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verify whole-file signature instead of jarsigner signatures

Browse source 
In recovery, verify a signature that covers the entire zip file,
instead of using the jarsigner format to verify individual files.

Bug: 1328985
This commit is contained in:
Doug Zongker 2009-08-12 18:30:03 -07:00
parent 0cf0e33b5f
commit 60151a295c
3 changed files with 157 additions and 332 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

34
install.c
View file

@ -234,20 +234,8 @@ try_update_binary(const char *path, ZipArchive *zip) {
}
static int
handle_update_package(const char *path, ZipArchive *zip,
const RSAPublicKey *keys, int numKeys)
handle_update_package(const char *path, ZipArchive *zip)
{
// Give verification half the progress bar...
ui_print("Verifying update package...\n");
ui_show_progress(
VERIFICATION_PROGRESS_FRACTION,
VERIFICATION_PROGRESS_TIME);
if (!verify_jar_signature(zip, keys, numKeys)) {
LOGE("Verification failed\n");
return INSTALL_CORRUPT;
}
// Update should take the rest of the progress bar.
ui_print("Installing update...\n");
@ -360,10 +348,25 @@ install_package(const char *root_path)
}
LOGI("%d key(s) loaded from %s\n", numKeys, PUBLIC_KEYS_FILE);
// Give verification half the progress bar...
ui_print("Verifying update package...\n");
ui_show_progress(
VERIFICATION_PROGRESS_FRACTION,
VERIFICATION_PROGRESS_TIME);
int err;
err = verify_file(path, loadedKeys, numKeys);
free(loadedKeys);
LOGI("verify_file returned %d\n", err);
if (err != VERIFY_SUCCESS) {
LOGE("signature verification failed\n");
return INSTALL_CORRUPT;
}
/* Try to open the package.
*/
ZipArchive zip;
int err = mzOpenZipArchive(path, &zip);
err = mzOpenZipArchive(path, &zip);
if (err != 0) {
LOGE("Can't open %s\n(%s)\n", path, err != -1 ? strerror(err) : "bad");
return INSTALL_CORRUPT;
@ -371,8 +374,7 @@ install_package(const char *root_path)
/* Verify and install the contents of the package.
*/
int status = handle_update_package(path, &zip, loadedKeys, numKeys);
int status = handle_update_package(path, &zip);
mzCloseZipArchive(&zip);
free(loadedKeys);
return status;
}

