Generate secrets for clients

author: Jesper Jensen <jesper@jnsn.dev> 2026-02-18 18:34:02 +0100
committer: Jesper Jensen <jesper@jnsn.dev> 2026-02-18 18:34:02 +0100
commit: 5fbbd990d6b42f5e7534cdb68fa5c368a4a69169 (patch)
tree: 3db3b955fcceb71fbb8ea161643a3a1044b2e4f2
parent: 78745e06f4a4365e9caa8ee12fb0d9e15fb59300 (diff)
3 files changed, 157 insertions, 17 deletions
diff --git a/src/web.c b/src/web.c
index 8c37bfe..df2dc81 100644
--- a/src/web.c
+++ b/src/web.c
@@ -13,6 +13,7 @@
 #include <microhttpd.h>
 #include <sqlite3.h>
 #include <cjson/cJSON.h>
+#include <fcntl.h>
 
 #define PAGE "<html><head><title>libmicrohttpd demo</title>"\
              "</head><body>libmicrohttpd demo</body></html>"
@@ -22,6 +23,21 @@ static void sqliteError(void *pArg, int iErrCode, const char *zMsg) {
 	fprintf(stderr, "(%d) %s\n", iErrCode, zMsg);
 }
 
+static int generate_secret(char *out) {
+	unsigned char bytes[16];
+	int fd = open("/dev/urandom", O_RDONLY);
+	if (fd < 0) return -1;
+	ssize_t n = read(fd, bytes, 16);
+	close(fd);
+	if (n != 16) return -1;
+	static const char hex[] = "0123456789abcdef";
+	for (int i = 0; i < 16; i++) {
+		out[i*2] = hex[(bytes[i] >> 4) & 0x0f];
+		out[i*2+1] = hex[bytes[i] & 0x0f];
+	}
+	out[32] = '\0';
+	return 0;
+}
 
 void prepare_database(struct App *app) {
 	// @CLEANUP: Move this to main? doesn't belong here at least
@@ -176,6 +192,36 @@ void prepare_database(struct App *app) {
 			abort();
 		}
 	}
+
+	if(maxVersion < 4) {
+		char *prog =
+			"BEGIN TRANSACTION;"
+			"ALTER TABLE clients ADD COLUMN secret TEXT NOT NULL DEFAULT ''";
+		if(sqlite3_exec(conn, prog, NULL, NULL, NULL) != SQLITE_OK) {
+			abort();
+		}
+
+		sqlite3_stmt *stmt;
+		if(sqlite3_prepare_v2(conn, "INSERT INTO migration (id) VALUES (?1)", -1, &stmt, NULL) != SQLITE_OK) {
+			abort();
+		}
+
+		if(sqlite3_bind_int64(stmt, 1, 4) != SQLITE_OK) {
+			abort();
+		}
+
+		if(sqlite3_step(stmt) != SQLITE_DONE) {
+			abort();
+		}
+
+		if(sqlite3_finalize(stmt) != SQLITE_OK) {
+			abort();
+		}
+
+		if(sqlite3_exec(conn, "COMMIT TRANSACTION", NULL, NULL, NULL) != SQLITE_OK) {
+			abort();
+		}
+	}
 }
 
 enum ReportEvent {
@@ -184,7 +230,8 @@ enum ReportEvent {
 };
 
 // @CLEANUP: This should live somewhere else, but I don't have a spot for it yet.
-int submit_report(struct App *app, char *client, enum ReportEvent event) {
+// Returns 0 on success, -1 on error, -2 on secret mismatch
+int submit_report(struct App *app, char *client, char *secret, enum ReportEvent event) {
 	sqlite3 *conn;
 	int err;
 	if((err = sqlite3_open(app->dbname, &conn)) != SQLITE_OK) {
@@ -196,7 +243,7 @@ int submit_report(struct App *app, char *client, enum ReportEvent event) {
 	int64_t clientId;
 	{
 		sqlite3_stmt *stmt;
-		if(sqlite3_prepare_v2(conn, "SELECT id FROM clients WHERE name = ?1", -1, &stmt, NULL) != SQLITE_OK) {
+		if(sqlite3_prepare_v2(conn, "SELECT id, secret FROM clients WHERE name = ?1", -1, &stmt, NULL) != SQLITE_OK) {
 			abort();
 		}
 		if(sqlite3_bind_text(stmt, 1, client, -1, SQLITE_STATIC) != SQLITE_OK) {
@@ -212,6 +259,13 @@ int submit_report(struct App *app, char *client, enum ReportEvent event) {
 		}
 		clientId = sqlite3_column_int64(stmt, 0);
 
