RPCSEC_GSS: Add support for privacy to krb5 rpcsec_gss mechanism.

 Add support for privacy to the krb5 rpcsec_gss mechanism.

 Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 370 insertions, 0 deletions

diff --git a/net/sunrpc/auth_gss/gss_krb5_wrap.c b/net/sunrpc/auth_gss/gss_krb5_wrap.c
new file mode 100644
index 000000000000..ddcde6e42b23
--- /dev/null
+++ b/net/sunrpc/auth_gss/gss_krb5_wrap.c
@@ -0,0 +1,370 @@
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/jiffies.h>
+#include <linux/sunrpc/gss_krb5.h>
+#include <linux/random.h>
+#include <linux/pagemap.h>
+#include <asm/scatterlist.h>
+#include <linux/crypto.h>
+
+#ifdef RPC_DEBUG
+# define RPCDBG_FACILITY        RPCDBG_AUTH
+#endif
+
+static inline int
+gss_krb5_padding(int blocksize, int length)
+{
+        /* Most of the code is block-size independent but currently we
+         * use only 8: */
+        BUG_ON(blocksize != 8);
+        return 8 - (length & 7);
+}
+
+static inline void
+gss_krb5_add_padding(struct xdr_buf *buf, int offset, int blocksize)
+{
+        int padding = gss_krb5_padding(blocksize, buf->len - offset);
+        char *p;
+        struct kvec *iov;
+
+        if (buf->page_len || buf->tail[0].iov_len)
+                iov = &buf->tail[0];
+        else
+                iov = &buf->head[0];
+        p = iov->iov_base + iov->iov_len;
+        iov->iov_len += padding;
+        buf->len += padding;
+        memset(p, padding, padding);
+}
+
+static inline int
+gss_krb5_remove_padding(struct xdr_buf *buf, int blocksize)
+{
+        u8 *ptr;
+        u8 pad;
+        int len = buf->len;
+
+        if (len <= buf->head[0].iov_len) {
+                pad = *(u8 *)(buf->head[0].iov_base + len - 1);
+                if (pad > buf->head[0].iov_len)
+                        return -EINVAL;
+                buf->head[0].iov_len -= pad;
+                goto out;
+        } else
+                len -= buf->head[0].iov_len;
+        if (len <= buf->page_len) {
+                int last = (buf->page_base + len - 1)
+                                        >>PAGE_CACHE_SHIFT;
+                int offset = (buf->page_base + len - 1)
+                                        & (PAGE_CACHE_SIZE - 1);
+                ptr = kmap_atomic(buf->pages[last], KM_SKB_SUNRPC_DATA);
+                pad = *(ptr + offset);
+                kunmap_atomic(ptr, KM_SKB_SUNRPC_DATA);
+                goto out;
+        } else
+                len -= buf->page_len;
+        BUG_ON(len > buf->tail[0].iov_len);
+        pad = *(u8 *)(buf->tail[0].iov_base + len - 1);
+out:
+        /* XXX: NOTE: we do not adjust the page lengths--they represent
+         * a range of data in the real filesystem page cache, and we need
+         * to know that range so the xdr code can properly place read data.
+         * However adjusting the head length, as we do above, is harmless.
+         * In the case of a request that fits into a single page, the server
+         * also uses length and head length together to determine the original
+         * start of the request to copy the request for deferal; so it's
+         * easier on the server if we adjust head and tail length in tandem.
+         * It's not really a problem that we don't fool with the page and
+         * tail lengths, though--at worst badly formed xdr might lead the
+         * server to attempt to parse the padding.
+         * XXX: Document all these weird requirements for gss mechanism
+         * wrap/unwrap functions. */
+        if (pad > blocksize)
+                return -EINVAL;
+        if (buf->len > pad)
+                buf->len -= pad;
+        else
+                return -EINVAL;
+        return 0;
+}
+
+static inline void
+make_confounder(char *p, int blocksize)
+{
+        static u64 i = 0;
+        u64 *q = (u64 *)p;
+
+        /* rfc1964 claims this should be "random".  But all that's really
+         * necessary is that it be unique.  And not even that is necessary in
+         * our case since our "gssapi" implementation exists only to support
+         * rpcsec_gss, so we know that the only buffers we will ever encrypt
+         * already begin with a unique sequence number.  Just to hedge my bets
+         * I'll make a half-hearted attempt at something unique, but ensuring
+         * uniqueness would mean worrying about atomicity and rollover, and I
+         * don't care enough. */
+
+        BUG_ON(blocksize != 8);
+        *q = i++;
+}
+
+/* Assumptions: the head and tail of inbuf are ours to play with.
