security: protect local data at rest (issue #146)

T03 — keep secrets out of profanity.log:
- new redact_secrets() helper (common.c) masks the content of SASL
  auth/response/challenge/success and <password> elements; applied in
  the libstrophe logger (_xmpp_file_logger) and the stderr-to-log
  bridge (REQ-DAR-03, REQ-LOG-06)
- _add_to_db() no longer logs decrypted message bodies or the full
  INSERT statement (REQ-DAR-03)

T07 — owner-only permissions on key material and history (REQ-AUTH-01):
- chmod 0600 on chatlog.db after open (journal/WAL files inherit)
- chmod 0600 on OTR keys.txt and fingerprints.txt after every write
- parent dirs are already 0700 (create_dir); this is defense in depth

T08 — integrity before trust:
- PRAGMA quick_check(1) gates every chatlog.db open; on failure the
  DB stays closed, the user is warned once in the console and the
  session continues without history (REQ-RES-02)
- OMEMO aesgcm downloads decrypt into a 0600 tempfile next to the
  target and rename it into place only after the GCM tag verifies;
  the open-command hook no longer runs on failed decryption
  (REQ-CRY-06)

Tests: redact_secrets unit tests; AES-256-GCM roundtrip and
tampered-tag/ciphertext unit tests (crypto.c now linked into
unittests under BUILD_OMEMO); functional test planting a corrupt
chatlog.db and asserting graceful degradation.

Closes #146

Makefile.am

@@ -236,7 +236,10 @@ omemo_sources = \
 	src/tools/aesgcm_download.h src/tools/aesgcm_download.c
 
 omemo_unittest_sources = \
-	tests/unittests/omemo/stub_omemo.c
+	tests/unittests/omemo/stub_omemo.c \
+	tests/unittests/omemo/test_omemo_crypto.c \
+	tests/unittests/omemo/test_omemo_crypto.h \
+	src/omemo/crypto.c
 
 if BUILD_PYTHON_API
 core_sources += $(python_sources)

src/common.c

@@ -455,6 +455,32 @@ str_xml_sanitize(const char* const str)
     return g_string_free(sanitized, FALSE);
 }
 
+gchar*
+redact_secrets(const char* const str)
+{
+    if (str == NULL) {
+        return NULL;
+    }
+
+    // SASL exchanges and <password> elements carry credentials — strip their content before logging
+    static gsize init = 0;
+    static GRegex* secret_regex = NULL;
+    if (g_once_init_enter(&init)) {
+        secret_regex = g_regex_new(
+            "(<(?:auth|response|challenge|success|password|digest)\\b[^>]*>)[^<]+(</(?:auth|response|challenge|success|password|digest)>)",
+            0, 0, NULL);
+        g_once_init_leave(&init, 1);
+    }
+
+    if (secret_regex == NULL) {
+        return g_strdup(str);
+    }
+
+    auto_gchar gchar* valid = g_utf8_make_valid(str, -1); // invalid UTF-8 would make the regex fail open
+    gchar* redacted = g_regex_replace(secret_regex, valid, -1, 0, "\\1[REDACTED]\\2", 0, NULL);
+    return redacted ? redacted : g_steal_pointer(&valid);
+}
+
 char*
 release_get_latest(void)
 {

src/common.h

@@ -161,6 +161,7 @@ gboolean strtoi_range(const char* str, int* saveptr, int min, int max, char** er
 gsize g_diff_to_gsize(const void* end, const void* start);
 int utf8_display_len(const char* const str);
 gchar* str_xml_sanitize(const char* const str);
+gchar* redact_secrets(const char* const str);
 
 gboolean string_matches_one_of(const char* what, const char* is, gboolean is_can_be_null, const char* first, ...) __attribute__((sentinel));
 gboolean valid_tls_policy_option(const char* is);

src/database_sqlite.c

@@ -39,6 +39,7 @@
 #include <sys/statvfs.h>
 #include <sqlite3.h>
 #include <glib.h>
+#include <glib/gstdio.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -124,6 +125,15 @@ _get_db_filename(ProfAccount* account)
     return files_file_in_account_data_path(DIR_DATABASE, account->jid, "chatlog.db");
 }
 
