hs-v3: Add a series of decoding error code

This commit introduces the hs_desc_decode_status_t enum which aims at having
more fine grained error code when decoding a descriptor.

This will be useful in later commits when we support keeping a descriptor that
can't be decrypted due to missing or bad client authorization creds.

No behavior change.

Part of #30382.

Signed-off-by: David Goulet <dgoulet@torproject.org>

3 files changed, 43 insertions, 39 deletions

diff --git a/src/feature/hs/hs_client.c b/src/feature/hs/hs_client.c
index 4e2c520b9b..4f6686143f 100644
--- a/src/feature/hs/hs_client.c
+++ b/src/feature/hs/hs_client.c
@@ -1320,7 +1320,7 @@ hs_client_decode_descriptor(const char *desc_str,
   ret = hs_desc_decode_descriptor(desc_str, subcredential,
                                   client_auht_sk, desc);
   memwipe(subcredential, 0, sizeof(subcredential));
-  if (ret < 0) {
+  if (ret != HS_DESC_DECODE_OK) {
     goto err;
   }
 
diff --git a/src/feature/hs/hs_descriptor.c b/src/feature/hs/hs_descriptor.c
index 60f2bfb0de..056dc81a61 100644
--- a/src/feature/hs/hs_descriptor.c
+++ b/src/feature/hs/hs_descriptor.c
@@ -2038,7 +2038,7 @@ desc_sig_is_valid(const char *b64_sig,
  * unknowns but requires that all v3 token be present and valid.
  *
  * Return 0 on success else a negative value. */
-static int
+static hs_desc_decode_status_t
 desc_decode_plaintext_v3(smartlist_t *tokens,
                          hs_desc_plaintext_data_t *desc,
                          const char *encoded_desc, size_t encoded_len)
@@ -2128,21 +2128,19 @@ desc_decode_plaintext_v3(smartlist_t *tokens,
     goto err;
   }
 
-  return 0;
-
+  return HS_DESC_DECODE_OK;
  err:
-  return -1;
+  return HS_DESC_DECODE_PLAINTEXT_ERROR;
 }
 
 /** Decode the version 3 superencrypted section of the given descriptor desc.
- * The desc_superencrypted_out will be populated with the decoded data.
- * Return 0 on success else -1. */
-static int
+ * The desc_superencrypted_out will be populated with the decoded data. */
+static hs_desc_decode_status_t
 desc_decode_superencrypted_v3(const hs_descriptor_t *desc,
                               hs_desc_superencrypted_data_t *
                               desc_superencrypted_out)
 {
-  int ret = -1;
+  int ret = HS_DESC_DECODE_SUPERENC_ERROR;
   char *message = NULL;
   size_t message_len;
   memarea_t *area = NULL;
@@ -2228,11 +2226,11 @@ desc_decode_superencrypted_v3(const hs_descriptor_t *desc,
                                               tok->object_size);
   superencrypted->encrypted_blob_size = tok->object_size;
 
-  ret = 0;
+  ret = HS_DESC_DECODE_OK;
   goto done;
 
  err:
-  tor_assert(ret < 0);
+  tor_assert(ret < HS_DESC_DECODE_OK);
   hs_desc_superencrypted_data_free_contents(desc_superencrypted_out);
 
  done:
@@ -2250,14 +2248,13 @@ desc_decode_superencrypted_v3(const hs_descriptor_t *desc,
 }
 
 /** Decode the version 3 encrypted section of the given descriptor desc. The
- * desc_encrypted_out will be populated with the decoded data. Return 0 on
- * success else -1. */
-static int
+ * desc_encrypted_out will be populated with the decoded data. */
+static hs_desc_decode_status_t
 desc_decode_encrypted_v3(const hs_descriptor_t *desc,
                          const curve25519_secret_key_t *client_auth_sk,
                          hs_desc_encrypted_data_t *desc_encrypted_out)
 {
-  int ret = -1;
+  int ret = HS_DESC_DECODE_ENCRYPTED_ERROR;
   char *message = NULL;
   size_t message_len;
   memarea_t *area = NULL;
@@ -2343,11 +2340,11 @@ desc_decode_encrypted_v3(const hs_descriptor_t *desc,
   /* NOTE: Unknown fields are allowed because this function could be used to
    * decode other descriptor version. */
 
