fix(skills): refuse a partial skill body on dashboard read

src/core/skill.c

@@ -325,15 +325,39 @@ int skill_list_names(const config_t *cfg, char **names_out, int max_count)
 
 int skill_get_content(const config_t *cfg, const char *name, char *out_buf, size_t out_size)
 {
-	if (!cfg || !name || !out_buf || out_size == 0) return -1;
 	char path[MAX_PATH_LEN];
-	if (build_skill_path(cfg, name, path, sizeof(path)) != 0) return -1;
-	FILE *f = fopen(path, "r");
-	if (!f) return -1;
+	FILE *f;
+	long sz;
+	size_t used;
+
+	if (!cfg || !name || !out_buf || out_size == 0)
+		return -1;
+	if (build_skill_path(cfg, name, path, sizeof(path)) != 0)
+		return -1;
+	f = fopen(path, "r");
+	if (!f)
+		return -1;
+	if (fseek(f, 0, SEEK_END) != 0) {
+		fclose(f);
+		return -1;
+	}
+	sz = ftell(f);
+	/* Dashboard GET copies this buffer into the editor and PUT writes it
+	 * back. A short read must not look like the whole file. */
+	if (sz < 0 || (size_t)sz >= out_size) {
+		fclose(f);
+		return (sz < 0) ? -1 : -2;
+	}
+	if (fseek(f, 0, SEEK_SET) != 0) {
+		fclose(f);
+		return -1;
+	}
 	out_buf[0] = '\0';
-	size_t used = 0;
+	used = 0;
 	append_file_content(f, out_buf, out_size, &used);
 	fclose(f);
+	if (used != (size_t)sz)
+		return -2;
 	return 0;
 }
 

src/core/skill.h

@@ -63,8 +63,11 @@ int skill_list_names(const config_t *cfg, char **names_out, int max_count);
  * @param cfg             Configuration (uses config_skills_dir).
  * @param name            Skill name (file base name).
  * @param out_buf         Buffer to receive content.
- * @param out_size        Size of out_buf.
- * @return 0 on success, -1 if not found or error.
+ * @param out_size        Size of out_buf. Must hold the whole file plus a NUL.
+ * @return 0 on success, -2 if the file does not fit in out_buf, -1 if not found or error.
+ *
+ * Example: skill_get_content(cfg, "deploy", buf, sizeof(buf)) == -2 means the
+ * caller must not treat buf as the skill body.
  */
 int skill_get_content(const config_t *cfg, const char *name, char *out_buf, size_t out_size);
 

src/gateway/routes.c

@@ -377,28 +377,76 @@ static void handle_skills_list(const config_t *cfg, char *buf, size_t size, int
 #define SKILL_CONTENT_MAX 32768
 #define MEMORY_RESULTS_MAX 16384
 
