Re: [PATCH] Updated audit failure query functionality

["Timothy R. Chavez" <tinytim@us.ibm.com>]

On Mon, 2006-06-26 at 15:23 -0400, Lisa Smith wrote:
> This is an updated patch for the audit failure query 
> functionality.  The patch has been completely rewritten
> to match the programming style and algorithms used in
> auditd-config.c.
<snip>
> 
> Lisa

Hi Lisa,

I had some comments below.  Thanks!

-tim

> 
> -------------------
> 
>  libaudit.c |  246 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  libaudit.h |   11 ++
>  2 files changed, 257 insertions(+)
> 
> diff -burN orig/libaudit.c src/libaudit.c
> --- orig/libaudit.c     2006-05-25 17:39:52.000000000 -0400
> +++ src/libaudit.c      2006-06-26 15:00:56.000000000 -0400
> @@ -42,13 +42,56 @@
>  #include "libaudit.h"
>  #include "private.h"
> 
> +/* Local prototypes */
> +struct nv_pair
> +{
> +        const char *name;
> +        const char *value;
> +};
> +
> +struct kw_pair
> +{
> +        const char *name;
> +        int (*parser)(const char *, int);
> +};
> +
> +struct nv_list
> +{
> +        const char *name;
> +        int option;
> +};
> +
> +struct libaudit_conf
> +{
> +        auditfail_t failure_action;
> +};
> 
>  int audit_archadded = 0;
>  int audit_syscalladded = 0;
>  unsigned int audit_elf = 0U;
> +static struct libaudit_conf config;
> +static int load_libaudit_config();
> +static char *get_line(FILE *f, char *buf);
> +static int nv_split(char *buf, struct nv_pair *nv);
> +static const struct kw_pair *kw_lookup(const char *val);
> +static int audit_failure_parser(const char *val, int line);
>  static int name_to_uid(const char *name, uid_t *uid);
>  static int name_to_gid(const char *name, gid_t *gid);
> 
> +static const struct kw_pair keywords[] =
> +{
> +  {"failure_action",           audit_failure_parser },
> +  { NULL,                      NULL }
> +};
> +
> +static const struct nv_list failure_actions[] =
> +{
> +  {"ignore",                   FA_IGNORE },
> +  {"log",                      FA_LOG },
> +  {"terminate",                FA_TERMINATE },
> +  { NULL,                      0 }
> +};
> +
> 
>  int audit_request_status(int fd)
>  {
> @@ -68,6 +111,209 @@
>         return rc;
>  }
> 
> +/*
> + * Set everything to its default value
> +*/
> +static void clear_config()
> +{
> +        config.failure_action = FA_IGNORE;
> +}
> +
> +static int load_libaudit_config()
> +{
> +        int fd, rc, lineno = 1;
> +        struct stat st;
> +        FILE *f;
> +        char buf[128];
> +
> +        clear_config();
> +
> +        /* open the file */
> +        rc = open(CONFIG_FILE, O_NOFOLLOW|O_RDONLY);
> +        if (rc < 0) {
> +                if (errno != ENOENT) {
> +                        audit_msg(LOG_ERR, "Error opening config file (%s)",
> +                                strerror(errno));
> +                        return 1;
> +                }
> +                audit_msg(LOG_WARNING,
> +                        "Config file %s doesn't exist, skipping", CONFIG_FILE);
> +                return 0;
> +        }
> +        fd = rc;
> +
> +        /* check the file's permissions: owned by root, not world writable,
> +         * not symlink.
> +         */
> +        audit_msg(LOG_DEBUG, "Config file %s opened for parsing",
> +                        CONFIG_FILE);
> +        if (fstat(fd, &st) < 0) {
> +                audit_msg(LOG_ERR, "Error fstat'ing config file (%s)",
> +                        strerror(errno));
> +                return 1;
> +        }
> +        if (st.st_uid != 0) {
> +                audit_msg(LOG_ERR, "Error - %s isn't owned by root",
> +                        CONFIG_FILE);
> +                return 1;
> +        }

Hm, you really want to hard-code in a root check?  What if you're acting
as another type of administrator with access to audit?  Done know, I
could be out of line here.

