)PORT_ZAlloc (sizeof(smime_capability));
	    if (cap == NULL)
		break;
	    smime_capabilities[capIndex] = cap;
	} else if (cap->cipher == smime_prefs[i]) {
	    continue;		/* no change to this one */
	}

	cap->capIDTag = map->algtag;
	oiddata = SECOID_FindOIDByTag (map->algtag);
	if (oiddata == NULL)
	    break;

	if (cap->capabilityID.data != NULL) {
	    SECITEM_FreeItem (&(cap->capabilityID), PR_FALSE);
	    cap->capabilityID.data = NULL;
	    cap->capabilityID.len = 0;
	}

	rv = SECITEM_CopyItem (NULL, &(cap->capabilityID), &(oiddata->oid));
	if (rv != SECSuccess)
	    break;

	if (map->parms == NULL) {
	    cap->parameters.data = NULL;
	    cap->parameters.len = 0;
	} else {
	    cap->parameters.data = map->parms->data;
	    cap->parameters.len = map->parms->len;
	}

	cap->cipher = smime_prefs[i];
    }

    if (i != smime_current_pref_index)
	return rv;

    while (capIndex < smime_symmetric_count) {
	cap = smime_capabilities[capIndex];
	if (cap != NULL) {
	    SECITEM_FreeItem (&(cap->capabilityID), PR_FALSE);
	    PORT_Free (cap);
	}
	smime_capabilities[capIndex] = NULL;
	capIndex++;
    }
    smime_capabilities[capIndex] = NULL;

    smime_encoded_caps = SEC_ASN1EncodeItem (NULL, NULL, &smime_capabilities,
					     smime_capabilities_template);
    if (smime_encoded_caps == NULL)
	return SECFailure;

    lastUsedFortezza = isFortezza;

    return SECSuccess;
}


static SECStatus
smime_add_profile (CERTCertificate *cert, SEC_PKCS7ContentInfo *cinfo)
{
    PRBool isFortezza = PR_FALSE;

    PORT_Assert (smime_prefs_complete);
    if (! smime_prefs_complete)
	return SECFailure;

    /* See if the sender's cert specifies Fortezza key exchange. */
    if (cert != NULL)
	isFortezza = PK11_FortezzaHasKEA(cert);

    /* For that matter, if capabilities haven't been initialized yet,
       do so now. */
    if (isFortezza != lastUsedFortezza || smime_encoded_caps == NULL || smime_prefs_changed) {
	SECStatus rv;

	rv = smime_init_caps(isFortezza);
	if (rv != SECSuccess)
	    return rv;

	PORT_Assert (smime_encoded_caps != NULL);
    }

    return SEC_PKCS7AddSignedAttribute (cinfo, SEC_OID_PKCS9_SMIME_CAPABILITIES,
					smime_encoded_caps);
}


/*
 * Start an S/MIME signing context.
 *
 * "scert" is the cert that will be used to sign the data.  It will be
 * checked for validity.
 *
 * "ecert" is the signer's encryption cert.  If it is different from
 * scert, then it will be included in the signed message so that the
 * recipient can save it for future encryptions.
 *
 * "certdb" is the cert database to use for verifying the cert.
 * It can be NULL if a default database is available (like in the client).
 * 
 * "digestalg" names the digest algorithm (e.g. SEC_OID_SHA1).
 * XXX There should be SECMIME functions for hashing, or the hashing should
 * be built into this interface, which we would like because we would
 * support more smartcards that way, and then this argument should go away.)
 *
 * "digest" is the actual digest of the data.  It must be provided in
 * the case of detached data or NULL if the content will be included.
 *
 * This function already does all of the stuff specific to S/MIME protocol
 * and local policy; the return value just needs to be passed to
 * SEC_PKCS7Encode() or to SEC_PKCS7EncoderStart() to create the encoded data,
 * and finally to SEC_PKCS7DestroyContentInfo().
 *
 * An error results in a return value of NULL and an error set.
 * (Retrieve specific errors via PORT_GetError()/XP_GetError().)
 */

SEC_PKCS7ContentInfo *
SECMIME_CreateSigned (CERTCertificate *scert,
		      CERTCertificate *ecert,
		      CERTCertDBHandle *certdb,
		      SECOidTag digestalg,
		      SECItem *digest,
		      SECKEYGetPasswordKey pwfn,
		      void *pwfn_arg)
{
    SEC_PKCS7ContentInfo *cinfo;
    SECStatus rv;

    /* See note in header comment above about digestalg. */
    /* Doesn't explain this. PORT_Assert (digestalg == SEC_OID_SHA1); */

    cinfo = SEC_PKCS7CreateSignedData (scert, certUsageEmailSigner,
				       certdb, digestalg, digest,
				       pwfn, pwfn_arg);
    if (cinfo == NULL)
	return NULL;

    if (SEC_PKCS7IncludeCertChain (cinfo, NULL) != SECSuccess) {
	SEC_PKCS7DestroyContentInfo (cinfo);
	return NULL;
    }

    /* if the encryption cert and the signing cert differ, then include
     * the encryption cert too.
     */
    /* it is ok to compare the pointers since we ref count, and the same
     * cert will always have the same pointer
     */
    if ( ( ecert != NULL ) && ( ecert != scert ) ) {
	rv = SEC_PKCS7AddCertificate(cinfo, ecert);
	if ( rv != SECSuccess ) {
	    SEC_PKCS7DestroyContentInfo (cinfo);
	    return NULL;
	}
    }
    /*
     * Add the signing time.  But if it fails for some reason,
     * may as well not give up altogether -- just assert.
     */
    rv = SEC_PKCS7AddSigningTime (cinfo);
    PORT_Assert (rv == SECSuccess);

    /*
     * Add the email profile.  Again, if it fails for some reason,
     * may as well not give up altogether -- just assert.
     */
    rv = smime_add_profile (ecert, cinfo);
    PORT_Assert (rv == SECSuccess);

    return cinfo;
}