| /* |
| * 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 "asn1_decoder.h" |
| #include "common.h" |
| #include "ui.h" |
| #include "verifier.h" |
| |
| #include "mincrypt/dsa_sig.h" |
| #include "mincrypt/p256.h" |
| #include "mincrypt/p256_ecdsa.h" |
| #include "mincrypt/rsa.h" |
| #include "mincrypt/sha.h" |
| #include "mincrypt/sha256.h" |
| |
| #include <string.h> |
| #include <stdio.h> |
| #include <errno.h> |
| |
| extern RecoveryUI* ui; |
| |
| /* |
| * 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(uint8_t* pkcs7_der, size_t pkcs7_der_len, uint8_t** sig_der, |
| size_t* sig_der_length) { |
| asn1_context_t* ctx = asn1_context_new(pkcs7_der, pkcs7_der_len); |
| if (ctx == NULL) { |
| return false; |
| } |
| |
| asn1_context_t* pkcs7_seq = asn1_sequence_get(ctx); |
| if (pkcs7_seq != NULL && asn1_sequence_next(pkcs7_seq)) { |
| asn1_context_t *signed_data_app = asn1_constructed_get(pkcs7_seq); |
| if (signed_data_app != NULL) { |
| asn1_context_t* signed_data_seq = asn1_sequence_get(signed_data_app); |
| if (signed_data_seq != NULL |
| && asn1_sequence_next(signed_data_seq) |
| && asn1_sequence_next(signed_data_seq) |
| && asn1_sequence_next(signed_data_seq) |
| && asn1_constructed_skip_all(signed_data_seq)) { |
| asn1_context_t *sig_set = asn1_set_get(signed_data_seq); |
| if (sig_set != NULL) { |
| asn1_context_t* sig_seq = asn1_sequence_get(sig_set); |
| if (sig_seq != NULL |
| && asn1_sequence_next(sig_seq) |
| && asn1_sequence_next(sig_seq) |
| && asn1_sequence_next(sig_seq) |
| && asn1_sequence_next(sig_seq)) { |
| uint8_t* sig_der_ptr; |
| if (asn1_octet_string_get(sig_seq, &sig_der_ptr, sig_der_length)) { |
| *sig_der = (uint8_t*) malloc(*sig_der_length); |
| if (*sig_der != NULL) { |
| memcpy(*sig_der, sig_der_ptr, *sig_der_length); |
| } |
| } |
| asn1_context_free(sig_seq); |
| } |
| asn1_context_free(sig_set); |
| } |
| asn1_context_free(signed_data_seq); |
| } |
| asn1_context_free(signed_data_app); |
| } |
| asn1_context_free(pkcs7_seq); |
| } |
| asn1_context_free(ctx); |
| |
| return *sig_der != NULL; |
| } |
| |
| // Look for an RSA signature embedded in the .ZIP file comment given |
| // the path to the zip. Verify it matches one of the given public |
| // keys. |
| // |
| // Return VERIFY_SUCCESS, VERIFY_FAILURE (if any error is encountered |
| // or no key matches the signature). |
| |
| int verify_file(unsigned char* addr, size_t length, |
| const Certificate* pKeys, unsigned int numKeys) { |
| ui->SetProgress(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) { |
| LOGE("not big enough to contain footer\n"); |
| return VERIFY_FAILURE; |
| } |
| |
| unsigned char* footer = addr + length - FOOTER_SIZE; |
| |
| if (footer[2] != 0xff || footer[3] != 0xff) { |
| LOGE("footer is wrong\n"); |
| return VERIFY_FAILURE; |
| } |
| |
| size_t comment_size = footer[4] + (footer[5] << 8); |
| size_t signature_start = footer[0] + (footer[1] << 8); |
| LOGI("comment is %zu bytes; signature %zu bytes from end\n", |
| comment_size, signature_start); |
| |
| if (signature_start <= FOOTER_SIZE) { |
| LOGE("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) { |
| LOGE("not big enough to contain EOCD\n"); |
| 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; |
| |
| 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) { |
| LOGE("signature length doesn't match EOCD marker\n"); |
| return VERIFY_FAILURE; |
| } |
| |
| size_t i; |
| for (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, minzip will find the later (wrong) one, |
