smimeutil.c

来自「支持SSL v2/v3, TLS, PKCS #5, PKCS #7, PKCS」· C语言 代码 · 共 715 行 · 第 1/2 页

/*
 * 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.
 *
 * $Id: smimeutil.c,v 1.4 2000/06/20 16:28:57 chrisk%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"
#include "cms.h"

/* various integer's ASN.1 encoding */
static unsigned char asn1_int40[] = { SEC_ASN1_INTEGER, 0x01, 0x28 };
static unsigned char asn1_int64[] = { SEC_ASN1_INTEGER, 0x01, 0x40 };
static unsigned char asn1_int128[] = { SEC_ASN1_INTEGER, 0x02, 0x00, 0x80 };

/* RC2 algorithm parameters (used in smime_cipher_map) */
static SECItem param_int40 = { siBuffer, asn1_int40, sizeof(asn1_int40) };
static SECItem param_int64 = { siBuffer, asn1_int64, sizeof(asn1_int64) };
static SECItem param_int128 = { siBuffer, asn1_int128, sizeof(asn1_int128) };

/*
 * 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 {
    SECItem capabilityID;
    SECItem parameters;
    long cipher;		/* optimization */
} NSSSMIMECapability;

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

static const SEC_ASN1Template NSSSMIMECapabilitiesTemplate[] = {
    { SEC_ASN1_SEQUENCE_OF, 0, NSSSMIMECapabilityTemplate }
};

/*
 * NSSSMIMEEncryptionKeyPreference - if we find one of these, it needs to prompt us
 *  to store this and only this certificate permanently for the sender email address.
 */
typedef enum {
    NSSSMIMEEncryptionKeyPref_IssuerSN,
    NSSSMIMEEncryptionKeyPref_RKeyID,
    NSSSMIMEEncryptionKeyPref_SubjectKeyID
} NSSSMIMEEncryptionKeyPrefSelector;

typedef struct {
    NSSSMIMEEncryptionKeyPrefSelector selector;
    union {
	CERTIssuerAndSN			*issuerAndSN;
	NSSCMSRecipientKeyIdentifier	*recipientKeyID;
	SECItem				*subjectKeyID;
    } id;
} NSSSMIMEEncryptionKeyPreference;

extern const SEC_ASN1Template NSSCMSRecipientKeyIdentifierTemplate[];

static const SEC_ASN1Template smime_encryptionkeypref_template[] = {
    { SEC_ASN1_CHOICE,
	  offsetof(NSSSMIMEEncryptionKeyPreference,selector), NULL,
	  sizeof(NSSSMIMEEncryptionKeyPreference) },
    { SEC_ASN1_POINTER | SEC_ASN1_CONTEXT_SPECIFIC | 0,
	  offsetof(NSSSMIMEEncryptionKeyPreference,id.issuerAndSN),
	  CERT_IssuerAndSNTemplate,
	  NSSSMIMEEncryptionKeyPref_IssuerSN },
    { SEC_ASN1_POINTER | SEC_ASN1_CONTEXT_SPECIFIC | 1,
	  offsetof(NSSSMIMEEncryptionKeyPreference,id.recipientKeyID),
	  NSSCMSRecipientKeyIdentifierTemplate,
	  NSSSMIMEEncryptionKeyPref_IssuerSN },
    { SEC_ASN1_POINTER | SEC_ASN1_CONTEXT_SPECIFIC | 2,
	  offsetof(NSSSMIMEEncryptionKeyPreference,id.subjectKeyID),
	  SEC_OctetStringTemplate,
	  NSSSMIMEEncryptionKeyPref_SubjectKeyID },
    { 0, }
};

/* smime_cipher_map - map of SMIME symmetric "ciphers" to algtag & parameters */
typedef struct {
    unsigned long cipher;
    SECOidTag algtag;
    SECItem *parms;
    PRBool enabled;	/* in the user's preferences */
    PRBool allowed;	/* per export policy */
} smime_cipher_map_entry;

/* global: list of supported SMIME symmetric ciphers, ordered roughly by increasing strength */
static smime_cipher_map_entry smime_cipher_map[] = {
/*    cipher			algtag			parms		enabled  allowed */
/*    ---------------------------------------------------------------------------------- */
    { SMIME_RC2_CBC_40,		SEC_OID_RC2_CBC,	&param_int40,	PR_TRUE, PR_TRUE },
    { SMIME_DES_CBC_56,		SEC_OID_DES_CBC,	NULL,		PR_TRUE, PR_TRUE },
    { SMIME_RC2_CBC_64,		SEC_OID_RC2_CBC,	&param_int64,	PR_TRUE, PR_TRUE },
    { SMIME_RC2_CBC_128,	SEC_OID_RC2_CBC,	&param_int128,	PR_TRUE, PR_TRUE },
    { SMIME_DES_EDE3_168,	SEC_OID_DES_EDE3_CBC,	NULL,		PR_TRUE, PR_TRUE },
    { SMIME_FORTEZZA,		SEC_OID_FORTEZZA_SKIPJACK, NULL,	PR_TRUE, PR_TRUE }
};
static const int smime_cipher_map_count = sizeof(smime_cipher_map) / sizeof(smime_cipher_map_entry);

