diff options
Diffstat (limited to 'runtime/staprun/staprun_funcs.c')
| -rw-r--r-- | runtime/staprun/staprun_funcs.c | 194 |
1 files changed, 130 insertions, 64 deletions
diff --git a/runtime/staprun/staprun_funcs.c b/runtime/staprun/staprun_funcs.c index 49b37988..40af1678 100644 --- a/runtime/staprun/staprun_funcs.c +++ b/runtime/staprun/staprun_funcs.c @@ -7,14 +7,20 @@ * Public License (GPL); either version 2, or (at your option) any * later version. * - * Copyright (C) 2007-2008 Red Hat Inc. + * Copyright (C) 2007-2009 Red Hat Inc. */ +#include "config.h" #include "staprun.h" +#if HAVE_NSS +#include "modverify.h" +#endif + #include <sys/mount.h> #include <sys/utsname.h> #include <grp.h> #include <pwd.h> +#include <assert.h> extern long init_module(void *, unsigned long, const char *); @@ -199,6 +205,44 @@ int mountfs(void) return 0; } +#if HAVE_NSS +/* + * Modules which have been signed using a certificate and private key + * corresponding to a certificate and public key in the database in + * the '$sysconfdir/systemtap/staprun' directory may be loaded by + * anyone. + * + * Returns: -1 on errors, 0 on failure, 1 on success. + */ +static int +check_signature(void) +{ + char module_realpath[PATH_MAX]; + char signature_realpath[PATH_MAX]; + int rc; + + dbug(2, "checking signature for %s\n", modpath); + + /* Use realpath() to canonicalize the module path. */ + if (realpath(modpath, module_realpath) == NULL) { + perr("Unable to canonicalize module path \"%s\"", modpath); + return MODULE_CHECK_ERROR; + } + + /* Now add the .sgn suffix to get the signature file name. */ + if (strlen (module_realpath) > PATH_MAX - 4) { + err("Path \"%s\" is too long.", modpath); + return MODULE_CHECK_ERROR; + } + sprintf (signature_realpath, "%s.sgn", module_realpath); + + rc = verify_module (module_realpath, signature_realpath); + + dbug(2, "verify_module returns %d\n", rc); + + return rc; +} +#endif /* HAVE_NSS */ /* * Members of the 'stapusr' group can only use "blessed" modules - @@ -302,35 +346,23 @@ check_path(void) } /* - * Check the user's permissions. Is he allowed to run staprun (or is - * he limited to "blessed" modules)? + * Check the user's group membership. Is he allowed to run staprun (or is * - * Returns: -1 on errors, 0 on failure, 1 on success. + * o members of stapdev can do anything + * o members of stapusr can load modules from /lib/modules/KVER/systemtap + * + * Returns: -2 if neither group exists + * -1 for other errors + * 0 on failure + * 1 on success */ -int check_permissions(void) +static int +check_groups (void) { gid_t gid, gidlist[NGROUPS_MAX]; gid_t stapdev_gid, stapusr_gid; int i, ngids; struct group *stgr; - int path_check = 0; - - /* If we're root, we can do anything. */ - if (getuid() == 0) { - /* ... like overriding the real UID */ - const char *env_id = getenv("SYSTEMTAP_REAL_UID"); - if (env_id && setreuid(atoi(env_id), -1)) - err("WARNING: couldn't set staprun UID to '%s': %s", - env_id, strerror(errno)); - - /* ... or overriding the real GID */ - env_id = getenv("SYSTEMTAP_REAL_GID"); - if (env_id && setregid(atoi(env_id), -1)) - err("WARNING: couldn't set staprun GID to '%s': %s", - env_id, strerror(errno)); - - return 1; - } /* Lookup the gid for group "stapdev" */ errno = 0; @@ -354,55 +386,42 @@ int check_permissions(void) else stapusr_gid = stgr->gr_gid; - /* If neither group was found, just return an error. */ - if (stapdev_gid == (gid_t)-1 && stapusr_gid == (gid_t)-1) { - err("ERROR: You are trying to run stap as a normal user.\n" - "You should either be root, or be part of either " - "group \"stapdev\" or group \"stapusr\".\n" - "Your system doesn't seem to have either group.