1 /*
2 * Copyright (c) 1997-8 Andrew G Morgan <morgan@kernel.org>
3 *
4 * This file deals with exchanging internal and external
5 * representations of capability sets.
6 */
7
8 #include "libcap.h"
9
10 /*
11 * External representation for capabilities. (exported as a fixed
12 * length)
13 */
14 #define CAP_EXT_MAGIC "\220\302\001\121"
15 #define CAP_EXT_MAGIC_SIZE 4
16 const static __u8 external_magic[CAP_EXT_MAGIC_SIZE+1] = CAP_EXT_MAGIC;
17
18 struct cap_ext_struct {
19 __u8 magic[CAP_EXT_MAGIC_SIZE];
20 __u8 length_of_capset;
21 /*
22 * note, we arrange these so the caps are stacked with byte-size
23 * resolution
24 */
25 __u8 bytes[CAP_SET_SIZE][NUMBER_OF_CAP_SETS];
26 };
27
28 /*
29 * return size of external capability set
30 */
31
cap_size(cap_t caps)32 ssize_t cap_size(cap_t caps)
33 {
34 return ssizeof(struct cap_ext_struct);
35 }
36
37 /*
38 * Copy the internal (cap_d) capability set into an external
39 * representation. The external representation is portable to other
40 * Linux architectures.
41 */
42
cap_copy_ext(void * cap_ext,cap_t cap_d,ssize_t length)43 ssize_t cap_copy_ext(void *cap_ext, cap_t cap_d, ssize_t length)
44 {
45 struct cap_ext_struct *result = (struct cap_ext_struct *) cap_ext;
46 int i;
47
48 /* valid arguments? */
49 if (!good_cap_t(cap_d) || length < ssizeof(struct cap_ext_struct)
50 || cap_ext == NULL) {
51 errno = EINVAL;
52 return -1;
53 }
54
55 /* fill external capability set */
56 memcpy(&result->magic, external_magic, CAP_EXT_MAGIC_SIZE);
57 result->length_of_capset = CAP_SET_SIZE;
58
59 for (i=0; i<NUMBER_OF_CAP_SETS; ++i) {
60 size_t j;
61 for (j=0; j<CAP_SET_SIZE; ) {
62 __u32 val;
63
64 val = cap_d->u[j/sizeof(__u32)].flat[i];
65
66 result->bytes[j++][i] = val & 0xFF;
67 result->bytes[j++][i] = (val >>= 8) & 0xFF;
68 result->bytes[j++][i] = (val >>= 8) & 0xFF;
69 result->bytes[j++][i] = (val >> 8) & 0xFF;
70 }
71 }
72
73 /* All done: return length of external representation */
74 return (ssizeof(struct cap_ext_struct));
75 }
76
77 /*
78 * Import an external representation to produce an internal rep.
79 * the internal rep should be liberated with cap_free().
80 */
81
cap_copy_int(const void * cap_ext)82 cap_t cap_copy_int(const void *cap_ext)
83 {
84 const struct cap_ext_struct *export =
85 (const struct cap_ext_struct *) cap_ext;
86 cap_t cap_d;
87 int set, blen;
88
89 /* Does the external representation make sense? */
90 if ((export == NULL)
91 || memcmp(export->magic, external_magic, CAP_EXT_MAGIC_SIZE)) {
92 errno = EINVAL;
93 return NULL;
94 }
95
96 /* Obtain a new internal capability set */
97 if (!(cap_d = cap_init()))
98 return NULL;
99
100 blen = export->length_of_capset;
101 for (set=0; set<NUMBER_OF_CAP_SETS; ++set) {
102 unsigned blk;
103 int bno = 0;
104 for (blk=0; blk<(CAP_SET_SIZE/sizeof(__u32)); ++blk) {
105 __u32 val = 0;
106
107 if (bno != blen)
108 val = export->bytes[bno++][set];
109 if (bno != blen)
110 val |= export->bytes[bno++][set] << 8;
111 if (bno != blen)
112 val |= export->bytes[bno++][set] << 16;
113 if (bno != blen)
114 val |= export->bytes[bno++][set] << 24;
115
116 cap_d->u[blk].flat[set] = val;
117 }
118 }
119
120 /* all done */
121 return cap_d;
122 }
123
124