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boringssl/include/openssl/bytestring.h
David Benjamin 375124b162 Parse BER for PKCS#12 more accurately. 
CBS_asn1_ber_to_der currently uses heuristics because implicitly-tagged
constructed strings in BER are ambiguous with implicitly-tagged sequences. It's
not possible to convert BER to DER without knowing the schema.

Fortunately, implicitly tagged strings don't appear often so instead split the
job up: CBS_asn1_ber_to_der fixes indefinite-length elements and constructed
strings it can see. Implicitly-tagged strings it leaves uncoverted, but they
will only nest one level down (because BER kindly allows one to nest
constructed strings arbitrarily!).

CBS_get_asn1_implicit_string then performs the final concatenation at parse
time. This isn't much more complex and lets us parse BER more accurately and
also reject a number of mis-encoded values (e.g. constructed INTEGERs are not a
thing) we'd previously let through. The downside is the post-conversion parsing
code must be aware of this limitation of CBS_asn1_ber_to_der. Fortunately,
there's only one implicitly-tagged string in our PKCS#12 code.

(In the category of things that really really don't matter, but I had spare
cycles and the old BER converter is weird.)

Change-Id: Iebdd13b08559fa158b308ef83a5bb07bfdf80ae8
Reviewed-on: https://boringssl-review.googlesource.com/7052
Reviewed-by: Adam Langley <agl@google.com>
2016-02-16 19:32:50 +00:00

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/* Copyright (c) 2014, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#ifndef OPENSSL_HEADER_BYTESTRING_H
#define OPENSSL_HEADER_BYTESTRING_H
#include <openssl/base.h>
#if defined(__cplusplus)
extern "C" {
#endif
/* Bytestrings are used for parsing and building TLS and ASN.1 messages.
*
* A "CBS" (CRYPTO ByteString) represents a string of bytes in memory and
* provides utility functions for safely parsing length-prefixed structures
* like TLS and ASN.1 from it.
*
* A "CBB" (CRYPTO ByteBuilder) is a memory buffer that grows as needed and
* provides utility functions for building length-prefixed messages. */
/* CRYPTO ByteString */
struct cbs_st {
const uint8_t *data;
size_t len;
};
/* CBS_init sets |cbs| to point to |data|. It does not take ownership of
* |data|. */
OPENSSL_EXPORT void CBS_init(CBS *cbs, const uint8_t *data, size_t len);
/* CBS_skip advances |cbs| by |len| bytes. It returns one on success and zero
* otherwise. */
OPENSSL_EXPORT int CBS_skip(CBS *cbs, size_t len);
/* CBS_data returns a pointer to the contents of |cbs|. */
OPENSSL_EXPORT const uint8_t *CBS_data(const CBS *cbs);
/* CBS_len returns the number of bytes remaining in |cbs|. */
OPENSSL_EXPORT size_t CBS_len(const CBS *cbs);
/* CBS_stow copies the current contents of |cbs| into |*out_ptr| and
* |*out_len|. If |*out_ptr| is not NULL, the contents are freed with
* OPENSSL_free. It returns one on success and zero on allocation failure. On
* success, |*out_ptr| should be freed with OPENSSL_free. If |cbs| is empty,
* |*out_ptr| will be NULL. */
OPENSSL_EXPORT int CBS_stow(const CBS *cbs, uint8_t **out_ptr, size_t *out_len);
/* CBS_strdup copies the current contents of |cbs| into |*out_ptr| as a
* NUL-terminated C string. If |*out_ptr| is not NULL, the contents are freed
* with OPENSSL_free. It returns one on success and zero on allocation
* failure. On success, |*out_ptr| should be freed with OPENSSL_free.
