| /* |
| * Copyright (C) 2008 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 "verifier.h" |
| |
| #include <errno.h> |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| |
| #include <algorithm> |
| #include <functional> |
| #include <memory> |
| #include <vector> |
| |
| #include <android-base/logging.h> |
| #include <openssl/bn.h> |
| #include <openssl/ecdsa.h> |
| #include <openssl/obj_mac.h> |
| |
| #include "asn1_decoder.h" |
| #include "print_sha1.h" |
| |
| static constexpr size_t MiB = 1024 * 1024; |
| |
| /* |
| * Simple version of PKCS#7 SignedData extraction. This extracts the |
| * signature OCTET STRING to be used for signature verification. |
| * |
| * For full details, see http://www.ietf.org/rfc/rfc3852.txt |
| * |
| * The PKCS#7 structure looks like: |
| * |
| * SEQUENCE (ContentInfo) |
| * OID (ContentType) |
| * [0] (content) |
| * SEQUENCE (SignedData) |
| * INTEGER (version CMSVersion) |
| * SET (DigestAlgorithmIdentifiers) |
| * SEQUENCE (EncapsulatedContentInfo) |
| * [0] (CertificateSet OPTIONAL) |
| * [1] (RevocationInfoChoices OPTIONAL) |
| * SET (SignerInfos) |
| * SEQUENCE (SignerInfo) |
| * INTEGER (CMSVersion) |
| * SEQUENCE (SignerIdentifier) |
| * SEQUENCE (DigestAlgorithmIdentifier) |
| * SEQUENCE (SignatureAlgorithmIdentifier) |
| * OCTET STRING (SignatureValue) |
| */ |
| static bool read_pkcs7(const uint8_t* pkcs7_der, size_t pkcs7_der_len, |
| std::vector<uint8_t>* sig_der) { |
| CHECK(sig_der != nullptr); |
| sig_der->clear(); |
| |
| asn1_context ctx(pkcs7_der, pkcs7_der_len); |
| |
| std::unique_ptr<asn1_context> pkcs7_seq(ctx.asn1_sequence_get()); |
| if (pkcs7_seq == nullptr || !pkcs7_seq->asn1_sequence_next()) { |
| return false; |
| } |
| |
| std::unique_ptr<asn1_context> signed_data_app(pkcs7_seq->asn1_constructed_get()); |
| if (signed_data_app == nullptr) { |
| return false; |
| } |
| |
| std::unique_ptr<asn1_context> signed_data_seq(signed_data_app->asn1_sequence_get()); |
| if (signed_data_seq == nullptr || |
| !signed_data_seq->asn1_sequence_next() || |
| !signed_data_seq->asn1_sequence_next() || |
| !signed_data_seq->asn1_sequence_next() || |
| !signed_data_seq->asn1_constructed_skip_all()) { |
| return false; |
| } |
| |
| std::unique_ptr<asn1_context> sig_set(signed_data_seq->asn1_set_get()); |
| if (sig_set == nullptr) { |
| return false; |
| } |
| |
| std::unique_ptr<asn1_context> sig_seq(sig_set->asn1_sequence_get()); |
| if (sig_seq == nullptr || |
| !sig_seq->asn1_sequence_next() || |
| !sig_seq->asn1_sequence_next() || |
| !sig_seq->asn1_sequence_next() || |
| !sig_seq->asn1_sequence_next()) { |
| return false; |
| } |
| |
| const uint8_t* sig_der_ptr; |
| size_t sig_der_length; |
| if (!sig_seq->asn1_octet_string_get(&sig_der_ptr, &sig_der_length)) { |
| return false; |
| } |
| |
| sig_der->resize(sig_der_length); |
| std::copy(sig_der_ptr, sig_der_ptr + sig_der_length, sig_der->begin()); |
| return true; |
| } |
| |
| /* |
| * Looks for an RSA signature embedded in the .ZIP file comment given the path to the zip. Verifies |
| * that it matches one of the given public keys. A callback function can be optionally provided for |
| * posting the progress. |
| * |
| * Returns VERIFY_SUCCESS or VERIFY_FAILURE (if any error is encountered or no key matches the |
| * signature). |
| */ |
| int verify_file(const unsigned char* addr, size_t length, const std::vector<Certificate>& keys, |
| const std::function<void(float)>& set_progress) { |
| if (set_progress) { |
| set_progress(0.0); |
| } |
| |
