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1 /* Copyright (c) 2014, Google Inc.
2  *
3  * Permission to use, copy, modify, and/or distribute this software for any
4  * purpose with or without fee is hereby granted, provided that the above
5  * copyright notice and this permission notice appear in all copies.
6  *
7  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10  * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14 
15 #ifndef OPENSSL_HEADER_BYTESTRING_H
16 #define OPENSSL_HEADER_BYTESTRING_H
17 
18 #include <openssl/base.h>
19 
20 #if defined(__cplusplus)
21 extern "C" {
22 #endif
23 
24 
25 /* Bytestrings are used for parsing and building TLS and ASN.1 messages.
26  *
27  * A "CBS" (CRYPTO ByteString) represents a string of bytes in memory and
28  * provides utility functions for safely parsing length-prefixed structures
29  * like TLS and ASN.1 from it.
30  *
31  * A "CBB" (CRYPTO ByteBuilder) is a memory buffer that grows as needed and
32  * provides utility functions for building length-prefixed messages. */
33 
34 
35 /* CRYPTO ByteString */
36 
37 struct cbs_st {
38   const uint8_t *data;
39   size_t len;
40 };
41 
42 /* CBS_init sets |cbs| to point to |data|. It does not take ownership of
43  * |data|. */
44 OPENSSL_EXPORT void CBS_init(CBS *cbs, const uint8_t *data, size_t len);
45 
46 /* CBS_skip advances |cbs| by |len| bytes. It returns one on success and zero
47  * otherwise. */
48 OPENSSL_EXPORT int CBS_skip(CBS *cbs, size_t len);
49 
50 /* CBS_data returns a pointer to the contents of |cbs|. */
51 OPENSSL_EXPORT const uint8_t *CBS_data(const CBS *cbs);
52 
53 /* CBS_len returns the number of bytes remaining in |cbs|. */
54 OPENSSL_EXPORT size_t CBS_len(const CBS *cbs);
55 
56 /* CBS_stow copies the current contents of |cbs| into |*out_ptr| and
57  * |*out_len|. If |*out_ptr| is not NULL, the contents are freed with
58  * OPENSSL_free. It returns one on success and zero on allocation failure. On
59  * success, |*out_ptr| should be freed with OPENSSL_free. If |cbs| is empty,
60  * |*out_ptr| will be NULL. */
61 OPENSSL_EXPORT int CBS_stow(const CBS *cbs, uint8_t **out_ptr, size_t *out_len);
62 
63 /* CBS_strdup copies the current contents of |cbs| into |*out_ptr| as a
64  * NUL-terminated C string. If |*out_ptr| is not NULL, the contents are freed
65  * with OPENSSL_free. It returns one on success and zero on allocation
66  * failure. On success, |*out_ptr| should be freed with OPENSSL_free.
67  *
68  * NOTE: If |cbs| contains NUL bytes, the string will be truncated. Call
69  * |CBS_contains_zero_byte(cbs)| to check for NUL bytes. */
70 OPENSSL_EXPORT int CBS_strdup(const CBS *cbs, char **out_ptr);
71 
72 /* CBS_contains_zero_byte returns one if the current contents of |cbs| contains
73  * a NUL byte and zero otherwise. */
74 OPENSSL_EXPORT int CBS_contains_zero_byte(const CBS *cbs);
75 
76 /* CBS_mem_equal compares the current contents of |cbs| with the |len| bytes
77  * starting at |data|. If they're equal, it returns one, otherwise zero. If the
78  * lengths match, it uses a constant-time comparison. */
79 OPENSSL_EXPORT int CBS_mem_equal(const CBS *cbs, const uint8_t *data,
80                                  size_t len);
81 
82 /* CBS_get_u8 sets |*out| to the next uint8_t from |cbs| and advances |cbs|. It
83  * returns one on success and zero on error. */
84 OPENSSL_EXPORT int CBS_get_u8(CBS *cbs, uint8_t *out);
85 
86 /* CBS_get_u16 sets |*out| to the next, big-endian uint16_t from |cbs| and
