| /* |
| * 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 "verifier.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; |
| |
| // 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, const Certificate* pKeys, unsigned int numKeys) { |
| ui->SetProgress(0.0); |
| |
| 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 > comment_size) { |
| LOGE("signature start: %zu is larger than comment size: %zu\n", signature_start, |
| comment_size); |
| fclose(f); |
| return VERIFY_FAILURE; |
| } |
| |
| 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); |
| } |
| } |
| 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; |
| } |