| // An archive with a whole-file signature will end in six bytes: |
| // |
| // (2-byte signature start) $ff $ff (2-byte comment size) |
| // |
| // (As far as the ZIP format is concerned, these are part of the archive comment.) We start by |
| // reading this footer, this tells us how far back from the end we have to start reading to find |
| // the whole comment. |
| |
| #define FOOTER_SIZE 6 |
| |
| if (length < FOOTER_SIZE) { |
| LOG(ERROR) << "not big enough to contain footer"; |
| return VERIFY_FAILURE; |
| } |
| |
| const unsigned char* footer = addr + length - FOOTER_SIZE; |
| |
| if (footer[2] != 0xff || footer[3] != 0xff) { |
| LOG(ERROR) << "footer is wrong"; |
| return VERIFY_FAILURE; |
| } |
| |
| size_t comment_size = footer[4] + (footer[5] << 8); |
| size_t signature_start = footer[0] + (footer[1] << 8); |
| LOG(INFO) << "comment is " << comment_size << " bytes; signature is " << signature_start |
| << " bytes from end"; |
| |
| if (signature_start > comment_size) { |
| LOG(ERROR) << "signature start: " << signature_start << " is larger than comment size: " |
| << comment_size; |
| return VERIFY_FAILURE; |
| } |
| |
| if (signature_start <= FOOTER_SIZE) { |
| LOG(ERROR) << "Signature start is in the footer"; |
| return VERIFY_FAILURE; |
| } |
| |
| #define EOCD_HEADER_SIZE 22 |
| |
| // The end-of-central-directory record is 22 bytes plus any comment length. |
| size_t eocd_size = comment_size + EOCD_HEADER_SIZE; |
| |
| if (length < eocd_size) { |
| LOG(ERROR) << "not big enough to contain EOCD"; |
| return VERIFY_FAILURE; |
| } |
| |
| // Determine how much of the file is covered by the signature. This is everything except the |
| // signature data and length, which includes all of the EOCD except for the comment length field |
| // (2 bytes) and the comment data. |
| size_t signed_len = length - eocd_size + EOCD_HEADER_SIZE - 2; |
| |
| const unsigned char* eocd = addr + length - eocd_size; |
| |
| // If this is really is the EOCD record, it will begin with the magic number $50 $4b $05 $06. |
| if (eocd[0] != 0x50 || eocd[1] != 0x4b || eocd[2] != 0x05 || eocd[3] != 0x06) { |
| LOG(ERROR) << "signature length doesn't match EOCD marker"; |
| return VERIFY_FAILURE; |
| } |
| |
| for (size_t i = 4; i < eocd_size-3; ++i) { |
| if (eocd[i] == 0x50 && eocd[i+1] == 0x4b && eocd[i+2] == 0x05 && eocd[i+3] == 0x06) { |
| // If the sequence $50 $4b $05 $06 appears anywhere after the real one, libziparchive will |
| // find the later (wrong) one, which could be exploitable. Fail the verification if this |
| // sequence occurs anywhere after the real one. |
| LOG(ERROR) << "EOCD marker occurs after start of EOCD"; |
| return VERIFY_FAILURE; |
| } |
| } |
| |
| bool need_sha1 = false; |
| bool need_sha256 = false; |
| for (const auto& key : keys) { |
| switch (key.hash_len) { |
| case SHA_DIGEST_LENGTH: need_sha1 = true; break; |
| case SHA256_DIGEST_LENGTH: need_sha256 = true; break; |
| } |
| } |
| |
| SHA_CTX sha1_ctx; |
| SHA256_CTX sha256_ctx; |
| SHA1_Init(&sha1_ctx); |
| SHA256_Init(&sha256_ctx); |
| |
| double frac = -1.0; |
| size_t so_far = 0; |
| while (so_far < signed_len) { |
| // On a Nexus 5X, experiment showed 16MiB beat 1MiB by 6% faster for a |
| // 1196MiB full OTA and 60% for an 89MiB incremental OTA. |
| // http://b/28135231. |
| size_t size = std::min(signed_len - so_far, 16 * MiB); |
| |
| if (need_sha1) SHA1_Update(&sha1_ctx, addr + so_far, size); |
| if (need_sha256) SHA256_Update(&sha256_ctx, addr + so_far, size); |
| so_far += size; |
| |