+ * The pages, however, may be real pages in the page cache and we replace
+ * them with scratch pages from **pages before writing to them. */
+/* XXX: obviously the above should be documentation of wrap interface,
+ * and shouldn't be in this kerberos-specific file. */
+
+/* XXX factor out common code with seal/unseal. */
+
+u32
+gss_wrap_kerberos(struct gss_ctx *ctx, u32 qop, int offset,
+                struct xdr_buf *buf, struct page **pages)
+{
+        struct krb5_ctx         *kctx = ctx->internal_ctx_id;
+        s32                     checksum_type;
+        struct xdr_netobj       md5cksum = {.len = 0, .data = NULL};
+        int                     blocksize = 0, plainlen;
+        unsigned char           *ptr, *krb5_hdr, *msg_start;
+        s32                     now;
+        int                     headlen;
+        struct page             **tmp_pages;
+
+        dprintk("RPC:     gss_wrap_kerberos\n");
+
+        now = get_seconds();
+
+        if (qop != 0)
+                goto out_err;
+
+        switch (kctx->signalg) {
+                case SGN_ALG_DES_MAC_MD5:
+                        checksum_type = CKSUMTYPE_RSA_MD5;
+                        break;
+                default:
+                        dprintk("RPC:      gss_krb5_seal: kctx->signalg %d not"
+                                " supported\n", kctx->signalg);
+                        goto out_err;
+        }
+        if (kctx->sealalg != SEAL_ALG_NONE && kctx->sealalg != SEAL_ALG_DES) {
+                dprintk("RPC:      gss_krb5_seal: kctx->sealalg %d not supported\n",
+                        kctx->sealalg);
+                goto out_err;
+        }
+
+        blocksize = crypto_tfm_alg_blocksize(kctx->enc);
+        gss_krb5_add_padding(buf, offset, blocksize);
+        BUG_ON((buf->len - offset) % blocksize);
+        plainlen = blocksize + buf->len - offset;
+
+        headlen = g_token_size(&kctx->mech_used, 22 + plainlen) -
+                                                (buf->len - offset);
+
+        ptr = buf->head[0].iov_base + offset;
+        /* shift data to make room for header. */
+        /* XXX Would be cleverer to encrypt while copying. */
+        /* XXX bounds checking, slack, etc. */
+        memmove(ptr + headlen, ptr, buf->head[0].iov_len - offset);
+        buf->head[0].iov_len += headlen;
+        buf->len += headlen;
+        BUG_ON((buf->len - offset - headlen) % blocksize);
+
+        g_make_token_header(&kctx->mech_used, 22 + plainlen, &ptr);
+
+
+        *ptr++ = (unsigned char) ((KG_TOK_WRAP_MSG>>8)&0xff);
+        *ptr++ = (unsigned char) (KG_TOK_WRAP_MSG&0xff);
+
+        /* ptr now at byte 2 of header described in rfc 1964, section 1.2.1: */
+        krb5_hdr = ptr - 2;
+        msg_start = krb5_hdr + 24;
+        /* XXXJBF: */ BUG_ON(buf->head[0].iov_base + offset + headlen != msg_start + blocksize);
+
+        *(u16 *)(krb5_hdr + 2) = htons(kctx->signalg);
+        memset(krb5_hdr + 4, 0xff, 4);
+        *(u16 *)(krb5_hdr + 4) = htons(kctx->sealalg);
+
+        make_confounder(msg_start, blocksize);
+
+        /* XXXJBF: UGH!: */
+        tmp_pages = buf->pages;
+        buf->pages = pages;
+        if (make_checksum(checksum_type, krb5_hdr, 8, buf,
+                                offset + headlen - blocksize, &md5cksum))
+                goto out_err;
+        buf->pages = tmp_pages;
+
+        switch (kctx->signalg) {
+        case SGN_ALG_DES_MAC_MD5:
+                if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
+                                  md5cksum.data, md5cksum.len))
+                        goto out_err;
+                memcpy(krb5_hdr + 16,
+                       md5cksum.data + md5cksum.len - KRB5_CKSUM_LENGTH,
+                       KRB5_CKSUM_LENGTH);
+
+                dprintk("RPC:      make_seal_token: cksum data: \n");
+                print_hexl((u32 *) (krb5_hdr + 16), KRB5_CKSUM_LENGTH, 0);
+                break;
+        default:
+                BUG();
+        }
+
+        kfree(md5cksum.data);
+
+        /* XXX would probably be more efficient to compute checksum
+         * and encrypt at the same time: */
+        if ((krb5_make_seq_num(kctx->seq, kctx->initiate ? 0 : 0xff,
+                               kctx->seq_send, krb5_hdr + 16, krb5_hdr + 8)))
+                goto out_err;
+
+        if (gss_encrypt_xdr_buf(kctx->enc, buf, offset + headlen - blocksize,
+                                                                        pages))
+                goto out_err;
+
+        kctx->seq_send++;
+
+        return ((kctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
+out_err:
+        if (md5cksum.data) kfree(md5cksum.data);
+        return GSS_S_FAILURE;
+}
+
+u32
+gss_unwrap_kerberos(struct gss_ctx *ctx, u32 *qop, int offset,
