1 files changed, 131 insertions, 308 deletions

diff --git a/verifier.c b/verifier.c
index 1180ae8d0..f2491a14a 100644
--- a/verifier.c
+++ b/verifier.c
@@ -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>
-
-/* 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;
+#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;
     }
 
-    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);
-        }
+    if (footer[2] != 0xff || footer[3] != 0xff) {
+        fclose(f);
+        return VERIFY_FAILURE;
     }
-    return true;
-}
 
+    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);
 
-/* 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 (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;
     }
 
-    memcpy(digest, SHA_final(&context.digest), SHA_DIGEST_SIZE);
-
-#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
-
-    return true;
-}
-
-
-/* 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";
-
-    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;
-            }
+#define EOCD_HEADER_SIZE 22
 
-            /* 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);
+    // The end-of-central-directory record is 22 bytes plus any
+    // comment length.
+    size_t eocd_size = comment_size + EOCD_HEADER_SIZE;
 
-            if (sfEntry == NULL) {
-                LOGW("Missing signature file %s\n", sfName);
-                free(sfName);
-                continue;
-            }
-
-            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);
-        }
+    if (fseek(f, -eocd_size, SEEK_END) != 0) {
+        LOGE("failed to seek in %s (%s)\n", path, strerror(errno));
+        fclose(f);
+        return VERIFY_FAILURE;
     }
 
-    LOGE("No signature (%d files)\n", mzZipEntryCount(pArchive));
-    return NULL;
-}
-
-
-/* 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;
-        }
+    // 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 = malloc(eocd_size);
+    if (eocd == NULL) {
+        LOGE("malloc for EOCD record failed\n");
+        fclose(f);
+        return VERIFY_FAILURE;
     }
-
-    free(sfBuf);
-
-    if (line == NULL) {
-        LOGE("No digest manifest in signature file\n");
-        return false;
+    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;
     }
 
-    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 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;
     }
 
-    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;
+    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;
+        }
     }
 
-    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";
+#define BUFFER_SIZE 4096
 
-    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;
+    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;
     }
 
-    /* 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;
+    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;
         }
-    }
-
-    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;
+        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;
         }
     }
-
-    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;
+    fclose(f);
+    free(buffer);
+
+    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;
+        }
     }
-
-    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;
 }