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I've pushed it to a pamcap-enhancements branch and I'll will try to
review it quickly.
Thanks
Andrew
KaiGai Kohei wrote:
> Sorry, any TABs are replaced by MUA.
> I'll send the patch again.
>
>> The attached patch provides several improvement for pam_cap module.
>> 1. It enables pam_cap to drop capabilities from process'es capability
>> bounding set.
>> 2. It enables to specify allowing inheritable capability set or dropping
>> bounding capability set for groups, not only users.
>> 3. It provide pam_sm_session() method, not only pam_sm_authenticate()
>> and pam_sm_setcred(). A system administrator can select more
>> appropriate mode for his purpose.
>> 4. In the auth/cred mode, it enables to cache the configuration file,
>> to avoid read and analyze it twice.
>> (Therefore, most of the part in the original one got replaced....)
>>
>> The default configuration file is "/etc/security/capability.conf".
>> You can describe as follows:
>> --------
>> # kaigai get cap_net_raw and cap_kill, tak get cap_sys_pacct pI.
>> # We can omit "i:" in the head of each line.
>> i:cap_net_raw,cap_kill kaigai
>> cap_sys_pacct tak
>>
>> # ymj and tak lost cap_sys_chroot from cap_bset
>> b:cap_sys_chroot ymj tak
>>
>> # Any user within webadm group get cap_net_bind_service pI.
>> i:cap_net_bind_service @webadm
>>
>> # Any user within users group lost cap_sys_module from cap_bset
>> b:cap_sys_module @users
>> --------
>>
>> When a user or groups he belongs is on several lines, all configurations
>> are simplly compounded.
>>
>> In the above example, if tak belongs to webadm and users group,
>> he will get cap_sys_pacct and cap_net_bind_service pI, and lost
>> cap_sys_chroot and cap_sys_module from his cap_bset.
>>
>> Thanks,
>
> Signed-off-by: KaiGai Kohei <[email protected]>
> --
> pam_cap/capability.conf | 6 +
> pam_cap/pam_cap.c | 495 ++++++++++++++++++++++++++++-------------------
> 2 files changed, 305 insertions(+), 196 deletions(-)
>
> diff --git a/pam_cap/capability.conf b/pam_cap/capability.conf
> index b543142..707cdc3 100644
> --- a/pam_cap/capability.conf
> +++ b/pam_cap/capability.conf
> @@ -24,6 +24,12 @@ cap_setfcap morgan
> ## 'everyone else' gets no inheritable capabilities
> none *
>
> +# user 'kaigai' lost CAP_NET_RAW capability from bounding set
> +b:cap_net_raw kaigai
> +
> +# group 'acctadm' get CAP_SYS_PACCT inheritable capability
> +i:cap_sys_pacct @acctadm
> +
> ## if there is no '*' entry, all users not explicitly mentioned will
> ## get all available capabilities. This is a permissive default, and
> ## probably not what you want...
> diff --git a/pam_cap/pam_cap.c b/pam_cap/pam_cap.c
> index 94c5ebc..a917d5c 100644
> --- a/pam_cap/pam_cap.c
> +++ b/pam_cap/pam_cap.c
> @@ -1,5 +1,6 @@
> /*
> * Copyright (c) 1999,2007 Andrew G. Morgan <[email protected]>
> + * Copyright (c) 2007 KaiGai Kohei <[email protected]>
> *
> * The purpose of this module is to enforce inheritable capability sets
> * for a specified user.
