From 35bd46f0c816948dc1a0430c8ba8b10a01167320 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Fri, 23 Dec 2022 15:18:29 -0800 Subject: [PATCH] file-has-acl: improve recent NFSv4 support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This fixes a link failure with emacsclient on GNU/Linux. This program wants file_has_acl but none of the other ACL primitives, so it doesn’t link acl-internal.o; this way it doesn’t need to link with -lacl. While I was at it I reviewed the recent changes, fixed some unlikely overflow bugs, and adjusted to GNU style. * doc/acl-nfsv4.txt: Remove. Its contents are now in a comment in lib/file-has-acl.c. * lib/acl-internal.c, lib/acl-internal.h: Move recent changes relating to acl_nfs4_nontrivial to lib/file-has-acl.c, so that there is no trouble linking programs that need only file_has_acl. * lib/file-has-acl.c (acl_nfs4_nontrivial): Move here from lib/acl-internal.c, so that we needn't link -lacl in programs that want only file_has_acl, such as emacsclient. Do not assume a char buffer is aligned for uint32_t. Check more carefully for buffer read overrun. Allow up to 6 ACEs, since other code does; but check that they’re distinct. Avoid integer overflow. Use memcmp rather than strncmp to compare memory blocks. (file_has_acl): Preserve initial errno instead of setting to 0. Allocate a bit more room for trivial ACL buffer. Use EINVAL for botchedk NFSv4 ACLs (which shouldn’t happen). --- ChangeLog | 25 +++++++++ doc/acl-nfsv4.txt | 17 ------ lib/acl-internal.c | 100 ----------------------------------- lib/acl-internal.h | 3 -- lib/file-has-acl.c | 129 +++++++++++++++++++++++++++++++++++++++------ 5 files changed, 138 insertions(+), 136 deletions(-) delete mode 100644 doc/acl-nfsv4.txt diff --git a/ChangeLog b/ChangeLog index 562845795d..3b6c6cf98e 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,28 @@ +2022-12-23 Paul Eggert + + file-has-acl: improve recent NFSv4 support + This fixes a link failure with emacsclient on GNU/Linux. This + program wants file_has_acl but none of the other ACL primitives, + so it doesn’t link acl-internal.o; this way it doesn’t need to + link with -lacl. While I was at it I reviewed the recent changes, + fixed some unlikely overflow bugs, and adjusted to GNU style. + * doc/acl-nfsv4.txt: Remove. Its contents are now in a + comment in lib/file-has-acl.c. + * lib/acl-internal.c, lib/acl-internal.h: Move recent changes + relating to acl_nfs4_nontrivial to lib/file-has-acl.c, so that + there is no trouble linking programs that need only file_has_acl. + * lib/file-has-acl.c (acl_nfs4_nontrivial): Move here from + lib/acl-internal.c, so that we needn't link -lacl in + programs that want only file_has_acl, such as emacsclient. + Do not assume a char buffer is aligned for uint32_t. + Check more carefully for buffer read overrun. + Allow up to 6 ACEs, since other code does; but check + that they’re distinct. Avoid integer overflow. + Use memcmp rather than strncmp to compare memory blocks. + (file_has_acl): Preserve initial errno instead of setting to 0. + Allocate a bit more room for trivial ACL buffer. + Use EINVAL for botchedk NFSv4 ACLs (which shouldn’t happen). + 2022-12-22 Paul Eggert posix_spawnp-tests: fix filename typo diff --git a/doc/acl-nfsv4.txt b/doc/acl-nfsv4.txt deleted file mode 100644 index 71352f58d0..0000000000 --- a/doc/acl-nfsv4.txt +++ /dev/null @@ -1,17 +0,0 @@ -General introduction: - https://linux.die.net/man/5/nfs4_acl - -The NFSv4 acls are defined in RFC7530 and as such, every NFSv4 server supporting ACLs -will support this kind of ACLs (note the difference from POSIX draft ACLs) - -The ACLs can be obtained via the nfsv4-acl-tools, i.e. - -$ nfs4_getfacl - -# file: -A::OWNER@:rwaDxtTnNcCy -A::GROUP@:rwaDxtTnNcy -A::EVERYONE@:rwaDxtTnNcy - -Gnulib is aiming to only provide a basic support of these, i.e. recognize trivial -and non-trivial ACLs diff --git a/lib/acl-internal.c b/lib/acl-internal.c