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 /* 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/. */

 /*

  * Stuff specific to S/MIME policy and interoperability.

  * Depends on PKCS7, but there should be no dependency the other way around.

  */

 #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 }

 };

 /*

  * 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;

 #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)

 {

     PLArenaPool *poolp;

     long chosen_cipher;

     int *cipher_abilities;

     int *cipher_votes;

     int strong_mapi;

     int rcount, mapi, max;

     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.)

      */

     /* Make triple-DES the strong cipher. */

     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_QuickDERDecodeItem (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 (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:

 	/*

 	 * 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 SECStatus

 smime_init_caps (void)

 {

     smime_capability *cap;

     smime_cipher_map *map;

     SECOidData *oiddata;

     SECStatus rv;

     int i;

     if (smime_encoded_caps != NULL && (! smime_prefs_changed))

 	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.)

     */

     for (i = 0; i < smime_current_pref_index; i++) {

 	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]);

 	/*

 	 * Convert the next preference found in smime_prefs into an

 	 * smime_capability.

 	 */

 	cap = smime_capabilities[i];

 	if (cap == NULL) {

 	    cap = (smime_capability*)PORT_ZAlloc (sizeof(smime_capability));

 	    if (cap == NULL)

 		break;

 	    smime_capabilities[i] = 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 (i < smime_symmetric_count) {

 	cap = smime_capabilities[i];

 	if (cap != NULL) {

 	    SECITEM_FreeItem (&(cap->capabilityID), PR_FALSE);

 	    PORT_Free (cap);

 	}

 	smime_capabilities[i] = NULL;

 	i++;

     }

     smime_capabilities[i] = NULL;

     smime_encoded_caps = SEC_ASN1EncodeItem (NULL, NULL, &smime_capabilities,

 					     smime_capabilities_template);

     if (smime_encoded_caps == NULL)

 	return SECFailure;

     return SECSuccess;

 }

 static SECStatus

 smime_add_profile (CERTCertificate *cert, SEC_PKCS7ContentInfo *cinfo)

 {

     PORT_Assert (smime_prefs_complete);

     if (! smime_prefs_complete)

 	return SECFailure;

     /* For that matter, if capabilities haven't been initialized yet,

        do so now. */

     if (smime_encoded_caps == NULL || smime_prefs_changed) {

 	SECStatus rv;

 	rv = smime_init_caps();

 	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;

 }