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capsicum_helpers: split stream cap bits out of caph_limit_stream()

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The goal here is to make it so applications can take the rights one would
normally get by calling caph_limit_stream() on a descriptor and build on
them as needed.

The tentatively planned use-case is an application that takes a socket and
hooks it up to std{err,out,in} for a fork()d child. It may be feasible to
apply limitations to such descriptors as long as it's a superset of those
normally applied to stdio.

Reviewed by:	markj, oshobo (prior version; sans manpage addition)
Differential Revision:	https://reviews.freebsd.org/D22993
This commit is contained in:
Kyle Evans 2020-01-02 23:07:45 +00:00
parent d0554d26d7
commit 990beb037d
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=356305
3 changed files with 37 additions and 15 deletions
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1
lib/libcapsicum/Makefile
View file

@ -6,6 +6,7 @@ MAN+= capsicum_helpers.3
MLINKS+=capsicum_helpers.3 caph_enter.3
MLINKS+=capsicum_helpers.3 caph_enter_casper.3
MLINKS+=capsicum_helpers.3 caph_stream_rights.3
MLINKS+=capsicum_helpers.3 caph_rights_limit.3
MLINKS+=capsicum_helpers.3 caph_fcntls_limit.3
MLINKS+=capsicum_helpers.3 caph_ioctls_limit.3

15
lib/libcapsicum/capsicum_helpers.3
View file

@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd January 21, 2019
.Dd January 2, 2020
.Dt CAPSICUM_HELPERS 3
.Os
.Sh NAME
@ -33,6 +33,7 @@
.Nm caph_limit_stderr ,
.Nm caph_limit_stdout ,
.Nm caph_limit_stdio ,
.Nm caph_stream_rights ,
.Nm caph_cache_tzdata ,
.Nm caph_cache_catpages ,
.Nm caph_enter ,
@ -50,7 +51,7 @@
.Ft int
.Fn caph_enter_casper "void"
.Ft int
.Fn caph_rights_limit "int fd" "const cap_righst_t *rights"
.Fn caph_rights_limit "int fd" "const cap_rights_t *rights"
.Ft int
.Fn caph_ioctls_limit "int fd" "const unsigned long *cmds" "size_t ncmds"
.Ft int
@ -66,6 +67,8 @@
.Ft int
.Fn caph_limit_stdio "void"
.Ft void
.Fn caph_stream_rights "cap_rights_t *" "int flags"
.Ft void
.Fn caph_cache_tzdata "void"
.Ft void
.Fn caph_cache_catpages "void"
@ -129,6 +132,14 @@ function.
.Fn caph_limit_stdio
limits stdin, stderr and stdout.
.Pp
.Nm caph_stream_rights
may be used to initialize
.Fa rights
with the same rights that a stream would be limited to, as if
.Fn caph_limit_stream
had been invoked using the same
.Fa flags .
.Pp
.Fn caph_cache_tzdata
precaches all timezone data needed to use
.Li libc

36
lib/libcapsicum/capsicum_helpers.h
View file

@ -48,32 +48,42 @@
__BEGIN_DECLS
static const unsigned long caph_stream_cmds[] =
{ TIOCGETA, TIOCGWINSZ, FIODTYPE };
static const uint32_t caph_stream_fcntls = CAP_FCNTL_GETFL;
static __inline void
caph_stream_rights(cap_rights_t *rights, int flags)
{
cap_rights_init(rights, CAP_EVENT, CAP_FCNTL, CAP_FSTAT,
CAP_IOCTL, CAP_SEEK);
if ((flags & CAPH_READ) != 0)
cap_rights_set(rights, CAP_READ);
if ((flags & CAPH_WRITE) != 0)
cap_rights_set(rights, CAP_WRITE);
if ((flags & CAPH_LOOKUP) != 0)
cap_rights_set(rights, CAP_LOOKUP);
}
static __inline int
caph_limit_stream(int fd, int flags)
{
cap_rights_t rights;
unsigned long cmds[] = { TIOCGETA, TIOCGWINSZ, FIODTYPE };
cap_rights_init(&rights, CAP_EVENT, CAP_FCNTL, CAP_FSTAT,
CAP_IOCTL, CAP_SEEK);
if ((flags & CAPH_READ) != 0)
cap_rights_set(&rights, CAP_READ);
if ((flags & CAPH_WRITE) != 0)
cap_rights_set(&rights, CAP_WRITE);
if ((flags & CAPH_LOOKUP) != 0)
cap_rights_set(&rights, CAP_LOOKUP);
caph_stream_rights(&rights, flags);
if (cap_rights_limit(fd, &rights) < 0 && errno != ENOSYS) {
if (errno == EBADF && (flags & CAPH_IGNORE_EBADF) != 0)
return (0);
return (-1);
}
if (cap_ioctls_limit(fd, cmds, nitems(cmds)) < 0 && errno != ENOSYS)
if (cap_ioctls_limit(fd, caph_stream_cmds,
nitems(caph_stream_cmds)) < 0 && errno != ENOSYS)
return (-1);
if (cap_fcntls_limit(fd, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS)
if (cap_fcntls_limit(fd, caph_stream_fcntls) < 0 && errno != ENOSYS)
return (-1);
return (0);