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Commit 725f2865 authored by Kevin Coffman's avatar Kevin Coffman Committed by Trond Myklebust
Browse files

gss_krb5: Introduce encryption type framework 



Make the client and server code consistent regarding the extra buffer
space made available for the auth code when wrapping data.

Add some comments/documentation about the available buffer space
in the xdr_buf head and tail when gss_wrap is called.

Add a compile-time check to make sure we are not exceeding the available
buffer space.

Add a central function to shift head data.

Signed-off-by: default avatarKevin Coffman <kwc@citi.umich.edu>
Signed-off-by: default avatarSteve Dickson <steved@redhat.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 4fc4c3ce

include/linux/sunrpc/gss_krb5.h

+25 −0
Original line number Diff line number Diff line
@@ -40,6 +40,12 @@ 
#include <linux/sunrpc/gss_err.h>

#include <linux/sunrpc/gss_asn1.h>



/* Maximum checksum function output for the supported crypto algorithms */

#define GSS_KRB5_MAX_CKSUM_LEN  (20)



/* Maximum blocksize for the supported crypto algorithms */

#define GSS_KRB5_MAX_BLOCKSIZE  (16)



struct krb5_ctx {

	int			initiate; /* 1 = initiating, 0 = accepting */

	struct crypto_blkcipher	*enc;
@@ -113,6 +119,22 @@ enum seal_alg { 
#define ENCTYPE_DES3_CBC_SHA1   0x0010

#define ENCTYPE_UNKNOWN         0x01ff



/*

 * This compile-time check verifies that we will not exceed the

 * slack space allotted by the client and server auth_gss code

 * before they call gss_wrap().

 */

#define GSS_KRB5_MAX_SLACK_NEEDED \

	(GSS_KRB5_TOK_HDR_LEN     /* gss token header */         \

	+ GSS_KRB5_MAX_CKSUM_LEN  /* gss token checksum */       \

	+ GSS_KRB5_MAX_BLOCKSIZE  /* confounder */               \

	+ GSS_KRB5_MAX_BLOCKSIZE  /* possible padding */         \

	+ GSS_KRB5_TOK_HDR_LEN    /* encrypted hdr in v2 token */\

	+ GSS_KRB5_MAX_CKSUM_LEN  /* encryption hmac */          \

	+ 4 + 4                   /* RPC verifier */             \

	+ GSS_KRB5_TOK_HDR_LEN                                   \

	+ GSS_KRB5_MAX_CKSUM_LEN)



s32

make_checksum(char *, char *header, int hdrlen, struct xdr_buf *body,

		   int body_offset, struct xdr_netobj *cksum);
@@ -157,3 +179,6 @@ s32 
krb5_get_seq_num(struct crypto_blkcipher *key,

	       unsigned char *cksum,

	       unsigned char *buf, int *direction, u32 *seqnum);



int

xdr_extend_head(struct xdr_buf *buf, unsigned int base, unsigned int shiftlen);

net/sunrpc/auth_gss/auth_gss.c

+1 −1
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ static const struct rpc_credops gss_nullops; 
# define RPCDBG_FACILITY	RPCDBG_AUTH

#endif



#define GSS_CRED_SLACK		1024

#define GSS_CRED_SLACK		(RPC_MAX_AUTH_SIZE * 2)

/* length of a krb5 verifier (48), plus data added before arguments when

 * using integrity (two 4-byte integers): */

#define GSS_VERF_SLACK		100

net/sunrpc/auth_gss/gss_krb5_crypto.c

+38 −0
Original line number Diff line number Diff line
@@ -325,3 +325,41 @@ gss_decrypt_xdr_buf(struct crypto_blkcipher *tfm, struct xdr_buf *buf, 


	return xdr_process_buf(buf, offset, buf->len - offset, decryptor, &desc);

}



/*

 * This function makes the assumption that it was ultimately called

 * from gss_wrap().

 *

 * The client auth_gss code moves any existing tail data into a

 * separate page before calling gss_wrap.

 * The server svcauth_gss code ensures that both the head and the

 * tail have slack space of RPC_MAX_AUTH_SIZE before calling gss_wrap.

 *

 * Even with that guarantee, this function may be called more than

 * once in the processing of gss_wrap().  The best we can do is

 * verify at compile-time (see GSS_KRB5_SLACK_CHECK) that the

 * largest expected shift will fit within RPC_MAX_AUTH_SIZE.

 * At run-time we can verify that a single invocation of this

 * function doesn't attempt to use more the RPC_MAX_AUTH_SIZE.

 */



int

xdr_extend_head(struct xdr_buf *buf, unsigned int base, unsigned int shiftlen)

{

	u8 *p;



	if (shiftlen == 0)

		return 0;



	BUILD_BUG_ON(GSS_KRB5_MAX_SLACK_NEEDED > RPC_MAX_AUTH_SIZE);

	BUG_ON(shiftlen > RPC_MAX_AUTH_SIZE);



	p = buf->head[0].iov_base + base;



	memmove(p + shiftlen, p, buf->head[0].iov_len - base);



	buf->head[0].iov_len += shiftlen;

	buf->len += shiftlen;



	return 0;

}

net/sunrpc/auth_gss/gss_krb5_wrap.c

+2 −4
Original line number Diff line number Diff line
@@ -155,11 +155,9 @@ gss_wrap_kerberos(struct gss_ctx *ctx, int offset, 


	ptr = buf->head[0].iov_base + offset;

	/* shift data to make room for header. */

	xdr_extend_head(buf, offset, headlen);



	/* 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,