On Thu, May 9, 2019 at 1:43 AM Petr Lautrbach <plautrba@xxxxxxxxxx> wrote: > > get_ordered_context_list() code used to ask the kernel to compute the complete > set of reachable contexts using /sys/fs/selinux/user aka > security_compute_user(). This set can be so huge so that it doesn't fit into a > kernel page and security_compute_user() fails. Even if it doesn't fail, > get_ordered_context_list() throws away the vast majority of the returned > contexts because they don't match anything in > /etc/selinux/targeted/contexts/default_contexts or > /etc/selinux/targeted/contexts/users/ > > get_ordered_context_list() is rewritten to compute set of contexts based on > /etc/selinux/targeted/contexts/users/ and > /etc/selinux/targeted/contexts/default_contexts files and to return only valid > contexts, using security_check_context(), from this set. Whats the best way to test this? > > Fixes: https://github.com/SELinuxProject/selinux/issues/28 > > Signed-off-by: Petr Lautrbach <plautrba@xxxxxxxxxx> > --- > libselinux/src/get_context_list.c | 185 ++++++++++-------------------- > 1 file changed, 60 insertions(+), 125 deletions(-) > > diff --git a/libselinux/src/get_context_list.c b/libselinux/src/get_context_list.c > index 689e4658..a36c6253 100644 > --- a/libselinux/src/get_context_list.c > +++ b/libselinux/src/get_context_list.c > @@ -114,61 +114,24 @@ int get_default_context(const char *user, > return 0; > } > > -static int find_partialcon(char ** list, > - unsigned int nreach, char *part) > -{ > - const char *conrole, *contype; > - char *partrole, *parttype, *ptr; > - context_t con; > - unsigned int i; > - > - partrole = part; > - ptr = part; > - while (*ptr && !isspace(*ptr) && *ptr != ':') > - ptr++; > - if (*ptr != ':') > - return -1; > - *ptr++ = 0; > - parttype = ptr; > - while (*ptr && !isspace(*ptr) && *ptr != ':') > - ptr++; > - *ptr = 0; > - > - for (i = 0; i < nreach; i++) { > - con = context_new(list[i]); > - if (!con) > - return -1; > - conrole = context_role_get(con); > - contype = context_type_get(con); > - if (!conrole || !contype) { > - context_free(con); > - return -1; > - } > - if (!strcmp(conrole, partrole) && !strcmp(contype, parttype)) { > - context_free(con); > - return i; > - } > - context_free(con); > - } > - > - return -1; > -} > - > -static int get_context_order(FILE * fp, > +static int get_context_user(FILE * fp, > char * fromcon, > - char ** reachable, > - unsigned int nreach, > - unsigned int *ordering, unsigned int *nordered) > + const char * user, > + char ***reachable, > + unsigned int *nreachable) > { > char *start, *end = NULL; > char *line = NULL; > size_t line_len = 0; > - ssize_t len; > + ssize_t len, ulen; > int found = 0; > - const char *fromrole, *fromtype; > + const char *fromrole, *fromtype, *fromlevel; > char *linerole, *linetype; > - unsigned int i; > + char **new_reachable = NULL; > + char *usercon_str; > context_t con; > + context_t usercon; > + > int rc; > > errno = -EINVAL; > @@ -180,7 +143,8 @@ static int get_context_order(FILE * fp, > return -1; > fromrole = context_role_get(con); > fromtype = context_type_get(con); > - if (!fromrole || !fromtype) { > + fromlevel = context_range_get(con); > + if (!fromrole || !fromtype || !fromlevel) { > context_free(con); > return -1; > } > @@ -243,23 +207,52 @@ static int get_context_order(FILE * fp, > if (*end) > *end++ = 0; > > - /* Check for a match in the reachable list. */ > - rc = find_partialcon(reachable, nreach, start); > - if (rc < 0) { > - /* No match, skip it. */ > - start = end; > - continue; > + /* Check whether a new context is valid */ > + ulen = strlen(user) + strlen(start) + 1; is their anything guaranteeing this doesn't overflow and result in malloc(0) which is undefined? also ulen is signed, why? All uses are where a size_t is valid, I think it can change to a size_t. > + usercon_str = malloc(ulen); spaces after tab, see: https://github.com/SELinuxProject/selinux/pull/146/files#diff-55a16252233f48b841c06ffbe22bb66dR211 > + if (!usercon_str) { > + rc = -1; > + goto out; > } > > - /* If a match is found and the entry is not already ordered > - (e.g. due to prior match in prior config file), then set > - the ordering for it. */ > - i = rc; > - if (ordering[i] == nreach) > - ordering[i] = (*nordered)++; > + /* set range from fromcon in the new usercon */ > + snprintf(usercon_str, ulen - 1, "%s:%s", user, start); > + if (!