From cd1dbf76b23d5ab2cba5e657fe20b1e236a408cc Mon Sep 17 00:00:00 2001 From: John Johansen Date: Tue, 18 Jul 2017 22:56:22 -0700 Subject: [PATCH] apparmor: add the ability to mediate signals Add signal mediation where the signal can be mediated based on the signal, direction, or the label or the peer/target. The signal perms are verified on a cross check to ensure policy consistency in the case of incremental policy load/replacement. The optimization of skipping the cross check when policy is guaranteed to be consistent (single compile unit) remains to be done. policy rules have the form of SIGNAL_RULE = [ QUALIFIERS ] 'signal' [ SIGNAL ACCESS PERMISSIONS ] [ SIGNAL SET ] [ SIGNAL PEER ] SIGNAL ACCESS PERMISSIONS = SIGNAL ACCESS | SIGNAL ACCESS LIST SIGNAL ACCESS LIST = '(' Comma or space separated list of SIGNAL ACCESS ')' SIGNAL ACCESS = ( 'r' | 'w' | 'rw' | 'read' | 'write' | 'send' | 'receive' ) SIGNAL SET = 'set' '=' '(' SIGNAL LIST ')' SIGNAL LIST = Comma or space separated list of SIGNALS SIGNALS = ( 'hup' | 'int' | 'quit' | 'ill' | 'trap' | 'abrt' | 'bus' | 'fpe' | 'kill' | 'usr1' | 'segv' | 'usr2' | 'pipe' | 'alrm' | 'term' | 'stkflt' | 'chld' | 'cont' | 'stop' | 'stp' | 'ttin' | 'ttou' | 'urg' | 'xcpu' | 'xfsz' | 'vtalrm' | 'prof' | 'winch' | 'io' | 'pwr' | 'sys' | 'emt' | 'exists' | 'rtmin+0' ... 'rtmin+32' ) SIGNAL PEER = 'peer' '=' AARE eg. signal, # allow all signals signal send set=(hup, kill) peer=foo, Signed-off-by: John Johansen Acked-by: Seth Arnold --- security/apparmor/apparmorfs.c | 7 ++ security/apparmor/include/apparmor.h | 1 + security/apparmor/include/audit.h | 2 + security/apparmor/include/ipc.h | 6 ++ security/apparmor/include/sig_names.h | 95 +++++++++++++++++++++++++ security/apparmor/ipc.c | 99 +++++++++++++++++++++++++++ security/apparmor/lsm.c | 21 ++++++ 7 files changed, 231 insertions(+) create mode 100644 security/apparmor/include/sig_names.h diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c index 2caeb748070cab..a5f9e1aa51f7f2 100644 --- a/security/apparmor/apparmorfs.c +++ b/security/apparmor/apparmorfs.c @@ -32,6 +32,7 @@ #include "include/audit.h" #include "include/context.h" #include "include/crypto.h" +#include "include/ipc.h" #include "include/policy_ns.h" #include "include/label.h" #include "include/policy.h" @@ -2129,6 +2130,11 @@ static struct aa_sfs_entry aa_sfs_entry_ptrace[] = { { } }; +static struct aa_sfs_entry aa_sfs_entry_signal[] = { + AA_SFS_FILE_STRING("mask", AA_SFS_SIG_MASK), + { } +}; + static struct aa_sfs_entry aa_sfs_entry_domain[] = { AA_SFS_FILE_BOOLEAN("change_hat", 1), AA_SFS_FILE_BOOLEAN("change_hatv", 1), @@ -2179,6 +2185,7 @@ static struct aa_sfs_entry aa_sfs_entry_features[] = { AA_SFS_DIR("rlimit", aa_sfs_entry_rlimit), AA_SFS_DIR("caps", aa_sfs_entry_caps), AA_SFS_DIR("ptrace", aa_sfs_entry_ptrace), + AA_SFS_DIR("signal", aa_sfs_entry_signal), AA_SFS_DIR("query", aa_sfs_entry_query), { } }; diff --git a/security/apparmor/include/apparmor.h b/security/apparmor/include/apparmor.h index aaf893f4e4f50c..962a20a75e010d 100644 --- a/security/apparmor/include/apparmor.h +++ b/security/apparmor/include/apparmor.h @@ -28,6 +28,7 @@ #define AA_CLASS_RLIMITS 5 #define AA_CLASS_DOMAIN 6 #define AA_CLASS_PTRACE 9 +#define AA_CLASS_SIGNAL 10 #define AA_CLASS_LABEL 16 #define AA_CLASS_LAST AA_CLASS_LABEL diff --git a/security/apparmor/include/audit.h b/security/apparmor/include/audit.h index c68839a44351e9..d9a156ae11b952 100644 --- a/security/apparmor/include/audit.h +++ b/security/apparmor/include/audit.h @@ -86,6 +86,7 @@ enum audit_type { #define OP_SHUTDOWN "socket_shutdown" #define OP_PTRACE "ptrace" +#define OP_SIGNAL "signal" #define OP_EXEC "exec" @@ -126,6 +127,7 @@ struct apparmor_audit_data { long pos; const char *ns; } iface; + int signal; struct { int rlim; unsigned long max; diff --git a/security/apparmor/include/ipc.h b/security/apparmor/include/ipc.h index 656fdb81c8a0a0..5ffc218d1e748a 100644 --- a/security/apparmor/include/ipc.h +++ b/security/apparmor/include/ipc.h @@ -27,8 +27,14 @@ struct aa_profile; #define AA_PTRACE_PERM_MASK (AA_PTRACE_READ | AA_PTRACE_TRACE | \ AA_MAY_BE_READ | AA_MAY_BE_TRACED) +#define AA_SIGNAL_PERM_MASK (MAY_READ | MAY_WRITE) + +#define AA_SFS_SIG_MASK "hup int quit ill trap abrt bus fpe kill usr1 " \ + "segv usr2 pipe alrm term stkflt chld cont stop stp ttin ttou urg " \ + "xcpu xfsz vtalrm prof winch io pwr sys emt lost" int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee, u32 request); +int aa_may_signal(struct aa_label *sender, struct aa_label *target, int sig); #endif /* __AA_IPC_H */ diff --git a/security/apparmor/include/sig_names.h b/security/apparmor/include/sig_names.h new file mode 100644 index 00000000000000..0d4395f231ca8b --- /dev/null +++ b/security/apparmor/include/sig_names.h @@ -0,0 +1,95 @@ +#include + +#define SIGUNKNOWN 0 +#define MAXMAPPED_SIG 35 +/* provide a mapping of arch signal to internal signal # for mediation + * those that are always an alias SIGCLD for SIGCLHD and SIGPOLL for SIGIO + * map to the same entry those that may/or may not get a separate entry + */ +static const int sig_map[MAXMAPPED_SIG] = { + [0] = MAXMAPPED_SIG, /* existence test */ + [SIGHUP] = 1, + [SIGINT] = 2, + [SIGQUIT] = 3, + [SIGILL] = 4, + [SIGTRAP] = 5, /* -, 5, - */ + [SIGABRT] = 6, /* SIGIOT: -, 6, - */ + [SIGBUS] = 7, /* 10, 7, 10 */ + [SIGFPE] = 8, + [SIGKILL] = 9, + [SIGUSR1] = 10, /* 30, 10, 16 */ + [SIGSEGV] = 11, + [SIGUSR2] = 12, /* 31, 12, 17 */ + [SIGPIPE] = 13, + [SIGALRM] = 14, + [SIGTERM] = 15, + [SIGSTKFLT] = 16, /* -, 16, - */ + [SIGCHLD] = 17, /* 20, 17, 18. SIGCHLD -, -, 18 */ + [SIGCONT] = 18, /* 19, 18, 25 */ + [SIGSTOP] = 19, /* 17, 19, 23 */ + [SIGTSTP] = 20, /* 18, 20, 24 */ + [SIGTTIN] = 21, /* 21, 21, 26 */ + [SIGTTOU] = 22, /* 22, 22, 27 */ + [SIGURG] = 23, /* 16, 23, 21 */ + [SIGXCPU] = 24, /* 24, 24, 30 */ + [SIGXFSZ] = 25, /* 25, 25, 31 */ + [SIGVTALRM] = 26, /* 26, 26, 28 */ + [SIGPROF] = 27, /* 27, 27, 29 */ + [SIGWINCH] = 28, /* 28, 28, 20 */ + [SIGIO] = 29, /* SIGPOLL: 23, 29, 22 */ + [SIGPWR] = 30, /* 29, 30, 19. SIGINFO 29, -, - */ +#ifdef SIGSYS + [SIGSYS] = 31, /* 12, 31, 12. often SIG LOST/UNUSED */ +#endif +#ifdef SIGEMT + [SIGEMT] = 32, /* 7, - , 7 */ +#endif +#if defined(SIGLOST) && SIGPWR != SIGLOST /* sparc */ + [SIGLOST] = 33, /* unused on Linux */ +#endif +#if defined(SIGLOST) && defined(SIGSYS) && SIGLOST != SIGSYS + [SIGUNUSED] = 34, /* -, 31, - */ +#endif +}; + +/* this table is ordered post sig_map[sig] mapping */ +static const char *const sig_names[MAXMAPPED_SIG + 1] = { + "unknown", + "hup", + "int", + "quit", + "ill", + "trap", + "abrt", + "bus", + "fpe", + "kill", + "usr1", + "segv", + "usr2", + "pipe", + "alrm", + "term", + "stkflt", + "chld", + "cont", + "stop", + "stp", + "ttin", + "ttou", + "urg", + "xcpu", + "xfsz", + "vtalrm", + "prof", + "winch", + "io", + "pwr", + "sys", + "emt", + "lost", + "unused", + + "exists", /* always last existence test mapped to MAXMAPPED_SIG */ +}; + diff --git a/security/apparmor/ipc.c b/security/apparmor/ipc.c index 11e66b5bbc4266..66fb9ede9447ad 100644 --- a/security/apparmor/ipc.c +++ b/security/apparmor/ipc.c @@ -20,6 +20,7 @@ #include "include/context.h" #include "include/policy.h" #include "include/ipc.h" +#include "include/sig_names.h" /** * audit_ptrace_mask - convert mask to permission string @@ -121,3 +122,101 @@ int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee, } +static inline int map_signal_num(int sig) +{ + if (sig > SIGRTMAX) + return SIGUNKNOWN; + else if (sig >= SIGRTMIN) + return sig - SIGRTMIN + 128; /* rt sigs mapped to 128 */ + else if (sig <= MAXMAPPED_SIG) + return