| if (set_progress) { |
| double f = so_far / (double)signed_len; |
| if (f > frac + 0.02 || size == so_far) { |
| set_progress(f); |
| frac = f; |
| } |
| } |
| } |
| |
| uint8_t sha1[SHA_DIGEST_LENGTH]; |
| SHA1_Final(sha1, &sha1_ctx); |
| uint8_t sha256[SHA256_DIGEST_LENGTH]; |
| SHA256_Final(sha256, &sha256_ctx); |
| |
| const uint8_t* signature = eocd + eocd_size - signature_start; |
| size_t signature_size = signature_start - FOOTER_SIZE; |
| |
| LOG(INFO) << "signature (offset: " << std::hex << (length - signature_start) << ", length: " |
| << signature_size << "): " << print_hex(signature, signature_size); |
| |
| std::vector<uint8_t> sig_der; |
| if (!read_pkcs7(signature, signature_size, &sig_der)) { |
| LOG(ERROR) << "Could not find signature DER block"; |
| return VERIFY_FAILURE; |
| } |
| |
| // Check to make sure at least one of the keys matches the signature. Since any key can match, |
| // we need to try each before determining a verification failure has happened. |
| size_t i = 0; |
| for (const auto& key : keys) { |
| const uint8_t* hash; |
| int hash_nid; |
| switch (key.hash_len) { |
| case SHA_DIGEST_LENGTH: |
| hash = sha1; |
| hash_nid = NID_sha1; |
| break; |
| case SHA256_DIGEST_LENGTH: |
| hash = sha256; |
| hash_nid = NID_sha256; |
| break; |
| default: |
| continue; |
| } |
| |
| // The 6 bytes is the "(signature_start) $ff $ff (comment_size)" that the signing tool appends |
| // after the signature itself. |
| if (key.key_type == Certificate::KEY_TYPE_RSA) { |
| if (!RSA_verify(hash_nid, hash, key.hash_len, sig_der.data(), sig_der.size(), |
| key.rsa.get())) { |
| LOG(INFO) << "failed to verify against RSA key " << i; |
| continue; |
| } |
| |
| LOG(INFO) << "whole-file signature verified against RSA key " << i; |
| return VERIFY_SUCCESS; |
| } else if (key.key_type == Certificate::KEY_TYPE_EC && key.hash_len == SHA256_DIGEST_LENGTH) { |
| if (!ECDSA_verify(0, hash, key.hash_len, sig_der.data(), sig_der.size(), key.ec.get())) { |
| LOG(INFO) << "failed to verify against EC key " << i; |
| continue; |
| } |
| |
| LOG(INFO) << "whole-file signature verified against EC key " << i; |
| return VERIFY_SUCCESS; |
| } else { |
| LOG(INFO) << "Unknown key type " << key.key_type; |
| } |
| i++; |
| } |
| |
| if (need_sha1) { |
| LOG(INFO) << "SHA-1 digest: " << print_hex(sha1, SHA_DIGEST_LENGTH); |
| } |
| if (need_sha256) { |
| LOG(INFO) << "SHA-256 digest: " << print_hex(sha256, SHA256_DIGEST_LENGTH); |
| } |
| LOG(ERROR) << "failed to verify whole-file signature"; |
| return VERIFY_FAILURE; |
| } |
| |
| std::unique_ptr<RSA, RSADeleter> parse_rsa_key(FILE* file, uint32_t exponent) { |
| // Read key length in words and n0inv. n0inv is a precomputed montgomery |
| // parameter derived from the modulus and can be used to speed up |
| // verification. n0inv is 32 bits wide here, assuming the verification logic |
| // uses 32 bit arithmetic. However, BoringSSL may use a word size of 64 bits |
| // internally, in which case we don't have a valid n0inv. Thus, we just |
| // ignore the montgomery parameters and have BoringSSL recompute them |
| // internally. If/When the speedup from using the montgomery parameters |
| // becomes relevant, we can add more sophisticated code here to obtain a |
| // 64-bit n0inv and initialize the montgomery parameters in the key object. |
| uint32_t key_len_words = 0; |
| uint32_t n0inv = 0; |
| if (fscanf(file, " %i , 0x%x", &key_len_words, &n0inv) != 2) { |
| return nullptr; |
| } |
| |
| if (key_len_words > 8192 / 32) { |