| // which could be exploitable. Fail verification if |
| // this sequence occurs anywhere after the real one. |
| LOGE("EOCD marker occurs after start of EOCD\n"); |
| return VERIFY_FAILURE; |
| } |
| } |
| |
| #define BUFFER_SIZE 4096 |
| |
| bool need_sha1 = false; |
| bool need_sha256 = false; |
| for (i = 0; i < numKeys; ++i) { |
| switch (pKeys[i].hash_len) { |
| case SHA_DIGEST_SIZE: need_sha1 = true; break; |
| case SHA256_DIGEST_SIZE: need_sha256 = true; break; |
| } |
| } |
| |
| SHA_CTX sha1_ctx; |
| SHA256_CTX sha256_ctx; |
| SHA_init(&sha1_ctx); |
| SHA256_init(&sha256_ctx); |
| |
| double frac = -1.0; |
| size_t so_far = 0; |
| while (so_far < signed_len) { |
| size_t size = signed_len - so_far; |
| if (size > BUFFER_SIZE) size = BUFFER_SIZE; |
| |
| if (need_sha1) SHA_update(&sha1_ctx, addr + so_far, size); |
| if (need_sha256) SHA256_update(&sha256_ctx, addr + so_far, size); |
| so_far += size; |
| |
| double f = so_far / (double)signed_len; |
| if (f > frac + 0.02 || size == so_far) { |
| ui->SetProgress(f); |
| frac = f; |
| } |
| } |
| |
| const uint8_t* sha1 = SHA_final(&sha1_ctx); |
| const uint8_t* sha256 = SHA256_final(&sha256_ctx); |
| |
| uint8_t* sig_der = NULL; |
| size_t sig_der_length = 0; |
| |
| size_t signature_size = signature_start - FOOTER_SIZE; |
| if (!read_pkcs7(eocd + eocd_size - signature_start, signature_size, &sig_der, |
| &sig_der_length)) { |
| LOGE("Could not find signature DER block\n"); |
| 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. |
| */ |
| for (i = 0; i < numKeys; ++i) { |
| const uint8_t* hash; |
| switch (pKeys[i].hash_len) { |
| case SHA_DIGEST_SIZE: hash = sha1; break; |
| case SHA256_DIGEST_SIZE: hash = 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 (pKeys[i].key_type == Certificate::RSA) { |
| if (sig_der_length < RSANUMBYTES) { |
| // "signature" block isn't big enough to contain an RSA block. |
| LOGI("signature is too short for RSA key %zu\n", i); |
| continue; |
| } |
| |
| if (!RSA_verify(pKeys[i].rsa, sig_der, RSANUMBYTES, |
| hash, pKeys[i].hash_len)) { |
| LOGI("failed to verify against RSA key %zu\n", i); |
| continue; |
| } |
| |
| LOGI("whole-file signature verified against RSA key %zu\n", i); |
| free(sig_der); |
| return VERIFY_SUCCESS; |
| } else if (pKeys[i].key_type == Certificate::EC |
| && pKeys[i].hash_len == SHA256_DIGEST_SIZE) { |
| p256_int r, s; |
| if (!dsa_sig_unpack(sig_der, sig_der_length, &r, &s)) { |
| LOGI("Not a DSA signature block for EC key %zu\n", i); |
| continue; |
| } |
| |
| p256_int p256_hash; |
| p256_from_bin(hash, &p256_hash); |
| if (!p256_ecdsa_verify(&(pKeys[i].ec->x), &(pKeys[i].ec->y), |
| &p256_hash, &r, &s)) { |
| LOGI("failed to verify against EC key %zu\n", i); |
| continue; |
| } |
| |
| LOGI("whole-file signature verified against EC key %zu\n", i); |
| free(sig_der); |
| return VERIFY_SUCCESS; |
| } else { |
| LOGI("Unknown key type %d\n", pKeys[i].key_type); |
| } |
| } |
| free(sig_der); |
| LOGE("failed to verify whole-file signature\n"); |
| return VERIFY_FAILURE; |
| } |
| |
| // 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 NULL if the file failed to parse, or if it contain zero keys. |
| Certificate* |
| load_keys(const char* filename, int* numKeys) { |
| Certificate* out = NULL; |
| *numKeys = 0; |
| |
| FILE* f = fopen(filename, "r"); |
| if (f == NULL) { |
| LOGE("opening %s: %s\n", filename, strerror(errno)); |
| goto exit; |
| } |
| |
| { |
| int i; |
| bool done = false; |