*
* NOTE: If |cbs| contains NUL bytes, the string will be truncated. Call
* |CBS_contains_zero_byte(cbs)| to check for NUL bytes. */
OPENSSL_EXPORT int CBS_strdup(const CBS *cbs, char **out_ptr);
/* CBS_contains_zero_byte returns one if the current contents of |cbs| contains
* a NUL byte and zero otherwise. */
OPENSSL_EXPORT int CBS_contains_zero_byte(const CBS *cbs);
/* CBS_mem_equal compares the current contents of |cbs| with the |len| bytes
* starting at |data|. If they're equal, it returns one, otherwise zero. If the
* lengths match, it uses a constant-time comparison. */
OPENSSL_EXPORT int CBS_mem_equal(const CBS *cbs, const uint8_t *data,
size_t len);
/* CBS_get_u8 sets |*out| to the next uint8_t from |cbs| and advances |cbs|. It
* returns one on success and zero on error. */
OPENSSL_EXPORT int CBS_get_u8(CBS *cbs, uint8_t *out);
/* CBS_get_u16 sets |*out| to the next, big-endian uint16_t from |cbs| and
* advances |cbs|. It returns one on success and zero on error. */
OPENSSL_EXPORT int CBS_get_u16(CBS *cbs, uint16_t *out);
/* CBS_get_u24 sets |*out| to the next, big-endian 24-bit value from |cbs| and
* advances |cbs|. It returns one on success and zero on error. */
OPENSSL_EXPORT int CBS_get_u24(CBS *cbs, uint32_t *out);
/* CBS_get_u32 sets |*out| to the next, big-endian uint32_t value from |cbs|
* and advances |cbs|. It returns one on success and zero on error. */
OPENSSL_EXPORT int CBS_get_u32(CBS *cbs, uint32_t *out);
/* CBS_get_bytes sets |*out| to the next |len| bytes from |cbs| and advances
* |cbs|. It returns one on success and zero on error. */
OPENSSL_EXPORT int CBS_get_bytes(CBS *cbs, CBS *out, size_t len);
/* CBS_copy_bytes copies the next |len| bytes from |cbs| to |out| and advances
* |cbs|. It returns one on success and zero on error. */
OPENSSL_EXPORT int CBS_copy_bytes(CBS *cbs, uint8_t *out, size_t len);
/* CBS_get_u8_length_prefixed sets |*out| to the contents of an 8-bit,
* length-prefixed value from |cbs| and advances |cbs| over it. It returns one
* on success and zero on error. */
OPENSSL_EXPORT int CBS_get_u8_length_prefixed(CBS *cbs, CBS *out);
/* CBS_get_u16_length_prefixed sets |*out| to the contents of a 16-bit,
* big-endian, length-prefixed value from |cbs| and advances |cbs| over it. It
* returns one on success and zero on error. */
OPENSSL_EXPORT int CBS_get_u16_length_prefixed(CBS *cbs, CBS *out);
/* CBS_get_u24_length_prefixed sets |*out| to the contents of a 24-bit,
* big-endian, length-prefixed value from |cbs| and advances |cbs| over it. It
* returns one on success and zero on error. */
OPENSSL_EXPORT int CBS_get_u24_length_prefixed(CBS *cbs, CBS *out);
/* Parsing ASN.1 */
#define CBS_ASN1_BOOLEAN 0x1
#define CBS_ASN1_INTEGER 0x2
#define CBS_ASN1_BITSTRING 0x3
#define CBS_ASN1_OCTETSTRING 0x4
#define CBS_ASN1_NULL 0x5
#define CBS_ASN1_OBJECT 0x6
#define CBS_ASN1_ENUMERATED 0xa
#define CBS_ASN1_SEQUENCE (0x10 | CBS_ASN1_CONSTRUCTED)
#define CBS_ASN1_SET (0x11 | CBS_ASN1_CONSTRUCTED)
#define CBS_ASN1_NUMERICSTRING 0x12
#define CBS_ASN1_PRINTABLESTRING 0x13
#define CBS_ASN1_T16STRING 0x14
#define CBS_ASN1_VIDEOTEXSTRING 0x15
#define CBS_ASN1_IA5STRING 0x16
#define CBS_ASN1_UTCTIME 0x17
#define CBS_ASN1_GENERALIZEDTIME 0x18
#define CBS_ASN1_GRAPHICSTRING 0x19
#define CBS_ASN1_VISIBLESTRING 0x1a
#define CBS_ASN1_GENERALSTRING 0x1b
#define CBS_ASN1_UNIVERSALSTRING 0x1c
#define CBS_ASN1_BMPSTRING 0x1e
#define CBS_ASN1_CONSTRUCTED 0x20
#define CBS_ASN1_CONTEXT_SPECIFIC 0x80
/* CBS_get_asn1 sets |*out| to the contents of DER-encoded, ASN.1 element (not
* including tag and length bytes) and advances |cbs| over it. The ASN.1
* element must match |tag_value|. It returns one on success and zero
* on error.