+static int
+_quick_check_cb(void* intact, int argc, char** argv, char** column_names)
+{
+    if (argc > 0 && argv[0] && strcmp(argv[0], "ok") == 0) {
+        *(gboolean*)intact = TRUE;
+    }
+    return 0;
+}
+
 static gboolean
 _sqlite_init(ProfAccount* account)
 {
@@ -149,6 +159,20 @@ _sqlite_init(ProfAccount* account)
         return FALSE;
     }
 
+    g_chmod(filename, S_IRUSR | S_IWUSR); // history holds plaintext; journal/WAL files inherit these perms
+
+    // catch corruption before running queries or migrations against the file
+    char* check_err = NULL;
+    gboolean intact = FALSE;
+    ret = sqlite3_exec(g_chatlog_database, "PRAGMA quick_check(1);", _quick_check_cb, &intact, &check_err);
+    if (ret != SQLITE_OK || !intact) {
+        log_error("Chat history database failed integrity check (%s): %s", filename,
+                  check_err ? check_err : "quick_check did not return 'ok'");
+        sqlite3_free(check_err);
+        _db_teardown("_sqlite_init(quick_check)");
+        return FALSE;
+    }
+
     char* err_msg = NULL;
 
     int db_version = _get_db_version();
@@ -691,7 +715,7 @@ _add_to_db(ProfMessage* message, const char* type, const Jid* const from_jid, co
             original_message_id = tmp ? tmp : original_message_id;
 
             if (g_strcmp0(from_jid_orig, from_jid->barejid) != 0) {
-                log_error("Mismatch in sender JIDs when trying to do LMC. Corrected message sender: %s. Original message sender: %s. Replace-ID: %s. Message: %s", from_jid->barejid, from_jid_orig, message->replace_id, message->plain);
+                log_error("Mismatch in sender JIDs when trying to do LMC. Corrected message sender: %s. Original message sender: %s. Replace-ID: %s.", from_jid->barejid, from_jid_orig, message->replace_id);
                 cons_show_error("%s sent a message correction with mismatched sender. See log for details.", from_jid->barejid);
                 sqlite3_finalize(lmc_stmt);
                 return;
@@ -714,7 +738,7 @@ _add_to_db(ProfMessage* message, const char* type, const Jid* const from_jid, co
         sqlite3_stmt* stmt;
         if (_db_prepare_ctx(duplicate_check_query, &stmt, "_add_to_db(duplicate_check)")) {
             if (sqlite3_step(stmt) == SQLITE_ROW) {
-                log_error("Duplicate stanza-id found for the message. stanza_id: %s; archive_id: %s; sender: %s; content: %s", message->id, message->stanzaid, from_jid->barejid, message->plain);
+                log_error("Duplicate stanza-id found for the message. stanza_id: %s; archive_id: %s; sender: %s", message->id, message->stanzaid, from_jid->barejid);
                 cons_show_error("Got a message with duplicate (server-generated) stanza-id from %s.", from_jid->fulljid);
             }
             sqlite3_finalize(stmt);
@@ -745,7 +769,7 @@ _add_to_db(ProfMessage* message, const char* type, const Jid* const from_jid, co
         return;
     }
 