443
verifier.c
View file

@ -17,345 +17,168 @@
#include "common.h"
#include "verifier.h"
#include "minzip/Zip.h"
#include "mincrypt/rsa.h"
#include "mincrypt/sha.h"
#include <netinet/in.h> /* required for resolv.h */
#include <resolv.h> /* for base64 codec */
#include <string.h>
#include <stdio.h>
#include <errno.h>
/* Return an allocated buffer with the contents of a zip file entry. */
static char *slurpEntry(const ZipArchive *pArchive, const ZipEntry *pEntry) {
if (!mzIsZipEntryIntact(pArchive, pEntry)) {
UnterminatedString fn = mzGetZipEntryFileName(pEntry);
LOGE("Invalid %.*s\n", fn.len, fn.str);
return 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(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;
}
int len = mzGetZipEntryUncompLen(pEntry);
char *buf = malloc(len + 1);
if (buf == NULL) {
UnterminatedString fn = mzGetZipEntryFileName(pEntry);
LOGE("Can't allocate %d bytes for %.*s\n", len, fn.len, fn.str);
return NULL;
// An archive with a whole-file signature will end in six bytes:
//
// $ff $ff (2-byte comment size) (2-byte signature start)
//
// (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;
}
if (!mzReadZipEntry(pArchive, pEntry, buf, len)) {
UnterminatedString fn = mzGetZipEntryFileName(pEntry);
LOGE("Can't read %.*s\n", fn.len, fn.str);
free(buf);
return NULL;
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;
}
buf[len] = '\0';
return buf;
}
struct DigestContext {
SHA_CTX digest;
unsigned *doneBytes;
unsigned totalBytes;
};
/* mzProcessZipEntryContents callback to update an SHA-1 hash context. */
static bool updateHash(const unsigned char *data, int dataLen, void *cookie) {
struct DigestContext *context = (struct DigestContext *) cookie;
SHA_update(&context->digest, data, dataLen);
if (context->doneBytes != NULL) {
*context->doneBytes += dataLen;
if (context->totalBytes > 0) {
ui_set_progress(*context->doneBytes * 1.0 / context->totalBytes);
}
}
return true;
}
/* Get the SHA-1 digest of a zip file entry. */
static bool digestEntry(const ZipArchive *pArchive, const ZipEntry *pEntry,
unsigned *doneBytes, unsigned totalBytes,
uint8_t digest[SHA_DIGEST_SIZE]) {
struct DigestContext context;
SHA_init(&context.digest);
context.doneBytes = doneBytes;
context.totalBytes = totalBytes;
if (!mzProcessZipEntryContents(pArchive, pEntry, updateHash, &context)) {
UnterminatedString fn = mzGetZipEntryFileName(pEntry);
LOGE("Can't digest %.*s\n", fn.len, fn.str);
return false;
if (footer[2] != 0xff || footer[3] != 0xff) {
fclose(f);
return VERIFY_FAILURE;
}
memcpy(digest, SHA_final(&context.digest), SHA_DIGEST_SIZE);
int comment_size = footer[4] + (footer[5] << 8);
int signature_start = footer[0] + (footer[1] << 8);
LOGI("comment is %d bytes; signature %d bytes from end\n",
comment_size, signature_start);
#ifdef LOG_VERBOSE
UnterminatedString fn = mzGetZipEntryFileName(pEntry);
char base64[SHA_DIGEST_SIZE * 3];
b64_ntop(digest, SHA_DIGEST_SIZE, base64, sizeof(base64));
LOGV("sha1(%.*s) = %s\n", fn.len, fn.str, base64);
#endif
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;
}
return true;
}
#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;
/* Find a /META-INF/xxx.SF signature file signed by a matching xxx.RSA file. */
static const ZipEntry *verifySignature(const ZipArchive *pArchive,
const RSAPublicKey *pKeys, unsigned int numKeys) {
static const char prefix[] = "META-INF/";
static const char rsa[] = ".RSA", sf[] = ".SF";
if (fseek(f, -eocd_size, SEEK_END) != 0) {
LOGE("failed to seek in %s (%s)\n", path, strerror(errno));
fclose(f);
return VERIFY_FAILURE;
}
unsigned int i, j;
for (i = 0; i < mzZipEntryCount(pArchive); ++i) {
const ZipEntry *rsaEntry = mzGetZipEntryAt(pArchive, i);
UnterminatedString rsaName = mzGetZipEntryFileName(rsaEntry);
int rsaLen = mzGetZipEntryUncompLen(rsaEntry);
if (rsaLen >= RSANUMBYTES && rsaName.len > sizeof(prefix) &&
!strncmp(rsaName.str, prefix, sizeof(prefix) - 1) &&
!strncmp(rsaName.str + rsaName.len - sizeof(rsa) + 1,
rsa, sizeof(rsa) - 1)) {
char *sfName = malloc(rsaName.len - sizeof(rsa) + sizeof(sf) + 1);
if (sfName == NULL) {
LOGE("Can't allocate %d bytes for filename\n", rsaName.len);
continue;
}