-  ret = 0;
+  ret = HS_DESC_DECODE_OK;
   goto done;
 
  err:
-  tor_assert(ret < 0);
+  tor_assert(ret < HS_DESC_DECODE_OK);
   hs_desc_encrypted_data_free_contents(desc_encrypted_out);
 
  done:
@@ -2366,7 +2363,7 @@ desc_decode_encrypted_v3(const hs_descriptor_t *desc,
 
 /** Table of encrypted decode function version specific. The function are
  * indexed by the version number so v3 callback is at index 3 in the array. */
-static int
+static hs_desc_decode_status_t
   (*decode_encrypted_handlers[])(
       const hs_descriptor_t *desc,
       const curve25519_secret_key_t *client_auth_sk,
@@ -2379,12 +2376,12 @@ static int
 /** Decode the encrypted data section of the given descriptor and store the
  * data in the given encrypted data object. Return 0 on success else a
  * negative value on error. */
-int
+hs_desc_decode_status_t
 hs_desc_decode_encrypted(const hs_descriptor_t *desc,
                          const curve25519_secret_key_t *client_auth_sk,
                          hs_desc_encrypted_data_t *desc_encrypted)
 {
-  int ret;
+  int ret = HS_DESC_DECODE_ENCRYPTED_ERROR;
   uint32_t version;
 
   tor_assert(desc);
@@ -2398,7 +2395,6 @@ hs_desc_decode_encrypted(const hs_descriptor_t *desc,
   /* Let's make sure we have a supported version as well. By correctly parsing
    * the plaintext, this should not fail. */
   if (BUG(!hs_desc_is_supported_version(version))) {
-    ret = -1;
     goto err;
   }
   /* Extra precaution. Having no handler for the supported version should
@@ -2419,7 +2415,7 @@ hs_desc_decode_encrypted(const hs_descriptor_t *desc,
 
 /** Table of superencrypted decode function version specific. The function are
  * indexed by the version number so v3 callback is at index 3 in the array. */
-static int
+static hs_desc_decode_status_t
   (*decode_superencrypted_handlers[])(
       const hs_descriptor_t *desc,
       hs_desc_superencrypted_data_t *desc_superencrypted) =
@@ -2429,14 +2425,13 @@ static int
 };
 
 /** Decode the superencrypted data section of the given descriptor and store
- * the data in the given superencrypted data object. Return 0 on success else
- * a negative value on error. */
-int
+ * the data in the given superencrypted data object. */
+hs_desc_decode_status_t
 hs_desc_decode_superencrypted(const hs_descriptor_t *desc,
                               hs_desc_superencrypted_data_t *
                               desc_superencrypted)
 {
-  int ret;
+  int ret = HS_DESC_DECODE_SUPERENC_ERROR;
   uint32_t version;
 
   tor_assert(desc);
@@ -2450,7 +2445,6 @@ hs_desc_decode_superencrypted(const hs_descriptor_t *desc,
   /* Let's make sure we have a supported version as well. By correctly parsing
    * the plaintext, this should not fail. */
   if (BUG(!hs_desc_is_supported_version(version))) {
-    ret = -1;
     goto err;
   }
   /* Extra precaution. Having no handler for the supported version should
@@ -2470,7 +2464,7 @@ hs_desc_decode_superencrypted(const hs_descriptor_t *desc,
 
 /** Table of plaintext decode function version specific. The function are
  * indexed by the version number so v3 callback is at index 3 in the array. */
-static int
+static hs_desc_decode_status_t
   (*decode_plaintext_handlers[])(
       smartlist_t *tokens,
       hs_desc_plaintext_data_t *desc,
@@ -2482,12 +2476,12 @@ static int
 };
 