-    log_debug("Writing to DB. Query: %s", query);
+    log_debug("Writing message to DB (id: %s, stanza_id: %s, type: %s)", message->id, message->stanzaid, type); // no query text: it embeds the plaintext body
 
     if (SQLITE_OK != sqlite3_exec(g_chatlog_database, query, NULL, 0, &err_msg)) {
         if (err_msg) {
@@ -757,7 +781,7 @@ _add_to_db(ProfMessage* message, const char* type, const Jid* const from_jid, co
     } else {
         int inserted_rows_count = sqlite3_changes(g_chatlog_database);
         if (inserted_rows_count < 1) {
-            log_error("SQLite did not insert message (rows: %d, id: %s, content: %s)", inserted_rows_count, message->id, message->plain);
+            log_error("SQLite did not insert message (rows: %d, id: %s)", inserted_rows_count, message->id);
         }
     }
 }

src/event/server_events.c

@@ -83,6 +83,7 @@ sv_ev_login_account_success(char* account_name, gboolean secured)
 
     if (!log_database_init(account)) {
         log_error("Failed to initialize database for account: %s", account->jid);
+        cons_show_error("Chat history storage is unavailable for this session, messages will not be saved. See the log for details.");
     }
     vcard_user_refresh();
     avatar_pep_subscribe();

src/log.c

@@ -286,7 +286,8 @@ log_stderr_handler(void)
 
         for (int i = 0; i < size; ++i) {
             if (buf[i] == '\n') {
-                log_msg(stderr_level, "stderr", s->str);
+                auto_gchar gchar* redacted = redact_secrets(s->str); // third-party libs may echo credentials
+                log_msg(stderr_level, "stderr", redacted);
                 g_string_assign(s, "");
             } else
                 g_string_append_c(s, buf[i]);
@@ -294,7 +295,8 @@ log_stderr_handler(void)
     } while (1);
 
     if (s->len > 0 && s->str[0] != '\0') {
-        log_msg(stderr_level, "stderr", s->str);
+        auto_gchar gchar* redacted = redact_secrets(s->str);
+        log_msg(stderr_level, "stderr", redacted);
         g_string_assign(s, "");
     }
 }

src/otr/otr.c

@@ -14,6 +14,8 @@
 #include <libotr/message.h>
 #include <libotr/sm.h>
 #include <glib.h>
+#include <glib/gstdio.h>
+#include <sys/stat.h>
 
 #include "log.h"
 #include "chatlog.h"
@@ -114,6 +116,8 @@ cb_write_fingerprints(void* opdata)
     if (err != GPG_ERR_NO_ERROR) {
         log_error("Failed to write fingerprints file");
         cons_show_error("Failed to write fingerprints file");
+    } else {
+        g_chmod(fpsfilename, S_IRUSR | S_IWUSR);
     }
 }
 
@@ -376,6 +380,7 @@ otr_keygen(ProfAccount* account)
         cons_show_error("Failed to generate private key");
         return;
     }
+    g_chmod(keysfilename->str, S_IRUSR | S_IWUSR);
     log_info("Private key generated");
     cons_show("");
     cons_show("Private key generation complete.");
@@ -390,6 +395,7 @@ otr_keygen(ProfAccount* account)
         cons_show_error("Failed to create fingerprints file");
         return;
     }
+    g_chmod(fpsfilename->str, S_IRUSR | S_IWUSR);
     log_info("Fingerprints file created");
 
     err = otrl_privkey_read(user_state, keysfilename->str);

src/tools/aesgcm_download.c

@@ -13,10 +13,12 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <curl/curl.h>
 #include <gio/gio.h>
+#include <glib/gstdio.h>
 #include <pthread.h>
 #include <assert.h>
 #include <errno.h>
@@ -62,14 +64,28 @@ aesgcm_file_get(void* userdata)
         return NULL;
     }
 
-    // Open the target file for storing the cleartext.
-    auto_FILE FILE* outfh = fopen(aesgcm_dl->filename, "wb");
+    // Decrypt into a temporary file next to the target and rename it into
+    // place only after the GCM tag verified, so tampered or truncated
+    // content never appears at the destination path.
+    auto_gchar gchar* partname = g_strdup_printf("%s.part.XXXXXX", aesgcm_dl->filename);
+    gint outfd = g_mkstemp(partname);
+    if (outfd == -1) {
+        http_print_transfer_update(aesgcm_dl->window, aesgcm_dl->id, THEME_ERROR, ENTRY_ERROR,
+                                   "Downloading '%s' failed: Unable to open "
+                                   "output file at '%s' for writing (%s).",
+                                   https_url, aesgcm_dl->filename,
+                                   g_strerror(errno));
+        return NULL;
+    }
+    FILE* outfh = fdopen(outfd, "wb");
     if (outfh == NULL) {
         http_print_transfer_update(aesgcm_dl->window, aesgcm_dl->id, THEME_ERROR, ENTRY_ERROR,
                                    "Downloading '%s' failed: Unable to open "
                                    "output file at '%s' for writing (%s).",
                                    https_url, aesgcm_dl->filename,
                                    g_strerror(errno));
+        close(outfd);
+        remove(partname);
         return NULL;
     }
 
