From 04716e6621ff4abb422d64ba7b48718f52716a3e Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Thu, 7 Aug 2008 13:00:20 -0400 Subject: [PATCH] nfsd: permit unauthenticated stat of export root RFC 2623 section 2.3.2 permits the server to bypass gss authentication checks for certain operations that a client may perform when mounting. In the case of a client that doesn't have some form of credentials available to it on boot, this allows it to perform the mount unattended. (Presumably real file access won't be needed until a user with credentials logs in.) Being slightly more lenient allows lots of old clients to access krb5-only exports, with the only loss being a small amount of information leaked about the root directory of the export. This affects only v2 and v3; v4 still requires authentication for all access. Thanks to Peter Staubach testing against a Solaris client, which suggesting addition of v3 getattr, to the list, and to Trond for noting that doing so exposes no additional information. Signed-off-by: J. Bruce Fields Cc: Peter Staubach Cc: Trond Myklebust --- fs/nfsd/nfs3proc.c | 8 +++++--- fs/nfsd/nfsfh.c | 30 ++++++++++++++++++++---------- fs/nfsd/nfsproc.c | 6 ++++-- fs/nfsd/vfs.c | 4 ++-- include/linux/nfsd/nfsd.h | 3 ++- 5 files changed, 33 insertions(+), 18 deletions(-) diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c index 4d617ea..9dbd2eb 100644 --- a/fs/nfsd/nfs3proc.c +++ b/fs/nfsd/nfs3proc.c @@ -63,7 +63,8 @@ nfsd3_proc_getattr(struct svc_rqst *rqstp, struct nfsd_fhandle *argp, SVCFH_fmt(&argp->fh)); fh_copy(&resp->fh, &argp->fh); - nfserr = fh_verify(rqstp, &resp->fh, 0, NFSD_MAY_NOP); + nfserr = fh_verify(rqstp, &resp->fh, 0, + NFSD_MAY_NOP | NFSD_MAY_BYPASS_GSS_ON_ROOT); if (nfserr) RETURN_STATUS(nfserr); @@ -530,7 +531,7 @@ nfsd3_proc_fsstat(struct svc_rqst * rqstp, struct nfsd_fhandle *argp, dprintk("nfsd: FSSTAT(3) %s\n", SVCFH_fmt(&argp->fh)); - nfserr = nfsd_statfs(rqstp, &argp->fh, &resp->stats); + nfserr = nfsd_statfs(rqstp, &argp->fh, &resp->stats, 0); fh_put(&argp->fh); RETURN_STATUS(nfserr); } @@ -558,7 +559,8 @@ nfsd3_proc_fsinfo(struct svc_rqst * rqstp, struct nfsd_fhandle *argp, resp->f_maxfilesize = ~(u32) 0; resp->f_properties = NFS3_FSF_DEFAULT; - nfserr = fh_verify(rqstp, &argp->fh, 0, NFSD_MAY_NOP); + nfserr = fh_verify(rqstp, &argp->fh, 0, + NFSD_MAY_NOP | NFSD_MAY_BYPASS_GSS_ON_ROOT); /* Check special features of the file system. May request * different read/write sizes for file systems known to have diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c index ea37c96..cd25d91 100644 --- a/fs/nfsd/nfsfh.c +++ b/fs/nfsd/nfsfh.c @@ -302,17 +302,27 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access) if (error) goto out; - if (!(access & NFSD_MAY_LOCK)) { - /* - * pseudoflavor restrictions are not enforced on NLM, - * which clients virtually always use auth_sys for, - * even while using RPCSEC_GSS for NFS. - */ - error = check_nfsd_access(exp, rqstp); - if (error) - goto out; - } + /* + * pseudoflavor restrictions are not enforced on NLM, + * which clients virtually always use auth_sys for, + * even while using RPCSEC_GSS for NFS. + */ + if (access & NFSD_MAY_LOCK) + goto skip_pseudoflavor_check; + /* + * Clients may expect to be able to use auth_sys during mount, + * even if they use gss for everything else; see section 2.3.2 + * of rfc 2623. + */ + if (access & NFSD_MAY_BYPASS_GSS_ON_ROOT + && exp->ex_path.dentry == dentry) + goto skip_pseudoflavor_check; + + error = check_nfsd_access(exp, rqstp); + if (error) + goto out; +skip_pseudoflavor_check: /* Finally, check access permissions. */ error = nfsd_permission(rqstp, exp, dentry, access); diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c index 0766f95..5cffeca 100644 --- a/fs/nfsd/nfsproc.c +++ b/fs/nfsd/nfsproc.c @@ -65,7 +65,8 @@ nfsd_proc_getattr(struct svc_rqst *rqstp, struct nfsd_fhandle *argp, dprintk("nfsd: GETATTR %s\n", SVCFH_fmt(&argp->fh)); fh_copy(&resp->fh, &argp->fh); - nfserr = fh_verify(rqstp, &resp->fh, 0, NFSD_MAY_NOP); + nfserr = fh_verify(rqstp, &resp->fh, 0, + NFSD_MAY_NOP | NFSD_MAY_BYPASS_GSS_ON_ROOT); return nfsd_return_attrs(nfserr, resp); } @@ -521,7 +522,8 @@ nfsd_proc_statfs(struct svc_rqst * rqstp, struct nfsd_fhandle *argp, dprintk("nfsd: STATFS %s\n", SVCFH_fmt(&argp->fh)); - nfserr = nfsd_statfs(rqstp, &argp->fh, &resp->stats); + nfserr = nfsd_statfs(rqstp, &argp->fh, &resp->stats, + NFSD_MAY_BYPASS_GSS_ON_ROOT); fh_put(&argp->fh); return nfserr; } diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 18060be..1319e80 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1866,9 +1866,9 @@ out: * N.B. After this call fhp needs an fh_put */ __be32 -nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat) +nfsd_statfs(struct svc_rqst *rqstp, struct svc_fh *fhp, struct kstatfs *stat, int access) { - __be32 err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP); + __be32 err = fh_verify(rqstp, fhp, 0, NFSD_MAY_NOP | access); if (!err && vfs_statfs(fhp->fh_dentry,stat)) err = nfserr_io; return err; diff --git a/include/linux/nfsd/nfsd.h b/include/linux/nfsd/nfsd.h index 108f47e..2126940 100644 --- a/include/linux/nfsd/nfsd.h +++ b/include/linux/nfsd/nfsd.h @@ -38,6 +38,7 @@ #define NFSD_MAY_LOCK 32 #define NFSD_MAY_OWNER_OVERRIDE 64 #define NFSD_MAY_LOCAL_ACCESS 128 /* IRIX doing local access check on device special file*/ +#define NFSD_MAY_BYPASS_GSS_ON_ROOT 256 #define NFSD_MAY_CREATE (NFSD_MAY_EXEC|NFSD_MAY_WRITE) #define NFSD_MAY_REMOVE (NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC) @@ -125,7 +126,7 @@ int nfsd_truncate(struct svc_rqst *, struct svc_fh *, __be32 nfsd_readdir(struct svc_rqst *, struct svc_fh *, loff_t *, struct readdir_cd *, filldir_t); __be32 nfsd_statfs(struct svc_rqst *, struct svc_fh *, - struct kstatfs *); + struct kstatfs *, int access); int nfsd_notify_change(struct inode *, struct iattr *); __be32 nfsd_permission(struct svc_rqst *, struct svc_export *, -- 1.8.2.3