| LOG(ERROR) << "key length (" << key_len_words << ") too large"; |
| return nullptr; |
| } |
| |
| // Read the modulus. |
| std::unique_ptr<uint32_t[]> modulus(new uint32_t[key_len_words]); |
| if (fscanf(file, " , { %u", &modulus[0]) != 1) { |
| return nullptr; |
| } |
| for (uint32_t i = 1; i < key_len_words; ++i) { |
| if (fscanf(file, " , %u", &modulus[i]) != 1) { |
| return nullptr; |
| } |
| } |
| |
| // Cconvert from little-endian array of little-endian words to big-endian |
| // byte array suitable as input for BN_bin2bn. |
| std::reverse((uint8_t*)modulus.get(), |
| (uint8_t*)(modulus.get() + key_len_words)); |
| |
| // The next sequence of values is the montgomery parameter R^2. Since we |
| // generally don't have a valid |n0inv|, we ignore this (see comment above). |
| uint32_t rr_value; |
| if (fscanf(file, " } , { %u", &rr_value) != 1) { |
| return nullptr; |
| } |
| for (uint32_t i = 1; i < key_len_words; ++i) { |
| if (fscanf(file, " , %u", &rr_value) != 1) { |
| return nullptr; |
| } |
| } |
| if (fscanf(file, " } } ") != 0) { |
| return nullptr; |
| } |
| |
| // Initialize the key. |
| std::unique_ptr<RSA, RSADeleter> key(RSA_new()); |
| if (!key) { |
| return nullptr; |
| } |
| |
| key->n = BN_bin2bn((uint8_t*)modulus.get(), |
| key_len_words * sizeof(uint32_t), NULL); |
| if (!key->n) { |
| return nullptr; |
| } |
| |
| key->e = BN_new(); |
| if (!key->e || !BN_set_word(key->e, exponent)) { |
| return nullptr; |
| } |
| |
| return key; |
| } |
| |
| struct BNDeleter { |
| void operator()(BIGNUM* bn) { |
| BN_free(bn); |
| } |
| }; |
| |
| std::unique_ptr<EC_KEY, ECKEYDeleter> parse_ec_key(FILE* file) { |
| uint32_t key_len_bytes = 0; |
| if (fscanf(file, " %i", &key_len_bytes) != 1) { |
| return nullptr; |
| } |
| |
| std::unique_ptr<EC_GROUP, void (*)(EC_GROUP*)> group( |
| EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1), EC_GROUP_free); |
| if (!group) { |
| return nullptr; |
| } |
| |
| // Verify that |key_len| matches the group order. |
| if (key_len_bytes != BN_num_bytes(EC_GROUP_get0_order(group.get()))) { |
| return nullptr; |
| } |
| |
| // Read the public key coordinates. Note that the byte order in the file is |
| // little-endian, so we convert to big-endian here. |
| std::unique_ptr<uint8_t[]> bytes(new uint8_t[key_len_bytes]); |
| std::unique_ptr<BIGNUM, BNDeleter> point[2]; |
| for (int i = 0; i < 2; ++i) { |
| unsigned int byte = 0; |
| if (fscanf(file, " , { %u", &byte) != 1) { |
| return nullptr; |
| } |
| bytes[key_len_bytes - 1] = byte; |
| |
| for (size_t i = 1; i < key_len_bytes; ++i) { |
| if (fscanf(file, " , %u", &byte) != 1) { |
| return nullptr; |
| } |
| bytes[key_len_bytes - i - 1] = byte; |
| } |
| |
| point[i].reset(BN_bin2bn(bytes.get(), key_len_bytes, nullptr)); |
| if (!point[i]) { |
| return nullptr; |
| } |
| |
| if (fscanf(file, " }") != 0) { |
| return nullptr; |
| } |
| } |
| |
| if (fscanf(file, " } ") != 0) { |
| return nullptr; |
| } |
| |
| // Create and initialize the key. |
| std::unique_ptr<EC_KEY, ECKEYDeleter> key(EC_KEY_new()); |
| if (!key || !EC_KEY_set_group(key.get(), group.get()) || |
| !EC_KEY_set_public_key_affine_coordinates(key.get(), point[0].get(), |
| point[1].get())) { |
| return nullptr; |
| } |
| |
| return key; |
| } |
| |
| // Reads a file containing one or more public keys as produced by |
| // DumpPublicKey: this is an RSAPublicKey struct as it would appear |
| // as a C source literal, eg: |
| // |
| // "{64,0xc926ad21,{1795090719,...,-695002876},{-857949815,...,1175080310}}" |