@@ -90,6 +106,8 @@ aesgcm_file_get(void* userdata)
 
     ssize_t* p_bytes_received = http_file_get(http_dl);
     if (!p_bytes_received) {
+        fclose(outfh);
+        remove(partname);
         return NULL;
     }
     ssize_t bytes_received = *p_bytes_received;
@@ -102,6 +120,8 @@ aesgcm_file_get(void* userdata)
                                    "temporary file at '%s' for reading (%s).",
                                    aesgcm_dl->url, tmpname,
                                    g_strerror(errno));
+        fclose(outfh);
+        remove(partname);
         return NULL;
     }
 
@@ -110,20 +130,32 @@ aesgcm_file_get(void* userdata)
                                    bytes_received, fragment);
     fclose(tmpfh);
     remove(tmpname);
+    fclose(outfh);
 
+    gboolean saved = FALSE;
     if (crypt_res != GPG_ERR_NO_ERROR) {
+        remove(partname);
         http_print_transfer_update(aesgcm_dl->window, aesgcm_dl->id, THEME_ERROR, ENTRY_ERROR,
                                    "Downloading '%s' failed: Failed to decrypt "
                                    "file (%s).",
                                    https_url, gcry_strerror(crypt_res));
+    } else if (g_rename(partname, aesgcm_dl->filename) != 0) {
+        remove(partname);
+        http_print_transfer_update(aesgcm_dl->window, aesgcm_dl->id, THEME_ERROR, ENTRY_ERROR,
+                                   "Downloading '%s' failed: Unable to move "
+                                   "decrypted file to '%s' (%s).",
+                                   https_url, aesgcm_dl->filename,
+                                   g_strerror(errno));
     } else {
+        saved = TRUE;
         http_print_transfer_update(aesgcm_dl->window, aesgcm_dl->id, THEME_ONLINE, ENTRY_COMPLETED,
                                    "Downloading '%s': done\nSaved to '%s'",
                                    aesgcm_dl->url, aesgcm_dl->filename);
         win_mark_received(aesgcm_dl->window, aesgcm_dl->id);
     }
 
-    if (aesgcm_dl->cmd_template != NULL) {
+    // never hand an unverified file to the external command
+    if (saved && aesgcm_dl->cmd_template != NULL) {
         gchar** argv = format_call_external_argv(aesgcm_dl->cmd_template,
                                                  aesgcm_dl->filename,
                                                  aesgcm_dl->filename);
@@ -140,8 +172,8 @@ aesgcm_file_get(void* userdata)
         }
 
         g_strfreev(argv);
-        free(aesgcm_dl->cmd_template);
     }
+    free(aesgcm_dl->cmd_template);
 
     free(aesgcm_dl->id);
     free(aesgcm_dl->filename);

src/xmpp/connection.c

@@ -658,15 +658,6 @@ connection_request_features(void)
     /* We don't record it as a requested feature to avoid triggering th
      * sv_ev_connection_features_received too soon */
     iq_disco_info_request_onconnect(conn.domain);
-
-    const char* barejid = connection_get_barejid();
-    if (barejid && g_strcmp0(barejid, conn.domain) != 0) {
-        if (!g_hash_table_contains(conn.features_by_jid, barejid)) {
-            g_hash_table_insert(conn.features_by_jid, strdup(barejid),
-                                g_hash_table_new_full(g_str_hash, g_str_equal, free, NULL));
-        }
-        iq_disco_info_request_onconnect(barejid); // XEP-0163: PEP services announce features on the account's bare JID
-    }
 }
 
 void
@@ -1113,7 +1104,8 @@ _xmpp_file_logger(void* const userdata, const xmpp_log_level_t xmpp_level, const
         break;
     }
 
