diff options
| -rw-r--r-- | ports/linux/xattr/portdefs.h | 1 | ||||
| -rw-r--r-- | ports/linux/xattr/pseudo_wrappers.c | 112 |
2 files changed, 113 insertions, 0 deletions
diff --git a/ports/linux/xattr/portdefs.h b/ports/linux/xattr/portdefs.h index ec030b7..367ca60 100644 --- a/ports/linux/xattr/portdefs.h +++ b/ports/linux/xattr/portdefs.h @@ -1 +1,2 @@ #include <attr/xattr.h> +#include <stdint.h> diff --git a/ports/linux/xattr/pseudo_wrappers.c b/ports/linux/xattr/pseudo_wrappers.c index 7fe44a6..c37c245 100644 --- a/ports/linux/xattr/pseudo_wrappers.c +++ b/ports/linux/xattr/pseudo_wrappers.c @@ -3,6 +3,100 @@ * a populated statbuf to use for sending messages to the server. */ +/* to avoid namespace pollution and such, we now duplicate the + * basic functionality of a POSIX ACL list, as used by libacl or + * the kernel. Documentation was obtained from the headers of libacl + * and from a page or two of _The Linux Programming Interface_, by + * Michael Kerrisk. + */ + +typedef struct { + uint16_t tag; + uint16_t perm; + uint32_t id; +} acl_entry; + +typedef struct { + uint32_t version; + acl_entry entries[]; +} acl_header; + +enum acl_tags { + ACL_UNDEFINED = 0x0, + ACL_USER_OBJ = 0x1, + ACL_USER = 0x2, + ACL_GROUP_OBJ = 0x4, + ACL_GROUP = 0x8, + ACL_MASK = 0x10, + ACL_OTHER = 0x20, +}; + +static const int endian_test = 1; +static const char *endian_tester = (char *) &endian_test; + +static inline int +le16(int x16) { + if (*endian_tester) { + return x16; + } else { + return ((x16 & 0xff) << 8) | ((x16 & 0xff00) >> 8); + } +} + +static inline int +le32(int x32) { + if (*endian_tester) { + return x32; + } else { + return ((x32 & 0xff) << 24) | ((x32 & 0xff00) << 8) | + ((x32 & 0xff0000) >> 8) | ((x32 & 0xff000000) >> 24); + } +} + +/* set mode to match the contents of header. Return non-zero on error. + * On a zero return, mode is a valid posix mode, and *extra is set to + * 1 if any of the entries are not reflected by that mode. On a non-zero + * return, no promises are made about *extra or *mode. + */ +static int +posix_permissions(const acl_header *header, int entries, int *extra, int *mode) { + int acl_seen = 0; + if (le32(header->version) != 2) { + pseudo_diag("Fatal: ACL support no available for header versio %d.\n", + le32(header->version)); + return 1; + } + *mode = 0; + *extra = 0; + for (int i = 0; i < entries; ++i) { + const acl_entry *e = &header->entries[i]; + int tag = le16(e->tag); + int perm = le16(e->perm); + acl_seen |= tag; + switch (tag) { + case ACL_USER_OBJ: + *mode = *mode | (perm << 6); + break; + case ACL_GROUP_OBJ: + *mode = *mode | (perm << 3); + break; + case ACL_OTHER: + *mode = *mode | perm; + break; + case ACL_USER: + case ACL_GROUP: + case ACL_MASK: + *extra = *extra + 1; + break; + default: + pseudo_debug(PDBGF_XATTR, "Unknown tag in ACL: 0x%x.\n", + tag); + return 1; + } + } + return 0; +} + #define RC_AND_BUF \ int rc; \ PSEUDO_STATBUF buf; \ @@ -67,6 +161,24 @@ static int shared_setxattr(const char *path, int fd, const char *name, const voi break; } + /* this may be a plain chmod */ + if (!strcmp(name, "system.posix_acl_access")) { + int extra; + int mode; + int entries = (size - sizeof(acl_header)) / sizeof(acl_entry); + if (!posix_permissions(value, entries, &extra, &mode)) { + pseudo_debug(PDBGF_XATTR, "posix_acl_access translated to mode %04o. Remaining attribute(s): %d.\n", + mode, extra); + buf.st_mode = mode; + pseudo_client_op(path ? OP_CHMOD : OP_FCHMOD, 0, fd, -1, path, &buf); + /* we are sneaky, and do not actually record this using + * extended attributes. */ + if (!extra) { + return 0; + } + } + } + pseudo_msg_t *result = pseudo_client_op(op, 0, fd, -1, path, &buf, combined, combined_len); /* we automatically assume success */ |