87  * advances |cbs|. It returns one on success and zero on error. */
88 OPENSSL_EXPORT int CBS_get_u16(CBS *cbs, uint16_t *out);
89 
90 /* CBS_get_u24 sets |*out| to the next, big-endian 24-bit value from |cbs| and
91  * advances |cbs|. It returns one on success and zero on error. */
92 OPENSSL_EXPORT int CBS_get_u24(CBS *cbs, uint32_t *out);
93 
94 /* CBS_get_u32 sets |*out| to the next, big-endian uint32_t value from |cbs|
95  * and advances |cbs|. It returns one on success and zero on error. */
96 OPENSSL_EXPORT int CBS_get_u32(CBS *cbs, uint32_t *out);
97 
98 /* CBS_get_last_u8 sets |*out| to the last uint8_t from |cbs| and shortens
99  * |cbs|. It returns one on success and zero on error. */
100 OPENSSL_EXPORT int CBS_get_last_u8(CBS *cbs, uint8_t *out);
101 
102 /* CBS_get_bytes sets |*out| to the next |len| bytes from |cbs| and advances
103  * |cbs|. It returns one on success and zero on error. */
104 OPENSSL_EXPORT int CBS_get_bytes(CBS *cbs, CBS *out, size_t len);
105 
106 /* CBS_copy_bytes copies the next |len| bytes from |cbs| to |out| and advances
107  * |cbs|. It returns one on success and zero on error. */
108 OPENSSL_EXPORT int CBS_copy_bytes(CBS *cbs, uint8_t *out, size_t len);
109 
110 /* CBS_get_u8_length_prefixed sets |*out| to the contents of an 8-bit,
111  * length-prefixed value from |cbs| and advances |cbs| over it. It returns one
112  * on success and zero on error. */
113 OPENSSL_EXPORT int CBS_get_u8_length_prefixed(CBS *cbs, CBS *out);
114 
115 /* CBS_get_u16_length_prefixed sets |*out| to the contents of a 16-bit,
116  * big-endian, length-prefixed value from |cbs| and advances |cbs| over it. It
117  * returns one on success and zero on error. */
118 OPENSSL_EXPORT int CBS_get_u16_length_prefixed(CBS *cbs, CBS *out);
119 
120 /* CBS_get_u24_length_prefixed sets |*out| to the contents of a 24-bit,
121  * big-endian, length-prefixed value from |cbs| and advances |cbs| over it. It
122  * returns one on success and zero on error. */
123 OPENSSL_EXPORT int CBS_get_u24_length_prefixed(CBS *cbs, CBS *out);
124 
125 
126 /* Parsing ASN.1 */
127 
128 /* The following values are tag numbers for UNIVERSAL elements. */
129 #define CBS_ASN1_BOOLEAN 0x1u
130 #define CBS_ASN1_INTEGER 0x2u
131 #define CBS_ASN1_BITSTRING 0x3u
132 #define CBS_ASN1_OCTETSTRING 0x4u
133 #define CBS_ASN1_NULL 0x5u
134 #define CBS_ASN1_OBJECT 0x6u
135 #define CBS_ASN1_ENUMERATED 0xau
136 #define CBS_ASN1_UTF8STRING 0xcu
137 #define CBS_ASN1_SEQUENCE (0x10u | CBS_ASN1_CONSTRUCTED)
138 #define CBS_ASN1_SET (0x11u | CBS_ASN1_CONSTRUCTED)
139 #define CBS_ASN1_NUMERICSTRING 0x12u
140 #define CBS_ASN1_PRINTABLESTRING 0x13u
141 #define CBS_ASN1_T61STRING 0x14u
142 #define CBS_ASN1_VIDEOTEXSTRING 0x15u
143 #define CBS_ASN1_IA5STRING 0x16u
144 #define CBS_ASN1_UTCTIME 0x17u
145 #define CBS_ASN1_GENERALIZEDTIME 0x18u
146 #define CBS_ASN1_GRAPHICSTRING 0x19u
147 #define CBS_ASN1_VISIBLESTRING 0x1au
148 #define CBS_ASN1_GENERALSTRING 0x1bu
149 #define CBS_ASN1_UNIVERSALSTRING 0x1cu
150 #define CBS_ASN1_BMPSTRING 0x1eu
151 
152 /* CBS_ASN1_CONSTRUCTED may be ORed into a tag to toggle the constructed
153  * bit. |CBS| and |CBB| APIs consider the constructed bit to be part of the
154  * tag. */
155 #define CBS_ASN1_CONSTRUCTED 0x20u
156 
157 /* The following values specify the constructed bit or tag class and may be ORed
158  * into a tag number to produce the final tag. If none is used, the tag will be
159  * UNIVERSAL.