> @@ -13,298 +14,400 @@
> #include <stdarg.h>
> #include <stdlib.h>
> #include <syslog.h>
> +#include <pwd.h>
> +#include <grp.h>
>
> #include <sys/capability.h>
> +#include <sys/prctl.h>
>
> #include <security/pam_modules.h>
> #include <security/_pam_macros.h>
>
> +#define MODULE_NAME "pam_cap"
> #define USER_CAP_FILE "/etc/security/capability.conf"
> #define CAP_FILE_BUFFER_SIZE 4096
> #define CAP_FILE_DELIMITERS " \t\n"
> -#define CAP_COMBINED_FORMAT "%s all-i %s+i"
> -#define CAP_DROP_ALL "%s all-i"
> +
> +#ifndef PR_CAPBSET_DROP
> +#define PR_CAPBSET_DROP 24
> +#endif
> +
> +extern char const *_cap_names[];
>
> struct pam_cap_s {
> int debug;
> const char *user;
> const char *conf_filename;
> + /* set in read_capabilities_for_user() */
> + cap_t result;
> + int do_set_inh : 1;
> + int do_set_bset : 1;
> };
>
> -/* obtain the inheritable capabilities for the current user */
> -
> -static char *read_capabilities_for_user(const char *user, const char *source)
> +/* obtain the inheritable/bounding capabilities for the current user */
> +static int read_capabilities_for_user(struct pam_cap_s *pcs)
> {
> - char *cap_string = NULL;
> - char buffer[CAP_FILE_BUFFER_SIZE], *line;
> + char buffer[CAP_FILE_BUFFER_SIZE];
> FILE *cap_file;
> + struct passwd *pwd;
> + int line_num = 0;
> + int rc = -1; /* PAM_(AUTH|CRED|SESSION)_ERR */
> +
> + pwd = getpwnam(pcs->user);
> + if (!pwd) {
> + syslog(LOG_ERR, "user %s not in passwd entries", pcs->user);
> + return PAM_AUTH_ERR;
> + }
>
> - cap_file = fopen(source, "r");
> - if (cap_file == NULL) {
> - D(("failed to open capability file"));
> - return NULL;
> + cap_file = fopen(pcs->conf_filename, "r");
> + if (!cap_file) {
> + if (errno == ENOENT) {
> + syslog(LOG_NOTICE, "%s is not found",
> + pcs->conf_filename);
> + return PAM_IGNORE;
> + } else {
> + syslog(LOG_ERR, "unable to open '%s' (%s)",
> + pcs->conf_filename, strerror(errno));
> + return rc;
> + }
> }
>
> - while ((line = fgets(buffer, CAP_FILE_BUFFER_SIZE, cap_file))) {
> - int found_one = 0;
> - const char *cap_text;
> + pcs->result = NULL;
> + while (fgets(buffer, CAP_FILE_BUFFER_SIZE, cap_file) != NULL) {
> + char *pos, *cap_text;
> + int matched = 0;
> + int line_ops = CAP_INHERITABLE;
>
> - cap_text = strtok(line, CAP_FILE_DELIMITERS);
> + line_num++;
>
> - if (cap_text == NULL) {
> - D(("empty line"));
> - continue;
> - }
> - if (*cap_text == '#') {
> - D(("comment line"));
> + /* remove comment */
> + pos = strchr(buffer, '#');
> + if (pos)
> + *pos = '\0';
> +
> + cap_text = strtok(buffer, CAP_FILE_DELIMITERS);
> + /* empty line */
> + if (!cap_text)
> continue;
> +
> + if (!strncmp(cap_text, "b:", 2)) {
> + /* permitted field is used to store bounding set */
> + line_ops = CAP_PERMITTED;
> + cap_text += 2;
> + } else if (!strncmp(cap_text, "i:", 2)) {
> + cap_text += 2;
> }
>
> - while ((line = strtok(NULL, CAP_FILE_DELIMITERS))) {
> + /* check members */
> + while ((pos = strtok(NULL, CAP_FILE_DELIMITERS)) != NULL) {
