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Limit length of base64 encoding buffers #2447

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Limit length of base64 encoding buffers #2447

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c402339
tests: characterize extacl base64 stack buffer overflow
kinkie Jun 15, 2026
2125dc5
icap: fix extacl credential buffer overflow in makeRequestHeaders
kinkie Jun 17, 2026
3d1055f
http: fix extacl credential buffer overflows in httpFixupAuthentication
kinkie Jun 17, 2026
1c410dc
Merge remote-tracking branch 'upstream/master' into fix-base64encode
kinkie Jun 19, 2026
f6c053e
Apply aaa
kinkie Jun 20, 2026
ef95154
Remove test harness
kinkie Jun 20, 2026
d7fa149
Use TextException
kinkie Jun 20, 2026
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14 changes: 11 additions & 3 deletions src/adaptation/icap/ModXact.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1399,12 +1399,20 @@ void Adaptation::Icap::ModXact::makeRequestHeaders(MemBuf &buf)
String vh=virgin.header->header.getById(Http::HdrType::PROXY_AUTHORIZATION);
buf.appendf("Proxy-Authorization: " SQUIDSTRINGPH "\r\n", SQUIDSTRINGPRINT(vh));
} else if (request->extacl_user.size() > 0 && request->extacl_passwd.size() > 0) {
const auto userLen = request->extacl_user.size();
const auto passwdLen = request->extacl_passwd.size();
// +1 for the ':' separator between user and passwd
const auto plainLen = userLen + 1 + passwdLen;
if (plainLen > MAX_LOGIN_SZ)
throw TextException("extacl credentials too long for Proxy-Authorization", Here());
// plainLen <= MAX_LOGIN_SZ, so base64_encode_len(plainLen) fits
// within the base64_encode_len(MAX_LOGIN_SZ) stack buffer.
char base64buf[base64_encode_len(MAX_LOGIN_SZ)];
Comment on lines +1406 to +1410

@yadij yadij Jun 22, 2026 •
edited
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Suggested change
if (plainLen > MAX_LOGIN_SZ)
throw TextException("extacl credentials too long for Proxy-Authorization", Here());
// plainLen <= MAX_LOGIN_SZ, so base64_encode_len(plainLen) fits
// within the base64_encode_len(MAX_LOGIN_SZ) stack buffer.
char base64buf[base64_encode_len(MAX_LOGIN_SZ)];
SBuf encoded; // TODO: when 'buf' is an SBuf we can write directly to it.
auto base64buf = encoded.rawAppendStart(base64_encode_len(plainLen));

struct base64_encode_ctx ctx;
base64_encode_init(&ctx);
char base64buf[base64_encode_len(MAX_LOGIN_SZ)];
size_t resultLen = base64_encode_update(&ctx, base64buf, request->extacl_user.size(), reinterpret_cast<const uint8_t*>(request->extacl_user.rawBuf()));
auto resultLen = base64_encode_update(&ctx, base64buf, userLen, reinterpret_cast<const uint8_t*>(request->extacl_user.rawBuf()));
resultLen += base64_encode_update(&ctx, base64buf+resultLen, 1, reinterpret_cast<const uint8_t*>(":"));
resultLen += base64_encode_update(&ctx, base64buf+resultLen, request->extacl_passwd.size(), reinterpret_cast<const uint8_t*>(request->extacl_passwd.rawBuf()));
resultLen += base64_encode_update(&ctx, base64buf+resultLen, passwdLen, reinterpret_cast<const uint8_t*>(request->extacl_passwd.rawBuf()));
resultLen += base64_encode_final(&ctx, base64buf+resultLen);
buf.appendf("Proxy-Authorization: Basic %.*s\r\n", (int)resultLen, base64buf);

@yadij yadij Jun 22, 2026

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Suggested change
buf.appendf("Proxy-Authorization: Basic %.*s\r\n", (int)resultLen, base64buf);
encoded.rawAppendFinish(base64buf, resultLen);
buf.appendf("Proxy-Authorization: Basic " SQUIDSBUFPH "\r\n", SQUIDSBUFPRINT(encoded));