160  *
161  * Note that although they currently match the DER serialization, consumers must
162  * use these bits rather than make assumptions about the representation. This is
163  * to allow for tag numbers beyond 31 in the future. */
164 #define CBS_ASN1_APPLICATION 0x40u
165 #define CBS_ASN1_CONTEXT_SPECIFIC 0x80u
166 #define CBS_ASN1_PRIVATE 0xc0u
167 
168 /* CBS_ASN1_CLASS_MASK may be ANDed with a tag to query its class. */
169 #define CBS_ASN1_CLASS_MASK 0xc0u
170 
171 /* CBS_ASN1_TAG_NUMBER_MASK may be ANDed with a tag to query its number. */
172 #define CBS_ASN1_TAG_NUMBER_MASK 0x1fu
173 
174 /* CBS_get_asn1 sets |*out| to the contents of DER-encoded, ASN.1 element (not
175  * including tag and length bytes) and advances |cbs| over it. The ASN.1
176  * element must match |tag_value|. It returns one on success and zero
177  * on error.
178  *
179  * Tag numbers greater than 30 are not supported (i.e. short form only). */
180 OPENSSL_EXPORT int CBS_get_asn1(CBS *cbs, CBS *out, unsigned tag_value);
181 
182 /* CBS_get_asn1_element acts like |CBS_get_asn1| but |out| will include the
183  * ASN.1 header bytes too. */
184 OPENSSL_EXPORT int CBS_get_asn1_element(CBS *cbs, CBS *out, unsigned tag_value);
185 
186 /* CBS_peek_asn1_tag looks ahead at the next ASN.1 tag and returns one
187  * if the next ASN.1 element on |cbs| would have tag |tag_value|. If
188  * |cbs| is empty or the tag does not match, it returns zero. Note: if
189  * it returns one, CBS_get_asn1 may still fail if the rest of the
190  * element is malformed. */
191 OPENSSL_EXPORT int CBS_peek_asn1_tag(const CBS *cbs, unsigned tag_value);
192 
193 /* CBS_get_any_asn1 sets |*out| to contain the next ASN.1 element from |*cbs|
194  * (not including tag and length bytes), sets |*out_tag| to the tag number, and
195  * advances |*cbs|. It returns one on success and zero on error. Either of |out|
196  * and |out_tag| may be NULL to ignore the value.
197  *
198  * Tag numbers greater than 30 are not supported (i.e. short form only). */
199 OPENSSL_EXPORT int CBS_get_any_asn1(CBS *cbs, CBS *out, unsigned *out_tag);
200 
201 /* CBS_get_any_asn1_element sets |*out| to contain the next ASN.1 element from
202  * |*cbs| (including header bytes) and advances |*cbs|. It sets |*out_tag| to
203  * the tag number and |*out_header_len| to the length of the ASN.1 header. Each
204  * of |out|, |out_tag|, and |out_header_len| may be NULL to ignore the value.
