usr/src/lib/librpc/secure_rpc/keyserv/setkey.c

#ifndef lint
static char sccsid[] =  "@(#)setkey.c   2.2 88/08/10 4.0 RPCSRC; from Copyr 1988 Sun Micro";
#endif
/*
 * Sun RPC is a product of Sun Microsystems, Inc. and is provided for
 * unrestricted use provided that this legend is included on all tape
 * media and as a part of the software program in whole or part.  Users
 * may copy or modify Sun RPC without charge, but are not authorized
 * to license or distribute it to anyone else except as part of a product or
 * program developed by the user.
 *
 * SUN RPC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE
 * WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
 *
 * Sun RPC is provided with no support and without any obligation on the
 * part of Sun Microsystems, Inc. to assist in its use, correction,
 * modification or enhancement.
 *
 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY SUN RPC
 * OR ANY PART THEREOF.
 *
 * In no event will Sun Microsystems, Inc. be liable for any lost revenue
 * or profits or other special, indirect and consequential damages, even if
 * Sun has been advised of the possibility of such damages.
 *
 * Sun Microsystems, Inc.
 * 2550 Garcia Avenue
 * Mountain View, California  94043
 */

/*
 * Copyright (C) 1986, Sun Microsystems, Inc.
 */

/*
 * Do the real work of the keyserver .
 * Store secret keys. Compute common keys,
 * and use them to decrypt and encrypt DES keys .
 * Cache the common keys, so the
 * expensive computation is avoided.
 */
#include <stdio.h>
#include <sys/file.h>
#include <mp.h>
#include <rpc/rpc.h>
#include <rpc/key_prot.h>
#include <des_crypt.h>
#include <sys/errno.h>

extern char *malloc();
extern char ROOTKEY[];

static MINT *MODULUS;
static char *fetchsecretkey();
static keystatus pk_crypt();


/*
 * Set the modulus for all our Diffie-Hellman operations
 */
setmodulus(modx)
        char *modx;
{
        MODULUS = xtom(modx);
}


/*
 * Set the secretkey key for this uid
 */
keystatus
pk_setkey(uid, skey)
        short uid;
        keybuf skey;
{
        if (!storesecretkey(uid, skey)) {
                return (KEY_SYSTEMERR);
        }
        return (KEY_SUCCESS);
}


/*
 * Encrypt the key using the public key associated with remote_name and the
 * secret key associated with uid.
 */
keystatus
pk_encrypt(uid, remote_name, key)
        short uid;
        char *remote_name;
        des_block *key;
{
        return (pk_crypt(uid, remote_name, key, DES_ENCRYPT));
}


/*
 * Decrypt the key using the public key associated with remote_name and the
 * secret key associated with uid.
 */
keystatus
pk_decrypt(uid, remote_name, key)
        short uid;
        char *remote_name;
        des_block *key;
{
        return (pk_crypt(uid, remote_name, key, DES_DECRYPT));
}


/*
 * Do the work of pk_encrypt && pk_decrypt
 */
static keystatus
pk_crypt(uid, remote_name, key, mode)
        short uid;
        char *remote_name;
        des_block *key;
        int mode;
{
        char *xsecret;
        char xpublic[HEXKEYBYTES + 1];
        char xsecret_hold[HEXKEYBYTES + 1];
        des_block deskey;
        int err;
        MINT *public;
        MINT *secret;
        MINT *common;
        char zero[8];

        xsecret = fetchsecretkey(uid);
        if (xsecret == NULL) {
                bzero(zero, sizeof(zero));
                xsecret = xsecret_hold;
                if (!getsecretkey("nobody", xsecret, zero) ||
                    xsecret[0] == 0) {
                        return (KEY_NOSECRET);
                }
        }
        if (!getpublickey(remote_name, xpublic) &&
            !getpublickey("nobody", xpublic)) {
                return (KEY_UNKNOWN);
        }
        if (!readcache(xpublic, xsecret, &deskey)) {
                public = xtom(xpublic);
                secret = xtom(xsecret);
                common = itom(0);
                pow(public, secret, MODULUS, common);
                extractdeskey(common, &deskey);
                writecache(xpublic, xsecret, &deskey);
                mfree(secret);
                mfree(public);
                mfree(common);
        }
        err = ecb_crypt(&deskey, key, sizeof(des_block), DES_HW | mode);
        if (DES_FAILED(err)) {
                return (KEY_SYSTEMERR);
        }
        return (KEY_SUCCESS);
}