*
* Tag numbers greater than 30 are not supported (i.e. short form only). */
OPENSSL_EXPORT int CBS_get_asn1(CBS *cbs, CBS *out, unsigned tag_value);
/* CBS_get_asn1_element acts like |CBS_get_asn1| but |out| will include the
* ASN.1 header bytes too. */
OPENSSL_EXPORT int CBS_get_asn1_element(CBS *cbs, CBS *out, unsigned tag_value);
/* CBS_peek_asn1_tag looks ahead at the next ASN.1 tag and returns one
* if the next ASN.1 element on |cbs| would have tag |tag_value|. If
* |cbs| is empty or the tag does not match, it returns zero. Note: if
* it returns one, CBS_get_asn1 may still fail if the rest of the
* element is malformed. */
OPENSSL_EXPORT int CBS_peek_asn1_tag(const CBS *cbs, unsigned tag_value);
/* CBS_get_any_asn1_element sets |*out| to contain the next ASN.1 element from
* |*cbs| (including header bytes) and advances |*cbs|. It sets |*out_tag| to
* the tag number and |*out_header_len| to the length of the ASN.1 header. Each
* of |out|, |out_tag|, and |out_header_len| may be NULL to ignore the value.
*
* Tag numbers greater than 30 are not supported (i.e. short form only). */
OPENSSL_EXPORT int CBS_get_any_asn1_element(CBS *cbs, CBS *out,
unsigned *out_tag,
size_t *out_header_len);
/* CBS_get_any_ber_asn1_element acts the same as |CBS_get_any_asn1_element| but
* also allows indefinite-length elements to be returned. In that case,
* |*out_header_len| and |CBS_len(out)| will both be two as only the header is
* returned, otherwise it behaves the same as the previous function. */
OPENSSL_EXPORT int CBS_get_any_ber_asn1_element(CBS *cbs, CBS *out,
unsigned *out_tag,
size_t *out_header_len);
/* CBS_get_asn1_uint64 gets an ASN.1 INTEGER from |cbs| using |CBS_get_asn1|
* and sets |*out| to its value. It returns one on success and zero on error,
* where error includes the integer being negative, or too large to represent
* in 64 bits. */
OPENSSL_EXPORT int CBS_get_asn1_uint64(CBS *cbs, uint64_t *out);
/* CBS_get_optional_asn1 gets an optional explicitly-tagged element from |cbs|
* tagged with |tag| and sets |*out| to its contents. If present and if
* |out_present| is not NULL, it sets |*out_present| to one, otherwise zero. It
* returns one on success, whether or not the element was present, and zero on
* decode failure. */
OPENSSL_EXPORT int CBS_get_optional_asn1(CBS *cbs, CBS *out, int *out_present,
unsigned tag);
/* CBS_get_optional_asn1_octet_string gets an optional
* explicitly-tagged OCTET STRING from |cbs|. If present, it sets
* |*out| to the string and |*out_present| to one. Otherwise, it sets
* |*out| to empty and |*out_present| to zero. |out_present| may be
* NULL. It returns one on success, whether or not the element was
* present, and zero on decode failure. */
OPENSSL_EXPORT int CBS_get_optional_asn1_octet_string(CBS *cbs, CBS *out,
int *out_present,
unsigned tag);
/* CBS_get_optional_asn1_uint64 gets an optional explicitly-tagged
* INTEGER from |cbs|. If present, it sets |*out| to the
* value. Otherwise, it sets |*out| to |default_value|. It returns one
* on success, whether or not the element was present, and zero on
* decode failure. */
OPENSSL_EXPORT int CBS_get_optional_asn1_uint64(CBS *cbs, uint64_t *out,
unsigned tag,
uint64_t default_value);
/* CBS_get_optional_asn1_bool gets an optional, explicitly-tagged BOOLEAN from
* |cbs|. If present, it sets |*out| to either zero or one, based on the
* boolean. Otherwise, it sets |*out| to |default_value|. It returns one on
* success, whether or not the element was present, and zero on decode
* failure. */
OPENSSL_EXPORT int CBS_get_optional_asn1_bool(CBS *cbs, int *out, unsigned tag,
int default_value);
/* CRYPTO ByteBuilder.