205  *
206  * Tag numbers greater than 30 are not supported (i.e. short form only). */
207 OPENSSL_EXPORT int CBS_get_any_asn1_element(CBS *cbs, CBS *out,
208                                             unsigned *out_tag,
209                                             size_t *out_header_len);
210 
211 /* CBS_get_any_ber_asn1_element acts the same as |CBS_get_any_asn1_element| but
212  * also allows indefinite-length elements to be returned. In that case,
213  * |*out_header_len| and |CBS_len(out)| will both be two as only the header is
214  * returned, otherwise it behaves the same as the previous function. */
215 OPENSSL_EXPORT int CBS_get_any_ber_asn1_element(CBS *cbs, CBS *out,
216                                                 unsigned *out_tag,
217                                                 size_t *out_header_len);
218 
219 /* CBS_get_asn1_uint64 gets an ASN.1 INTEGER from |cbs| using |CBS_get_asn1|
220  * and sets |*out| to its value. It returns one on success and zero on error,
221  * where error includes the integer being negative, or too large to represent
222  * in 64 bits. */
223 OPENSSL_EXPORT int CBS_get_asn1_uint64(CBS *cbs, uint64_t *out);
224 
225 /* CBS_get_optional_asn1 gets an optional explicitly-tagged element from |cbs|
226  * tagged with |tag| and sets |*out| to its contents. If present and if
227  * |out_present| is not NULL, it sets |*out_present| to one, otherwise zero. It
228  * returns one on success, whether or not the element was present, and zero on
229  * decode failure. */
230 OPENSSL_EXPORT int CBS_get_optional_asn1(CBS *cbs, CBS *out, int *out_present,
231                                          unsigned tag);
232 
233 /* CBS_get_optional_asn1_octet_string gets an optional
234  * explicitly-tagged OCTET STRING from |cbs|. If present, it sets
235  * |*out| to the string and |*out_present| to one. Otherwise, it sets
236  * |*out| to empty and |*out_present| to zero. |out_present| may be
237  * NULL. It returns one on success, whether or not the element was
238  * present, and zero on decode failure. */
239 OPENSSL_EXPORT int CBS_get_optional_asn1_octet_string(CBS *cbs, CBS *out,
240                                                       int *out_present,
241                                                       unsigned tag);
242 
243 /* CBS_get_optional_asn1_uint64 gets an optional explicitly-tagged
244  * INTEGER from |cbs|. If present, it sets |*out| to the
245  * value. Otherwise, it sets |*out| to |default_value|. It returns one
246  * on success, whether or not the element was present, and zero on
247  * decode failure. */
248 OPENSSL_EXPORT int CBS_get_optional_asn1_uint64(CBS *cbs, uint64_t *out,
249                                                 unsigned tag,
250                                                 uint64_t default_value);
251 
252 /* CBS_get_optional_asn1_bool gets an optional, explicitly-tagged BOOLEAN from
253  * |cbs|. If present, it sets |*out| to either zero or one, based on the
254  * boolean. Otherwise, it sets |*out| to |default_value|. It returns one on
255  * success, whether or not the element was present, and zero on decode
256  * failure. */
257 OPENSSL_EXPORT int CBS_get_optional_asn1_bool(CBS *cbs, int *out, unsigned tag,
258                                               int default_value);
259 
260 /* CBS_is_valid_asn1_bitstring returns one if |cbs| is a valid ASN.1 BIT STRING
261  * and zero otherwise. */
262 OPENSSL_EXPORT int CBS_is_valid_asn1_bitstring(const CBS *cbs);
263 
264 /* CBS_asn1_bitstring_has_bit returns one if |cbs| is a valid ASN.1 BIT STRING
265  * and the specified bit is present and set. Otherwise, it returns zero. |bit|
266  * is indexed starting from zero. */
267 OPENSSL_EXPORT int CBS_asn1_bitstring_has_bit(const CBS *cbs, unsigned bit);
268 
269 
270 /* CRYPTO ByteBuilder.
271  *
272  * |CBB| objects allow one to build length-prefixed serialisations. A |CBB|
273  * object is associated with a buffer and new buffers are created with
274  * |CBB_init|. Several |CBB| objects can point at the same buffer when a
275  * length-prefix is pending, however only a single |CBB| can be 'current' at
276  * any one time. For example, if one calls |CBB_add_u8_length_prefixed| then
277  * the new |CBB| points at the same buffer as the original. But if the original
278  * |CBB| is used then the length prefix is written out and the new |CBB| must
279  * not be used again.
