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crypto: Support DER encodings
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Add encoding interfaces for DER encoding:
1. support decoding of 'bit string', 'octet string', 'object id'
and 'context specific tag' for DER encoder.
2. implemented a simple DER encoder.
3. add more testsuits for DER encoder.

Signed-off-by: lei he <[email protected]>
Message-Id: <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Daniel P. Berrangé <[email protected]>
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@mstsirkin
Lei He authored and mstsirkin committed Nov 2, 2022
1 parent 2fda101 commit 3b34cca
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Showing 3 changed files with 597 additions and 47 deletions.
307 changes: 285 additions & 22 deletions crypto/der.c
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Original file line number Diff line number Diff line change
Expand Up @@ -22,20 +22,93 @@
#include "qemu/osdep.h"
#include "crypto/der.h"

typedef struct QCryptoDerEncodeNode {
uint8_t tag;
struct QCryptoDerEncodeNode *parent;
struct QCryptoDerEncodeNode *next;
/* for constructed type, data is null */
const uint8_t *data;
size_t dlen;
} QCryptoDerEncodeNode;

typedef struct QCryptoEncodeContext {
QCryptoDerEncodeNode root;
QCryptoDerEncodeNode *current_parent;
QCryptoDerEncodeNode *tail;
} QCryptoEncodeContext;

enum QCryptoDERTypeTag {
QCRYPTO_DER_TYPE_TAG_BOOL = 0x1,
QCRYPTO_DER_TYPE_TAG_INT = 0x2,
QCRYPTO_DER_TYPE_TAG_BIT_STR = 0x3,
QCRYPTO_DER_TYPE_TAG_OCT_STR = 0x4,
QCRYPTO_DER_TYPE_TAG_OCT_NULL = 0x5,
QCRYPTO_DER_TYPE_TAG_OCT_OID = 0x6,
QCRYPTO_DER_TYPE_TAG_NULL = 0x5,
QCRYPTO_DER_TYPE_TAG_OID = 0x6,
QCRYPTO_DER_TYPE_TAG_SEQ = 0x10,
QCRYPTO_DER_TYPE_TAG_SET = 0x11,
};

#define QCRYPTO_DER_CONSTRUCTED_MASK 0x20
enum QCryptoDERTagClass {
QCRYPTO_DER_TAG_CLASS_UNIV = 0x0,
QCRYPTO_DER_TAG_CLASS_APPL = 0x1,
QCRYPTO_DER_TAG_CLASS_CONT = 0x2,
QCRYPTO_DER_TAG_CLASS_PRIV = 0x3,
};

enum QCryptoDERTagEnc {
QCRYPTO_DER_TAG_ENC_PRIM = 0x0,
QCRYPTO_DER_TAG_ENC_CONS = 0x1,
};

#define QCRYPTO_DER_TAG_ENC_MASK 0x20
#define QCRYPTO_DER_TAG_ENC_SHIFT 5

#define QCRYPTO_DER_TAG_CLASS_MASK 0xc0
#define QCRYPTO_DER_TAG_CLASS_SHIFT 6

#define QCRYPTO_DER_TAG_VAL_MASK 0x1f
#define QCRYPTO_DER_SHORT_LEN_MASK 0x80

#define QCRYPTO_DER_TAG(class, enc, val) \
(((class) << QCRYPTO_DER_TAG_CLASS_SHIFT) | \
((enc) << QCRYPTO_DER_TAG_ENC_SHIFT) | (val))