-static void handle_skill_get(const config_t *cfg, const char *name, char *buf, size_t size, int *status)
+static void skill_too_large(char *buf, size_t size, int *status, const char *name,
+                           const char *limit_desc)
 {
-	char *content = malloc(SKILL_CONTENT_MAX);
-	if (!content) { json_error(buf, size, status, 500, "Out of memory"); return; }
-	if (skill_get_content(cfg, name, content, SKILL_CONTENT_MAX) != 0) {
-		free(content);
-		json_error(buf, size, status, 404, "Skill not found");
+	char msg[256];
+	int n;
+
+	n = snprintf(msg, sizeof(msg), "skill \"%s\" exceeds %s",
+	             name ? name : "", limit_desc ? limit_desc : "edit buffer");
+	if (n < 0 || (size_t)n >= sizeof(msg))
+		json_error(buf, size, status, 413, "skill exceeds edit buffer");
+	else
+		json_error(buf, size, status, 413, msg);
+}
+
+static void skill_get_send(const char *name, const char *content, char *buf, size_t size,
+                          int *status)
+{
+	cJSON *obj;
+	char *printed;
+	char limit_desc[64];
+
+	obj = cJSON_CreateObject();
+	if (!obj) {
+		json_error(buf, size, status, 500, "Internal error");
 		return;
 	}
-	cJSON *obj = cJSON_CreateObject();
-	if (!obj) { free(content); json_error(buf, size, status, 500, "Internal error"); return; }
 	cJSON_AddItemToObject(obj, "name", cJSON_CreateString(name));
 	cJSON_AddItemToObject(obj, "content", cJSON_CreateString(content));
-	free(content);
-	char *s = cJSON_PrintUnformatted(obj);
+	printed = cJSON_PrintUnformatted(obj);
 	cJSON_Delete(obj);
-	if (s) {
-		json_response(buf, size, status, s);
-		free(s);
-	} else {
+	if (!printed) {
 		json_error(buf, size, status, 500, "Internal error");
+		return;
+	}
+	/* A cut-off 200 body parses as empty in the dashboard and Save wipes the file. */
+	if (strlen(printed) >= size) {
+		free(printed);
+		snprintf(limit_desc, sizeof(limit_desc), "%zu byte response buffer", size);
+		skill_too_large(buf, size, status, name, limit_desc);
+		return;
+	}
+	json_response(buf, size, status, printed);
+	free(printed);
+}
+
+static void handle_skill_get(const config_t *cfg, const char *name, char *buf, size_t size, int *status)
+{
+	char *content;
+	char limit_desc[64];
+	int rc;
+
+	content = malloc(SKILL_CONTENT_MAX);
+	if (!content) {
+		json_error(buf, size, status, 500, "Out of memory");
+		return;
+	}
+	rc = skill_get_content(cfg, name, content, SKILL_CONTENT_MAX);
+	if (rc != 0) {
+		free(content);
+		if (rc == -2) {
+			snprintf(limit_desc, sizeof(limit_desc), "%d byte edit buffer",
+			         SKILL_CONTENT_MAX - 1);
+			skill_too_large(buf, size, status, name, limit_desc);
+		} else {
+			json_error(buf, size, status, 404, "Skill not found");
+		}
+		return;
 	}
+	skill_get_send(name, content, buf, size, status);
+	free(content);
 }
 
 static void handle_skill_create(const config_t *cfg, const char *body, size_t body_len,

tests/test_gateway_http.c

@@ -1179,13 +1179,79 @@ static int test_api_skill_create_delete(const char *token)
 	ASSERT(code == 200 || code == 201);
 	free(body);
 	body = NULL;
+	r = http_get_auth(gw_url("/api/skills/test_integration_skill"), token, &code, &body);
+	ASSERT(r == 0);
+	ASSERT(code == 200);
+	ASSERT(body != NULL);
+	ASSERT(strstr(body, "Test skill for integration") != NULL);
+	free(body);
+	body = NULL;
 	r = http_delete_auth(gw_url("/api/skills/test_integration_skill"), token, &code, &body);
 	ASSERT(r == 0);
 	ASSERT(code == 200);
 	free(body);
 	return 0;
 }
 
+/* A skill larger than the edit buffer must not come back as HTTP 200.
+ * The dashboard saves whatever GET returned, which used to drop the tail. */
+static int test_api_skill_get_refuses_oversize(const char *token)
+{
+	enum { BODY_N = 40000 };
+	const char *tail = "SKILL_TAIL_KEEP";
+	char *content;
+	char *json;
+	char path[256];
+	char disk[32];
+	long code;
+	char *body = NULL;
+	FILE *f;
+	size_t tail_len;
+	size_t json_cap;
+	int n;
+	int r;
+
+	tail_len = strlen(tail);
+	content = malloc((size_t)BODY_N + 1);
+	ASSERT(content != NULL);
+	memset(content, 'B', (size_t)BODY_N);
+	memcpy(content + (size_t)BODY_N - tail_len, tail, tail_len);
+	content[BODY_N] = '\0';
+	json_cap = (size_t)BODY_N + 64;
+	json = malloc(json_cap);
+	ASSERT(json != NULL);
+	n = snprintf(json, json_cap, "{\"name\":\"big_skill\",\"content\":\"%s\"}", content);
+	ASSERT(n > 0 && (size_t)n < json_cap);
+	r = http_post_auth(gw_url("/api/skills"), token, json, &code, &body);
+	ASSERT(r == 0);
+	ASSERT(code == 200 || code == 201);
+	free(body);
+	body = NULL;
+	r = http_get_auth(gw_url("/api/skills/big_skill"), token, &code, &body);
+	ASSERT(r == 0);
+	ASSERT(code == 413);
+	ASSERT(body != NULL);
+	ASSERT(strstr(body, "big_skill") != NULL);
+	ASSERT(strstr(body, "exceeds") != NULL);
+	free(body);
+	snprintf(path, sizeof(path), "%s/.shellclaw/skills/big_skill.md", g_test_home);
+	f = fopen(path, "r");
+	ASSERT(f != NULL);
+	ASSERT(fseek(f, -((long)tail_len), SEEK_END) == 0);
+	ASSERT(fread(disk, 1, tail_len, f) == tail_len);
+	disk[tail_len] = '\0';
+	fclose(f);
+	ASSERT(strcmp(disk, tail) == 0);
+	free(content);
+	free(json);
+	body = NULL;
+	r = http_delete_auth(gw_url("/api/skills/big_skill"), token, &code, &body);
+	ASSERT(r == 0);
+	ASSERT(code == 200);
+	free(body);
+	return 0;
+}
+
 static int test_api_memory(const char *token)
 {
 	long code;
@@ -1728,6 +1794,10 @@ int main(int argc, char **argv)
 		if (test_api_context_snapshot_get(token) != 0) { fprintf(stderr, "test_api_context_snapshot_get failed\n"); failed++; }
 		if (test_api_skills_list(token) != 0) { fprintf(stderr, "test_api_skills_list failed\n"); failed++; }
 		if (test_api_skill_create_delete(token) != 0) { fprintf(stderr, "test_api_skill_create_delete failed\n"); failed++; }
+		if (test_api_skill_get_refuses_oversize(token) != 0) {
+			fprintf(stderr, "test_api_skill_get_refuses_oversize failed\n");
+			failed++;
+		}
 		if (test_api_memory(token) != 0) { fprintf(stderr, "test_api_memory failed\n"); failed++; }
 		if (test_api_cron_list(token) != 0) { fprintf(stderr, "test_api_cron_list failed\n"); failed++; }
 		if (test_api_cron_create_delete(token) != 0) { fprintf(stderr, "test_api_cron_create_delete failed\n"); failed++; }