 /** Fully decode the given descriptor plaintext and store the data in the
- * plaintext data object. Returns 0 on success else a negative value. */
-int
+ * plaintext data object. */
+hs_desc_decode_status_t
 hs_desc_decode_plaintext(const char *encoded,
                          hs_desc_plaintext_data_t *plaintext)
 {
-  int ok = 0, ret = -1;
+  int ok = 0, ret = HS_DESC_DECODE_PLAINTEXT_ERROR;
   memarea_t *area = NULL;
   smartlist_t *tokens = NULL;
   size_t encoded_len;
@@ -2537,11 +2531,11 @@ hs_desc_decode_plaintext(const char *encoded,
   /* Run the version specific plaintext decoder. */
   ret = decode_plaintext_handlers[plaintext->version](tokens, plaintext,
                                                       encoded, encoded_len);
-  if (ret < 0) {
+  if (ret != HS_DESC_DECODE_OK) {
     goto err;
   }
   /* Success. Descriptor has been populated with the data. */
-  ret = 0;
+  ret = HS_DESC_DECODE_OK;
 
  err:
   if (tokens) {
@@ -2560,13 +2554,13 @@ hs_desc_decode_plaintext(const char *encoded,
  *
  * Return 0 on success. A negative value is returned on error and desc_out is
  * set to NULL. */
-int
+hs_desc_decode_status_t
 hs_desc_decode_descriptor(const char *encoded,
                           const uint8_t *subcredential,
                           const curve25519_secret_key_t *client_auth_sk,
                           hs_descriptor_t **desc_out)
 {
-  int ret = -1;
+  hs_desc_decode_status_t ret = HS_DESC_DECODE_GENERIC_ERROR;
   hs_descriptor_t *desc;
 
   tor_assert(encoded);
@@ -2583,17 +2577,17 @@ hs_desc_decode_descriptor(const char *encoded,
   memcpy(desc->subcredential, subcredential, sizeof(desc->subcredential));
 
   ret = hs_desc_decode_plaintext(encoded, &desc->plaintext_data);
-  if (ret < 0) {
+  if (ret != HS_DESC_DECODE_OK) {
     goto err;
   }
 
   ret = hs_desc_decode_superencrypted(desc, &desc->superencrypted_data);
-  if (ret < 0) {
+  if (ret != HS_DESC_DECODE_OK) {
     goto err;
   }
 
   ret = hs_desc_decode_encrypted(desc, client_auth_sk, &desc->encrypted_data);
-  if (ret < 0) {
+  if (ret != HS_DESC_DECODE_OK) {
     goto err;
   }
 
@@ -2672,7 +2666,8 @@ hs_desc_encode_descriptor,(const hs_descriptor_t *desc,
   if (!descriptor_cookie) {
     ret = hs_desc_decode_descriptor(*encoded_out, desc->subcredential,
                                     NULL, NULL);
-    if (BUG(ret < 0)) {
+    if (BUG(ret != HS_DESC_DECODE_OK)) {
+      ret = -1;
       goto err;
     }
   }
diff --git a/src/feature/hs/hs_descriptor.h b/src/feature/hs/hs_descriptor.h
index 731e0c5ce9..8d9dac1747 100644
--- a/src/feature/hs/hs_descriptor.h
+++ b/src/feature/hs/hs_descriptor.h
@@ -69,6 +69,15 @@ typedef enum {
   HS_DESC_AUTH_ED25519 = 1
 } hs_desc_auth_type_t;
 
+/** Error code when decoding a descriptor. */
+typedef enum {
+  HS_DESC_DECODE_ENCRYPTED_ERROR = -4,
+  HS_DESC_DECODE_SUPERENC_ERROR  = -3,
+  HS_DESC_DECODE_PLAINTEXT_ERROR = -2,
+  HS_DESC_DECODE_GENERIC_ERROR   = -1,
+  HS_DESC_DECODE_OK              =  0,
+} hs_desc_decode_status_t;
+
 /** Introduction point information located in a descriptor. */
 typedef struct hs_desc_intro_point_t {
   /** Link specifier(s) which details how to extend to the relay. This list