/**
* qcrypto_der_encode_length:
* @src_len: the length of source data
* @dst: distination to save the encoded 'length', if dst is NULL, only compute
* the expected buffer size in bytes.
* @dst_len: output parameter, indicates how many bytes wrote.
*
* Encode the 'length' part of TLV tuple.
*/
static void qcrypto_der_encode_length(size_t src_len,
uint8_t *dst, size_t *dst_len)
{
size_t max_length = 0xFF;
uint8_t length_bytes = 0, header_byte;

if (src_len < QCRYPTO_DER_SHORT_LEN_MASK) {
header_byte = src_len;
*dst_len = 1;
} else {
for (length_bytes = 1; max_length < src_len; length_bytes++) {
max_length = (max_length << 8) + max_length;
}
header_byte = length_bytes;
header_byte |= QCRYPTO_DER_SHORT_LEN_MASK;
*dst_len = length_bytes + 1;
}
if (!dst) {
return;
}
*dst++ = header_byte;
/* Bigendian length bytes */
for (; length_bytes > 0; length_bytes--) {
*dst++ = ((src_len >> (length_bytes - 1) * 8) & 0xFF);
}
}

static uint8_t qcrypto_der_peek_byte(const uint8_t **data, size_t *dlen)
{
return **data;
Expand Down Expand Up @@ -150,40 +223,230 @@ static int qcrypto_der_extract_data(const uint8_t **data, size_t *dlen,
return qcrypto_der_extract_definite_data(data, dlen, cb, ctx, errp);
}

int qcrypto_der_decode_int(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
static int qcrypto_der_decode_tlv(const uint8_t expected_tag,
const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb,
void *ctx, Error **errp)
{
const uint8_t *saved_data = *data;
size_t saved_dlen = *dlen;
uint8_t tag;
int data_length;

if (*dlen < 1) {
error_setg(errp, "Need more data");
return -1;
}
tag = qcrypto_der_cut_byte(data, dlen);
if (tag != expected_tag) {
error_setg(errp, "Unexpected tag: expected: %u, actual: %u",
expected_tag, tag);
goto error;
}

/* INTEGER must encoded in primitive-form */
if (tag != QCRYPTO_DER_TYPE_TAG_INT) {
error_setg(errp, "Invalid integer type tag: %u", tag);
return -1;
data_length = qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
if (data_length < 0) {
goto error;
}
return data_length;

return qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
error:
*data = saved_data;
*dlen = saved_dlen;
return -1;
}

int qcrypto_der_decode_int(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
{
const uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_INT);
return qcrypto_der_decode_tlv(tag, data, dlen, cb, ctx, errp);
}

int qcrypto_der_decode_seq(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
{
uint8_t tag;
if (*dlen < 1) {
error_setg(errp, "Need more data");
return -1;
}
tag = qcrypto_der_cut_byte(data, dlen);
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_CONS,
QCRYPTO_DER_TYPE_TAG_SEQ);
return qcrypto_der_decode_tlv(tag, data, dlen, cb, ctx, errp);
}

/* SEQUENCE must use constructed form */
if (tag != (QCRYPTO_DER_TYPE_TAG_SEQ | QCRYPTO_DER_CONSTRUCTED_MASK)) {
error_setg(errp, "Invalid type sequence tag: %u", tag);
return -1;
}
int qcrypto_der_decode_octet_str(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_OCT_STR);
return qcrypto_der_decode_tlv(tag, data, dlen, cb, ctx, errp);
}

int qcrypto_der_decode_bit_str(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_BIT_STR);
return qcrypto_der_decode_tlv(tag, data, dlen, cb, ctx, errp);
}

int qcrypto_der_decode_oid(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_OID);
return qcrypto_der_decode_tlv(tag, data, dlen, cb, ctx, errp);
}

int qcrypto_der_decode_ctx_tag(const uint8_t **data, size_t *dlen, int tag_id,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_CONT,
QCRYPTO_DER_TAG_ENC_CONS,
tag_id);
return qcrypto_der_decode_tlv(tag, data, dlen, cb, ctx, errp);
}

return qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
static void qcrypto_der_encode_prim(QCryptoEncodeContext *ctx, uint8_t tag,
const uint8_t *data, size_t dlen)
{
QCryptoDerEncodeNode *node = g_new0(QCryptoDerEncodeNode, 1);
size_t nbytes_len;

node->tag = tag;
node->data = data;
node->dlen = dlen;
node->parent = ctx->current_parent;