// 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;
/* Replace .RSA with .SF */
strncpy(sfName, rsaName.str, rsaName.len - sizeof(rsa) + 1);
strcpy(sfName + rsaName.len - sizeof(rsa) + 1, sf);
const ZipEntry *sfEntry = mzFindZipEntry(pArchive, sfName);
unsigned char* eocd = 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 (sfEntry == NULL) {
LOGW("Missing signature file %s\n", sfName);
free(sfName);
continue;
}
// 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;
}
free(sfName);
uint8_t sfDigest[SHA_DIGEST_SIZE];
if (!digestEntry(pArchive, sfEntry, NULL, 0, sfDigest)) continue;
char *rsaBuf = slurpEntry(pArchive, rsaEntry);
if (rsaBuf == NULL) continue;
/* Try to verify the signature with all the keys. */
uint8_t *sig = (uint8_t *) rsaBuf + rsaLen - RSANUMBYTES;
for (j = 0; j < numKeys; ++j) {
if (RSA_verify(&pKeys[j], sig, RSANUMBYTES, sfDigest)) {
free(rsaBuf);
LOGI("Verified %.*s\n", rsaName.len, rsaName.str);
return sfEntry;
}
}
free(rsaBuf);
LOGW("Can't verify %.*s\n", rsaName.len, rsaName.str);
int i;
for (i = 4; i < eocd_size-3; ++i) {
if (eocd[i ] == 0x50 && eocd[i+1] == 0x4b &&
eocd[i+2] == 0x05 && eocd[i+1] == 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;
}
}
LOGE("No signature (%d files)\n", mzZipEntryCount(pArchive));
return NULL;
}
#define BUFFER_SIZE 4096
SHA_CTX ctx;
SHA_init(&ctx);
unsigned char* buffer = malloc(BUFFER_SIZE);
if (buffer == NULL) {
LOGE("failed to alloc memory for sha1 buffer\n");
fclose(f);
return VERIFY_FAILURE;
}
/* Verify /META-INF/MANIFEST.MF against the digest in a signature file. */
static const ZipEntry *verifyManifest(const ZipArchive *pArchive,
const ZipEntry *sfEntry) {
static const char prefix[] = "SHA1-Digest-Manifest: ", eol[] = "\r\n";
uint8_t expected[SHA_DIGEST_SIZE + 3], actual[SHA_DIGEST_SIZE];
char *sfBuf = slurpEntry(pArchive, sfEntry);
if (sfBuf == NULL) return NULL;
char *line, *save;
for (line = strtok_r(sfBuf, eol, &save); line != NULL;
line = strtok_r(NULL, eol, &save)) {
if (!strncasecmp(prefix, line, sizeof(prefix) - 1)) {
UnterminatedString fn = mzGetZipEntryFileName(sfEntry);
const char *digest = line + sizeof(prefix) - 1;
int n = b64_pton(digest, expected, sizeof(expected));
if (n != SHA_DIGEST_SIZE) {
LOGE("Invalid base64 in %.*s: %s (%d)\n",
fn.len, fn.str, digest, n);
line = NULL;
}
break;
double frac = -1.0;
size_t so_far = 0;
fseek(f, 0, SEEK_SET);
while (so_far < signed_len) {
int 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);
free(sfBuf);
if (line == NULL) {
LOGE("No digest manifest in signature file\n");
return false;
}
const char *mfName = "META-INF/MANIFEST.MF";
const ZipEntry *mfEntry = mzFindZipEntry(pArchive, mfName);
if (mfEntry == NULL) {
LOGE("No manifest file %s\n", mfName);
return NULL;
}
if (!digestEntry(pArchive, mfEntry, NULL, 0, actual)) return NULL;
if (memcmp(expected, actual, SHA_DIGEST_SIZE)) {
UnterminatedString fn = mzGetZipEntryFileName(sfEntry);
LOGE("Wrong digest for %s in %.*s\n", mfName, fn.len, fn.str);
return NULL;
}
LOGI("Verified %s\n", mfName);
return mfEntry;
}
/* Verify all the files in a Zip archive against the manifest. */
static bool verifyArchive(const ZipArchive *pArchive, const ZipEntry *mfEntry) {
static const char namePrefix[] = "Name: ";
static const char contPrefix[] = " "; // Continuation of the filename
static const char digestPrefix[] = "SHA1-Digest: ";
static const char eol[] = "\r\n";
char *mfBuf = slurpEntry(pArchive, mfEntry);
if (mfBuf == NULL) return false;
/* we're using calloc() here, so the initial state of the array is false */
bool *unverified = (bool *) calloc(mzZipEntryCount(pArchive), sizeof(bool));
if (unverified == NULL) {
LOGE("Can't allocate valid flags\n");
free(mfBuf);
return false;
}
/* Mark all the files in the archive that need to be verified.
* As we scan the manifest and check signatures, we'll unset these flags.
* At the end, we'll make sure that all the flags are unset.
*/
unsigned i, totalBytes = 0;
for (i = 0; i < mzZipEntryCount(pArchive); ++i) {
const ZipEntry *entry = mzGetZipEntryAt(pArchive, i);
UnterminatedString fn = mzGetZipEntryFileName(entry);
int len = mzGetZipEntryUncompLen(entry);