(usercon = context_new(usercon_str))) { You can drop the too free(usercon_str) if you rework this logic: usercon = context_new(usercon_str)) free(usercon_str); if (!usercon) { // error continue; } > + fprintf(stderr, > + "%s: can't create a context from %s\n", > + __FUNCTION__, usercon_str); > + free(usercon_str); > + > + continue; Why is it OK to continue? > + } > + free(usercon_str); > + context_range_set(usercon, fromlevel); > + usercon_str = context_str(usercon); > + > + if (security_check_context(usercon_str) == 0) { > + if (*nreachable == 0) { > + new_reachable = malloc(2 * sizeof(char *)); > + if (!new_reachable) { > + context_free(usercon); > + rc = -1; > + goto out; > + } > + } else { > + new_reachable = realloc(*reachable, (*nreachable + 2) * sizeof(char *)); > + if (!new_reachable) { > + context_free(usercon); > + rc = -1; > + goto out; > + } > + } > + new_reachable[*nreachable] = strdup(usercon_str); oom error > + new_reachable[*nreachable + 1] = 0; > + *reachable = new_reachable; > + *nreachable += 1; > + } > + context_free(usercon); > start = end; > } > - > rc = 0; > > out: > @@ -313,21 +306,6 @@ static int get_failsafe_context(const char *user, char ** newcon) > return 0; > } > > -struct context_order { > - char * con; > - unsigned int order; > -}; > - > -static int order_compare(const void *A, const void *B) > -{ > - const struct context_order *c1 = A, *c2 = B; > - if (c1->order < c2->order) > - return -1; > - else if (c1->order > c2->order) > - return 1; > - return strcmp(c1->con, c2->con); > -} > - > int get_ordered_context_list_with_level(const char *user, > const char *level, > char * fromcon, > @@ -395,11 +373,8 @@ int get_ordered_context_list(const char *user, > char *** list) > { > char **reachable = NULL; > - unsigned int *ordering = NULL; > - struct context_order *co = NULL; > - char **ptr; > int rc = 0; > - unsigned int nreach = 0, nordered = 0, freefrom = 0, i; > + unsigned nreachable = 0, freefrom = 0; > FILE *fp; > char *fname = NULL; > size_t fname_len; > @@ -413,23 +388,6 @@ int get_ordered_context_list(const char *user, > freefrom = 1; > } > > - /* Determine the set of reachable contexts for the user. */ > - rc = security_compute_user(fromcon, user, &reachable); > - if (rc < 0) > - goto failsafe; > - nreach = 0; > - for (ptr = reachable; *ptr; ptr++) > - nreach++; > - if (!nreach) > - goto failsafe; > - > - /* Initialize ordering array. */ > - ordering = malloc(nreach * sizeof(unsigned int)); > - if (!ordering) > - goto failsafe; > - for (i = 0; i < nreach; i++) > - ordering[i] = nreach; > - > /* Determine the ordering to apply from the optional per-user config > and from the global config. */ > fname_len = strlen(user_contexts_path) + strlen(user) + 2; > @@ -440,8 +398,8 @@ int get_ordered_context_list(const char *user, > fp = fopen(fname, "re"); > if (fp) { > __fsetlocking(fp, FSETLOCKING_BYCALLER); > - rc = get_context_order(fp, fromcon, reachable, nreach, ordering, > - &nordered); > + rc = get_context_user(fp, fromcon, user, &reachable, &nreachable); > + > fclose(fp); > if (rc < 0 && errno != ENOENT) { > fprintf(stderr, > @@ -454,8 +412,7 @@ int get_ordered_context_list(const char *user, > fp = fopen(selinux_default_context_path(), "re"); > if (fp) { > __fsetlocking(fp, FSETLOCKING_BYCALLER); > - rc = get_context_order(fp, fromcon, reachable, nreach, ordering, > - &nordered); > + rc = get_context_user(fp, fromcon, user, &reachable, &nreachable); > fclose(fp); > if (rc < 0 && errno != ENOENT) { > fprintf(stderr, > @@ -463,40 +420,18 @@ int get_ordered_context_list(const char *user, > __FUNCTION__, selinux_default_context_path()); > /* Fall through */ > } > - rc = 0; > + rc = nreachable; > } > > - if (!nordered) > + if (!nreachable) > goto failsafe; > > - /* Apply the ordering. */ > - co = malloc(nreach * sizeof(struct context_order)); > - if (!co) > - goto failsafe; > - for (i = 0; i < nreach; i++) { > - co[i].con = reachable[i]; > - co[i].order = ordering[i]; > - } > - qsort(co, nreach, sizeof(struct context_order), order_compare); > - for (i = 0; i < nreach; i++) > - reachable[i] = co[i].con; > - free(co); > - > - /* Only report the ordered entries to the caller. */ > - if (nordered <= nreach) { > - for (i = nordered; i < nreach; i++) > - free(reachable[i]); > - reachable[nordered] = NULL; > - rc = nordered; > - } > - > out: > if (rc > 0) > *list = reachable; > else > freeconary(reachable); > > - free(ordering); > if (freefrom) > freecon(fromcon); > > -- > 2.21.0 >
