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;
+}