> + /* wildcard */
> + if (!strcmp("*", pos)) {
> + matched = 1;
> + break;
> + }
>
> - if (strcmp("*", line) == 0) {
> - D(("wildcard matched"));
> - found_one = 1;
> - cap_string = strdup(cap_text);
> + /* It it group name? */
> + if (*pos == '@') {
> + struct group *grp;
> + int i;
> +
> + pos++;
> + grp = getgrnam(pos);
> + if (!grp) {
> + if (pcs->debug)
> + syslog(LOG_DEBUG, "group '%s' not found at line:%d",
> + pos, line_num);
> + continue;
> + }
> +
> + if (pwd->pw_gid == grp->gr_gid) {
> + if (pcs->debug)
> + syslog(LOG_DEBUG, "user %s matched with group %s at line:%d",
> + pcs->user, pos, line_num);
> + matched = 1;
> + break;
> + }
> +
> + for (i=0; grp->gr_mem[i]; i++) {
> + if (!strcmp(pcs->user, grp->gr_mem[i])) {
> + if (pcs->debug)
> + syslog(LOG_DEBUG, "user %s matched with group %s at line:%d",
> + pcs->user, pos, line_num);
> + matched = 1;
> + break;
> + }
> + }
> + syslog(LOG_ERR, "no matching %s", pos);
> + } else if (!strcmp(pcs->user, pos)) {
> + if (pcs->debug)
> + syslog(LOG_DEBUG, "user '%s' matched at line:%d",
> + pos, line_num);
> + matched = 1;
> break;
> }
> + }
> +
> + if (matched) {
> + char tmpbuf[CAP_FILE_BUFFER_SIZE];
> + cap_t tmp;
> + cap_value_t value;
> + cap_flag_value_t code;
> +
> + if (!pcs->result) {
> + pcs->result = cap_init();
> + if (!pcs->result) {
> + syslog(LOG_ERR, "unable to allocate cap_t object (%s)",
> + strerror(errno));
> + goto out;
> + }
> + }
>
> - if (strcmp(user, line) == 0) {
> - D(("exact match for user"));
> - found_one = 1;
> - cap_string = strdup(cap_text);
> + switch (line_ops) {
> + case CAP_INHERITABLE:
> + pcs->do_set_inh = 1;
> + break;
> + case CAP_PERMITTED:
> + pcs->do_set_bset = 1;
> break;
> }
>
> - D(("user is not [%s] - skipping", line));
> + if (!strcmp(cap_text, "none"))
> + continue;
> +
> + snprintf(tmpbuf, sizeof(tmpbuf), "%s=p", cap_text);
> + tmp = cap_from_text(tmpbuf);
> + if (!tmp) {
> + syslog(LOG_ERR, "unable to convert '%s' (%s)",
> + tmpbuf, strerror(errno));
> + cap_free(pcs->result);
> + pcs->result = NULL;
> + goto out;
> + }
> +
> + for (value=0; ;value++) {
> + if (cap_get_flag(tmp, value, CAP_PERMITTED, &code) < 0)
> + break; /* If value == __CAP_BITS, we get EINVAL */
> + if (code == CAP_SET)
> + cap_set_flag(pcs->result, line_ops, 1, &value, CAP_SET);
> + }
> + cap_free(tmp);
> }
> + }
>
> - cap_text = NULL;
> - line = NULL;
> + if (pcs->debug) {
> + char *tmp = cap_to_text(pcs->result, NULL);
>
> - if (found_one) {
> - D(("user [%s] matched - caps are [%s]", user, cap_string));
> - break;
> - }
> + syslog(LOG_DEBUG, "configuration for user %s is %s",
> + pcs->user, tmp);
> + cap_free(tmp);
> }
> + rc = PAM_SUCCESS;
>
> + out:
> fclose(cap_file);
>
> - memset(buffer, 0, CAP_FILE_BUFFER_SIZE);
> -
> - return cap_string;
> + return rc;
> }
>
> /*
> * Set capabilities for current process to match the current
> * permitted+executable sets combined with the configured inheritable
> - * set.
> + * and bounding set.
