[src-draft/trunk]: src/sys/dev Fix encblkno8 legacy support. Add a test vect...

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src-all/rev/15e56943f4ad
branches:  trunk
changeset: 934523:15e56943f4ad
user:      Taylor R Campbell <riastradh%NetBSD.org@localhost>
date:      Sat Jun 13 22:04:45 2020 +0000

description:
Fix encblkno8 legacy support.  Add a test vector while here.

What a crock!

This is deliberately _not_ neatly abstracted because the whole
configurable `iv method' mechanism is a mistake and should never be
used for anything new.

diffstat:

 sys/dev/cgd.c |  83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 80 insertions(+), 3 deletions(-)

diffs (153 lines):

diff -r e760bae42624 -r 15e56943f4ad sys/dev/cgd.c
--- a/sys/dev/cgd.c     Sat Jun 13 22:02:44 2020 +0000
+++ b/sys/dev/cgd.c     Sat Jun 13 22:04:45 2020 +0000
@@ -64,6 +64,7 @@
 
 struct selftest_params {
        const char *alg;
+       int encblkno8;
        int blocksize;  /* number of bytes */
        int secsize;
        daddr_t blkno;
@@ -292,6 +293,18 @@
        0xb8, 0xbf, 0x69, 0x17, 0x20, 0x0a, 0xf7, 0xda,
 };
 
+static const uint8_t selftest_aes_cbc_encblkno8_zero64[64];
+static const uint8_t selftest_aes_cbc_encblkno8_ctxt[64] = {
+       0xa2, 0x06, 0x26, 0x26, 0xac, 0xdc, 0xe7, 0xcf,
+       0x47, 0x68, 0x24, 0x0e, 0xfa, 0x40, 0x44, 0x83,
+       0x07, 0xe1, 0xf4, 0x5d, 0x53, 0x47, 0xa0, 0xfe,
+       0xc0, 0x6e, 0x4e, 0xf8, 0x9d, 0x98, 0x63, 0xb8,
+       0x2c, 0x27, 0xfa, 0x3a, 0xd5, 0x40, 0xda, 0xdb,
+       0xe6, 0xc3, 0xe4, 0xfb, 0x85, 0x53, 0xfb, 0x78,
+       0x5d, 0xbd, 0x8f, 0x4c, 0x1a, 0x04, 0x9c, 0x88,
+       0x85, 0xec, 0x3c, 0x56, 0x46, 0x1a, 0x6e, 0xf5,
+};
+
 const struct selftest_params selftests[] = {
        {
                .alg = "aes-xts",
@@ -359,6 +372,18 @@
                .ptxt = selftest_bf_cbc_ptxt,
                .ctxt = selftest_bf_cbc_ctxt,
        },
+       {
+               .alg = "aes-cbc",
+               .encblkno8 = 1,
+               .blocksize = 16,
+               .secsize = 512,
+               .blkno = 0,
+               .keylen = 128,
+               .txtlen = sizeof(selftest_aes_cbc_encblkno8_zero64),
+               .key = selftest_aes_cbc_encblkno8_zero64,
+               .ptxt = selftest_aes_cbc_encblkno8_zero64,
+               .ctxt = selftest_aes_cbc_encblkno8_ctxt,
+       },
 };
 
 static int cgd_match(device_t, cfdata_t, void *);
@@ -1264,6 +1289,25 @@
 
        sc->sc_cdata.cf_blocksize = ci->ci_blocksize;
        sc->sc_cdata.cf_mode = encblkno[i].v;
+
+       /*
+        * Print a warning if the user selected the legacy encblkno8
+        * mistake, and reject it altogether for ciphers that it
+        * doesn't apply to.
+        */
+       if (encblkno[i].v != CGD_CIPHER_CBC_ENCBLKNO1) {
+               if (strcmp(sc->sc_cfuncs->cf_name, "aes-cbc") &&
+                   strcmp(sc->sc_cfuncs->cf_name, "3des-cbc") &&
+                   strcmp(sc->sc_cfuncs->cf_name, "bf-cbc")) {
+                       log(LOG_WARNING, "cgd: %s only makes sense for cbc,"
+                           " not for %s; ignoring\n",
+                           encblkno[i].n, sc->sc_cfuncs->cf_name);
+                       sc->sc_cdata.cf_mode = CGD_CIPHER_CBC_ENCBLKNO1;
+               } else {
+                       log(LOG_WARNING, "cgd: enabling legacy encblkno8\n");
+               }
+       }
+
        sc->sc_cdata.cf_keylen = ci->ci_keylen;
        sc->sc_cdata.cf_priv = sc->sc_cfuncs->cf_init(ci->ci_keylen, inbuf,
            &sc->sc_cdata.cf_blocksize);
@@ -1547,6 +1591,9 @@
 
