API docs

docs/backend_api/becca_entities_abstract_becca_entity.js.html

@@ -35,6 +35,8 @@ const eventService = require("../../services/events");
 const dateUtils = require("../../services/date_utils");
 const cls = require("../../services/cls");
 const log = require("../../services/log");
+const protectedSessionService = require("../../services/protected_session");
+const blobService = require("../../services/blob");
 
 let becca = null;
 
@@ -146,10 +148,140 @@ class AbstractBeccaEntity {
         return this;
     }
 
+    /** @protected */
+    _setContent(content, opts = {}) {
+        // client code asks to save entity even if blobId didn't change (something else was changed)
+        opts.forceSave = !!opts.forceSave;
+        opts.forceFrontendReload = !!opts.forceFrontendReload;
+
+        if (content === null || content === undefined) {
+            throw new Error(`Cannot set null content to ${this.constructor.primaryKeyName} '${this[this.constructor.primaryKeyName]}'`);
+        }
+
+        if (this.hasStringContent()) {
+            content = content.toString();
+        }
+        else {
+            content = Buffer.isBuffer(content) ? content : Buffer.from(content);
+        }
+
+        const unencryptedContentForHashCalculation = this.#getUnencryptedContentForHashCalculation(content);
+
+        if (this.isProtected) {
+            if (protectedSessionService.isProtectedSessionAvailable()) {
+                content = protectedSessionService.encrypt(content);
+            } else {
+                throw new Error(`Cannot update content of blob since protected session is not available.`);
+            }
+        }
+
+        sql.transactional(() => {
+            const newBlobId = this.#saveBlob(content, unencryptedContentForHashCalculation, opts);
+            const oldBlobId = this.blobId;
+
+            if (newBlobId !== oldBlobId || opts.forceSave) {
+                this.blobId = newBlobId;
+                this.save();
+
+                if (newBlobId !== oldBlobId) {
+                    this.#deleteBlobIfNoteUsed(oldBlobId);
+                }
+            }
+        });
+    }
+
+    #deleteBlobIfNoteUsed(blobId) {
+        if (sql.getValue("SELECT 1 FROM notes WHERE blobId = ? LIMIT 1", [blobId])) {
+            return;
+        }
+
+        if (sql.getValue("SELECT 1 FROM attachments WHERE blobId = ? LIMIT 1", [blobId])) {
+            return;
+        }
+
+        if (sql.getValue("SELECT 1 FROM revisions WHERE blobId = ? LIMIT 1", [blobId])) {
+            return;
+        }
+
+        sql.execute("DELETE FROM blobs WHERE blobId = ?", [blobId]);
+        sql.execute("DELETE FROM entity_changes WHERE entityName = 'blobs' AND entityId = ?", [blobId]);
+    }
+
+    #getUnencryptedContentForHashCalculation(unencryptedContent) {
+        if (this.isProtected) {
+            // a "random" prefix make sure that the calculated hash/blobId is different for an encrypted note and decrypted
+            const encryptedPrefixSuffix = "t$[nvQg7q)&_ENCRYPTED_?M:Bf&j3jr_";
+            return Buffer.isBuffer(unencryptedContent)
+                ? Buffer.concat([Buffer.from(encryptedPrefixSuffix), unencryptedContent])
+                : `${encryptedPrefixSuffix}${unencryptedContent}`;
+        } else {
+            return unencryptedContent;
+        }
+    }
+
+    #saveBlob(content, unencryptedContentForHashCalculation, opts = {}) {
+        /*
+         * We're using the unencrypted blob for the hash calculation, because otherwise the random IV would
+         * cause every content blob to be unique which would balloon the database size (esp. with revisioning).
+         * This has minor security implications (it's easy to infer that given content is shared between different
+         * notes/attachments, but the trade-off comes out clearly positive).
+         */
+        const newBlobId = utils.hashedBlobId(unencryptedContentForHashCalculation);
+        const blobNeedsInsert = !sql.getValue('SELECT 1 FROM blobs WHERE blobId = ?', [newBlobId]);
+
+        if (!blobNeedsInsert) {
+            return newBlobId;
+        }
+
+        const pojo = {
+            blobId: newBlobId,
+            content: content,
+            dateModified: dateUtils.localNowDateTime(),
+            utcDateModified: dateUtils.utcNowDateTime()
+        };
+
+        sql.upsert("blobs", "blobId", pojo);
+
+        const hash = utils.hash(`${newBlobId}|${pojo.content.toString()}`);
+
+        entityChangesService.addEntityChange({
+            entityName: 'blobs',
+            entityId: newBlobId,
+            hash: hash,
+            isErased: false,
+            utcDateChanged: pojo.utcDateModified,
+            isSynced: true,
+            // overriding componentId will cause frontend to think the change is coming from a different component
+            // and thus reload
+            componentId: opts.forceFrontendReload ? utils.randomString(10) : null
+        });
+
+        eventService.emit(eventService.ENTITY_CHANGED, {
+            entityName: 'blobs',
+            entity: this
+        });
+
+        return newBlobId;
+    }
+
+    /**
+     * @protected
+     * @returns {string|Buffer}
+     */
+    _getContent() {
+        const row = sql.getRow(`SELECT content FROM blobs WHERE blobId = ?`, [this.blobId]);
+
+        if (!row) {
+            throw new Error(`Cannot find content for ${this.constructor.primaryKeyName} '${this[this.constructor.primaryKeyName]}', blobId '${this.blobId}'`);
+        }
+
+        return blobService.processContent(row.content, this.isProtected, this.hasStringContent());
+    }
+
     /**
      * Mark the entity as (soft) deleted. It will be completely erased later.
      *
-     * This is a low level method, for notes and branches use `note.deleteNote()` and 'branch.deleteBranch()` instead.
+     * This is a low-level method, for notes and branches use `note.deleteNote()` and 'branch.deleteBranch()` instead.
      *
      * @param [deleteId=null]
      */
@@ -206,7 +338,7 @@ module.exports = AbstractBeccaEntity;
 </div>
 
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