Commit 520a0c97f8081e4531fc9c88cda705a92afbddaf
2020-03-23T21:08:17
compute pack file's checksum during download and check it in got-fetch-pack
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93
diff --git a/libexec/got-fetch-pack/got-fetch-pack.c b/libexec/got-fetch-pack/got-fetch-pack.c
index fe49bfb..a139835 100644
--- a/libexec/got-fetch-pack/got-fetch-pack.c
+++ b/libexec/got-fetch-pack/got-fetch-pack.c
@@ -648,7 +648,6 @@ send_fetch_ref(struct imsgbuf *ibuf, struct got_object_id *refid,
return got_privsep_flush_imsg(ibuf);
}
-
static const struct got_error *
fetch_pack(int fd, int packfd, struct got_object_id *packid,
struct got_pathlist_head *have_refs, int fetch_all_branches,
@@ -670,8 +669,14 @@ fetch_pack(int fd, int packfd, struct got_object_id *packid,
struct got_pathlist_entry *pe;
int sent_my_capabilites = 0, have_sidebands = 0;
int found_branch = 0;
+ SHA1_CTX sha1_ctx;
+ uint8_t pack_sha1[SHA1_DIGEST_LENGTH];
+ uint8_t sha1_buf[SHA1_DIGEST_LENGTH];
+ size_t sha1_buf_len = 0;
+ ssize_t w;
TAILQ_INIT(&symrefs);
+ SHA1Init(&sha1_ctx);
have = malloc(refsz * sizeof(have[0]));
if (have == NULL)
@@ -925,7 +930,7 @@ fetch_pack(int fd, int packfd, struct got_object_id *packid,
have_sidebands = 1;
while (1) {
- ssize_t r = 0, w;
+ ssize_t r = 0;
int datalen = -1;
if (have_sidebands) {
@@ -1000,6 +1005,42 @@ fetch_pack(int fd, int packfd, struct got_object_id *packid,
break;
}
+ /*
+ * An expected SHA1 checksum sits at the end of the pack file.
+ * Since we don't know the file size ahead of time we have to
+ * keep SHA1_DIGEST_LENGTH bytes buffered and avoid mixing
+ * those bytes into our SHA1 checksum computation until we
+ * know for sure that additional pack file data bytes follow.
+ *
+ * We can assume r > 0 since otherwise the loop would exit.
+ */
+ if (r >= SHA1_DIGEST_LENGTH) {
+ /* Mix in any previously buffered bytes. */
+ SHA1Update(&sha1_ctx, sha1_buf, sha1_buf_len);
+
+ /* Mix in bytes read minus potential checksum bytes. */
+ SHA1Update(&sha1_ctx, buf, r - SHA1_DIGEST_LENGTH);
+
+ /* Buffer potential checksum bytes. */
+ memcpy(sha1_buf, buf + r - SHA1_DIGEST_LENGTH,
+ SHA1_DIGEST_LENGTH);
+ sha1_buf_len = SHA1_DIGEST_LENGTH;
+ } else if (sha1_buf_len > r) {
+ /*
+ * Mix in previously buffered bytes which
+ * are not part of the checksum after all.
+ */
+ SHA1Update(&sha1_ctx, sha1_buf, r);
+
+ /* Update potential checksum buffer. */
+ memmove(sha1_buf, sha1_buf + r, sha1_buf_len - r);
+ memcpy(sha1_buf + sha1_buf_len - r, buf, r);
+ } else {
+ /* Short initial packet. Just buffer data for now. */
+ memcpy(sha1_buf, buf, r);
+ sha1_buf_len = r;
+ }
+
/* Write packfile data to temporary pack file. */
w = write(packfd, buf, r);
if (w == -1) {
@@ -1023,6 +1064,13 @@ fetch_pack(int fd, int packfd, struct got_object_id *packid,
err = send_fetch_download_progress(ibuf, packsz);
if (err)
goto done;
+
+ SHA1Final(pack_sha1, &sha1_ctx);
+ if (sha1_buf_len != SHA1_DIGEST_LENGTH ||
+ memcmp(pack_sha1, sha1_buf, sha1_buf_len) != 0) {
+ err = got_error_msg(GOT_ERR_BAD_PACKFILE,
+ "pack file checksum mismatch");
+ }
done:
TAILQ_FOREACH(pe, &symrefs, entry) {
free((void *)pe->path);