[LTP] [RFC PATCH 1/1] capability: Introduce capability API

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
>  include/tst_capability.h | 56 +++++++++++++++++++++++++++++
>  include/tst_test.h       |  6 ++++
>  lib/tst_capability.c     | 78 ++++++++++++++++++++++++++++++++++++++++
>  lib/tst_test.c           |  3 ++
>  4 files changed, 143 insertions(+)
>  create mode 100644 include/tst_capability.h
>  create mode 100644 lib/tst_capability.c

This is missing a documentation in the test-writing-guidelines I do
expect that you will add that later on.

> diff --git a/include/tst_capability.h b/include/tst_capability.h
> new file mode 100644
> index 000000000..6342b667e
> --- /dev/null
> +++ b/include/tst_capability.h
> @@ -0,0 +1,56 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (c) 2019 Richard Palethorpe <rpalethorpe@suse.com>
> + */
> +/**
> + * @file tst_capability.h
> + *
> + * Limited capability operations without libcap.
> + */
> +
> +#include <stdint.h>
> +
> +#include "lapi/syscalls.h"
               ^
	       What is this needed for here?

> +#ifndef TST_CAPABILITY_H
> +#define TST_CAPABILITY_H
> +
> +#ifndef CAP_SYS_ADMIN
> +# define CAP_SYS_ADMIN        21
> +#endif
>
> +#ifndef CAP_TO_MASK
> +# define CAP_TO_MASK(x)      (1 << ((x) & 31))
> +#endif

These bits should probably go to lapi/capability.h

> +#define TST_DROP 1
> +#define TST_REQUIRE 1 << 1

Maybe these should be TST_CAP_DROP and TST_CAP_REQ

> +#define TST_CAP(action, capability) {action, capability, #capability}
> +
> +struct tst_cap_user_header {
> +	uint32_t version;
> +	int pid;
> +};
> +
> +struct tst_cap_user_data {
> +	uint32_t effective;
> +	uint32_t permitted;
> +	uint32_t inheritable;
> +};

This two should probably go to lapi as well.

> +struct tst_cap {
> +	uint32_t action;
> +	uint32_t id;
> +	char *name;
> +};

I wonder if we should build a table of capability names for translation
just as we do errnos and signals instead of storing the name here. But I
guess that unless we will need a function to translate capabilitities
into strings on runtime this approach is simpler.

> +int tst_capget(struct tst_cap_user_header *hdr,
> +	       struct tst_cap_user_data *data);
> +int tst_capset(struct tst_cap_user_header *hdr,
> +	       const struct tst_cap_user_data *data);
> +
> +void tst_cap_action(struct tst_cap *cap);
> +void tst_cap_setup(struct tst_cap *cap);
> +
> +#endif
> diff --git a/include/tst_test.h b/include/tst_test.h
> index cdeaf6ad0..84acf2c59 100644
> --- a/include/tst_test.h
> +++ b/include/tst_test.h
> @@ -36,6 +36,7 @@
>  #include "tst_sys_conf.h"
>  #include "tst_coredump.h"
>  #include "tst_buffers.h"
> +#include "tst_capability.h"
>  
>  /*
>   * Reports testcase result.
> @@ -206,6 +207,11 @@ struct tst_test {
>  	 * NULL-terminated array to be allocated buffers.
>  	 */
>  	struct tst_buffers *bufs;
> +
> +	/*
> +	 * NULL-terminated array of capability settings
> +	 */
> +	struct tst_cap *caps;
>  };
>  
>  /*
> diff --git a/lib/tst_capability.c b/lib/tst_capability.c
> new file mode 100644
> index 000000000..d229491ae
> --- /dev/null
> +++ b/lib/tst_capability.c
> @@ -0,0 +1,78 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (c) 2019 Richard Palethorpe <rpalethorpe@suse.com>
> + */
> +
> +#define TST_NO_DEFAULT_MAIN
> +#include "tst_test.h"
> +#include "tst_capability.h"
> +
> +int tst_capget(struct tst_cap_user_header *hdr,
> +	       struct tst_cap_user_data *data)
> +{
> +	return tst_syscall(__NR_capget, hdr, data);
> +}
> +
> +int tst_capset(struct tst_cap_user_header *hdr,
> +	       const struct tst_cap_user_data *data)
> +{
> +	return tst_syscall(__NR_capset, hdr, data);
> +}
> +
> +void tst_cap_action(struct tst_cap *cap)
> +{
> +	struct tst_cap_user_header hdr = {
> +		.version = 0x20080522,
> +		.pid = tst_syscall(__NR_gettid),
> +	};
> +	struct tst_cap_user_data cur = { 0 };
> +	struct tst_cap_user_data new = { 0 };
> +	uint32_t mask = CAP_TO_MASK(cap->id);
> +	uint32_t act = cap->action;
> +
> +	if (tst_capget(&hdr, &cur))
> +		tst_brk(TBROK | TTERRNO, "tst_capget()");
> +
> +	new = cur;
> +
> +	switch (act) {
> +	case TST_DROP:
> +		if (cur.effective & mask) {
> +			tst_res(TINFO, "Dropping %s(%d)",
> +				cap->name, cap->id);
> +			new.effective &= ~mask;
> +			new.permitted &= ~mask;
> +			new.inheritable &= ~mask;
> +		}
> +		break;
> +	case TST_REQUIRE:
> +		if (cur.permitted ^ mask) {
> +			tst_brk(TCONF, "Need %s(%d)",
> +				cap->name, cap->id);
> +		} else if (cur.effective ^ mask) {
> +			tst_res(TINFO, "Permitting %s(%d)",
> +				cap->name, cap->id);
> +			new.effective |= mask;
> +			new.inheritable |= mask;
> +		}
> +		break;
> +	default:
> +		tst_brk(TBROK, "Unrecognised action %d", cap->action);
> +	}
> +
> +	if (cur.effective != new.effective) {
> +		if (tst_capset(&hdr, &new))
> +			tst_brk(TBROK | TERRNO, "tst_capset(%s)", cap->name);
> +	} else {
> +		tst_res(TINFO, "No capability changes needed");
> +	}
> +}
> +
> +void tst_cap_setup(struct tst_cap *caps)
> +{
> +	struct tst_cap *cap;
> +
> +	for (cap = caps; cap->action; cap++) {
> +		tst_cap_action(cap);
> +	}

No need for the curly braces here :-).

> +}
> diff --git a/lib/tst_test.c b/lib/tst_test.c
> index 8dc71dbb3..62e54d071 100644
> --- a/lib/tst_test.c
> +++ b/lib/tst_test.c
> @@ -893,6 +893,9 @@ static void do_test_setup(void)
>  
>  	if (main_pid != getpid())
>  		tst_brk(TBROK, "Runaway child in setup()!");
> +
> +	if (tst_test->caps)
> +		tst_cap_setup(tst_test->caps);
>  }

Other than the minor things and missing docs this patch looks good to me.

-- 
Cyril Hrubis
chrubis@suse.cz