/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 1999-2006 Robert N. M. Watson * All rights reserved. * * This software was developed by Robert Watson for the TrustedBSD Project. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Developed by the TrustedBSD Project. * * ACL support routines specific to POSIX.1e access control lists. These are * utility routines for code common across file systems implementing POSIX.1e * ACLs. */ #include #include #include #include #include #include #include #include #include #include #include /* * Implement a version of vaccess() that understands POSIX.1e ACL semantics; * the access ACL has already been prepared for evaluation by the file system * and is passed via 'uid', 'gid', and 'acl'. Return 0 on success, else an * errno value. */ int vaccess_acl_posix1e(__enum_uint8(vtype) type, uid_t file_uid, gid_t file_gid, struct acl *acl, accmode_t accmode, struct ucred *cred) { struct acl_entry *acl_other, *acl_mask; accmode_t dac_granted; accmode_t priv_granted; accmode_t acl_mask_granted; int group_matched, i; KASSERT((accmode & ~(VEXEC | VWRITE | VREAD | VADMIN | VAPPEND)) == 0, ("invalid bit in accmode")); KASSERT((accmode & VAPPEND) == 0 || (accmode & VWRITE), ("VAPPEND without VWRITE")); /* * Look for a normal, non-privileged way to access the file/directory * as requested. If it exists, go with that. Otherwise, attempt to * use privileges granted via priv_granted. In some cases, which * privileges to use may be ambiguous due to "best match", in which * case fall back on first match for the time being. */ /* * Determine privileges now, but don't apply until we've found a DAC * entry that matches but has failed to allow access. * * XXXRW: Ideally, we'd determine the privileges required before * asking for them. */ priv_granted = 0; if (type == VDIR) { if ((accmode & VEXEC) && !priv_check_cred(cred, PRIV_VFS_LOOKUP)) priv_granted |= VEXEC; } else { /* * Ensure that at least one execute bit is on. Otherwise, * a privileged user will always succeed, and we don't want * this to happen unless the file really is executable. */ if ((accmode & VEXEC) && (acl_posix1e_acl_to_mode(acl) & (S_IXUSR | S_IXGRP | S_IXOTH)) != 0 && !priv_check_cred(cred, PRIV_VFS_EXEC)) priv_granted |= VEXEC; } if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ)) priv_granted |= VREAD; if (((accmode & VWRITE) || (accmode & VAPPEND)) && !priv_check_cred(cred, PRIV_VFS_WRITE)) priv_granted |= (VWRITE | VAPPEND); if ((accmode & VADMIN) && !priv_check_cred(cred, PRIV_VFS_ADMIN)) priv_granted |= VADMIN; /* * The owner matches if the effective uid associated with the * credential matches that of the ACL_USER_OBJ entry. While we're * doing the first scan, also cache the location of the ACL_MASK and * ACL_OTHER entries, preventing some future iterations. */ acl_mask = acl_other = NULL; for (i = 0; i < acl->acl_cnt; i++) { switch (acl->acl_entry[i].ae_tag) { case ACL_USER_OBJ: if (file_uid != cred->cr_uid) break; dac_granted = 0; dac_granted |= VADMIN; if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) dac_granted |= VEXEC; if (acl->acl_entry[i].ae_perm & ACL_READ) dac_granted |= VREAD; if (acl->acl_entry[i].ae_perm & ACL_WRITE) dac_granted |= (VWRITE | VAPPEND); if ((accmode & dac_granted) == accmode) return (0); /* * XXXRW: Do privilege lookup here. */ if ((accmode & (dac_granted | priv_granted)) == accmode) { return (0); } goto error; case ACL_MASK: acl_mask = &acl->acl_entry[i]; break; case ACL_OTHER: acl_other = &acl->acl_entry[i]; break; default: break; } } /* * An ACL_OTHER entry should always exist in a valid access ACL. If * it doesn't, then generate a serious failure. For now, this means * a debugging message and EPERM, but in the future should probably * be a panic. */ if (acl_other == NULL) { /* * XXX This should never happen */ printf("vaccess_acl_posix1e: ACL_OTHER missing\n"); return (EPERM); } /* * Checks against ACL_USER, ACL_GROUP_OBJ, and ACL_GROUP fields are * masked by an ACL_MASK entry, if any. As such, first identify the * ACL_MASK field, then iterate through identifying potential user * matches, then group matches. If there is no ACL_MASK, assume that * the mask allows all requests to succeed. */ if (acl_mask != NULL) { acl_mask_granted = 0; if (acl_mask->ae_perm & ACL_EXECUTE) acl_mask_granted |= VEXEC; if (acl_mask->ae_perm & ACL_READ) acl_mask_granted |= VREAD; if (acl_mask->ae_perm & ACL_WRITE) acl_mask_granted |= (VWRITE | VAPPEND); } else acl_mask_granted = VEXEC | VREAD | VWRITE | VAPPEND; /* * Check ACL_USER ACL entries. There will either be one or no * matches; if there is one, we accept or rejected based on the * match; otherwise, we continue on to groups. */ for (i = 0; i < acl->acl_cnt; i++) { switch (acl->acl_entry[i].ae_tag) { case ACL_USER: if (acl->acl_entry[i].ae_id != cred->cr_uid) break; dac_granted = 0; if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) dac_granted |= VEXEC; if (acl->acl_entry[i].ae_perm & ACL_READ) dac_granted |= VREAD; if (acl->acl_entry[i].ae_perm & ACL_WRITE) dac_granted |= (VWRITE | VAPPEND); dac_granted &= acl_mask_granted; if ((accmode & dac_granted) == accmode) return (0); /* * XXXRW: Do privilege lookup here. */ if ((accmode & (dac_granted | priv_granted)) != accmode) goto error; return (0); } } /* * Group match is best-match, not first-match, so find a "best" * match. Iterate across, testing each potential group match. Make * sure we keep track of whether we found a match or not, so that we * know if we should try again with any available privilege, or if we * should move on to ACL_OTHER. */ group_matched = 0; for (i = 0; i < acl->acl_cnt; i++) { switch (acl->acl_entry[i].ae_tag) { case ACL_GROUP_OBJ: if (!groupmember(file_gid, cred)) break; dac_granted = 0; if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) dac_granted |= VEXEC; if (acl->acl_entry[i].ae_perm & ACL_READ) dac_granted |= VREAD; if (acl->acl_entry[i].ae_perm & ACL_WRITE) dac_granted |= (VWRITE | VAPPEND); dac_granted &= acl_mask_granted; if ((accmode & dac_granted) == accmode) return (0); group_matched = 1; break; case ACL_GROUP: if (!groupmember(acl->acl_entry[i].ae_id, cred)) break; dac_granted = 0; if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) dac_granted |= VEXEC; if (acl->acl_entry[i].ae_perm & ACL_READ) dac_granted |= VREAD; if (acl->acl_entry[i].ae_perm & ACL_WRITE) dac_granted |= (VWRITE | VAPPEND); dac_granted &= acl_mask_granted; if ((accmode & dac_granted) == accmode) return (0); group_matched = 1; break; default: break; } } if (group_matched == 1) { /* * There was a match, but it did not grant rights via pure * DAC. Try again, this time with privilege. */ for (i = 0; i < acl->acl_cnt; i++) { switch (acl->acl_entry[i].ae_tag) { case ACL_GROUP_OBJ: if (!groupmember(file_gid, cred)) break; dac_granted = 0; if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) dac_granted |= VEXEC; if (acl->acl_entry[i].ae_perm & ACL_READ) dac_granted |= VREAD; if (acl->acl_entry[i].ae_perm & ACL_WRITE) dac_granted |= (VWRITE | VAPPEND); dac_granted &= acl_mask_granted; /* * XXXRW: Do privilege lookup here. */ if ((accmode & (dac_granted | priv_granted)) != accmode) break; return (0); case ACL_GROUP: if (!groupmember(acl->acl_entry[i].ae_id, cred)) break; dac_granted = 0; if (acl->acl_entry[i].ae_perm & ACL_EXECUTE) dac_granted |= VEXEC; if (acl->acl_entry[i].ae_perm & ACL_READ) dac_granted |= VREAD; if (acl->acl_entry[i].ae_perm & ACL_WRITE) dac_granted |= (VWRITE | VAPPEND); dac_granted &= acl_mask_granted; /* * XXXRW: Do privilege lookup here. */ if ((accmode & (dac_granted | priv_granted)) != accmode) break; return (0); default: break; } } /* * Even