diff options
Diffstat (limited to 'verifierold.cpp')
| -rw-r--r-- | verifierold.cpp | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/verifierold.cpp b/verifierold.cpp new file mode 100644 index 000000000..4387ab5a4 --- /dev/null +++ b/verifierold.cpp @@ -0,0 +1,344 @@ +/* + * 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 "common.h" +#include "verifierold.h" +#include "ui.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; + +#define PUBLIC_KEYS_FILE "/res/keys" + +// 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(const char* path) { + //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); + + FILE* f = fopen(path, "rb"); + if (f == NULL) { + LOGE("failed to open %s (%s)\n", path, strerror(errno)); + return VERIFY_FAILURE; + } + + // 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 (fseek(f, -FOOTER_SIZE, SEEK_END) != 0) { + LOGE("failed to seek in %s (%s)\n", path, strerror(errno)); + fclose(f); + return VERIFY_FAILURE; + } + + unsigned char footer[FOOTER_SIZE]; + if (fread(footer, 1, FOOTER_SIZE, f) != FOOTER_SIZE) { + LOGE("failed to read footer from %s (%s)\n", path, strerror(errno)); + fclose(f); + return VERIFY_FAILURE; + } + + if (footer[2] != 0xff || footer[3] != 0xff) { + LOGE("footer is wrong\n"); + fclose(f); + return VERIFY_FAILURE; + } + + size_t comment_size = footer[4] + (footer[5] << 8); + size_t signature_start = footer[0] + (footer[1] << 8); + LOGI("comment is %d bytes; signature %d bytes from end\n", + comment_size, signature_start); + + if (signature_start - FOOTER_SIZE < RSANUMBYTES) { + // "signature" block isn't big enough to contain an RSA block. + LOGE("signature is too short\n"); + fclose(f); + 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 (fseek(f, -eocd_size, SEEK_END) != 0) { + LOGE("failed to seek in %s (%s)\n", path, strerror(errno)); + fclose(f); + 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 = ftell(f) + EOCD_HEADER_SIZE - 2; + + unsigned char* eocd = (unsigned char*)malloc(eocd_size); + if (eocd == NULL) { + LOGE("malloc for EOCD record failed\n"); + fclose(f); + return VERIFY_FAILURE; + } + if (fread(eocd, 1, eocd_size, f) != eocd_size) { + LOGE("failed to read eocd from %s (%s)\n", path, strerror(errno)); + fclose(f); + return VERIFY_FAILURE; + } + + // 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"); + fclose(f); + 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"); + fclose(f); + 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); + unsigned char* buffer = (unsigned char*)malloc(BUFFER_SIZE); + if (buffer == NULL) { + LOGE("failed to alloc memory for sha1 buffer\n"); + fclose(f); + return VERIFY_FAILURE; + } + + double frac = -1.0; + size_t so_far = 0; + fseek(f, 0, SEEK_SET); + while (so_far < signed_len) { + size_t size = BUFFER_SIZE; + if (signed_len - so_far < size) size = signed_len - so_far; + if (fread(buffer, 1, size, f) != size) { + LOGE("failed to read data from %s (%s)\n", path, strerror(errno)); + fclose(f); + return VERIFY_FAILURE; + } + if (need_sha1) SHA_update(&sha1_ctx, buffer, size); + if (need_sha256) SHA256_update(&sha256_ctx, buffer, size); + so_far += size; + double f = so_far / (double)signed_len; + if (f > frac + 0.02 || size == so_far) { + //ui->SetProgress(f); + frac = f; + } + } + fclose(f); + free(buffer); + + const uint8_t* sha1 = SHA_final(&sha1_ctx); + const uint8_t* sha256 = SHA256_final(&sha256_ctx); + + 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 (RSA_verify(pKeys[i].public_key, eocd + eocd_size - 6 - RSANUMBYTES, + RSANUMBYTES, hash, pKeys[i].hash_len)) { + LOGI("whole-file signature verified against key %d\n", i); + free(eocd); + return VERIFY_SUCCESS; + } else { + LOGI("failed to verify against key %d\n", i); + } + LOGI("i: %i, eocd_size: %i, RSANUMBYTES: %i\n", i, eocd_size, RSANUMBYTES); + } + free(eocd); + 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 +// +// 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); + cert->public_key = (RSAPublicKey*)malloc(sizeof(RSAPublicKey)); + + char start_char; + if (fscanf(f, " %c", &start_char) != 1) goto exit; + if (start_char == '{') { + // a version 1 key has no version specifier. + cert->public_key->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->public_key->exponent = 65537; + cert->hash_len = SHA_DIGEST_SIZE; + break; + case 3: + cert->public_key->exponent = 3; + cert->hash_len = SHA256_DIGEST_SIZE; + break; + case 4: + cert->public_key->exponent = 65537; + cert->hash_len = SHA256_DIGEST_SIZE; + break; + default: + goto exit; + } + } + + RSAPublicKey* key = cert->public_key; + 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, " } } "); + + // 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; + } + LOGI("read key e=%d hash=%d\n", key->exponent, cert->hash_len); + } + } + + fclose(f); + return out; + +exit: + if (f) fclose(f); + free(out); + *numKeys = 0; + return NULL; +} |