/*
 * Choose middle 64 bits of the common key to use as our des key, possibly
 * overwriting the lower order bits by setting parity.
 */
static
extractdeskey(ck, deskey)
        MINT *ck;
        des_block *deskey;
{
        MINT *a;
        short r;
        int i;
        short base = (1 << 8);
        char *k;


        a = itom(0);
        move(ck, a);
        for (i = 0; i < ((KEYSIZE - 64) / 2) / 8; i++) {
                sdiv(a, base, a, &r);
        }
        k = deskey->c;
        for (i = 0; i < 8; i++) {
                sdiv(a, base, a, &r);
                *k++ = r;
        }
        mfree(a);
        des_setparity(deskey);
}


/*
 * Key storage management
 */

struct secretkey_list {
        short uid;
        char secretkey[HEXKEYBYTES+1];
        struct secretkey_list *next;
};

static struct secretkey_list *g_secretkeys;

/*
 * Fetch the secret key for this uid
 */
static char *
fetchsecretkey(uid)
        short uid;
{
        struct secretkey_list *l;

        for (l = g_secretkeys; l != NULL; l = l->next) {
                if (l->uid == uid) {
                        return (l->secretkey);
                }
        }
        return (NULL);
}

/*
 * Store the secretkey for this uid
 */
storesecretkey(uid, key)
        short uid;
        keybuf key;
{
        struct secretkey_list *new;
        struct secretkey_list **l;
        int nitems;


        nitems = 0;
        for (l = &g_secretkeys; *l != NULL && (*l)->uid != uid;
             l = &(*l)->next) {
                nitems++;
        }
        if (*l == NULL) {
                new = (struct secretkey_list *)malloc(sizeof(*new));
                if (new == NULL) {
                        return (0);
                }
                new->uid = uid;
                new->next = NULL;
                *l = new;
        } else {
                new = *l;
        }
        bcopy(key, new->secretkey, HEXKEYBYTES);
        new->secretkey[HEXKEYBYTES] = 0;
        seekitem(nitems);
        writeitem(uid, new->secretkey);
        return (1);
}


hexdigit(val)
        int val;
{
        return ("0123456789abcdef"[val]);

}
bin2hex(bin, hex, size)
        unsigned char *bin;
        unsigned char *hex;
        int size;
{
        int i;

        for (i = 0; i < size; i++) {
                *hex++ = hexdigit(*bin >> 4);
                *hex++ = hexdigit(*bin++ & 0xf);
        }
}

hexval(dig)
        char dig;
{
        if ('0' <= dig && dig <= '9') {
                return (dig - '0');
        } else if ('a' <= dig && dig <= 'f') {
                return (dig - 'a' + 10);
        } else if ('A' <= dig && dig <= 'F') {
                return (dig - 'A' + 10);
        } else {
                return (-1);
        }
}

hex2bin(hex, bin, size)
        unsigned char *hex;
        unsigned char *bin;
        int size;
{
        int i;

        for (i = 0; i < size; i++) {
                *bin = hexval(*hex++) << 4;
                *bin++ |= hexval(*hex++);
        }
}

static char KEYSTORE[] = "/etc/keystore";
FILE *kf;

openstore()
{
        kf = fopen(KEYSTORE, "r+");
        if (kf == NULL) {
                kf = fopen(KEYSTORE, "w+");
                if (kf == NULL) {
                        return (0);
                }
        }
        setbuf(kf, NULL);
        return (1);
}

static char rootkey[KEYBYTES];
static int haverootkey;
struct storedkey {
        short uid;
        char crypt[KEYBYTES];
};

readkeys()
{
        struct secretkey_list *node;
        struct secretkey_list **l;
        int uid;
        char secretkey[HEXKEYBYTES+1];

        if (kf == NULL) {
                return;
        }
        l = &g_secretkeys;
        seekitem(0);
        while (readitem(&uid, secretkey)) {
                node = (struct secretkey_list *)malloc(sizeof(*node));
                if (node == NULL) {
                        return;
                }
                node->uid = uid;
                bcopy(secretkey, node->secretkey, HEXKEYBYTES + 1);
                node->next = NULL;
                *l = node;
                l = &node->next;
        }
}