with privilege, group membership was not sufficient. * Return failure. */ goto error; } /* * Fall back on ACL_OTHER. ACL_MASK is not applied to ACL_OTHER. */ dac_granted = 0; if (acl_other->ae_perm & ACL_EXECUTE) dac_granted |= VEXEC; if (acl_other->ae_perm & ACL_READ) dac_granted |= VREAD; if (acl_other->ae_perm & ACL_WRITE) dac_granted |= (VWRITE | VAPPEND); if ((accmode & dac_granted) == accmode) return (0); /* * XXXRW: Do privilege lookup here. */ if ((accmode & (dac_granted | priv_granted)) == accmode) { return (0); } error: return ((accmode & VADMIN) ? EPERM : EACCES); } /* * For the purposes of filesystems maintaining the _OBJ entries in an inode * with a mode_t field, this routine converts a mode_t entry to an * acl_perm_t. */ acl_perm_t acl_posix1e_mode_to_perm(acl_tag_t tag, mode_t mode) { acl_perm_t perm = 0; switch(tag) { case ACL_USER_OBJ: if (mode & S_IXUSR) perm |= ACL_EXECUTE; if (mode & S_IRUSR) perm |= ACL_READ; if (mode & S_IWUSR) perm |= ACL_WRITE; return (perm); case ACL_GROUP_OBJ: if (mode & S_IXGRP) perm |= ACL_EXECUTE; if (mode & S_IRGRP) perm |= ACL_READ; if (mode & S_IWGRP) perm |= ACL_WRITE; return (perm); case ACL_OTHER: if (mode & S_IXOTH) perm |= ACL_EXECUTE; if (mode & S_IROTH) perm |= ACL_READ; if (mode & S_IWOTH) perm |= ACL_WRITE; return (perm); default: printf("acl_posix1e_mode_to_perm: invalid tag (%d)\n", tag); return (0); } } /* * Given inode information (uid, gid, mode), return an acl entry of the * appropriate type. */ struct acl_entry acl_posix1e_mode_to_entry(acl_tag_t tag, uid_t uid, gid_t gid, mode_t mode) { struct acl_entry acl_entry; acl_entry.ae_tag = tag; acl_entry.ae_perm = acl_posix1e_mode_to_perm(tag, mode); acl_entry.ae_entry_type = 0; acl_entry.ae_flags = 0; switch(tag) { case ACL_USER_OBJ: acl_entry.ae_id = uid; break; case ACL_GROUP_OBJ: acl_entry.ae_id = gid; break; case ACL_OTHER: acl_entry.ae_id = ACL_UNDEFINED_ID; break; default: acl_entry.ae_id = ACL_UNDEFINED_ID; printf("acl_posix1e_mode_to_entry: invalid tag (%d)\n", tag); } return (acl_entry); } /* * Utility function to generate a file mode given appropriate ACL entries. */ mode_t acl_posix1e_perms_to_mode(struct acl_entry *acl_user_obj_entry, struct acl_entry *acl_group_obj_entry, struct acl_entry *acl_other_entry) { mode_t mode; mode = 0; if (acl_user_obj_entry->ae_perm & ACL_EXECUTE) mode |= S_IXUSR; if (acl_user_obj_entry->ae_perm & ACL_READ) mode |= S_IRUSR; if (acl_user_obj_entry->ae_perm & ACL_WRITE) mode |= S_IWUSR; if (acl_group_obj_entry->ae_perm & ACL_EXECUTE) mode |= S_IXGRP; if (acl_group_obj_entry->ae_perm & ACL_READ) mode |= S_IRGRP; if (acl_group_obj_entry->ae_perm & ACL_WRITE) mode |= S_IWGRP; if (acl_other_entry->ae_perm & ACL_EXECUTE) mode |= S_IXOTH; if (acl_other_entry->ae_perm & ACL_READ) mode |= S_IROTH; if (acl_other_entry->ae_perm & ACL_WRITE) mode |= S_IWOTH; return (mode); } /* * Utility function to generate a file mode given a complete POSIX.1e access * ACL. Note that if the ACL is improperly formed, this may result in a * panic. */ mode_t acl_posix1e_acl_to_mode(struct acl *acl) { struct acl_entry *acl_mask, *acl_user_obj, *acl_group_obj, *acl_other; int i; /* * Find the ACL entries relevant to a POSIX permission mode. */ acl_user_obj = acl_group_obj = acl_other = acl_mask = NULL; for (i = 0; i < acl->acl_cnt; i++) { switch (acl->acl_entry[i].ae_tag) { case ACL_USER_OBJ: acl_user_obj = &acl->acl_entry[i]; break; case ACL_GROUP_OBJ: acl_group_obj = &acl->acl_entry[i]; break; case ACL_OTHER: acl_other = &acl->acl_entry[i]; break; case ACL_MASK: acl_mask = &acl->acl_entry[i]; break; case ACL_USER: case ACL_GROUP: break; default: panic("acl_posix1e_acl_to_mode: bad ae_tag"); } } if (acl_user_obj == NULL || acl_group_obj == NULL || acl_other == NULL) panic("acl_posix1e_acl_to_mode: missing base ae_tags"); /* * POSIX.1e