// Don't validate: directories, the manifest, *.RSA, and *.SF.
if (entry == mfEntry) {
LOGV("Skipping manifest %.*s\n", fn.len, fn.str);
} else if (fn.len > 0 && fn.str[fn.len-1] == '/' && len == 0) {
LOGV("Skipping directory %.*s\n", fn.len, fn.str);
} else if (!strncasecmp(fn.str, "META-INF/", 9) && (
!strncasecmp(fn.str + fn.len - 4, ".RSA", 4) ||
!strncasecmp(fn.str + fn.len - 3, ".SF", 3))) {
LOGV("Skipping signature %.*s\n", fn.len, fn.str);
} else {
unverified[i] = true;
totalBytes += len;
const uint8_t* sha1 = SHA_final(&ctx);
for (i = 0; i < numKeys; ++i) {
// The 6 bytes is the "$ff $ff (signature_start) (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\n");
free(eocd);
return VERIFY_SUCCESS;
}
}
unsigned doneBytes = 0;
char *line, *save, *name = NULL;
for (line = strtok_r(mfBuf, eol, &save); line != NULL;
line = strtok_r(NULL, eol, &save)) {
if (!strncasecmp(line, namePrefix, sizeof(namePrefix) - 1)) {
// "Name:" introducing a new stanza
if (name != NULL) {
LOGE("No digest:\n %s\n", name);
break;
}
name = strdup(line + sizeof(namePrefix) - 1);
if (name == NULL) {
LOGE("Can't copy filename in %s\n", line);
break;
}
} else if (!strncasecmp(line, contPrefix, sizeof(contPrefix) - 1)) {
// Continuing a long name (nothing else should be continued)
const char *tail = line + sizeof(contPrefix) - 1;
if (name == NULL) {
LOGE("Unexpected continuation:\n %s\n", tail);
}
char *concat;
if (asprintf(&concat, "%s%s", name, tail) < 0) {
LOGE("Can't append continuation %s\n", tail);
break;
}
free(name);
name = concat;
} else if (!strncasecmp(line, digestPrefix, sizeof(digestPrefix) - 1)) {
// "Digest:" supplying a hash code for the current stanza
const char *base64 = line + sizeof(digestPrefix) - 1;
if (name == NULL) {
LOGE("Unexpected digest:\n %s\n", base64);
break;
}
const ZipEntry *entry = mzFindZipEntry(pArchive, name);
if (entry == NULL) {
LOGE("Missing file:\n %s\n", name);
break;
}
if (!mzIsZipEntryIntact(pArchive, entry)) {
LOGE("Corrupt file:\n %s\n", name);
break;
}
if (!unverified[mzGetZipEntryIndex(pArchive, entry)]) {
LOGE("Unexpected file:\n %s\n", name);
break;
}
uint8_t expected[SHA_DIGEST_SIZE + 3], actual[SHA_DIGEST_SIZE];
int n = b64_pton(base64, expected, sizeof(expected));
if (n != SHA_DIGEST_SIZE) {
LOGE("Invalid base64:\n %s\n %s\n", name, base64);
break;
}
if (!digestEntry(pArchive, entry, &doneBytes, totalBytes, actual) ||
memcmp(expected, actual, SHA_DIGEST_SIZE) != 0) {
LOGE("Wrong digest:\n %s\n", name);
break;
}
LOGI("Verified %s\n", name);
unverified[mzGetZipEntryIndex(pArchive, entry)] = false;
free(name);
name = NULL;
}
}
if (name != NULL) free(name);
free(mfBuf);
for (i = 0; i < mzZipEntryCount(pArchive) && !unverified[i]; ++i) ;
free(unverified);
// This means we didn't get to the end of the manifest successfully.
if (line != NULL) return false;
if (i < mzZipEntryCount(pArchive)) {
const ZipEntry *entry = mzGetZipEntryAt(pArchive, i);
UnterminatedString fn = mzGetZipEntryFileName(entry);
LOGE("No digest for %.*s\n", fn.len, fn.str);
return false;
}
return true;
}
bool verify_jar_signature(const ZipArchive *pArchive,
const RSAPublicKey *pKeys, int numKeys) {
const ZipEntry *sfEntry = verifySignature(pArchive, pKeys, numKeys);
if (sfEntry == NULL) return false;
const ZipEntry *mfEntry = verifyManifest(pArchive, sfEntry);
if (mfEntry == NULL) return false;
return verifyArchive(pArchive, mfEntry);
free(eocd);
LOGE("failed to verify whole-file signature\n");
return VERIFY_FAILURE;
}

12
verifier.h
View file

@ -17,14 +17,14 @@
#ifndef _RECOVERY_VERIFIER_H
#define _RECOVERY_VERIFIER_H
#include "minzip/Zip.h"
#include "mincrypt/rsa.h"
/*
* Check the digital signature (as applied by jarsigner) on a Zip archive.
* Every file in the archive must be signed by one of the supplied RSA keys.
/* Look in the file for a signature footer, and verify that it
* matches one of the given keys. Return one of the constants below.
*/
bool verify_jar_signature(const ZipArchive *pArchive,
const RSAPublicKey *pKeys, int numKeys);
int verify_file(const char* path, const RSAPublicKey *pKeys, unsigned int numKeys);
#define VERIFY_SUCCESS 0
#define VERIFY_FAILURE 1
#endif /* _RECOVERY_VERIFIER_H */