Subversion Repositories planix.SVN

/* encrypt file by writing
        v2hdr,
        16byte initialization vector,
        AES-CBC(key, random | file),
    HMAC_SHA1(md5(key), AES-CBC(random | file))
*/
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <mp.h>
#include <libsec.h>
#include <authsrv.h>

extern char* getpassm(char*);

enum{ CHK = 16, BUF = 4096 };

uchar v2hdr[AESbsize+1] = "AES CBC SHA1  2\n";
Biobuf bin;
Biobuf bout;

void
safewrite(uchar *buf, int n)
{
        if(Bwrite(&bout, buf, n) != n)
                sysfatal("write error");
}

void
saferead(uchar *buf, int n)
{
        if(Bread(&bin, buf, n) != n)
                sysfatal("read error");
}

int
main(int argc, char **argv)
{
        int encrypt = 0;  /* 0=decrypt, 1=encrypt */
        int n, nkey, pass_stdin = 0, pass_nvram = 0;
        char *pass;
        uchar key[AESmaxkey], key2[SHA1dlen];
        uchar buf[BUF+SHA1dlen];    /* assumption: CHK <= SHA1dlen */
        AESstate aes;
        DigestState *dstate;
        Nvrsafe nvr;

        ARGBEGIN{
        case 'e':
                encrypt = 1;
                break;
        case 'i':
                pass_stdin = 1;
                break;
        case 'n':
                pass_nvram = 1;
                break;
        }ARGEND;
        if(argc!=0){
                fprint(2,"usage: %s -d < cipher.aes > clear.txt\n", argv0);
                fprint(2,"   or: %s -e < clear.txt > cipher.aes\n", argv0);
                exits("usage");
        }
        Binit(&bin, 0, OREAD);
        Binit(&bout, 1, OWRITE);

        if(pass_stdin){
                n = readn(3, buf, (sizeof buf)-1);
                if(n < 1)
                        exits("usage: echo password |[3=1] auth/aescbc -i ...");
                buf[n] = 0;
                while(buf[n-1] == '\n')
                        buf[--n] = 0;
        }else if(pass_nvram){
                if(readnvram(&nvr, 0) < 0)
                        exits("readnvram: %r");
                strecpy((char*)buf, (char*)buf+sizeof buf, (char*)nvr.config);
                n = strlen((char*)buf);
        }else{
                pass = getpassm("aescbc key:");
                n = strlen(pass);
                if(n >= BUF)
                        exits("key too long");
                strcpy((char*)buf, pass);
                memset(pass, 0, n);
                free(pass);
        }
        if(n <= 0)
                sysfatal("no key");
        dstate = sha1((uchar*)"aescbc file", 11, nil, nil);
        sha1(buf, n, key2, dstate);
        memcpy(key, key2, 16);
        nkey = 16;
        md5(key, nkey, key2, 0);  /* so even if HMAC_SHA1 is broken, encryption key is protected */

        if(encrypt){
                safewrite(v2hdr, AESbsize);
                genrandom(buf,2*AESbsize); /* CBC is semantically secure if IV is unpredictable. */
                setupAESstate(&aes, key, nkey, buf);  /* use first AESbsize bytes as IV */
                aesCBCencrypt(buf+AESbsize, AESbsize, &aes);  /* use second AESbsize bytes as initial plaintext */
                safewrite(buf, 2*AESbsize);
                dstate = hmac_sha1(buf+AESbsize, AESbsize, key2, MD5dlen, 0, 0);
                for(;;){
                        n = Bread(&bin, buf, BUF);
                        if(n < 0)
                                sysfatal("read error");
                        aesCBCencrypt(buf, n, &aes);
                        safewrite(buf, n);
                        dstate = hmac_sha1(buf, n, key2, MD5dlen, 0, dstate);
                        if(n < BUF)
                                break; /* EOF */
                }
                hmac_sha1(0, 0, key2, MD5dlen, buf, dstate);
                safewrite(buf, SHA1dlen);
        }else{ /* decrypt */
                saferead(buf, AESbsize);
                if(memcmp(buf, v2hdr, AESbsize) == 0){
                        saferead(buf, 2*AESbsize);  /* read IV and random initial plaintext */
                        setupAESstate(&aes, key, nkey, buf);
                        dstate = hmac_sha1(buf+AESbsize, AESbsize, key2, MD5dlen, 0, 0);
                        aesCBCdecrypt(buf+AESbsize, AESbsize, &aes);
                        saferead(buf, SHA1dlen);
                        while((n = Bread(&bin, buf+SHA1dlen, BUF)) > 0){
                                dstate = hmac_sha1(buf, n, key2, MD5dlen, 0, dstate);
                                aesCBCdecrypt(buf, n, &aes);
                                safewrite(buf, n);
                                memmove(buf, buf+n, SHA1dlen);  /* these bytes are not yet decrypted */
                        }
                        hmac_sha1(0, 0, key2, MD5dlen, buf+SHA1dlen, dstate);
                        if(memcmp(buf, buf+SHA1dlen, SHA1dlen) != 0)
                                sysfatal("decrypted file failed to authenticate");
                }else{ /* compatibility with past mistake */
                        // if file was encrypted with bad aescbc use this:
                        //         memset(key, 0, AESmaxkey);
                        //    else assume we're decrypting secstore files
                        setupAESstate(&aes, key, AESbsize, buf);
                        saferead(buf, CHK);
                        aesCBCdecrypt(buf, CHK, &aes);
                        while((n = Bread(&bin, buf+CHK, BUF)) > 0){
                                aesCBCdecrypt(buf+CHK, n, &aes);
                                safewrite(buf, n);
                                memmove(buf, buf+n, CHK);
                        }
                        if(memcmp(buf, "XXXXXXXXXXXXXXXX", CHK) != 0)
                                sysfatal("decrypted file failed to authenticate");
                }
        }
        exits("");
        return 1;  /* keep  other compilers happy */
}