+		const char *stored_secret = (const char *)sqlite3_column_text(stmt, 1);
+		if(stored_secret == NULL || strcmp(stored_secret, secret) != 0) {
+			sqlite3_finalize(stmt);
+			sqlite3_close(conn);
+			return -2;
+		}
+
 		if(sqlite3_step(stmt) != SQLITE_DONE) {
 			abort();
 		}
@@ -313,14 +367,21 @@ int create_client(struct Request *req, char *name, struct CreateClientResult *re
 		abort();
 	}
 
+	if(generate_secret(result->secret) != 0) {
+		abort();
+	}
+
 	{
 		sqlite3_stmt *stmt;
-		if(sqlite3_prepare_v2(conn, "INSERT INTO clients (name) VALUES (?1)", -1, &stmt, NULL) != SQLITE_OK) {
+		if(sqlite3_prepare_v2(conn, "INSERT INTO clients (name, secret) VALUES (?1, ?2)", -1, &stmt, NULL) != SQLITE_OK) {
 			abort();
 		}
 		if(sqlite3_bind_text(stmt, 1, name, -1, SQLITE_STATIC) != SQLITE_OK) {
 			abort();
 		}
+		if(sqlite3_bind_text(stmt, 2, result->secret, -1, SQLITE_STATIC) != SQLITE_OK) {
+			abort();
+		}
 
 		if(sqlite3_step(stmt) != SQLITE_DONE) {
 			abort();
@@ -373,7 +434,7 @@ int list_clients(struct Request *req, struct ListClientResult *result) {
 
 	{
 		sqlite3_stmt *stmt;
-		if(sqlite3_prepare_v2(conn, "SELECT c.id, c.name FROM clients c WHERE c.id > ?1 ORDER BY c.id ASC LIMIT ?2", -1, &stmt, NULL) != SQLITE_OK) {
+		if(sqlite3_prepare_v2(conn, "SELECT c.id, c.name, c.secret FROM clients c WHERE c.id > ?1 ORDER BY c.id ASC LIMIT ?2", -1, &stmt, NULL) != SQLITE_OK) {
 			abort();
 		}
 		if(sqlite3_bind_int64(stmt, 1, -1) != SQLITE_OK) {
@@ -394,9 +455,11 @@ int list_clients(struct Request *req, struct ListClientResult *result) {
 
 			int64_t clientId = sqlite3_column_int64(stmt, 0);
 			const uint8_t *name = sqlite3_column_text(stmt, 1);
+			const uint8_t *secret = sqlite3_column_text(stmt, 2);
 
 			result->clients[index].id = clientId;
 			strncpy(result->clients[index].name, (char*)name, CLIENT_NAME_MAX);
+			strncpy(result->clients[index].secret, (char*)secret, CLIENT_SECRET_LEN);
 
 			index++;
 		}
@@ -443,12 +506,13 @@ static char *render_clients_page(struct Request *request, size_t *out_len) {
 		"<body>\n"
 		"  <h1>Clients</h1>\n"
 		"  <table border=\"1\">\n"
-		"    <tr><th>Name</th><th>Actions</th></tr>\n");
+		"    <tr><th>Name</th><th>Secret</th><th>Actions</th></tr>\n");
 
 	for (int i = 0; i < result->clients_len; i++) {
 		fprintf(f,
 			"    <tr>\n"
 			"      <td>%s</td>\n"
+			"      <td>%s</td>\n"
 			"      <td>\n"
 			"        <form method=\"POST\" action=\"/clients/delete\" style=\"display:inline\">\n"
 			"          <input type=\"hidden\" name=\"client_id\" value=\"%ld\">\n"
@@ -457,6 +521,7 @@ static char *render_clients_page(struct Request *request, size_t *out_len) {
 			"      </td>\n"
 			"    </tr>\n",
 			result->clients[i].name,
+			result->clients[i].secret,
 			result->clients[i].id
 		);
 	}
@@ -639,6 +704,11 @@ static enum MHD_Result handler(
 				abort();
 			}
 