*
* |CBB| objects allow one to build length-prefixed serialisations. A |CBB|
* object is associated with a buffer and new buffers are created with
* |CBB_init|. Several |CBB| objects can point at the same buffer when a
* length-prefix is pending, however only a single |CBB| can be 'current' at
* any one time. For example, if one calls |CBB_add_u8_length_prefixed| then
* the new |CBB| points at the same buffer as the original. But if the original
* |CBB| is used then the length prefix is written out and the new |CBB| must
* not be used again.
*
* If one needs to force a length prefix to be written out because a |CBB| is
* going out of scope, use |CBB_flush|. */
struct cbb_buffer_st {
uint8_t *buf;
size_t len; /* The number of valid bytes. */
size_t cap; /* The size of buf. */
char can_resize; /* One iff |buf| is owned by this object. If not then |buf|
cannot be resized. */
};
struct cbb_st {
struct cbb_buffer_st *base;
/* child points to a child CBB if a length-prefix is pending. */
CBB *child;
/* offset is the number of bytes from the start of |base->buf| to this |CBB|'s
* pending length prefix. */
size_t offset;
/* pending_len_len contains the number of bytes in this |CBB|'s pending
* length-prefix, or zero if no length-prefix is pending. */
uint8_t pending_len_len;
char pending_is_asn1;
/* is_top_level is true iff this is a top-level |CBB| (as opposed to a child
* |CBB|). Top-level objects are valid arguments for |CBB_finish|. */
char is_top_level;
};
/* CBB_zero sets an uninitialised |cbb| to the zero state. It must be
* initialised with |CBB_init| or |CBB_init_fixed| before use, but it is safe to
* call |CBB_cleanup| without a successful |CBB_init|. This may be used for more
* uniform cleanup of a |CBB|. */
OPENSSL_EXPORT void CBB_zero(CBB *cbb);
/* CBB_init initialises |cbb| with |initial_capacity|. Since a |CBB| grows as
* needed, the |initial_capacity| is just a hint. It returns one on success or
* zero on error. */
OPENSSL_EXPORT int CBB_init(CBB *cbb, size_t initial_capacity);
/* CBB_init_fixed initialises |cbb| to write to |len| bytes at |buf|. Since
* |buf| cannot grow, trying to write more than |len| bytes will cause CBB
* functions to fail. It returns one on success or zero on error. */
OPENSSL_EXPORT int CBB_init_fixed(CBB *cbb, uint8_t *buf, size_t len);
/* CBB_cleanup frees all resources owned by |cbb| and other |CBB| objects
* writing to the same buffer. This should be used in an error case where a
* serialisation is abandoned.
*
* This function can only be called on a "top level" |CBB|, i.e. one initialised
* with |CBB_init| or |CBB_init_fixed|, or a |CBB| set to the zero state with
* |CBB_zero|. */
OPENSSL_EXPORT void CBB_cleanup(CBB *cbb);
/* CBB_finish completes any pending length prefix and sets |*out_data| to a
* malloced buffer and |*out_len| to the length of that buffer. The caller
* takes ownership of the buffer and, unless the buffer was fixed with
* |CBB_init_fixed|, must call |OPENSSL_free| when done.
*
* It can only be called on a "top level" |CBB|, i.e. one initialised with
* |CBB_init| or |CBB_init_fixed|. It returns one on success and zero on
* error. */
OPENSSL_EXPORT int CBB_finish(CBB *cbb, uint8_t **out_data, size_t *out_len);
/* CBB_flush causes any pending length prefixes to be written out and any child
* |CBB| objects of |cbb| to be invalidated. It returns one on success or zero
* on error. */
OPENSSL_EXPORT int CBB_flush(CBB *cbb);
/* CBB_data returns a pointer to the bytes written to |cbb|. It does not flush
* |cbb|. The pointer is valid until the next operation to |cbb|.
*
* To avoid unfinalized length prefixes, it is a fatal error to call this on a
* CBB with any active children. */
OPENSSL_EXPORT const uint8_t *CBB_data(const CBB *cbb);
/* CBB_len returns the number of bytes written to |cbb|. It does not flush
* |cbb|.