| while (!done) { |
| ++*numKeys; |
| out = (Certificate*)realloc(out, *numKeys * sizeof(Certificate)); |
| Certificate* cert = out + (*numKeys - 1); |
| memset(cert, '\0', sizeof(Certificate)); |
| |
| char start_char; |
| if (fscanf(f, " %c", &start_char) != 1) goto exit; |
| if (start_char == '{') { |
| // a version 1 key has no version specifier. |
| cert->key_type = Certificate::RSA; |
| cert->rsa = (RSAPublicKey*)malloc(sizeof(RSAPublicKey)); |
| cert->rsa->exponent = 3; |
| cert->hash_len = SHA_DIGEST_SIZE; |
| } else if (start_char == 'v') { |
| int version; |
| if (fscanf(f, "%d {", &version) != 1) goto exit; |
| switch (version) { |
| case 2: |
| cert->key_type = Certificate::RSA; |
| cert->rsa = (RSAPublicKey*)malloc(sizeof(RSAPublicKey)); |
| cert->rsa->exponent = 65537; |
| cert->hash_len = SHA_DIGEST_SIZE; |
| break; |
| case 3: |
| cert->key_type = Certificate::RSA; |
| cert->rsa = (RSAPublicKey*)malloc(sizeof(RSAPublicKey)); |
| cert->rsa->exponent = 3; |
| cert->hash_len = SHA256_DIGEST_SIZE; |
| break; |
| case 4: |
| cert->key_type = Certificate::RSA; |
| cert->rsa = (RSAPublicKey*)malloc(sizeof(RSAPublicKey)); |
| cert->rsa->exponent = 65537; |
| cert->hash_len = SHA256_DIGEST_SIZE; |
| break; |
| case 5: |
| cert->key_type = Certificate::EC; |
| cert->ec = (ECPublicKey*)calloc(1, sizeof(ECPublicKey)); |
| cert->hash_len = SHA256_DIGEST_SIZE; |
| break; |
| default: |
| goto exit; |
| } |
| } |
| |
| if (cert->key_type == Certificate::RSA) { |
| RSAPublicKey* key = cert->rsa; |
| if (fscanf(f, " %i , 0x%x , { %u", |
| &(key->len), &(key->n0inv), &(key->n[0])) != 3) { |
| goto exit; |
| } |
| if (key->len != RSANUMWORDS) { |
| LOGE("key length (%d) does not match expected size\n", key->len); |
| goto exit; |
| } |
| for (i = 1; i < key->len; ++i) { |
| if (fscanf(f, " , %u", &(key->n[i])) != 1) goto exit; |
| } |
| if (fscanf(f, " } , { %u", &(key->rr[0])) != 1) goto exit; |
| for (i = 1; i < key->len; ++i) { |
| if (fscanf(f, " , %u", &(key->rr[i])) != 1) goto exit; |
| } |
| fscanf(f, " } } "); |
| |
| LOGI("read key e=%d hash=%d\n", key->exponent, cert->hash_len); |
| } else if (cert->key_type == Certificate::EC) { |
| ECPublicKey* key = cert->ec; |
| int key_len; |
| unsigned int byte; |
| uint8_t x_bytes[P256_NBYTES]; |
| uint8_t y_bytes[P256_NBYTES]; |
| if (fscanf(f, " %i , { %u", &key_len, &byte) != 2) goto exit; |
| if (key_len != P256_NBYTES) { |
| LOGE("Key length (%d) does not match expected size %d\n", key_len, P256_NBYTES); |
| goto exit; |
| } |
| x_bytes[P256_NBYTES - 1] = byte; |
| for (i = P256_NBYTES - 2; i >= 0; --i) { |
| if (fscanf(f, " , %u", &byte) != 1) goto exit; |
| x_bytes[i] = byte; |
| } |
| if (fscanf(f, " } , { %u", &byte) != 1) goto exit; |
| y_bytes[P256_NBYTES - 1] = byte; |
| for (i = P256_NBYTES - 2; i >= 0; --i) { |
| if (fscanf(f, " , %u", &byte) != 1) goto exit; |
| y_bytes[i] = byte; |
| } |
| fscanf(f, " } } "); |
| p256_from_bin(x_bytes, &key->x); |
| p256_from_bin(y_bytes, &key->y); |
| } else { |
| LOGE("Unknown key type %d\n", cert->key_type); |
| goto exit; |
| } |
| |
| // if the line ends in a comma, this file has more keys. |
| switch (fgetc(f)) { |
| case ',': |
| // more keys to come. |
| break; |
| |
| case EOF: |
| done = true; |
| break; |
| |
| default: |
| LOGE("unexpected character between keys\n"); |
| goto exit; |
| } |
| } |
| } |
| |
| fclose(f); |
| return out; |
| |
| exit: |
| if (f) fclose(f); |
| free(out); |
| *numKeys = 0; |
| return NULL; |
| } |