        DPRINTF_FOLLOW(("cgd_cipher() dir=%d\n", dir));
 
+       if (sc->sc_cdata.cf_mode == CGD_CIPHER_CBC_ENCBLKNO8)
+               blocksize /= 8;
+
        KASSERT(len % blocksize == 0);
        /* ensure that sizeof(daddr_t) <= blocksize (for encblkno IVing) */
        KASSERT(sizeof(daddr_t) <= blocksize);
@@ -1560,6 +1607,32 @@
                IFDEBUG(CGDB_CRYPTO, hexprint("step 1: blkno_buf",
                    blkno_buf, blocksize));
 
+               /*
+                * Handle bollocksed up encblkno8 mistake.  We used to
+                * compute the encryption of a zero block with blkno as
+                * the CBC IV -- except in an early mistake arising
+                * from bit/byte confusion, we actually computed the
+                * encryption of the last of _eight_ zero blocks under
+                * CBC as the CBC IV.
+                *
+                * Encrypting the block number is handled inside the
+                * cipher dispatch now (even though in practice, both
+                * CBC and XTS will do the same thing), so we have to
+                * simulate the block number that would yield the same
+                * result.  So we encrypt _six_ zero blocks -- the
+                * first one and the last one are handled inside the
+                * cipher dispatch.
+                */
+               if (sc->sc_cdata.cf_mode == CGD_CIPHER_CBC_ENCBLKNO8) {
+                       static const uint8_t zero[CGD_MAXBLOCKSIZE];
+                       uint8_t iv[CGD_MAXBLOCKSIZE];
+
+                       memcpy(iv, blkno_buf, blocksize);
+                       cipher(sc->sc_cdata.cf_priv, blkno_buf, zero,
+                           6*blocksize, iv, CGD_CIPHER_ENCRYPT);
+                       memmove(blkno_buf, blkno_buf + 5*blocksize, blocksize);
+               }
+
                cipher(sc->sc_cdata.cf_priv, dst, src, todo, blkno_buf, dir);
 
                dst += todo;
@@ -1589,11 +1662,13 @@
 
        for (size_t i = 0; i < __arraycount(selftests); i++) {
                const char *alg = selftests[i].alg;
+               int encblkno8 = selftests[i].encblkno8;
                const uint8_t *key = selftests[i].key;
                int keylen = selftests[i].keylen;
                int txtlen = selftests[i].txtlen;
 
-               aprint_verbose("cgd: self-test %s-%d\n", alg, keylen);
+               aprint_verbose("cgd: self-test %s-%d%s\n", alg, keylen,
+                   encblkno8 ? " (encblkno8)" : "");
 
                memset(&sc, 0, sizeof(sc));
 
@@ -1602,7 +1677,8 @@
                        panic("%s not implemented", alg);
 
                sc.sc_cdata.cf_blocksize = 8 * selftests[i].blocksize;
-               sc.sc_cdata.cf_mode = CGD_CIPHER_CBC_ENCBLKNO1;
+               sc.sc_cdata.cf_mode = encblkno8 ? CGD_CIPHER_CBC_ENCBLKNO8 :
+                   CGD_CIPHER_CBC_ENCBLKNO1;
                sc.sc_cdata.cf_keylen = keylen;
 
                sc.sc_cdata.cf_priv = sc.sc_cfuncs->cf_init(keylen,
@@ -1612,7 +1688,8 @@
                if (sc.sc_cdata.cf_blocksize > CGD_MAXBLOCKSIZE)
                        panic("bad block size %zu", sc.sc_cdata.cf_blocksize);
 
-               sc.sc_cdata.cf_blocksize /= 8;
+               if (!encblkno8)
+                       sc.sc_cdata.cf_blocksize /= 8;
 
                buf = kmem_alloc(txtlen, KM_SLEEP);
                memcpy(buf, selftests[i].ptxt, txtlen);