| // |
| // For key versions newer than the original 2048-bit e=3 keys |
| // supported by Android, the string is preceded by a version |
| // identifier, eg: |
| // |
| // "v2 {64,0xc926ad21,{1795090719,...,-695002876},{-857949815,...,1175080310}}" |
| // |
| // (Note that the braces and commas in this example are actual |
| // characters the parser expects to find in the file; the ellipses |
| // indicate more numbers omitted from this example.) |
| // |
| // The file may contain multiple keys in this format, separated by |
| // commas. The last key must not be followed by a comma. |
| // |
| // A Certificate is a pair of an RSAPublicKey and a particular hash |
| // (we support SHA-1 and SHA-256; we store the hash length to signify |
| // which is being used). The hash used is implied by the version number. |
| // |
| // 1: 2048-bit RSA key with e=3 and SHA-1 hash |
| // 2: 2048-bit RSA key with e=65537 and SHA-1 hash |
| // 3: 2048-bit RSA key with e=3 and SHA-256 hash |
| // 4: 2048-bit RSA key with e=65537 and SHA-256 hash |
| // 5: 256-bit EC key using the NIST P-256 curve parameters and SHA-256 hash |
| // |
| // Returns true on success, and appends the found keys (at least one) to certs. |
| // Otherwise returns false if the file failed to parse, or if it contains zero |
| // keys. The contents in certs would be unspecified on failure. |
| bool load_keys(const char* filename, std::vector<Certificate>& certs) { |
| std::unique_ptr<FILE, decltype(&fclose)> f(fopen(filename, "r"), fclose); |
| if (!f) { |
| PLOG(ERROR) << "error opening " << filename; |
| return false; |
| } |
| |
| while (true) { |
| certs.emplace_back(0, Certificate::KEY_TYPE_RSA, nullptr, nullptr); |
| Certificate& cert = certs.back(); |
| uint32_t exponent = 0; |
| |
| char start_char; |
| if (fscanf(f.get(), " %c", &start_char) != 1) return false; |
| if (start_char == '{') { |
| // a version 1 key has no version specifier. |
| cert.key_type = Certificate::KEY_TYPE_RSA; |
| exponent = 3; |
| cert.hash_len = SHA_DIGEST_LENGTH; |
| } else if (start_char == 'v') { |
| int version; |
| if (fscanf(f.get(), "%d {", &version) != 1) return false; |
| switch (version) { |
| case 2: |
| cert.key_type = Certificate::KEY_TYPE_RSA; |
| exponent = 65537; |
| cert.hash_len = SHA_DIGEST_LENGTH; |
| break; |
| case 3: |
| cert.key_type = Certificate::KEY_TYPE_RSA; |
| exponent = 3; |
| cert.hash_len = SHA256_DIGEST_LENGTH; |
| break; |
| case 4: |
| cert.key_type = Certificate::KEY_TYPE_RSA; |
| exponent = 65537; |
| cert.hash_len = SHA256_DIGEST_LENGTH; |
| break; |
| case 5: |
| cert.key_type = Certificate::KEY_TYPE_EC; |
| cert.hash_len = SHA256_DIGEST_LENGTH; |
| break; |
| default: |
| return false; |
| } |
| } |
| |
| if (cert.key_type == Certificate::KEY_TYPE_RSA) { |
| cert.rsa = parse_rsa_key(f.get(), exponent); |
| if (!cert.rsa) { |
| return false; |
| } |
| |
| LOG(INFO) << "read key e=" << exponent << " hash=" << cert.hash_len; |
| } else if (cert.key_type == Certificate::KEY_TYPE_EC) { |
| cert.ec = parse_ec_key(f.get()); |
| if (!cert.ec) { |
| return false; |
| } |
| } else { |
| LOG(ERROR) << "Unknown key type " << cert.key_type; |
| return false; |
| } |
| |
| // if the line ends in a comma, this file has more keys. |
| int ch = fgetc(f.get()); |
| if (ch == ',') { |
| // more keys to come. |
| continue; |
| } else if (ch == EOF) { |
| break; |
| } else { |
| LOG(ERROR) << "unexpected character between keys"; |
| return false; |
| } |
| } |
| |
| return true; |
| } |