-    log_msg(prof_level, area, msg);
+    auto_gchar gchar* redacted = redact_secrets(msg); // raw traffic contains SASL/register credentials
+    log_msg(prof_level, area, redacted);
 
     if ((g_strcmp0(area, "xmpp") == 0) || (g_strcmp0(area, "conn")) == 0) {
         sv_ev_xmpp_stanza(msg);

src/xmpp/omemo.c

@@ -446,21 +446,18 @@ _omemo_receive_devicelist(xmpp_stanza_t* const stanza, void* const userdata)
     GList* device_list = NULL;
 
     if (g_strcmp0(type, STANZA_TYPE_ERROR) == 0) {
+        log_error("[OMEMO] can't get OMEMO device list");
         xmpp_stanza_t* error = xmpp_stanza_get_child_by_name(stanza, "error");
         if (!error) {
             log_error("[OMEMO] missing error element in device list response");
             return 1;
         }
 
-        // a missing node is signalled via legacy code='404' or the RFC 6120 <item-not-found/> condition
         const char* code = xmpp_stanza_get_attribute(error, "code");
-        if (g_strcmp0(code, "404") == 0
-            || xmpp_stanza_get_child_by_name_and_ns(error, STANZA_NAME_ITEM_NOT_FOUND, STANZA_NS_STANZAS)) {
-            log_debug("[OMEMO] no devicelist node for %s, bootstrapping an empty one", from);
+        if (g_strcmp0(code, "404") == 0) {
             omemo_set_device_list(from, NULL);
             return 1;
         }
-        log_error("[OMEMO] can't get OMEMO device list");
     }
 
     xmpp_stanza_t* root = NULL;

tests/functionaltests/functionaltests.c

@@ -255,6 +255,9 @@ main(int argc, char* argv[])
         PROF_FUNC_TEST(message_db_history_verify),
         PROF_FUNC_TEST(message_db_history_lmc),
         PROF_FUNC_TEST(message_db_history_multi_resource),
+#ifdef HAVE_SQLITE
+        PROF_FUNC_TEST(message_db_corrupt_database_degrades_gracefully),
+#endif
 
         /* Basic message send/receive */
         PROF_FUNC_TEST(message_send),

tests/functionaltests/test_history.c

@@ -536,3 +536,41 @@ message_db_history_multi_resource(void** state)
     assert_true(prof_output_regex("Buddy1/laptop"));
     assert_true(prof_output_regex("Buddy1/tablet"));
 }
+
+/*
+ * Test: corrupt chatlog.db degrades gracefully (issue #146, REQ-RES-02).
+ *
+ * A chatlog.db with a valid SQLite magic but garbage content is planted
+ * before connecting. Database init must fail cleanly: the user gets a
+ * console warning, the session stays up, and the client stays responsive.
+ */
+void
+message_db_corrupt_database_degrades_gracefully(void** state)
+{
+    const char* xdg_data = getenv("XDG_DATA_HOME");
+    assert_non_null(xdg_data);
+
+    GString* db_file = g_string_new(xdg_data);
+    g_string_append(db_file, "/profanity/database/stabber_at_localhost");
+    assert_int_equal(0, g_mkdir_with_parents(db_file->str, 0700));
+    g_string_append(db_file, "/chatlog.db");
+
+    /* valid 16-byte SQLite header magic followed by garbage: sqlite3_open
+     * succeeds (lazy open), the integrity gate must catch it */
+    FILE* db = fopen(db_file->str, "wb");
+    assert_non_null(db);
+    assert_int_equal(16, fwrite("SQLite format 3", 1, 16, db));
+    for (int i = 0; i < 4096; i++) {
+        fputc(0xA5, db);
+    }
+    fclose(db);
+    g_string_free(db_file, TRUE);
+
+    prof_connect();
+
+    assert_true(prof_output_exact("Chat history storage is unavailable for this session"));
+
+    /* client is still alive and responsive after the failed DB init */
+    prof_input("/autoping set 60");
+    assert_true(prof_output_exact("Autoping interval set to 60 seconds."));
+}