+                        struct xdr_buf *buf)
+{
+        struct krb5_ctx         *kctx = ctx->internal_ctx_id;
+        int                     signalg;
+        int                     sealalg;
+        s32                     checksum_type;
+        struct xdr_netobj       md5cksum = {.len = 0, .data = NULL};
+        s32                     now;
+        int                     direction;
+        s32                     seqnum;
+        unsigned char           *ptr;
+        int                     bodysize;
+        u32                     ret = GSS_S_DEFECTIVE_TOKEN;
+        void                    *data_start, *orig_start;
+        int                     data_len;
+        int                     blocksize;
+
+        dprintk("RPC:      gss_unwrap_kerberos\n");
+
+        ptr = (u8 *)buf->head[0].iov_base + offset;
+        if (g_verify_token_header(&kctx->mech_used, &bodysize, &ptr,
+                                        buf->len - offset))
+                goto out;
+
+        if ((*ptr++ != ((KG_TOK_WRAP_MSG>>8)&0xff)) ||
+            (*ptr++ !=  (KG_TOK_WRAP_MSG    &0xff))   )
+                goto out;
+
+        /* XXX sanity-check bodysize?? */
+
+        /* get the sign and seal algorithms */
+
+        signalg = ptr[0] + (ptr[1] << 8);
+        sealalg = ptr[2] + (ptr[3] << 8);
+
+        /* Sanity checks */
+
+        if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
+                goto out;
+
+        if (sealalg == 0xffff)
+                goto out;
+
+        /* in the current spec, there is only one valid seal algorithm per
+           key type, so a simple comparison is ok */
+
+        if (sealalg != kctx->sealalg)
+                goto out;
+
+        /* there are several mappings of seal algorithms to sign algorithms,
+           but few enough that we can try them all. */
+
+        if ((kctx->sealalg == SEAL_ALG_NONE && signalg > 1) ||
+            (kctx->sealalg == SEAL_ALG_1 && signalg != SGN_ALG_3) ||
+            (kctx->sealalg == SEAL_ALG_DES3KD &&
+             signalg != SGN_ALG_HMAC_SHA1_DES3_KD))
+                goto out;
+
+        if (gss_decrypt_xdr_buf(kctx->enc, buf,
+                        ptr + 22 - (unsigned char *)buf->head[0].iov_base))
+                goto out;
+
+        /* compute the checksum of the message */
+
+        /* initialize the the cksum */
+        switch (signalg) {
+        case SGN_ALG_DES_MAC_MD5:
+                checksum_type = CKSUMTYPE_RSA_MD5;
+                break;
+        default:
+                ret = GSS_S_DEFECTIVE_TOKEN;
+                goto out;
+        }
+
+        switch (signalg) {
+        case SGN_ALG_DES_MAC_MD5:
+                ret = make_checksum(checksum_type, ptr - 2, 8, buf,
+                         ptr + 22 - (unsigned char *)buf->head[0].iov_base, &md5cksum);
+                if (ret)
+                        goto out;
+
+                ret = krb5_encrypt(kctx->seq, NULL, md5cksum.data,
+                                   md5cksum.data, md5cksum.len);
+                if (ret)
+                        goto out;
+
+                if (memcmp(md5cksum.data + 8, ptr + 14, 8)) {
+                        ret = GSS_S_BAD_SIG;
+                        goto out;
+                }
+                break;
+        default:
+                ret = GSS_S_DEFECTIVE_TOKEN;
+                goto out;
+        }
+
+        /* it got through unscathed.  Make sure the context is unexpired */
+
+        if (qop)
+                *qop = GSS_C_QOP_DEFAULT;
+
+        now = get_seconds();
+
+        ret = GSS_S_CONTEXT_EXPIRED;
+        if (now > kctx->endtime)
+                goto out;
+
+        /* do sequencing checks */
+
+        ret = GSS_S_BAD_SIG;
+        if ((ret = krb5_get_seq_num(kctx->seq, ptr + 14, ptr + 6, &direction,
+                                    &seqnum)))
+                goto out;
+
+        if ((kctx->initiate && direction != 0xff) ||
+            (!kctx->initiate && direction != 0))
+                goto out;
+
+        /* Copy the data back to the right position.  XXX: Would probably be
+         * better to copy and encrypt at the same time. */
+
+        blocksize = crypto_tfm_alg_blocksize(kctx->enc);
+        data_start = ptr + 22 + blocksize;
+        orig_start = buf->head[0].iov_base + offset;
+        data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
+        memmove(orig_start, data_start, data_len);
+        buf->head[0].iov_len -= (data_start - orig_start);
+        buf->len -= (data_start - orig_start);
+
+        ret = GSS_S_DEFECTIVE_TOKEN;
+        if (gss_krb5_remove_padding(buf, blocksize))
+                goto out;
+
+        ret = GSS_S_COMPLETE;
+out:
+        if (md5cksum.data) kfree(md5cksum.data);
+        return ret;
+}