+			cJSON *secretJson = cJSON_GetObjectItemCaseSensitive(rootJson, "secret");
+			if(!cJSON_IsString(secretJson) || secretJson->valuestring == NULL) {
+				abort();
+			}
+
 			cJSON *eventJson = cJSON_GetObjectItemCaseSensitive(rootJson, "event");
 			if(!cJSON_IsString(eventJson) || eventJson->valuestring == NULL) {
 				abort();
@@ -653,7 +723,26 @@ static enum MHD_Result handler(
 			}
 
 
-			ret = submit_report(server->app, clientJson->valuestring, event);
+			ret = submit_report(server->app, clientJson->valuestring, secretJson->valuestring, event);
+			if(ret == -2) {
+				cJSON_Delete(rootJson);
+				destroy_post_collector(&request->pp);
+
+				struct MHD_Response *response = MHD_create_response_from_buffer(
+					0,
+					"",
+					MHD_RESPMEM_PERSISTENT
+				);
+				ret = MHD_add_response_header(response, "Content-Type", "application/json");
+				if(ret != MHD_YES) return ret;
+				ret = MHD_queue_response(
+					connection,
+					MHD_HTTP_UNAUTHORIZED,
+					response
+				);
+				MHD_destroy_response(response);
+				return ret;
+			}
 			if(ret != 0) {
 				// Should actually return an error page, but this will do for now
 				return MHD_NO;
@@ -697,7 +786,7 @@ static enum MHD_Result handler(
 			destroy_post_collector(&request->pp);
 
 			char *buf = malloc(1024);
-			size_t buf_len = snprintf(buf, 1024, "{ \"id\": \"%ld\" }", result.id);
+			size_t buf_len = snprintf(buf, 1024, "{ \"id\": \"%ld\", \"secret\": \"%s\" }", result.id, result.secret);
 			if(buf_len >= 1024) {
 				abort();
 			}
diff --git a/src/web.h b/src/web.h
index 96e5f7f..95c0e27 100644
--- a/src/web.h
+++ b/src/web.h
@@ -21,6 +21,7 @@ int web_begin(struct Server *server, int port);
 int web_join(struct Server *server);
 
 #define CLIENT_NAME_MAX 32
+#define CLIENT_SECRET_LEN 33
 
 struct PostCollector {
 	char *data;
@@ -45,6 +46,7 @@ struct Request {
 struct CreateClientResult {
 	int64_t id;
 	char* name;
+	char secret[CLIENT_SECRET_LEN];
 };
 
 int create_client(struct Request *req, char *name, struct CreateClientResult *result);
@@ -53,6 +55,7 @@ int delete_client(struct Request *req, int64_t client_id);
 struct ListClientResultClient {
 	int64_t id;
 	char name[CLIENT_NAME_MAX];
+	char secret[CLIENT_SECRET_LEN];
 };
 
 struct ListClientResult {
diff --git a/test/http.c b/test/http.c
index fa7755d..8309d5e 100644
--- a/test/http.c
+++ b/test/http.c
@@ -6,6 +6,7 @@
 #include <curl/curl.h>
 #include <stdlib.h>
 #include <string.h>
+#include <cjson/cJSON.h>
 
 // @PASTE Stolen from libcurl documentation
 struct memory {
@@ -83,6 +84,7 @@ int main(int argc, char **argv) {
 
 	}
 
+	char client_secret[CLIENT_SECRET_LEN] = {0};
 	{
 		curlRes = curl_easy_setopt(curl, CURLOPT_URL, "http://localhost:8080/api/client");
 		assert(curlRes == CURLE_OK);
@@ -124,12 +126,18 @@ int main(int argc, char **argv) {
 		assert(strcmp(ct, "application/json") == 0);
 
 		assert(body.size >= 0);
-		assert(strcmp(
-			body.body,
-			"{ "
-				"\"id\": \"1\" "
-			"}"
-		) == 0);
+		// Parse response to extract secret
+		cJSON *rootJson = cJSON_ParseWithLength(body.body, body.size);
+		assert(rootJson != NULL);
+		cJSON *idJson = cJSON_GetObjectItemCaseSensitive(rootJson, "id");
+		assert(cJSON_IsString(idJson));
+		assert(strcmp(idJson->valuestring, "1") == 0);
+		cJSON *secretJson = cJSON_GetObjectItemCaseSensitive(rootJson, "secret");
+		assert(cJSON_IsString(secretJson));
+		assert(strlen(secretJson->valuestring) == 32);
+		strncpy(client_secret, secretJson->valuestring, CLIENT_SECRET_LEN);
+		cJSON_Delete(rootJson);
+		free(body.body);
 		body = (struct memory){0};
 	}
 