*
* To avoid unfinalized length prefixes, it is a fatal error to call this on a
* CBB with any active children. */
OPENSSL_EXPORT size_t CBB_len(const CBB *cbb);
/* CBB_add_u8_length_prefixed sets |*out_contents| to a new child of |cbb|. The
* data written to |*out_contents| will be prefixed in |cbb| with an 8-bit
* length. It returns one on success or zero on error. */
OPENSSL_EXPORT int CBB_add_u8_length_prefixed(CBB *cbb, CBB *out_contents);
/* CBB_add_u16_length_prefixed sets |*out_contents| to a new child of |cbb|.
* The data written to |*out_contents| will be prefixed in |cbb| with a 16-bit,
* big-endian length. It returns one on success or zero on error. */
OPENSSL_EXPORT int CBB_add_u16_length_prefixed(CBB *cbb, CBB *out_contents);
/* CBB_add_u24_length_prefixed sets |*out_contents| to a new child of |cbb|.
* The data written to |*out_contents| will be prefixed in |cbb| with a 24-bit,
* big-endian length. It returns one on success or zero on error. */
OPENSSL_EXPORT int CBB_add_u24_length_prefixed(CBB *cbb, CBB *out_contents);
/* CBB_add_asn1 sets |*out_contents| to a |CBB| into which the contents of an
* ASN.1 object can be written. The |tag| argument will be used as the tag for
* the object. Passing in |tag| number 31 will return in an error since only
* single octet identifiers are supported. It returns one on success or zero
* on error. */
OPENSSL_EXPORT int CBB_add_asn1(CBB *cbb, CBB *out_contents, uint8_t tag);
/* CBB_add_bytes appends |len| bytes from |data| to |cbb|. It returns one on
* success and zero otherwise. */
OPENSSL_EXPORT int CBB_add_bytes(CBB *cbb, const uint8_t *data, size_t len);
/* CBB_add_space appends |len| bytes to |cbb| and sets |*out_data| to point to
* the beginning of that space. The caller must then write |len| bytes of
* actual contents to |*out_data|. It returns one on success and zero
* otherwise. */
OPENSSL_EXPORT int CBB_add_space(CBB *cbb, uint8_t **out_data, size_t len);
/* CBB_reserve ensures |cbb| has room for |len| additional bytes and sets
* |*out_data| to point to the beginning of that space. It returns one on
* success and zero otherwise. The caller may write up to |len| bytes to
* |*out_data| and call |CBB_did_write| to complete the write. |*out_data| is
* valid until the next operation on |cbb| or an ancestor |CBB|. */
OPENSSL_EXPORT int CBB_reserve(CBB *cbb, uint8_t **out_data, size_t len);
/* CBB_did_write advances |cbb| by |len| bytes, assuming the space has been
* written to by the caller. It returns one on success and zero on error. */
OPENSSL_EXPORT int CBB_did_write(CBB *cbb, size_t len);
/* CBB_add_u8 appends an 8-bit number from |value| to |cbb|. It returns one on
* success and zero otherwise. */
OPENSSL_EXPORT int CBB_add_u8(CBB *cbb, uint8_t value);
/* CBB_add_u16 appends a 16-bit, big-endian number from |value| to |cbb|. It
* returns one on success and zero otherwise. */
OPENSSL_EXPORT int CBB_add_u16(CBB *cbb, uint16_t value);
/* CBB_add_u24 appends a 24-bit, big-endian number from |value| to |cbb|. It
* returns one on success and zero otherwise. */
OPENSSL_EXPORT int CBB_add_u24(CBB *cbb, uint32_t value);
/* CBB_discard_child discards the current unflushed child of |cbb|. Neither the
* child's contents nor the length prefix will be included in the output. */
OPENSSL_EXPORT void CBB_discard_child(CBB *cbb);
/* CBB_add_asn1_uint64 writes an ASN.1 INTEGER into |cbb| using |CBB_add_asn1|
* and writes |value| in its contents. It returns one on success and zero on
* error. */
OPENSSL_EXPORT int CBB_add_asn1_uint64(CBB *cbb, uint64_t value);
#if defined(__cplusplus)
} /* extern C */
#endif
#endif /* OPENSSL_HEADER_BYTESTRING_H */
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