tests/test_skill.c

@@ -249,6 +249,45 @@ static int test_skill_update_write_failure_preserves_existing(void)
 	return 0;
 }
 
+/*
+ * Dashboard GET /api/skills/:name loads this buffer into a textarea and PUT
+ * saves it back. A short buffer must not succeed with a prefix, or Save
+ * deletes the rest of the skill file.
+ */
+static int test_skill_get_content_refuses_short_buffer(void)
+{
+	char cmd[256];
+	char small[32];
+	char exact[64];
+	char full[128];
+	const char *body = "HEAD_MARKER_skill_body_TAIL_MARKER_must_survive";
+	size_t body_len;
+	config_t *cfg = NULL;
+	char errbuf[256];
+
+	snprintf(cmd, sizeof(cmd), "rm -rf \"%s\" && mkdir -p \"%s\"", TMP_DIR, TMP_DIR);
+	ASSERT(system(cmd) == 0);
+	ASSERT(write_minimal_config(TMP_DIR) == 0);
+	ASSERT(config_load(TMP_CONFIG, &cfg, errbuf, sizeof(errbuf)) == 0);
+	ASSERT(skill_create(cfg, "longskill", body) == 0);
+	body_len = strlen(body);
+	ASSERT(body_len + 1 <= sizeof(exact));
+
+	memset(small, 'X', sizeof(small));
+	ASSERT(skill_get_content(cfg, "longskill", small, sizeof(small)) == -2);
+	ASSERT(skill_get_content(cfg, "longskill", exact, body_len) == -2);
+	ASSERT(skill_get_content(cfg, "longskill", exact, body_len + 1) == 0);
+	ASSERT(strcmp(exact, body) == 0);
+	ASSERT(skill_get_content(cfg, "longskill", full, sizeof(full)) == 0);
+	ASSERT(strstr(full, "TAIL_MARKER_must_survive") != NULL);
+
+	config_free(cfg);
+	remove(TMP_CONFIG);
+	snprintf(cmd, sizeof(cmd), "rm -rf \"%s\"", TMP_DIR);
+	(void)system(cmd);
+	return 0;
+}
+
 static int test_hot_reload_watch(void)
 {
 	char cmd[256];
@@ -287,6 +326,7 @@ int main(void)
 	RUN(test_system_prompt_base_order());
 	RUN(test_skill_crud());
 	RUN(test_skill_update_write_failure_preserves_existing());
+	RUN(test_skill_get_content_refuses_short_buffer());
 	RUN(test_hot_reload_watch());
 	printf("test_skill: all tests passed\n");
 	return 0;