[..]
> +        if ((st.st_mode & S_IWOTH) == S_IWOTH) {
> +                audit_msg(LOG_ERR, "Error - %s is world writable",
> +                        CONFIG_FILE);
> +                return 1;
> +        }
> +        if (!S_ISREG(st.st_mode)) {
> +                audit_msg(LOG_ERR, "Error - %s is not a regular file",
> +                        CONFIG_FILE);
> +                return 1;
> +        }
> +
> +        /* it's ok, read line by line */
> +        f = fdopen(fd, "r");
> +        if (f == NULL) {
> +                audit_msg(LOG_ERR, "Error - fdopen failed (%s)",
> +                        strerror(errno));
> +                return 1;
> +        }
> +
> +        while (get_line(f, buf)) {
> +                // convert line into name-value pair
> +                const struct kw_pair *kw;
> +                struct nv_pair nv;
> +                rc = nv_split(buf, &nv);
> +                switch (rc) {
> +                        case 0: // fine
> +                                break;
> +                        case 1: // not the right number of tokens.
> +                                audit_msg(LOG_ERR,
> +                                "Wrong number of arguments for line %d in %s",
> +                                        lineno, CONFIG_FILE);
> +                                break;
> +                        case 2: // no '=' sign
> +                                audit_msg(LOG_ERR,
> +                                        "Missing equal sign for line %d in %s",
> +                                        lineno, CONFIG_FILE);
> +                                break;
> +                        default: // something else went wrong...
> +                                audit_msg(LOG_ERR,
> +                                        "Unknown error for line %d in %s",
> +                                        lineno, CONFIG_FILE);
> +                                break;
> +                }
> +                if (nv.name == NULL) {
> +                        lineno++;
> +                        continue;
> +                }
> +
> +                /* identify keyword or error */
> +                kw = kw_lookup(nv.name);
> +                if (kw->name == NULL) {
> +                        audit_msg(LOG_ERR,
> +                                "Unknown keyword \"%s\" in line %d of %s",
> +                                nv.name, lineno, CONFIG_FILE);
> +                        fclose(f);
> +                        return 1;
> +                }
> +
> +                /* dispatch to keyword's local parser */
> +                rc = kw->parser(nv.value, lineno);
> +                if (rc != 0) {
> +                        fclose(f);
> +                        return 1; // local parser puts message out
> +                }
> +
> +                lineno++;
> +        }
> +
> +        fclose(f);
> +        return 0;
> +}
> +
> +int get_auditfail_action(auditfail_t *failmode)
> +{
> +       if (load_libaudit_config())
> +               *failmode = config.failure_action;
> +               return 1;

Missing brackets?

[..]
> +
> +       *failmode = config.failure_action;
> +       return 0;
> +}
> +
> +
> +static char *get_line(FILE *f, char *buf)
> +{
> +        if (fgets_unlocked(buf, 128, f)) {
> +                /* remove newline */
> +                char *ptr = strchr(buf, 0x0a);
> +                if (ptr)
> +                        *ptr = 0;
> +                return buf;
> +        }
> +        return NULL;
> +}
> +
> +static int nv_split(char *buf, struct nv_pair *nv)
> +{
> +        /* Get the name part */
> +        char *ptr;
> +
> +        nv->name = NULL;
> +        nv->value = NULL;
> +        ptr = strtok(buf, " ");
> +        if (ptr == NULL)
> +                return 0; /* If there's nothing, go to next line */
> +        if (ptr[0] == '#')
> +                return 0; /* If there's a comment, go to next line */

I still think this will break if ptr[0] happens to be a space followed
by a '#'.  I suppose it could break by design if the first character of
the line is not '#', but I wouldn't like that much as a user myself.

