[tor-commits] [tor/master] Use write_str_if_not_equal() for onion services

[asn at torproject.org]

commit 67a62ccf51f46bde75e0675b1ee19c024152f088
Author: Neel Chauhan <neel at neelc.org>
Date:   Fri Jul 24 18:23:50 2020 -0700

    Use write_str_if_not_equal() for onion services
---
 changes/bug40062               | 6 ++++++
 src/feature/hs/hs_service.c    | 2 +-
 src/feature/relay/router.c     | 5 ++---
 src/feature/rend/rendservice.c | 2 +-
 4 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/changes/bug40062 b/changes/bug40062
new file mode 100644
index 0000000000..9f18685a94
--- /dev/null
+++ b/changes/bug40062
@@ -0,0 +1,6 @@
+  o Minor features (onion services):
+    - When writing an onion service hostname file, first read it to make
+      sure it contains what we want before attempting to write it. Now
+      onion services can set their existing onion service directories to
+      read-only and Tor will still work. Resolves ticket 40062. Patch by
+      Neel Chauhan.
diff --git a/src/feature/hs/hs_service.c b/src/feature/hs/hs_service.c
index b56b7f4368..3e264b4686 100644
--- a/src/feature/hs/hs_service.c
+++ b/src/feature/hs/hs_service.c
@@ -990,7 +990,7 @@ write_address_to_file(const hs_service_t *service, const char *fname_)
   tor_asprintf(&addr_buf, "%s.%s\n", service->onion_address, address_tld);
   /* Notice here that we use the given "fname_". */
   fname = hs_path_from_filename(service->config.directory_path, fname_);
-  if (write_str_to_file(fname, addr_buf, 0) < 0) {
+  if (write_str_to_file_if_not_equal(fname, addr_buf)) {
     log_warn(LD_REND, "Could not write onion address to hostname file %s",
              escaped(fname));
     goto end;
diff --git a/src/feature/relay/router.c b/src/feature/relay/router.c
index 25263468c8..675b977ade 100644
--- a/src/feature/relay/router.c
+++ b/src/feature/relay/router.c
@@ -835,7 +835,7 @@ router_initialize_tls_context(void)
 STATIC int
 router_write_fingerprint(int hashed, int ed25519_identity)
 {
-  char *keydir = NULL, *cp = NULL;
+  char *keydir = NULL;
   const char *fname = hashed ? "hashed-fingerprint" :
                       (ed25519_identity ? "fingerprint-ed25519" :
                                           "fingerprint");
@@ -870,7 +870,7 @@ router_write_fingerprint(int hashed, int ed25519_identity)
   tor_asprintf(&fingerprint_line, "%s %s\n", options->Nickname, fingerprint);
 
   /* Check whether we need to write the (hashed-)fingerprint file. */
-  if (write_str_if_not_equal(keydir, fingerprint_line)) {
+  if (write_str_to_file_if_not_equal(keydir, fingerprint_line)) {
     log_err(LD_FS, "Error writing %s%s line to file",
             hashed ? "hashed " : "",
             ed25519_identity ? "ed25519 identity" : "fingerprint");
@@ -884,7 +884,6 @@ router_write_fingerprint(int hashed, int ed25519_identity)
 
   result = 0;
  done:
-  tor_free(cp);
   tor_free(keydir);
   tor_free(fingerprint_line);
   return result;
diff --git a/src/feature/rend/rendservice.c b/src/feature/rend/rendservice.c
index 1ac88d0eb7..8e1a22fb39 100644
--- a/src/feature/rend/rendservice.c
+++ b/src/feature/rend/rendservice.c
@@ -1554,7 +1554,7 @@ rend_service_load_keys(rend_service_t *s)
   fname = rend_service_path(s, hostname_fname);
 
   tor_snprintf(buf, sizeof(buf),"%s.onion\n", s->service_id);
-  if (write_str_to_file(fname,buf,0)<0) {
+  if (write_str_to_file_if_not_equal(fname, buf)) {
     log_warn(LD_CONFIG, "Could not write onion address to hostname file.");
     goto err;
   }