@@ -146,9 +154,11 @@ int main(int argc, char **argv) {
 		curlRes = curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_from_memory);
 		assert(curlRes == CURLE_OK);
 
+		char req_buf[256];
+		snprintf(req_buf, sizeof(req_buf), "{\"client\": \"client1\", \"secret\": \"%s\", \"event\": \"begin_backup\"}", client_secret);
 		struct memory req_body = {
-			.body = "{\"client\": \"client1\", \"event\": \"begin_backup\"}",
-			.size = strlen(req_body.body),
+			.body = req_buf,
+			.size = strlen(req_buf),
 		};
 		curlRes = curl_easy_setopt(curl, CURLOPT_READDATA, &req_body);
 		assert(curlRes == CURLE_OK);
@@ -192,9 +202,11 @@ int main(int argc, char **argv) {
 		curlRes = curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_from_memory);
 		assert(curlRes == CURLE_OK);
 
+		char req_buf[256];
+		snprintf(req_buf, sizeof(req_buf), "{\"client\": \"client1\", \"secret\": \"%s\", \"event\": \"end_backup\"}", client_secret);
 		struct memory req_body = {
-			.body = "{\"client\": \"client1\", \"event\": \"end_backup\"}",
-			.size = strlen(req_body.body),
+			.body = req_buf,
+			.size = strlen(req_buf),
 		};
 		curlRes = curl_easy_setopt(curl, CURLOPT_READDATA, &req_body);
 		assert(curlRes == CURLE_OK);
@@ -223,5 +235,41 @@ int main(int argc, char **argv) {
 		body = (struct memory){0};
 	}
 
+	// Test: wrong secret should return 401
+	{
+		curlRes = curl_easy_setopt(curl, CURLOPT_URL, "http://localhost:8080/api/report");
+		assert(curlRes == CURLE_OK);
+
+		curlRes = curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
+		assert(curlRes == CURLE_OK);
+
+		curlRes = curl_easy_setopt(curl, CURLOPT_POST, 1L);
+		assert(curlRes == CURLE_OK);
+
+		curlRes = curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_from_memory);
+		assert(curlRes == CURLE_OK);
+
+		struct memory req_body = {
+			.body = "{\"client\": \"client1\", \"secret\": \"wrongsecret\", \"event\": \"begin_backup\"}",
+			.size = strlen("{\"client\": \"client1\", \"secret\": \"wrongsecret\", \"event\": \"begin_backup\"}"),
+		};
+		curlRes = curl_easy_setopt(curl, CURLOPT_READDATA, &req_body);
+		assert(curlRes == CURLE_OK);
+
+		curlRes = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_to_memory);
+		assert(curlRes == CURLE_OK);
+
+		struct memory body = {0};
+		curlRes = curl_easy_setopt(curl, CURLOPT_WRITEDATA, &body);
+		assert(curlRes == CURLE_OK);
+
+		curlRes = curl_easy_perform(curl);
+		assert(curlRes == CURLE_OK);
+
+		long code;
+		curlRes = curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &code);
+		assert(code == 401);  // Unauthorized
+	}
+
 	web_join(&server);
 }
author	Jesper Jensen <jesper@jnsn.dev>	2026-02-18 18:34:02 +0100
committer	Jesper Jensen <jesper@jnsn.dev>	2026-02-18 18:34:02 +0100
commit	5fbbd990d6b42f5e7534cdb68fa5c368a4a69169 (patch)
tree	3db3b955fcceb71fbb8ea161643a3a1044b2e4f2
parent	78745e06f4a4365e9caa8ee12fb0d9e15fb59300 (diff)