280  *
281  * If one needs to force a length prefix to be written out because a |CBB| is
282  * going out of scope, use |CBB_flush|. If an operation on a |CBB| fails, it is
283  * in an undefined state and must not be used except to call |CBB_cleanup|. */
284 
285 struct cbb_buffer_st {
286   uint8_t *buf;
287   size_t len;      /* The number of valid bytes. */
288   size_t cap;      /* The size of buf. */
289   char can_resize; /* One iff |buf| is owned by this object. If not then |buf|
290                       cannot be resized. */
291   char error;      /* One iff there was an error writing to this CBB. All future
292                       operations will fail. */
293 };
294 
295 struct cbb_st {
296   struct cbb_buffer_st *base;
297   /* child points to a child CBB if a length-prefix is pending. */
298   CBB *child;
299   /* offset is the number of bytes from the start of |base->buf| to this |CBB|'s
300    * pending length prefix. */
301   size_t offset;
302   /* pending_len_len contains the number of bytes in this |CBB|'s pending
303    * length-prefix, or zero if no length-prefix is pending. */
304   uint8_t pending_len_len;
305   char pending_is_asn1;
306   /* is_top_level is true iff this is a top-level |CBB| (as opposed to a child
307    * |CBB|). Top-level objects are valid arguments for |CBB_finish|. */
308   char is_top_level;
309 };
310 
311 /* CBB_zero sets an uninitialised |cbb| to the zero state. It must be
312  * initialised with |CBB_init| or |CBB_init_fixed| before use, but it is safe to
313  * call |CBB_cleanup| without a successful |CBB_init|. This may be used for more
314  * uniform cleanup of a |CBB|. */
315 OPENSSL_EXPORT void CBB_zero(CBB *cbb);
316 
317 /* CBB_init initialises |cbb| with |initial_capacity|. Since a |CBB| grows as
318  * needed, the |initial_capacity| is just a hint. It returns one on success or
319  * zero on error. */
320 OPENSSL_EXPORT int CBB_init(CBB *cbb, size_t initial_capacity);
321 
322 /* CBB_init_fixed initialises |cbb| to write to |len| bytes at |buf|. Since
323  * |buf| cannot grow, trying to write more than |len| bytes will cause CBB
324  * functions to fail. It returns one on success or zero on error. */
325 OPENSSL_EXPORT int CBB_init_fixed(CBB *cbb, uint8_t *buf, size_t len);
326 
327 /* CBB_cleanup frees all resources owned by |cbb| and other |CBB| objects
328  * writing to the same buffer. This should be used in an error case where a
329  * serialisation is abandoned.
330  *
331  * This function can only be called on a "top level" |CBB|, i.e. one initialised
332  * with |CBB_init| or |CBB_init_fixed|, or a |CBB| set to the zero state with
333  * |CBB_zero|. */
334 OPENSSL_EXPORT void CBB_cleanup(CBB *cbb);
335 
336 /* CBB_finish completes any pending length prefix and sets |*out_data| to a
337  * malloced buffer and |*out_len| to the length of that buffer. The caller
338  * takes ownership of the buffer and, unless the buffer was fixed with
339  * |CBB_init_fixed|, must call |OPENSSL_free| when done.
340  *
341  * It can only be called on a "top level" |CBB|, i.e. one initialised with
342  * |CBB_init| or |CBB_init_fixed|. It returns one on success and zero on
343  * error. */
344 OPENSSL_EXPORT int CBB_finish(CBB *cbb, uint8_t **out_data, size_t *out_len);
345 
346 /* CBB_flush causes any pending length prefixes to be written out and any child
347  * |CBB| objects of |cbb| to be invalidated. This allows |cbb| to continue to be
348  * used after the children go out of scope, e.g. when local |CBB| objects are
349  * added as children to a |CBB| that persists after a function returns. This
350  * function returns one on success or zero on error. */
351 OPENSSL_EXPORT int CBB_flush(CBB *cbb);
352 
353 /* CBB_data returns a pointer to the bytes written to |cbb|. It does not flush
354  * |cbb|. The pointer is valid until the next operation to |cbb|.
355  *
356  * To avoid unfinalized length prefixes, it is a fatal error to call this on a
357  * CBB with any active children. */
358 OPENSSL_EXPORT const uint8_t *CBB_data(const CBB *cbb);
359 
360 /* CBB_len returns the number of bytes written to |cbb|. It does not flush
361  * |cbb|.
362  *
363  * To avoid unfinalized length prefixes, it is a fatal error to call this on a
364  * CBB with any active children. */
365 OPENSSL_EXPORT size_t CBB_len(const CBB *cbb);
366 
367 /* CBB_add_u8_length_prefixed sets |*out_contents| to a new child of |cbb|. The
368  * data written to |*out_contents| will be prefixed in |cbb| with an 8-bit
369  * length. It returns one on success or zero on error. */
370 OPENSSL_EXPORT int CBB_add_u8_length_prefixed(CBB *cbb, CBB *out_contents);
371 
372 /* CBB_add_u16_length_prefixed sets |*out_contents| to a new child of |cbb|.
373  * The data written to |*out_contents| will be prefixed in |cbb| with a 16-bit,
374  * big-endian length. It returns one on success or zero on error. */
375 OPENSSL_EXPORT int CBB_add_u16_length_prefixed(CBB *cbb, CBB *out_contents);
376 
377 /* CBB_add_u24_length_prefixed sets |*out_contents| to a new child of |cbb|.