specifies that if there is an ACL_MASK entry, we replace * the mode "group" bits with its permissions. If there isn't, we * use the ACL_GROUP_OBJ permissions. */ if (acl_mask != NULL) return (acl_posix1e_perms_to_mode(acl_user_obj, acl_mask, acl_other)); else return (acl_posix1e_perms_to_mode(acl_user_obj, acl_group_obj, acl_other)); } /* * Perform a syntactic check of the ACL, sufficient to allow an implementing * filesystem to determine if it should accept this and rely on the POSIX.1e * ACL properties. */ int acl_posix1e_check(struct acl *acl) { int num_acl_user_obj, num_acl_user, num_acl_group_obj, num_acl_group; int num_acl_mask, num_acl_other, i; /* * Verify that the number of entries does not exceed the maximum * defined for acl_t. * * Verify that the correct number of various sorts of ae_tags are * present: * Exactly one ACL_USER_OBJ * Exactly one ACL_GROUP_OBJ * Exactly one ACL_OTHER * If any ACL_USER or ACL_GROUP entries appear, then exactly one * ACL_MASK entry must also appear. * * Verify that all ae_perm entries are in ACL_PERM_BITS. * * Verify all ae_tag entries are understood by this implementation. * * Note: Does not check for uniqueness of qualifier (ae_id) field. */ num_acl_user_obj = num_acl_user = num_acl_group_obj = num_acl_group = num_acl_mask = num_acl_other = 0; if (acl->acl_cnt > ACL_MAX_ENTRIES) return (EINVAL); for (i = 0; i < acl->acl_cnt; i++) { /* * Check for a valid tag. */ switch(acl->acl_entry[i].ae_tag) { case ACL_USER_OBJ: acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) return (EINVAL); num_acl_user_obj++; break; case ACL_GROUP_OBJ: acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) return (EINVAL); num_acl_group_obj++; break; case ACL_USER: if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID) return (EINVAL); num_acl_user++; break; case ACL_GROUP: if (acl->acl_entry[i].ae_id == ACL_UNDEFINED_ID) return (EINVAL); num_acl_group++; break; case ACL_OTHER: acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) return (EINVAL); num_acl_other++; break; case ACL_MASK: acl->acl_entry[i].ae_id = ACL_UNDEFINED_ID; /* XXX */ if (acl->acl_entry[i].ae_id != ACL_UNDEFINED_ID) return (EINVAL); num_acl_mask++; break; default: return (EINVAL); } /* * Check for valid perm entries. */ if ((acl->acl_entry[i].ae_perm | ACL_PERM_BITS) != ACL_PERM_BITS) return (EINVAL); } if ((num_acl_user_obj != 1) || (num_acl_group_obj != 1) || (num_acl_other != 1) || (num_acl_mask != 0 && num_acl_mask != 1)) return (EINVAL); if (((num_acl_group != 0) || (num_acl_user != 0)) && (num_acl_mask != 1)) return (EINVAL); return (0); } /* * Given a requested mode for a new object, and a default ACL, combine the * two to produce a new mode. Be careful not to clear any bits that aren't * intended to be affected by the POSIX.1e ACL. Eventually, this might also * take the cmask as an argument, if we push that down into * per-filesystem-code. */ mode_t acl_posix1e_newfilemode(mode_t cmode, struct acl *dacl) { mode_t mode; mode = cmode; /* * The current composition policy is that a permission bit must be * set in *both* the ACL and the requested creation mode for it to * appear in the resulting mode/ACL. First clear any possibly * effected bits, then reconstruct. */ mode &= ACL_PRESERVE_MASK; mode |= (ACL_OVERRIDE_MASK & cmode & acl_posix1e_acl_to_mode(dacl)); return (mode); } static int acl_posix1e_modload(module_t mod, int what, void *arg) { int ret; ret = 0; switch (what) { case MOD_LOAD: case MOD_SHUTDOWN: break; case MOD_QUIESCE: /* XXX TODO */ ret = 0; break; case MOD_UNLOAD: /* XXX TODO */ ret = 0; break; default: ret = EINVAL; break; } return (ret); } static moduledata_t acl_posix1e_mod = { "acl_posix1e", acl_posix1e_modload, NULL }; DECLARE_MODULE(acl_posix1e, acl_posix1e_mod, SI_SUB_VFS, SI_ORDER_FIRST); MODULE_VERSION(acl_posix1e, 1);