[..]
> +        nv->name = ptr;
> +
> +        /* Check for a '=' */
> +        ptr = strtok(NULL, " ");
> +        if (ptr == NULL)
> +                return 1;
> +        if (strcmp(ptr, "=") != 0)

No real need to do a strcmp here.

if (ptr && *ptr == '=')

[..]
> +                return 2;
> +
> +        /* get the value */
> +        ptr = strtok(NULL, " ");
> +        if (ptr == NULL)
> +                return 1;
> +        nv->value = ptr;

I'll be the first to admit that I relatively little experience with
strtok, but is this pointer assignment even safe?  You're pointing into
a buffer that could potentially be overwritten by another app, right?

Here's my off-the-top-of-the-head, uncompiled, and untested example
using strtok_r... 

char *buf;
char *ptr;

buf = (char *)malloc(128);
if (!buf) {
	/* handle memory error */
}
ptr = strtok_r(line, "=", buf);
if (!ptr || *buf == '\0') {
	/* not "token=value", free memory */
}
/* <do comment check here> */
nv->name = (char*)malloc(strlen(ptr)+1);
if (!nv->name) {
	/* handle memory error */
}
strcpy(nv->name, ptr);
nv->value = (char*)malloc(strlen(buf)+1);
if (!nv->value) {
	/* handle memory error */
}
strcpy(nv->value, buf);

/* clean up memory */
return 0;

You may not care about whether or not you're thread-safe or being able
to have multiple word token values... but at least by providing your own
buffer, you can keep track of your position in the parsed string in a
lovely way.  

[..]
> +
> +        /* Make sure there's nothing else */
> +        ptr = strtok(NULL, " ");
> +        if (ptr)
> +                return 1;
> +
> +        /* Everything is OK */
> +        return 0;
> +}
> +
> +static const struct kw_pair *kw_lookup(const char *val)
> +{
> +        int i = 0;
> +        while (keywords[i].name != NULL) {
> +                if (strcasecmp(keywords[i].name, val) == 0)
> +                        break;
> +                i++;
> +        }
> +        return &keywords[i];

So I think this would look better a for-loop as you're in fact iterating
anyway :) *oh my, looks down at next function*

[..]
> +}
> +
> +static int audit_failure_parser(const char *val, int line)
> +{
> +        int i;
> +
> +        audit_msg(LOG_DEBUG, "audit_failure_parser called with: %s", val);
> +        for (i=0; failure_actions[i].name != NULL; i++) {
> +                if (strcasecmp(val, failure_actions[i].name) == 0) {
> +                        config.failure_action = failure_actions[i].option;
> +                        return 0;
> +                }
> +        }

:)

[..]
> +        audit_msg(LOG_ERR, "Option %s not found - line %d", val, line);
> +        return 1;
> +}
> +
>  int audit_set_enabled(int fd, uint32_t enabled)
>  {
>         int rc;
> diff -burN orig/libaudit.h src/libaudit.h
> --- orig/libaudit.h     2006-05-25 17:38:21.000000000 -0400
> +++ src/libaudit.h      2006-06-26 14:58:53.000000000 -0400
> @@ -248,6 +248,16 @@
>          MACH_ALPHA
>  } machine_t;
> 
> +/* These are the valid audit failure tunable enum values */
> +typedef enum {
> +       FA_IGNORE=0,
> +       FA_LOG,
> +       FA_TERMINATE
> +} auditfail_t;
> +
> +/* #defines for the audit failure query  */
> +#define CONFIG_FILE "/etc/libaudit.conf"
> +
>  /*
>   * audit_rule_data supports filter rules with both integer and string
>   * fields. It corresponds with AUDIT_ADD_RULE, AUDIT_DEL_RULE and
> @@ -362,6 +372,7 @@
>  /* AUDIT_GET */
>  extern int audit_request_status(int fd);
>  extern int audit_is_enabled(int fd);
> +extern int get_auditfail_action(auditfail_t *failmode);
> 
>  /* AUDIT_SET */
>  typedef enum { WAIT_NO, WAIT_YES } rep_wait_t;