> */
>
> -static int set_capabilities(struct pam_cap_s *cs)
> +static int set_capabilities(struct pam_cap_s *pcs)
> {
> - cap_t cap_s;
> - ssize_t length = 0;
> - char *conf_icaps;
> - char *proc_epcaps;
> - char *combined_caps;
> - int ok = 0;
> -
> - cap_s = cap_get_proc();
> - if (cap_s == NULL) {
> - D(("your kernel is capability challenged - upgrade: %s",
> - strerror(errno)));
> - return 0;
> - }
> -
> - conf_icaps =
> - read_capabilities_for_user(cs->user,
> - cs->conf_filename
> - ? cs->conf_filename:USER_CAP_FILE );
> - if (conf_icaps == NULL) {
> - D(("no capabilities found for user [%s]", cs->user));
> - goto cleanup_cap_s;
> - }
> -
> - proc_epcaps = cap_to_text(cap_s, &length);
> - if (proc_epcaps == NULL) {
> - D(("unable to convert process capabilities to text"));
> - goto cleanup_icaps;
> - }
> -
> - /*
> - * This is a pretty inefficient way to combine
> - * capabilities. However, it seems to be the most straightforward
> - * one, given the limitations of the POSIX.1e draft spec. The spec
> - * is optimized for applications that know the capabilities they
> - * want to manipulate at compile time.
> - */
> -
> - combined_caps = malloc(1+strlen(CAP_COMBINED_FORMAT)
> - +strlen(proc_epcaps)+strlen(conf_icaps));
> - if (combined_caps == NULL) {
> - D(("unable to combine capabilities into one string - no memory"));
> - goto cleanup_epcaps;
> - }
> -
> - if (!strcmp(conf_icaps, "none")) {
> - sprintf(combined_caps, CAP_DROP_ALL, proc_epcaps);
> - } else if (!strcmp(conf_icaps, "all")) {
> - /* no change */
> - sprintf(combined_caps, "%s", proc_epcaps);
> - } else {
> - sprintf(combined_caps, CAP_COMBINED_FORMAT, proc_epcaps, conf_icaps);
> - }
> - D(("combined_caps=[%s]", combined_caps));
> -
> - cap_free(cap_s);
> - cap_s = cap_from_text(combined_caps);
> - _pam_overwrite(combined_caps);
> - _pam_drop(combined_caps);
> -
> -#ifdef DEBUG
> - {
> - char *temp = cap_to_text(cap_s, NULL);
> - D(("abbreviated caps for process will be [%s]", temp));
> - cap_free(temp);
> - }
> -#endif /* DEBUG */
> -
> - if (cap_s == NULL) {
> - D(("no capabilies to set"));
> - } else if (cap_set_proc(cap_s) == 0) {
> - D(("capabilities were set correctly"));
> - ok = 1;
> - } else {
> - D(("failed to set specified capabilities: %s", strerror(errno)));
> - }
> -
> -cleanup_epcaps:
> - cap_free(proc_epcaps);
> -
> -cleanup_icaps:
> - _pam_overwrite(conf_icaps);
> - _pam_drop(conf_icaps);
> + cap_value_t value;
> + cap_flag_value_t code;
> + int rc = -1; /* PAM_(AUTH|CRED|SESSION)_ERR */
> +
> + /* set inheritable capability set */
> + if (pcs->do_set_inh) {
> + cap_t cap_s = cap_get_proc();
> + if (!cap_s) {
> + syslog(LOG_ERR, "your kernel is capability challenged - upgrade: %s",
> + strerror(errno));
> + goto out;
> + }
> + for (value=0; ;value++) {
> + if (cap_get_flag(pcs->result, value, CAP_INHERITABLE, &code))
> + break;
> + cap_set_flag(cap_s, CAP_INHERITABLE, 1, &value, code);
> + }
> + if (cap_set_proc(cap_s) < 0) {
> + if (errno == EPERM)
> + rc = PAM_PERM_DENIED;
> + syslog(LOG_ERR, "unable to set inheritable capabilities (%s)",
> + strerror(errno));
> + cap_free(cap_s);
> + goto out;
> + }
> + if (pcs->debug) {
> + char *tmp = cap_to_text(cap_s, NULL);
>
> -cleanup_cap_s:
> - if (cap_s) {
> + syslog(LOG_DEBUG, "user %s new capabilities: %s",
> + pcs->user, tmp);
> + cap_free(tmp);
> + }
> cap_free(cap_s);
> - cap_s = NULL;
> }
> + /* drop capability bounding set */
> + if (pcs->do_set_bset) {
> + for (value=0; ;value++) {
> + if (cap_get_flag(pcs->result, value, CAP_PERMITTED, &code))
> + break;
> + if (code == CAP_SET) {
> + if (prctl(PR_CAPBSET_DROP, value) < 0) {
> + syslog(LOG_ERR, "unable to drop capability b-set %u (%s)",
> + value, strerror(errno));
> + goto out;
> + }
> + if (pcs->debug)
> + syslog(LOG_DEBUG, "%s drops capability %s from bounding set",
> + pcs->user, _cap_names[value]);
> + }
> + }
> + }
> + rc = PAM_SUCCESS;
>
> - return ok;
> -}
> -
> -/* log errors */
> -
> -static void _pam_log(int err, const char *format, ...)
