diff options
Diffstat (limited to 'verifier24')
| -rw-r--r-- | verifier24/README | 2 | ||||
| -rw-r--r-- | verifier24/verifier.cpp | 471 | ||||
| -rw-r--r-- | verifier24/verifier.h | 58 |
3 files changed, 531 insertions, 0 deletions
diff --git a/verifier24/README b/verifier24/README new file mode 100644 index 000000000..44d9422e9 --- /dev/null +++ b/verifier24/README @@ -0,0 +1,2 @@ +This is older code from Android 5.1 Marshmallow (SDK ver 24) and older +that still used mincrypt instead of libcrypto. diff --git a/verifier24/verifier.cpp b/verifier24/verifier.cpp new file mode 100644 index 000000000..98c733732 --- /dev/null +++ b/verifier24/verifier.cpp @@ -0,0 +1,471 @@ +/* + * 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 <errno.h> +#include <malloc.h> +#include <stdio.h> +#include <string.h> + +//extern RecoveryUI* ui; + +#define PUBLIC_KEYS_FILE "/res/keys" + +/* + * 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) { + //ui->SetProgress(0.0); + + int numKeys; + Certificate* pKeys = load_keys(PUBLIC_KEYS_FILE, &numKeys); + if (pKeys == NULL) { + LOGE("Failed to load keys\n"); + return INSTALL_CORRUPT; + } + LOGI("%d key(s) loaded from %s\n", numKeys, PUBLIC_KEYS_FILE); + + // 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); + } + LOGI("i: %i, eocd_size: %i, RSANUMBYTES: %i\n", i, eocd_size, RSANUMBYTES); + } + 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; +} diff --git a/verifier24/verifier.h b/verifier24/verifier.h new file mode 100644 index 000000000..17ab257ad --- /dev/null +++ b/verifier24/verifier.h @@ -0,0 +1,58 @@ +/* + * 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. + */ + +#ifndef _RECOVERY_VERIFIER_H +#define _RECOVERY_VERIFIER_H + +#include "mincrypt/p256.h" +#include "mincrypt/rsa.h" + +#define ASSUMED_UPDATE_BINARY_NAME "META-INF/com/google/android/update-binary" + +enum { INSTALL_SUCCESS, INSTALL_ERROR, INSTALL_CORRUPT }; + +static const float VERIFICATION_PROGRESS_FRACTION = 0.25; + +typedef struct { + p256_int x; + p256_int y; +} ECPublicKey; + +typedef struct { + typedef enum { + RSA, + EC, + } KeyType; + + int hash_len; // SHA_DIGEST_SIZE (SHA-1) or SHA256_DIGEST_SIZE (SHA-256) + KeyType key_type; + RSAPublicKey* rsa; + ECPublicKey* ec; +} Certificate; + +/* addr and length define a an update package file that has been + * loaded (or mmap'ed, or whatever) into memory. Verify that the file + * is signed and the signature matches one of the given keys. Return + * one of the constants below. + */ +int verify_file(unsigned char* addr, size_t length); + +Certificate* load_keys(const char* filename, int* numKeys); + +#define VERIFY_SUCCESS 0 +#define VERIFY_FAILURE 1 + +#endif /* _RECOVERY_VERIFIER_H */ |