index 4c65dffcc6..be244c67a2 100644 --- a/lib/acl-internal.c +++ b/lib/acl-internal.c @@ -25,9 +25,6 @@ #if USE_ACL && HAVE_ACL_GET_FILE /* Linux, FreeBSD, Mac OS X, IRIX, Tru64, Cygwin >= 2.5 */ -# include -# include - # if HAVE_ACL_TYPE_EXTENDED /* Mac OS X */ /* ACL is an ACL, from a file, stored as type ACL_TYPE_EXTENDED. @@ -125,103 +122,6 @@ acl_default_nontrivial (acl_t acl) return (acl_entries (acl) > 0); } -# define ACE4_WHO_OWNER "OWNER@" -# define ACE4_WHO_GROUP "GROUP@" -# define ACE4_WHO_EVERYONE "EVERYONE@" - -# define ACE4_ACCESS_ALLOWED_ACE_TYPE 0 -# define ACE4_ACCESS_DENIED_ACE_TYPE 1 - -/* ACE flag values */ -# define ACE4_IDENTIFIER_GROUP 0x00000040 -# define ROUNDUP(x, y) (((x) + (y) - 1) & - (y)) - -int -acl_nfs4_nontrivial (char *xattr, int len) -{ - int bufs = len; - uint32_t num_aces = ntohl (*((uint32_t*)(xattr))), /* Grab the number of aces in the acl */ - num_a_aces = 0, - num_d_aces = 0; - char *bufp = xattr; - - bufp += 4; /* sizeof(uint32_t); */ - bufs -= 4; - - for (uint32_t ace_n = 0; num_aces > ace_n ; ace_n++) - { - int d_ptr; - uint32_t flag, - wholen, - type; - - /* Get the acl type */ - if (bufs <= 0) - return -1; - - type = ntohl (*((uint32_t*)bufp)); - - bufp += 4; - bufs -= 4; - if (bufs <= 0) - return -1; - - flag = ntohl (*((uint32_t*)bufp)); - /* As per RFC 7530, the flag should be 0, but we are just generous to Netapp - * and also accept the Group flag - */ - if (flag & ~ACE4_IDENTIFIER_GROUP) - return 1; - - /* we skip mask - - * it's too risky to test it and it does not seem to be actually needed */ - bufp += 2*4; - bufs -= 2*4; - - if (bufs <= 0) - return -1; - - wholen = ntohl (*((uint32_t*)bufp)); - - bufp += 4; - bufs -= 4; - - /* Get the who string */ - if (bufs <= 0) - return -1; - - /* for trivial ACL, we expect max 5 (typically 3) ACES, 3 Allow, 2 deny */ - if (((strncmp (bufp, ACE4_WHO_OWNER, wholen) == 0) - || (strncmp (bufp, ACE4_WHO_GROUP, wholen) == 0)) - && wholen == 6) - { - if (type == ACE4_ACCESS_ALLOWED_ACE_TYPE) - num_a_aces++; - if (type == ACE4_ACCESS_DENIED_ACE_TYPE) - num_d_aces++; - } - else - if ((strncmp (bufp, ACE4_WHO_EVERYONE, wholen) == 0) - && (type == ACE4_ACCESS_ALLOWED_ACE_TYPE) - && (wholen == 9)) - num_a_aces++; - else - return 1; - - d_ptr = ROUNDUP (wholen, 4); - bufp += d_ptr; - bufs -= d_ptr; - - /* Make sure we aren't outside our domain */ - if (bufs < 0) - return -1; - - } - return !((num_a_aces <= 3) && (num_d_aces <= 2) - && (num_a_aces + num_d_aces == num_aces)); - -} - # endif #elif USE_ACL && HAVE_FACL && defined GETACL /* Solaris, Cygwin < 2.5, not HP-UX */ diff --git a/lib/acl-internal.h b/lib/acl-internal.h index 5da7c115c6..94553fab25 100644 --- a/lib/acl-internal.h +++ b/lib/acl-internal.h @@ -146,9 +146,6 @@ rpl_acl_set_fd (int fd, acl_t acl) # define acl_entries rpl_acl_entries extern int acl_entries (acl_t); # endif -/* Return 1 if given ACL in XDR format is non-trivial - * Return 0 if it is trivial */ -extern int acl_nfs4_nontrivial (char *, int); # if HAVE_ACL_TYPE_EXTENDED /* Mac OS X */ /* ACL is an ACL, from a file, stored as type ACL_TYPE_EXTENDED. diff --git a/lib/file-has-acl.c b/lib/file-has-acl.c index 171023488c..676523ba82 100644 --- a/lib/file-has-acl.c +++ b/lib/file-has-acl.c @@ -29,14 +29,97 @@ #include "acl-internal.h" -#if GETXATTR_WITH_POSIX_ACLS +#if USE_ACL && GETXATTR_WITH_POSIX_ACLS +# include +# include # include # include -# include # ifndef XATTR_NAME_NFSV4_ACL # define XATTR_NAME_NFSV4_ACL "system.nfs4_acl" # endif -# define TRIVIAL_NFS4_ACL_MAX_LENGTH 128 + +enum { + /* ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000, */ + ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001, + ACE4_IDENTIFIER_GROUP = 0x00000040 +}; + +/* Return 1 if given ACL in XDR format is non-trivial, 0 if it is trivial. + -1 upon failure to determine it. Possibly change errno. Assume that + the ACL is valid, except avoid undefined behavior even if invalid. + + See . The