> -{
> - va_list args;
> + out:
> + cap_free(pcs->result);
>
> - va_start(args, format);
> - openlog("pam_cap", LOG_CONS|LOG_PID, LOG_AUTH);
> - vsyslog(err, format, args);
> - va_end(args);
> - closelog();
> + return rc;
> }
>
> -static void parse_args(int argc, const char **argv, struct pam_cap_s *pcs)
> +static int init_pam_cap(pam_handle_t *pamh, int argc, const char **argv,
> + struct pam_cap_s *pcs)
> {
> - int ctrl=0;
> + int ctrl, rc;
> +
> + /* Initialization */
> + memset(pcs, 0, sizeof(struct pam_cap_s));
> + pcs->conf_filename = USER_CAP_FILE;
> + rc = pam_get_user(pamh, &pcs->user, NULL);
> + if (rc == PAM_CONV_AGAIN) {
> + syslog(LOG_INFO, "user conversation is not available yet");
> + return PAM_INCOMPLETE;
> + }
> + if (rc != PAM_SUCCESS) {
> + syslog(LOG_INFO, "pam_get_user failed: %s", pam_strerror(pamh, rc));
> + return -1;
> + }
>
> /* step through arguments */
> for (ctrl=0; argc-- > 0; ++argv) {
> -
> if (!strcmp(*argv, "debug")) {
> pcs->debug = 1;
> } else if (!strcmp(*argv, "config=")) {
> pcs->conf_filename = strlen("config=") + *argv;
> } else {
> - _pam_log(LOG_ERR, "unknown option; %s", *argv);
> + syslog(LOG_ERR, "unknown option: %s", *argv);
> + return -1;
> }
> + }
> + return PAM_SUCCESS;
> +}
>
> +static void cleanup_pam_cap(pam_handle_t *pamh, void *data, int error_status)
> +{
> + struct pam_cap_s *pcs = (struct pam_cap_s *) data;
> +
> + if (pcs) {
> + if (pcs->result)
> + cap_free(pcs->result);
> + free(pcs);
> }
> }
>
> int pam_sm_authenticate(pam_handle_t *pamh, int flags,
> int argc, const char **argv)
> {
> - int retval;
> - struct pam_cap_s pcs;
> - char *conf_icaps;
> + struct pam_cap_s *pcs = NULL;
> + int rc = PAM_BUF_ERR;
>
> - memset(&pcs, 0, sizeof(pcs));
> + openlog(MODULE_NAME, LOG_CONS|LOG_PID, LOG_AUTHPRIV);
>
> - parse_args(argc, argv, &pcs);
> + pcs = malloc(sizeof(struct pam_cap_s));
> + if (!pcs)
> + goto error;
>
> - retval = pam_get_user(pamh, &pcs.user, NULL);
> + rc = init_pam_cap(pamh, argc, argv, pcs);
> + if (rc != PAM_SUCCESS)
> + goto error;
>
> - if (retval == PAM_CONV_AGAIN) {
> - D(("user conversation is not available yet"));
> - memset(&pcs, 0, sizeof(pcs));
> - return PAM_INCOMPLETE;
> - }
> + rc = read_capabilities_for_user(pcs);
> + if (rc != PAM_SUCCESS)
> + goto error;
>
> - if (retval != PAM_SUCCESS) {
> - D(("pam_get_user failed: %s", pam_strerror(pamh, retval)));
> - memset(&pcs, 0, sizeof(pcs));
> - return PAM_AUTH_ERR;
> + rc = pam_set_data(pamh, MODULE_NAME, pcs, cleanup_pam_cap);
> + if (rc == PAM_SUCCESS) {
> + /* OK, pam_sm_setcred() will be called next */
> + closelog();
> + return rc;
> }
>
> - conf_icaps =
> - read_capabilities_for_user(pcs.user,