\n" - "For more information, please consult the \"SAFETY AND SECURITY\" section of the \"stap(1)\" manpage\n"); - return -1; - } + /* If neither group was found, then return -2. */ + if (stapdev_gid == (gid_t)-1 && stapusr_gid == (gid_t)-1) + return -2; /* According to the getgroups() man page, getgroups() may not * return the effective gid, so try to match it first. */ gid = getegid(); if (gid == stapdev_gid) return 1; - else if (gid == stapusr_gid) - path_check = 1; - /* Get the list of the user's groups. */ - ngids = getgroups(NGROUPS_MAX, gidlist); - if (ngids < 0) { - perr("Unable to retrieve group list"); - return -1; - } - - for (i = 0; i < ngids; i++) { - /* If the user is a member of 'stapdev', then we're - * done, since he can use staprun without any - * restrictions. */ - if (gidlist[i] == stapdev_gid) - return 1; - - /* If the user is a member of 'stapusr', then we'll - * need to check the module path. However, we'll keep - * checking groups since it is possible the user is a - * member of both groups and we haven't seen the - * 'stapdev' group yet. */ - if (gidlist[i] == stapusr_gid) - path_check = 1; - } + if (gid != stapusr_gid) { + /* Get the list of the user's groups. */ + ngids = getgroups(NGROUPS_MAX, gidlist); + if (ngids < 0) { + perr("Unable to retrieve group list"); + return -1; + } - /* If path_check is 0, then the user isn't a member of either - * group. Error out. */ - if (path_check == 0) { - err("ERROR: You are trying to run stap as a normal user.\n" - "You must be a member of either group \"stapdev\" or group \"stapusr\".\n" - "Please contact your system administrator to get yourself membership to either of those groups.\n" - "For more information, please consult the \"SAFETY AND SECURITY\" section of the \"stap(1)\" manpage.\n"); - return 0; + for (i = 0; i < ngids; i++) { + /* If the user is a member of 'stapdev', then we're + * done, since he can use staprun without any + * restrictions. */ + if (gidlist[i] == stapdev_gid) + return 1; + + /* If the user is a member of 'stapusr', then we'll + * need to check the module path. However, we'll keep + * checking groups since it is possible the user is a + * member of both groups and we haven't seen the + * 'stapdev' group yet. */ + if (gidlist[i] == stapusr_gid) + gid = stapusr_gid; + } + /* Not a member of stapusr? */ + if (gid != stapusr_gid) + return 0; } /* At this point the user is only a member of the 'stapusr' @@ -411,3 +430,50 @@ int check_permissions(void) * is in that directory. */ return check_path(); } + +/* + * Check the user's permissions. Is he allowed to run staprun (or is + * he limited to "blessed" modules)? + * + * There are several levels of possible permission: + * + * 1) root can do anything + * 2) members of stapdev can do anything + * 3) members of stapusr can load modules from /lib/modules/KVER/systemtap + * + * It is only an error if all 3 levels of checking fail + * + * Returns: -1 on errors, 0 on failure, 1 on success. + */ +int check_permissions(void) +{ + int check_groups_rc; + int check_signature_rc = 0; + +#if HAVE_NSS + /* Attempt to verify the module against its signature. Return failure + if the module has been tampered with (altered). */ + check_signature_rc = check_signature (); + if (check_signature_rc == MODULE_ALTERED) + return 0; +#endif + + /* If we're root, we can do anything. */ + if (getuid() == 0) + return 1; + + /* Check permissions for group membership. */ + check_groups_rc = check_groups (); + if (check_groups_rc == 1) + return 1; + + err("ERROR: You are trying to run stap as a normal user.\n" + "You should either be root, or be part of either " + "group \"stapdev\" or group \"stapusr\".\n"); + if (check_groups_rc == -2) { + err("Your system doesn't seem to have either group.\n"); + check_groups_rc = -1; + } + + return check_groups_rc; +} |