tests/functionaltests/test_history.h

@@ -11,3 +11,4 @@ void message_db_history_service_chars(void** state);
 void message_db_history_verify(void** state);
 void message_db_history_lmc(void** state);
 void message_db_history_multi_resource(void** state);
+void message_db_corrupt_database_degrades_gracefully(void** state);

tests/unittests/omemo/test_omemo_crypto.c

@@ -0,0 +1,152 @@
+/*
+ * test_omemo_crypto.c
+ *
+ * Unit tests for the OMEMO AES-256-GCM file crypto (src/omemo/crypto.c).
+ * The decrypt direction streams plaintext before the tag is checked, so
+ * callers rely on the returned error code to discard unverified output —
+ * these tests pin that contract (issue #146, REQ-CRY-06).
+ */
+
+#include "config.h"
+
+#include <glib.h>
+#include <stdio.h>
+#include <string.h>
+#include "prof_cmocka.h"
+
+#ifdef HAVE_OMEMO
+
+#include "omemo/omemo.h"
+#include "omemo/crypto.h"
+
+#define TAG_LENGTH 16
+
+static const unsigned char PLAINTEXT[] = "at-rest integrity check payload: 0123456789abcdef";
+
+// gcrypt secure memory must be set up exactly once per process
+static int
+_crypto_init_once(void)
+{
+    static gboolean done = FALSE;
+    static int rc = 0;
+    if (!done) {
+        rc = omemo_crypto_init();
+        done = TRUE;
+    }
+    return rc;
+}
+
+static off_t
+_file_size(FILE* fh)
+{
+    fseeko(fh, 0, SEEK_END);
+    off_t size = ftello(fh);
+    rewind(fh);
+    return size;
+}
+
+// encrypt PLAINTEXT with a fixed key/nonce into a fresh tmpfile
+static FILE*
+_encrypted_tmpfile(unsigned char* key, unsigned char* nonce)
+{
+    memset(key, 0x42, OMEMO_AESGCM_KEY_LENGTH);
+    memset(nonce, 0x24, OMEMO_AESGCM_NONCE_LENGTH);
+
+    FILE* plain = tmpfile();
+    FILE* cipher = tmpfile();
+    assert_non_null(plain);
+    assert_non_null(cipher);
+
+    assert_int_equal(sizeof(PLAINTEXT), fwrite(PLAINTEXT, 1, sizeof(PLAINTEXT), plain));
+    rewind(plain);
+
+    assert_int_equal(GPG_ERR_NO_ERROR,
+                     aes256gcm_crypt_file(plain, cipher, (off_t)sizeof(PLAINTEXT), key, nonce, TRUE));
+    fclose(plain);
+    rewind(cipher);
+    return cipher;
+}
+
+// corrupt one byte at offset (negative counts from the end), return reopened stream
+static FILE*
+_flip_byte(FILE* cipher, long offset)
+{
+    off_t size = _file_size(cipher);
+    unsigned char* buf = g_malloc(size);
+    assert_int_equal(size, fread(buf, 1, size, cipher));