> - pcs.conf_filename
> - ? pcs.conf_filename:USER_CAP_FILE );
> -
> - memset(&pcs, 0, sizeof(pcs));
> -
> - if (conf_icaps) {
> - D(("it appears that there are capabilities for this user [%s]",
> - conf_icaps));
> + error:
> + cleanup_pam_cap(pamh, pcs, rc);
> + closelog();
> + return rc < 0 ? PAM_AUTH_ERR : rc;
> +}
>
> - /* We could also store this as a pam_[gs]et_data item for use
> - by the setcred call to follow. As it is, there is a small
> - race associated with a redundant read. Oh well, if you
> - care, send me a patch.. */
> +int pam_sm_setcred(pam_handle_t *pamh, int flags,
> + int argc, const char **argv)
> +{
> + struct pam_cap_s *pcs = NULL;
> + int rc = PAM_IGNORE;
>
> - _pam_overwrite(conf_icaps);
> - _pam_drop(conf_icaps);
> + openlog(MODULE_NAME, LOG_CONS|LOG_PID, LOG_AUTHPRIV);
>
> - return PAM_SUCCESS;
> + if (!(flags & PAM_ESTABLISH_CRED))
> + goto out;
>
> - } else {
> + rc = pam_get_data(pamh, MODULE_NAME, (void *)&pcs);
> + if (rc != PAM_SUCCESS)
> + return rc;
>
> - D(("there are no capabilities restrctions on this user"));
> - return PAM_IGNORE;
> + rc = set_capabilities(pcs);
>
> - }
> + out:
> + closelog();
> + return rc < 0 ? PAM_CRED_ERR : rc;
> }
>
> -int pam_sm_setcred(pam_handle_t *pamh, int flags,
> - int argc, const char **argv)
> +int pam_sm_open_session(pam_handle_t *pamh, int flags,
> + int argc, const char **argv)
> {
> - int retval;
> struct pam_cap_s pcs;
> + int rc;
>
> - if (!(flags & PAM_ESTABLISH_CRED)) {
> - D(("we don't handle much in the way of credentials"));
> - return PAM_IGNORE;
> - }
> + openlog(MODULE_NAME, LOG_CONS|LOG_PID, LOG_AUTHPRIV);
>
> - memset(&pcs, 0, sizeof(pcs));
> + rc = init_pam_cap(pamh, argc, argv, &pcs);
> + if (rc != PAM_SUCCESS)
> + goto out;
>
> - parse_args(argc, argv, &pcs);
> + rc = read_capabilities_for_user(&pcs);
> + if (rc != PAM_SUCCESS)
> + goto out;
>
> - retval = pam_get_item(pamh, PAM_USER, (const void **)&pcs.user);
> - if ((retval != PAM_SUCCESS) || (pcs.user == NULL) || !(pcs.user[0])) {
> + rc = set_capabilities(&pcs);
>
> - D(("user's name is not set"));
> - return PAM_AUTH_ERR;
> + if (rc == PAM_SUCCESS) {
> + rc = set_capabilities(&pcs);
> + if (pcs.result)
> + cap_free(pcs.result);
> }
>
> - retval = set_capabilities(&pcs);
> + out:
> + if (pcs.result)
> + cap_free(pcs.result);
> + closelog();
>
> - memset(&pcs, 0, sizeof(pcs));
> + return rc < 0 ? PAM_SESSION_ERR : rc;
> +}
>
> - return (retval ? PAM_SUCCESS:PAM_IGNORE );
> +int pam_sm_close_session(pam_handle_t *pamh, int flags,
> + int argc, const char **argv)
> +{
> + return PAM_SUCCESS; /* do nothing */
> }
>
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