From 7a4adb5268ae71260c86788ccdeb7a699c80ee0a Mon Sep 17 00:00:00 2001 From: Kenny Root Date: Wed, 9 Oct 2013 10:14:35 -0700 Subject: Add support for ECDSA signatures This adds support for key version 5 which is an EC key using the NIST P-256 curve parameters. OTAs may be signed with these keys using the ECDSA signature algorithm with SHA-256. Change-Id: Id88672a3deb70681c78d5ea0d739e10f839e4567 --- asn1_decoder.cpp | 190 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 190 insertions(+) create mode 100644 asn1_decoder.cpp (limited to 'asn1_decoder.cpp') diff --git a/asn1_decoder.cpp b/asn1_decoder.cpp new file mode 100644 index 0000000..7280f74 --- /dev/null +++ b/asn1_decoder.cpp @@ -0,0 +1,190 @@ +/* + * Copyright (C) 2013 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#include +#include + +#include "asn1_decoder.h" + + +typedef struct asn1_context { + size_t length; + uint8_t* p; + int app_type; +} asn1_context_t; + + +static const int kMaskConstructed = 0xE0; +static const int kMaskTag = 0x7F; +static const int kMaskAppType = 0x1F; + +static const int kTagOctetString = 0x04; +static const int kTagOid = 0x06; +static const int kTagSequence = 0x30; +static const int kTagSet = 0x31; +static const int kTagConstructed = 0xA0; + +asn1_context_t* asn1_context_new(uint8_t* buffer, size_t length) { + asn1_context_t* ctx = (asn1_context_t*) calloc(1, sizeof(asn1_context_t)); + if (ctx == NULL) { + return NULL; + } + ctx->p = buffer; + ctx->length = length; + return ctx; +} + +void asn1_context_free(asn1_context_t* ctx) { + free(ctx); +} + +static inline int peek_byte(asn1_context_t* ctx) { + if (ctx->length <= 0) { + return -1; + } + return *ctx->p; +} + +static inline int get_byte(asn1_context_t* ctx) { + if (ctx->length <= 0) { + return -1; + } + int byte = *ctx->p; + ctx->p++; + ctx->length--; + return byte; +} + +static inline bool skip_bytes(asn1_context_t* ctx, size_t num_skip) { + if (ctx->length < num_skip) { + return false; + } + ctx->p += num_skip; + ctx->length -= num_skip; + return true; +} + +static bool decode_length(asn1_context_t* ctx, size_t* out_len) { + int num_octets = get_byte(ctx); + if (num_octets == -1) { + return false; + } + if ((num_octets & 0x80) == 0x00) { + *out_len = num_octets; + return 1; + } + num_octets &= kMaskTag; + if ((size_t)num_octets >= sizeof(size_t)) { + return false; + } + size_t length = 0; + for (int i = 0; i < num_octets; ++i) { + int byte = get_byte(ctx); + if (byte == -1) { + return false; + } + length <<= 8; + length += byte; + } + *out_len = length; + return true; +} + +/** + * Returns the constructed type and advances the pointer. E.g. A0 -> 0 + */ +asn1_context_t* asn1_constructed_get(asn1_context_t* ctx) { + int type = get_byte(ctx); + if (type == -1 || (type & kMaskConstructed) != kTagConstructed) { + return NULL; + } + size_t length; + if (!decode_length(ctx, &length) || length > ctx->length) { + return NULL; + } + asn1_context_t* app_ctx = asn1_context_new(ctx->p, length); + app_ctx->app_type = type & kMaskAppType; + return app_ctx; +} + +bool asn1_constructed_skip_all(asn1_context_t* ctx) { + int byte = peek_byte(ctx); + while (byte != -1 && (byte & kMaskConstructed) == kTagConstructed) { + skip_bytes(ctx, 1); + size_t length; + if (!decode_length(ctx, &length) || !skip_bytes(ctx, length)) { + return false; + } + byte = peek_byte(ctx); + } + return byte != -1; +} + +int asn1_constructed_type(asn1_context_t* ctx) { + return ctx->app_type; +} + +asn1_context_t* asn1_sequence_get(asn1_context_t* ctx) { + if ((get_byte(ctx) & kMaskTag) != kTagSequence) { + return NULL; + } + size_t length; + if (!decode_length(ctx, &length) || length > ctx->length) { + return NULL; + } + return asn1_context_new(ctx->p, length); +} + +asn1_context_t* asn1_set_get(asn1_context_t* ctx) { + if ((get_byte(ctx) & kMaskTag) != kTagSet) { + return NULL; + } + size_t length; + if (!decode_length(ctx, &length) || length > ctx->length) { + return NULL; + } + return asn1_context_new(ctx->p, length); +} + +bool asn1_sequence_next(asn1_context_t* ctx) { + size_t length; + if (get_byte(ctx) == -1 || !decode_length(ctx, &length) || !skip_bytes(ctx, length)) { + return false; + } + return true; +} + +bool asn1_oid_get(asn1_context_t* ctx, uint8_t** oid, size_t* length) { + if (get_byte(ctx) != kTagOid) { + return false; + } + if (!decode_length(ctx, length) || *length == 0 || *length > ctx->length) { + return false; + } + *oid = ctx->p; + return true; +} + +bool asn1_octet_string_get(asn1_context_t* ctx, uint8_t** octet_string, size_t* length) { + if (get_byte(ctx) != kTagOctetString) { + return false; + } + if (!decode_length(ctx, length) || *length == 0 || *length > ctx->length) { + return false; + } + *octet_string = ctx->p; + return true; +} -- cgit v1.1