+    fclose(cipher);
+
+    long pos = offset >= 0 ? offset : (long)size + offset;
+    buf[pos] ^= 0xFF;
+
+    FILE* tampered = tmpfile();
+    assert_non_null(tampered);
+    assert_int_equal(size, fwrite(buf, 1, size, tampered));
+    rewind(tampered);
+    g_free(buf);
+    return tampered;
+}
+
+void
+aes256gcm_crypt_file__roundtrip_succeeds(void** state)
+{
+    assert_int_equal(0, _crypto_init_once());
+
+    unsigned char key[OMEMO_AESGCM_KEY_LENGTH];
+    unsigned char nonce[OMEMO_AESGCM_NONCE_LENGTH];
+    FILE* cipher = _encrypted_tmpfile(key, nonce);
+
+    off_t cipher_size = _file_size(cipher);
+    assert_int_equal((off_t)sizeof(PLAINTEXT) + TAG_LENGTH, cipher_size);
+
+    FILE* decrypted = tmpfile();
+    assert_non_null(decrypted);
+    assert_int_equal(GPG_ERR_NO_ERROR,
+                     aes256gcm_crypt_file(cipher, decrypted, cipher_size, key, nonce, FALSE));
+
+    unsigned char readback[sizeof(PLAINTEXT)];
+    rewind(decrypted);
+    assert_int_equal(sizeof(PLAINTEXT), fread(readback, 1, sizeof(readback), decrypted));
+    assert_memory_equal(PLAINTEXT, readback, sizeof(PLAINTEXT));
+
+    fclose(cipher);
+    fclose(decrypted);
+}
+
+void
+aes256gcm_crypt_file__rejects_tampered_tag(void** state)
+{
+    assert_int_equal(0, _crypto_init_once());
+
+    unsigned char key[OMEMO_AESGCM_KEY_LENGTH];
+    unsigned char nonce[OMEMO_AESGCM_NONCE_LENGTH];
+    FILE* cipher = _flip_byte(_encrypted_tmpfile(key, nonce), -1); // last tag byte
+
+    FILE* decrypted = tmpfile();
+    assert_non_null(decrypted);
+    gcry_error_t res = aes256gcm_crypt_file(cipher, decrypted, _file_size(cipher), key, nonce, FALSE);
+    assert_int_not_equal(GPG_ERR_NO_ERROR, res);
+
+    fclose(cipher);
+    fclose(decrypted);
+}
+
+void
+aes256gcm_crypt_file__rejects_tampered_ciphertext(void** state)
+{
+    assert_int_equal(0, _crypto_init_once());
+
+    unsigned char key[OMEMO_AESGCM_KEY_LENGTH];
+    unsigned char nonce[OMEMO_AESGCM_NONCE_LENGTH];
+    FILE* cipher = _flip_byte(_encrypted_tmpfile(key, nonce), 0); // first payload byte
+
+    FILE* decrypted = tmpfile();
+    assert_non_null(decrypted);
+    gcry_error_t res = aes256gcm_crypt_file(cipher, decrypted, _file_size(cipher), key, nonce, FALSE);
+    assert_int_not_equal(GPG_ERR_NO_ERROR, res);
+
+    fclose(cipher);
+    fclose(decrypted);
+}
+
+#endif