378  * The data written to |*out_contents| will be prefixed in |cbb| with a 24-bit,
379  * big-endian length. It returns one on success or zero on error. */
380 OPENSSL_EXPORT int CBB_add_u24_length_prefixed(CBB *cbb, CBB *out_contents);
381 
382 /* CBB_add_asn1 sets |*out_contents| to a |CBB| into which the contents of an
383  * ASN.1 object can be written. The |tag| argument will be used as the tag for
384  * the object. Passing in |tag| number 31 will return in an error since only
385  * single octet identifiers are supported. It returns one on success or zero
386  * on error. */
387 OPENSSL_EXPORT int CBB_add_asn1(CBB *cbb, CBB *out_contents, unsigned tag);
388 
389 /* CBB_add_bytes appends |len| bytes from |data| to |cbb|. It returns one on
390  * success and zero otherwise. */
391 OPENSSL_EXPORT int CBB_add_bytes(CBB *cbb, const uint8_t *data, size_t len);
392 
393 /* CBB_add_space appends |len| bytes to |cbb| and sets |*out_data| to point to
394  * the beginning of that space. The caller must then write |len| bytes of
395  * actual contents to |*out_data|. It returns one on success and zero
396  * otherwise. */
397 OPENSSL_EXPORT int CBB_add_space(CBB *cbb, uint8_t **out_data, size_t len);
398 
399 /* CBB_reserve ensures |cbb| has room for |len| additional bytes and sets
400  * |*out_data| to point to the beginning of that space. It returns one on
401  * success and zero otherwise. The caller may write up to |len| bytes to
402  * |*out_data| and call |CBB_did_write| to complete the write. |*out_data| is
403  * valid until the next operation on |cbb| or an ancestor |CBB|. */
404 OPENSSL_EXPORT int CBB_reserve(CBB *cbb, uint8_t **out_data, size_t len);
405 
406 /* CBB_did_write advances |cbb| by |len| bytes, assuming the space has been
407  * written to by the caller. It returns one on success and zero on error. */
408 OPENSSL_EXPORT int CBB_did_write(CBB *cbb, size_t len);
409 
410 /* CBB_add_u8 appends an 8-bit number from |value| to |cbb|. It returns one on
411  * success and zero otherwise. */
412 OPENSSL_EXPORT int CBB_add_u8(CBB *cbb, uint8_t value);
413 
414 /* CBB_add_u16 appends a 16-bit, big-endian number from |value| to |cbb|. It
415  * returns one on success and zero otherwise. */
416 OPENSSL_EXPORT int CBB_add_u16(CBB *cbb, uint16_t value);
417 
418 /* CBB_add_u24 appends a 24-bit, big-endian number from |value| to |cbb|. It
419  * returns one on success and zero otherwise. */
420 OPENSSL_EXPORT int CBB_add_u24(CBB *cbb, uint32_t value);
421 
422 /* CBB_add_u32 appends a 32-bit, big-endian number from |value| to |cbb|. It
423  * returns one on success and zero otherwise. */
424 OPENSSL_EXPORT int CBB_add_u32(CBB *cbb, uint32_t value);
425 
426 /* CBB_discard_child discards the current unflushed child of |cbb|. Neither the
427  * child's contents nor the length prefix will be included in the output. */
428 OPENSSL_EXPORT void CBB_discard_child(CBB *cbb);
429 
430 /* CBB_add_asn1_uint64 writes an ASN.1 INTEGER into |cbb| using |CBB_add_asn1|
431  * and writes |value| in its contents. It returns one on success and zero on
432  * error. */
433 OPENSSL_EXPORT int CBB_add_asn1_uint64(CBB *cbb, uint64_t value);
434 
435 
436 #if defined(__cplusplus)
437 }  /* extern C */
438 
439 
440 #if !defined(BORINGSSL_NO_CXX)
441 extern "C++" {
442 
443 namespace bssl {
444 
445 using ScopedCBB = internal::StackAllocated<CBB, void, CBB_zero, CBB_cleanup>;
446 
447 }  // namespace bssl
448 
449 }  // extern C++
450 #endif
451 
452 #endif
453 
454 #endif  /* OPENSSL_HEADER_BYTESTRING_H */
455