sig_map[sig]; + return SIGUNKNOWN; +} + +/** + * audit_file_mask - convert mask to permission string + * @buffer: buffer to write string to (NOT NULL) + * @mask: permission mask to convert + */ +static void audit_signal_mask(struct audit_buffer *ab, u32 mask) +{ + if (mask & MAY_READ) + audit_log_string(ab, "receive"); + if (mask & MAY_WRITE) + audit_log_string(ab, "send"); +} + +/** + * audit_cb - call back for signal specific audit fields + * @ab: audit_buffer (NOT NULL) + * @va: audit struct to audit values of (NOT NULL) + */ +static void audit_signal_cb(struct audit_buffer *ab, void *va) +{ + struct common_audit_data *sa = va; + + if (aad(sa)->request & AA_SIGNAL_PERM_MASK) { + audit_log_format(ab, " requested_mask="); + audit_signal_mask(ab, aad(sa)->request); + if (aad(sa)->denied & AA_SIGNAL_PERM_MASK) { + audit_log_format(ab, " denied_mask="); + audit_signal_mask(ab, aad(sa)->denied); + } + } + if (aad(sa)->signal <= MAXMAPPED_SIG) + audit_log_format(ab, " signal=%s", sig_names[aad(sa)->signal]); + else + audit_log_format(ab, " signal=rtmin+%d", + aad(sa)->signal - 128); + audit_log_format(ab, " peer="); + aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer, + FLAGS_NONE, GFP_ATOMIC); +} + +/* TODO: update to handle compound name&name2, conditionals */ +static void profile_match_signal(struct aa_profile *profile, const char *label, + int signal, struct aa_perms *perms) +{ + unsigned int state; + + /* TODO: secondary cache check */ + state = aa_dfa_next(profile->policy.dfa, + profile->policy.start[AA_CLASS_SIGNAL], + signal); + state = aa_dfa_match(profile->policy.dfa, state, label); + aa_compute_perms(profile->policy.dfa, state, perms); +} + +static int profile_signal_perm(struct aa_profile *profile, + struct aa_profile *peer, u32 request, + struct common_audit_data *sa) +{ + struct aa_perms perms; + + if (profile_unconfined(profile) || + !PROFILE_MEDIATES(profile, AA_CLASS_SIGNAL)) + return 0; + + aad(sa)->peer = &peer->label; + profile_match_signal(profile, peer->base.hname, aad(sa)->signal, + &perms); + aa_apply_modes_to_perms(profile, &perms); + return aa_check_perms(profile, &perms, request, sa, audit_signal_cb); +} + +static int aa_signal_cross_perm(struct aa_profile *sender, + struct aa_profile *target, + struct common_audit_data *sa) +{ + return xcheck(profile_signal_perm(sender, target, MAY_WRITE, sa), + profile_signal_perm(target, sender, MAY_READ, sa)); +} + +int aa_may_signal(struct aa_label *sender, struct aa_label *target, int sig) +{ + DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, OP_SIGNAL); + + aad(&sa)->signal = map_signal_num(sig); + return xcheck_labels_profiles(sender, target, aa_signal_cross_perm, + &sa); +} diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c index 867bcd154c7e63..af22f3dfbcce03 100644 --- a/security/apparmor/lsm.c +++ b/security/apparmor/lsm.c @@ -656,6 +656,26 @@ static int apparmor_task_setrlimit(struct task_struct *task, return error; } +static int apparmor_task_kill(struct task_struct *target, struct siginfo *info, + int sig, u32 secid) +{ + struct aa_label *cl, *tl; + int error; + + if (secid) + /* TODO: after secid to label mapping is done. + * Dealing with USB IO specific behavior + */ + return 0; + cl = __begin_current_label_crit_section(); + tl = aa_get_task_label(target); + error = aa_may_signal(cl, tl, sig); + aa_put_label(tl); + __end_current_label_crit_section(cl); + + return error; +} + static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(ptrace_access_check, apparmor_ptrace_access_check), LSM_HOOK_INIT(ptrace_traceme, apparmor_ptrace_traceme), @@ -697,6 +717,7 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(bprm_secureexec, apparmor_bprm_secureexec), LSM_HOOK_INIT(task_setrlimit, apparmor_task_setrlimit), + LSM_HOOK_INIT(task_kill, apparmor_task_kill), }; /*