writekeys()
{
        struct secretkey_list *k;

        seekitem(0);
        for (k = g_secretkeys; k != NULL; k = k->next) {
                writeitem(k->uid, k->secretkey);
        }
}

seekitem(item)
        int item;
{
        if (kf != NULL) {
                fseek(kf, item * sizeof(struct storedkey), 0);
        }
}

writeitem(uid, key)
        int uid;
        char *key;
{
        struct storedkey item;
        char rootkey_tmp[KEYBYTES];
        int reencrypt;

        if (kf == NULL) {
                return (1);
        }
        if (uid == 0) {
                writerootkey(key);
                hex2bin(key, rootkey_tmp, KEYBYTES);
                reencrypt = (haverootkey &&
                             bcmp(rootkey, rootkey_tmp, KEYBYTES) != 0);
                bcopy(rootkey_tmp, rootkey, KEYBYTES);
                haverootkey = 1;
                if (reencrypt) {
                        writekeys();
                        return (1);
                }
        }
        if (!haverootkey) {
                return (1);
        }
        item.uid = uid;
        hex2bin(key, item.crypt, KEYBYTES);
        ecb_crypt(rootkey, item.crypt, KEYBYTES, DES_ENCRYPT|DES_HW);
        return (fwrite(&item, sizeof(item), 1, kf) >= 0);
}


readitem(uidp, key)
        int *uidp;
        char *key;
{
        struct storedkey item;

        if (!haverootkey || kf == NULL) {
                return (0);
        }
        if (fread(&item, sizeof(item), 1, kf) != 1) {
                return (0);
        }
        *uidp = item.uid;
        ecb_crypt(rootkey, item.crypt, KEYBYTES, DES_DECRYPT|DES_HW);
        bin2hex(item.crypt, key, KEYBYTES);
        key[HEXKEYBYTES] = 0;
        return (1);
}

/*
 * Root users store their key in /etc/$ROOTKEY so
 * that they can auto reboot without having to be
 * around to type a password. Storing this in a file
 * is rather dubious: it should really be in the EEPROM
 * so it does not go over the net for diskless machines.
 */
writerootkey(secret)
        char *secret;
{
        char newline = '\n';
        int fd;

        fd = open(ROOTKEY, O_WRONLY|O_TRUNC|O_CREAT, 0);
        if (fd < 0) {
                perror(ROOTKEY);
        } else {
                if (write(fd, secret, strlen(secret)) < 0 ||
                    write(fd, &newline, sizeof(newline)) < 0) {
                        (void)fprintf(stderr, "%s: ", ROOTKEY);
                        perror("write");
                }
                close(fd);
        }
}


/*
 * Exponential caching management
 */
struct cachekey_list {
        keybuf secret;
        keybuf public;
        des_block deskey;
        struct cachekey_list *next;
};
static struct cachekey_list *g_cachedkeys;


/*
 * cache result of expensive multiple precision exponential operation
 */
static
writecache(pub, sec, deskey)
        char *pub;
        char *sec;
        des_block *deskey;
{
        struct cachekey_list *new;

        new = (struct cachekey_list *) malloc(sizeof(struct cachekey_list));
        if (new == NULL) {
                return;
        }
        bcopy(pub, new->public, sizeof(keybuf));
        bcopy(sec, new->secret, sizeof(keybuf));
        new->deskey = *deskey;
        new->next = g_cachedkeys;
        g_cachedkeys = new;
}

/*
 * Try to find the common key in the cache
 */
static
readcache(pub, sec, deskey)
        char *pub;
        char *sec;
        des_block *deskey;
{
        struct cachekey_list *found;
        register struct cachekey_list **l;

#define cachehit(pub, sec, list)        \
                (bcmp(pub, (list)->public, sizeof(keybuf)) == 0 && \
                bcmp(sec, (list)->secret, sizeof(keybuf)) == 0)

        for (l = &g_cachedkeys;
             (*l) != NULL && !cachehit(pub, sec, *l);
             l = &(*l)->next);
        if ((*l) == NULL) {
                return (0);
        }
        found = *l;
        (*l) = (*l)->next;
        found->next = g_cachedkeys;
        g_cachedkeys = found;
        *deskey = found->deskey;
        return (1);
}