/*
 * smime_mapi_by_cipher - find index into smime_cipher_map by cipher
 */
static int
smime_mapi_by_cipher(unsigned long cipher)
{
    int i;

    for (i = 0; i < smime_cipher_map_count; i++) {
	if (smime_cipher_map[i].cipher == cipher)
	    return i;	/* bingo */
    }
    return -1;		/* should not happen if we're consistent, right? */
}

/*
 * NSS_SMIME_EnableCipher - this function locally records the user's preference
 */
SECStatus 
NSS_SMIMEUtil_EnableCipher(unsigned long which, PRBool on)
{
    unsigned long mask;
    int mapi;

    mask = which & CIPHER_FAMILYID_MASK;

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

    mapi = smime_mapi_by_cipher(which);
    if (mapi < 0)
	/* XXX set an error */
	return SECFailure;

    /* do we try to turn on a forbidden cipher? */
    if (!smime_cipher_map[mapi].allowed && on) {
	PORT_SetError (SEC_ERROR_BAD_EXPORT_ALGORITHM);
	return SECFailure;
    }

    if (smime_cipher_map[mapi].enabled != on)
	smime_cipher_map[mapi].enabled = on;

    return SECSuccess;
}


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

    mask = which & CIPHER_FAMILYID_MASK;

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

    mapi = smime_mapi_by_cipher(which);
    if (mapi < 0)
	/* XXX set an error */
	return SECFailure;

    if (smime_cipher_map[mapi].allowed != on)
	smime_cipher_map[mapi].allowed = on;

    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 SECStatus
nss_smime_get_cipher_for_alg_and_key(SECAlgorithmID *algid, PK11SymKey *key, unsigned long *cipher)
{
    SECOidTag algtag;
    unsigned int keylen_bits;
    SECStatus rv = SECSuccess;
    unsigned long c;

    algtag = SECOID_GetAlgorithmTag(algid);
    switch (algtag) {
    case SEC_OID_RC2_CBC:
	keylen_bits = PK11_GetKeyStrength(key, algid);
	switch (keylen_bits) {
	case 40:
	    c = SMIME_RC2_CBC_40;
	case 64:
	    c = SMIME_RC2_CBC_64;
	case 128:
	    c = SMIME_RC2_CBC_128;
	default:
	    rv = SECFailure;
	    break;
	}
	break;
    case SEC_OID_DES_CBC:
	c = SMIME_DES_CBC_56;
    case SEC_OID_DES_EDE3_CBC:
	c = SMIME_DES_EDE3_168;
    case SEC_OID_FORTEZZA_SKIPJACK:
	c = SMIME_FORTEZZA;
    default:
	rv = SECFailure;
    }
    if (rv == SECSuccess)
	*cipher = c;
    return rv;
}

static PRBool
nss_smime_cipher_allowed(unsigned long which)
{
    int mapi;

    mapi = smime_mapi_by_cipher(which);
    if (mapi < 0)
	return PR_FALSE;
    return smime_cipher_map[mapi].allowed;
}

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

    if (nss_smime_get_cipher_for_alg_and_key(algid, key, &which) != SECSuccess)
	return PR_FALSE;

    return nss_smime_cipher_allowed(which);
}


/*
 * NSS_SMIME_EncryptionPossible - check if any encryption is allowed
 *
 * 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
NSS_SMIMEUtil_EncryptionPossible(void)
{
    int i;

    for (i = 0; i < smime_cipher_map_count; i++) {
	if (smime_cipher_map[i].allowed)
	    return PR_TRUE;
    }
    return PR_FALSE;
}


static int
nss_SMIME_FindCipherForSMIMECap(NSSSMIMECapability *cap)
{
    int i;
    SECOidTag capIDTag;

    /* we need the OIDTag here */
    capIDTag = SECOID_FindOIDTag(&(cap->capabilityID));

    /* go over all the SMIME ciphers we know and see if we find a match */
    for (i = 0; i < smime_cipher_map_count; i++) {
	if (smime_cipher_map[i].algtag != capIDTag)
	    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 && smime_cipher_map[i].parms == NULL)
	    break;	/* both empty: bingo */

	if (cap->parameters.data != NULL && smime_cipher_map[i].parms != NULL &&
	    cap->parameters.len == smime_cipher_map[i].parms->len &&
	    PORT_Memcmp (cap->parameters.data, smime_cipher_map[i].parms->data,
			     cap->parameters.len) == 0)
	{
	    break;	/* both not empty, same length & equal content: bingo */
	}
    }

    if (i == smime_cipher_map_count)
	return 0;				/* no match found */
    else
	return smime_cipher_map[i].cipher;	/* match found, point to cipher */
}

/*