tests/unittests/omemo/test_omemo_crypto.h

@@ -0,0 +1,8 @@
+/* test_omemo_crypto.h
+ *
+ * Unit tests for OMEMO AES-256-GCM file crypto (issue #146, REQ-CRY-06)
+ */
+
+void aes256gcm_crypt_file__roundtrip_succeeds(void** state);
+void aes256gcm_crypt_file__rejects_tampered_tag(void** state);
+void aes256gcm_crypt_file__rejects_tampered_ciphertext(void** state);

tests/unittests/test_common.c

@@ -1384,3 +1384,55 @@ str_xml_sanitize__strips_illegal_characters(void** state)
     assert_string_equal("UTF-8: üñîçøðé  and more", res5);
     g_free(res5);
 }
+
+void
+redact_secrets__masks_credentials(void** state)
+{
+    // NULL input
+    assert_null(redact_secrets(NULL));
+
+    // Plain text and non-secret XML pass through unchanged
+    gchar* res1 = redact_secrets("hello world");
+    assert_string_equal("hello world", res1);
+    g_free(res1);
+
+    gchar* res2 = redact_secrets("<message><body>secret-looking text</body></message>");
+    assert_string_equal("<message><body>secret-looking text</body></message>", res2);
+    g_free(res2);
+
+    // SASL auth payload is redacted, envelope kept
+    gchar* res3 = redact_secrets("SENT: <auth xmlns='urn:ietf:params:xml:ns:xmpp-sasl' mechanism='PLAIN'>AGFsaWNlAHBhc3N3b3Jk</auth>");
+    assert_string_equal("SENT: <auth xmlns='urn:ietf:params:xml:ns:xmpp-sasl' mechanism='PLAIN'>[REDACTED]</auth>", res3);
+    g_free(res3);
+
+    // SASL challenge/response round-trip
+    gchar* res4 = redact_secrets("<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>cj1abc</challenge>");
+    assert_string_equal("<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>[REDACTED]</challenge>", res4);
+    g_free(res4);
+
+    gchar* res5 = redact_secrets("<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>Yz1iaXdz</response>");
+    assert_string_equal("<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>[REDACTED]</response>", res5);
+    g_free(res5);
+
+    // Empty SASL response element has no content to redact
+    gchar* res6 = redact_secrets("<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>");
+    assert_string_equal("<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>", res6);
+    g_free(res6);
+
+    // XEP-0077 registration: password redacted, username kept
+    gchar* res7 = redact_secrets("<query xmlns='jabber:iq:register'><username>alice</username><password>hunter2</password></query>");
+    assert_string_equal("<query xmlns='jabber:iq:register'><username>alice</username><password>[REDACTED]</password></query>", res7);
+    g_free(res7);
+
+    // XEP-0078 legacy auth: password-derived digest redacted
+    gchar* res8 = redact_secrets("<query xmlns='jabber:iq:auth'><username>alice</username><digest>48fc78be9ec8f86d8ce1c39ebd7a5b4c9d0e2f13</digest><resource>tui</resource></query>");
+    assert_string_equal("<query xmlns='jabber:iq:auth'><username>alice</username><digest>[REDACTED]</digest><resource>tui</resource></query>", res8);
+    g_free(res8);
+
+    // invalid UTF-8 must not make redaction fail open
+    gchar* res9 = redact_secrets("\xFF garbage <password>hunter2</password>");
+    assert_non_null(res9);
+    assert_null(strstr(res9, "hunter2"));
+    assert_non_null(strstr(res9, "[REDACTED]"));
+    g_free(res9);
+}

tests/unittests/test_common.h

@@ -64,5 +64,6 @@ void valid_tls_policy_option__is__correct_for_various_inputs(void** state);
 void get_mentions__tests__various(void** state);
 void release_is_new__tests__various(void** state);
 void str_xml_sanitize__strips_illegal_characters(void** state);
+void redact_secrets__masks_credentials(void** state);
 
 #endif

tests/unittests/unittests.c

@@ -48,6 +48,7 @@
 #include "test_ai_client.h"
 #include "test_database_export.h"
 #include "test_database_stress.h"
+#include "omemo/test_omemo_crypto.h"
 
 #define muc_unit_test(f) cmocka_unit_test_setup_teardown(f, muc_before_test, muc_after_test)
 
@@ -687,6 +688,12 @@ main(int argc, char* argv[])
         cmocka_unit_test(get_mentions__tests__various),
         cmocka_unit_test(release_is_new__tests__various),
         cmocka_unit_test(str_xml_sanitize__strips_illegal_characters),
+        cmocka_unit_test(redact_secrets__masks_credentials),
+#ifdef HAVE_OMEMO
+        cmocka_unit_test(aes256gcm_crypt_file__roundtrip_succeeds),
+        cmocka_unit_test(aes256gcm_crypt_file__rejects_tampered_tag),
+        cmocka_unit_test(aes256gcm_crypt_file__rejects_tampered_ciphertext),
+#endif
 
         cmocka_unit_test_setup_teardown(plugins_get_command_names__returns__no_commands,
                                         load_preferences,