NFSv4 acls are + defined in Internet RFC 7530 and as such, every NFSv4 server + supporting ACLs should support NFSv4 ACLs (they differ from from + POSIX draft ACLs). The ACLs can be obtained via the + nfsv4-acl-tools, e.g., the nfs4_getfacl command. Gnulib provides + only basic support of NFSv4 ACLs, i.e., recognize trivial vs + nontrivial ACLs. */ + +static int +acl_nfs4_nontrivial (uint32_t *xattr, ssize_t nbytes) +{ + enum { BYTES_PER_NETWORK_UINT = 4}; + + /* Grab the number of aces in the acl. */ + nbytes -= BYTES_PER_NETWORK_UINT; + if (nbytes < 0) + return -1; + uint32_t num_aces = ntohl (*xattr++); + if (6 < num_aces) + return 1; + int ace_found = 0; + + for (int ace_n = 0; ace_n < num_aces; ace_n++) + { + /* Get the acl type and flag. Skip the mask; it's too risky to + test it and it does not seem to be needed. Get the wholen. */ + nbytes -= 4 * BYTES_PER_NETWORK_UINT; + if (nbytes < 0) + return -1; + uint32_t type = ntohl (xattr[0]); + uint32_t flag = ntohl (xattr[1]); + uint32_t wholen = ntohl (xattr[3]); + xattr += 4; + int64_t wholen4 = wholen; + wholen4 = ((wholen4 + (BYTES_PER_NETWORK_UINT)) + & ~ (BYTES_PER_NETWORK_UINT - 1)); + + /* Trivial ACLs have only ACE4_ACCESS_ALLOWED_ACE_TYPE or + ACE4_ACCESS_DENIED_ACE_TYPE. */ + if (ACE4_ACCESS_DENIED_ACE_TYPE < type) + return 1; + + /* RFC 7530 says FLAG should be 0, but be generous to NetApp and + also accept the group flag. */ + if (flag & ~ACE4_IDENTIFIER_GROUP) + return 1; + + /* Get the who string. Check NBYTES - WHOLEN4 before storing + into NBYTES, to avoid truncation on conversion. */ + if (nbytes - wholen4 < 0) + return -1; + nbytes -= wholen4; + + /* For a trivial ACL, max 6 (typically 3) ACEs, 3 allow, 3 deny. + Check that there is at most one ACE of each TYPE and WHO. */ + int who2 + = (wholen == 6 && memcmp (xattr, "OWNER@", 6) == 0 ? 0 + : wholen == 6 && memcmp (xattr, "GROUP@", 6) == 0 ? 2 + : wholen == 9 && memcmp (xattr, "EVERYONE@", 9) == 0 ? 4 + : -1); + if (who2 < 0) + return 1; + int ace_found_bit = 1 << (who2 | type); + if (ace_found & ace_found_bit) + return 1; + ace_found |= ace_found_bit; + + xattr = (uint32_t *) ((char *) xattr + wholen4); + } + + return 0; +} #endif /* Return 1 if NAME has a nontrivial access control list, @@ -56,6 +139,7 @@ file_has_acl (char const *name, struct stat const *sb) # if GETXATTR_WITH_POSIX_ACLS ssize_t ret; + int initial_errno = errno; ret = getxattr (name, XATTR_NAME_POSIX_ACL_ACCESS, NULL, 0); if (ret < 0 && errno == ENODATA) @@ -73,20 +157,33 @@ file_has_acl (char const *name, struct stat const *sb) } if (ret < 0) - { /* we might be on NFS, so try to check NFSv4 ACLs too */ - char xattr[TRIVIAL_NFS4_ACL_MAX_LENGTH]; - - errno = 0; /* we need to reset errno set by the previous getxattr() */ - ret = getxattr (name, XATTR_NAME_NFSV4_ACL, xattr, TRIVIAL_NFS4_ACL_MAX_LENGTH); - if (ret < 0 && errno == ENODATA) - ret = 0; + { + /* Check for NFSv4 ACLs. The max length of a trivial + ACL is 6 words for owner, 6 for group, 7 for everyone, + all times 2 because there are both allow and deny ACEs. + There are 6 words for owner because of type, flag, mask, + wholen, "OWNER@"+pad and similarly for group; everyone is + another word to hold "EVERYONE@". */ + uint32_t xattr[2 * (6 + 6 + 7)]; + + ret = getxattr (name, XATTR_NAME_NFSV4_ACL, xattr, sizeof xattr); + if (ret < 0) + switch (errno) + { + case ENODATA: return 0; + case ERANGE : return 1; /* ACL must be nontrivial. */ + } else - if (ret < 0 && errno == ERANGE) - return 1; /* we won't fit into the buffer, so non-trivial ACL is presented */ - else - if (ret > 0) - /* looks like trivial ACL, but we need to investigate further */ - return acl_nfs4_nontrivial (xattr, ret); + { + /* It looks like a trivial ACL, but investigate further. */ + ret = acl_nfs4_nontrivial (xattr, ret); + if (ret < 0) + { + errno = EINVAL; + return ret; + } + errno = initial_errno; + } } if (ret < 0) return - acl_errno_valid (errno); -- 2.25.1