diff options
Diffstat (limited to 'verifier.cpp')
| -rw-r--r-- | verifier.cpp | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/verifier.cpp b/verifier.cpp new file mode 100644 index 000000000..58ca72393 --- /dev/null +++ b/verifier.cpp @@ -0,0 +1,185 @@ +/* + * 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 <string.h> +#include <stdio.h> +#include <errno.h> + +// 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 RSAPublicKey *pKeys, unsigned int numKeys) { + ui_set_progress(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) { + 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 + + SHA_CTX ctx; + SHA_init(&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; + } + SHA_update(&ctx, buffer, size); + so_far += size; + double f = so_far / (double)signed_len; + if (f > frac + 0.02 || size == so_far) { + ui_set_progress(f); + frac = f; + } + } + fclose(f); + free(buffer); + + const uint8_t* sha1 = SHA_final(&ctx); + for (i = 0; i < numKeys; ++i) { + // 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, eocd + eocd_size - 6 - RSANUMBYTES, + RSANUMBYTES, sha1)) { + LOGI("whole-file signature verified against key %d\n", i); + free(eocd); + return VERIFY_SUCCESS; + } + } + free(eocd); + LOGE("failed to verify whole-file signature\n"); + return VERIFY_FAILURE; +} |