qcrypto_der_encode_length(dlen, NULL, &nbytes_len);
/* 1 byte for Tag, nbyte_len for Length, and dlen for Value */
node->parent->dlen += 1 + nbytes_len + dlen;

ctx->tail->next = node;
ctx->tail = node;
}

QCryptoEncodeContext *qcrypto_der_encode_ctx_new(void)
{
QCryptoEncodeContext *ctx = g_new0(QCryptoEncodeContext, 1);
ctx->current_parent = &ctx->root;
ctx->tail = &ctx->root;
return ctx;
}

static void qcrypto_der_encode_cons_begin(QCryptoEncodeContext *ctx,
uint8_t tag)
{
QCryptoDerEncodeNode *node = g_new0(QCryptoDerEncodeNode, 1);

node->tag = tag;
node->parent = ctx->current_parent;
ctx->current_parent = node;
ctx->tail->next = node;
ctx->tail = node;
}

static void qcrypto_der_encode_cons_end(QCryptoEncodeContext *ctx)
{
QCryptoDerEncodeNode *cons_node = ctx->current_parent;
size_t nbytes_len;

qcrypto_der_encode_length(cons_node->dlen, NULL, &nbytes_len);
/* 1 byte for Tag, nbyte_len for Length, and dlen for Value */
cons_node->parent->dlen += 1 + nbytes_len + cons_node->dlen;
ctx->current_parent = cons_node->parent;
}

void qcrypto_der_encode_seq_begin(QCryptoEncodeContext *ctx)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_CONS,
QCRYPTO_DER_TYPE_TAG_SEQ);
qcrypto_der_encode_cons_begin(ctx, tag);
}

void qcrypto_der_encode_seq_end(QCryptoEncodeContext *ctx)
{
qcrypto_der_encode_cons_end(ctx);
}

void qcrypto_der_encode_oid(QCryptoEncodeContext *ctx,
const uint8_t *src, size_t src_len)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_OID);
qcrypto_der_encode_prim(ctx, tag, src, src_len);
}

void qcrypto_der_encode_int(QCryptoEncodeContext *ctx,
const uint8_t *src, size_t src_len)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_INT);
qcrypto_der_encode_prim(ctx, tag, src, src_len);
}

void qcrypto_der_encode_null(QCryptoEncodeContext *ctx)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_NULL);
qcrypto_der_encode_prim(ctx, tag, NULL, 0);
}

void qcrypto_der_encode_octet_str(QCryptoEncodeContext *ctx,
const uint8_t *src, size_t src_len)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_OCT_STR);
qcrypto_der_encode_prim(ctx, tag, src, src_len);
}

void qcrypto_der_encode_octet_str_begin(QCryptoEncodeContext *ctx)
{
uint8_t tag = QCRYPTO_DER_TAG(QCRYPTO_DER_TAG_CLASS_UNIV,
QCRYPTO_DER_TAG_ENC_PRIM,
QCRYPTO_DER_TYPE_TAG_OCT_STR);
qcrypto_der_encode_cons_begin(ctx, tag);
}

void qcrypto_der_encode_octet_str_end(QCryptoEncodeContext *ctx)
{
qcrypto_der_encode_cons_end(ctx);
}

size_t qcrypto_der_encode_ctx_buffer_len(QCryptoEncodeContext *ctx)
{
return ctx->root.dlen;
}

void qcrypto_der_encode_ctx_flush_and_free(QCryptoEncodeContext *ctx,
uint8_t *dst)
{
QCryptoDerEncodeNode *node, *prev;
size_t len;

for (prev = &ctx->root;
(node = prev->next) && (prev->next = node->next, 1);) {
/* Tag */
*dst++ = node->tag;

/* Length */
qcrypto_der_encode_length(node->dlen, dst, &len);
dst += len;

/* Value */
if (node->data) {
memcpy(dst, node->data, node->dlen);
dst += node->dlen;
}
g_free(node);
}
g_free(ctx);
}
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