}
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22 changes: 17 additions & 5 deletions src/http.cc
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Expand Up @@ -1850,8 +1850,12 @@ httpFixupAuthentication(HttpRequest * request, const HttpHeader * hdr_in, HttpHe
username = request->auth_user_request->username();
#endif

blen = base64_encode_update(&ctx, loginbuf, strlen(username), reinterpret_cast<const uint8_t*>(username));
blen += base64_encode_update(&ctx, loginbuf+blen, strlen(request->peer_login +1), reinterpret_cast<const uint8_t*>(request->peer_login +1));
const auto usernameLen = strlen(username);
const auto suffixLen = strlen(request->peer_login + 1);
if (usernameLen + suffixLen > MAX_LOGIN_SZ)
throw TextException("peer login credentials too long", Here());
blen = base64_encode_update(&ctx, loginbuf, usernameLen, reinterpret_cast<const uint8_t*>(username));
blen += base64_encode_update(&ctx, loginbuf+blen, suffixLen, reinterpret_cast<const uint8_t*>(request->peer_login +1));
blen += base64_encode_final(&ctx, loginbuf+blen);
httpHeaderPutStrf(hdr_out, header, "Basic %.*s", (int)blen, loginbuf);
return;
Expand All @@ -1862,9 +1866,14 @@ httpFixupAuthentication(HttpRequest * request, const HttpHeader * hdr_in, HttpHe
(strcmp(request->peer_login, "PASS") == 0 ||
strcmp(request->peer_login, "PROXYPASS") == 0)) {

blen = base64_encode_update(&ctx, loginbuf, request->extacl_user.size(), reinterpret_cast<const uint8_t*>(request->extacl_user.rawBuf()));
const auto userLen = request->extacl_user.size();
const auto passwdLen = request->extacl_passwd.size();
// +1 for the ':' separator between user and passwd
if (userLen + 1 + passwdLen > MAX_LOGIN_SZ)
throw TextException("extacl credentials too long for peer login", Here());
blen = base64_encode_update(&ctx, loginbuf, userLen, reinterpret_cast<const uint8_t*>(request->extacl_user.rawBuf()));
blen += base64_encode_update(&ctx, loginbuf+blen, 1, reinterpret_cast<const uint8_t*>(":"));
blen += base64_encode_update(&ctx, loginbuf+blen, request->extacl_passwd.size(), reinterpret_cast<const uint8_t*>(request->extacl_passwd.rawBuf()));
blen += base64_encode_update(&ctx, loginbuf+blen, passwdLen, reinterpret_cast<const uint8_t*>(request->extacl_passwd.rawBuf()));
blen += base64_encode_final(&ctx, loginbuf+blen);
httpHeaderPutStrf(hdr_out, header, "Basic %.*s", (int)blen, loginbuf);
return;
Expand Down Expand Up @@ -1894,7 +1903,10 @@ httpFixupAuthentication(HttpRequest * request, const HttpHeader * hdr_in, HttpHe
}
#endif /* HAVE_KRB5 && HAVE_GSSAPI */

blen = base64_encode_update(&ctx, loginbuf, strlen(request->peer_login), reinterpret_cast<const uint8_t*>(request->peer_login));
const auto loginLen = strlen(request->peer_login);
if (loginLen > MAX_LOGIN_SZ)
throw TextException("peer_login too long", Here());
blen = base64_encode_update(&ctx, loginbuf, loginLen, reinterpret_cast<const uint8_t*>(request->peer_login));
blen += base64_encode_final(&ctx, loginbuf+blen);
httpHeaderPutStrf(hdr_out, header, "Basic %.*s", (int)blen, loginbuf);

@rousskov rousskov Jun 20, 2026 •
edited
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Please add Assure(request->url.userInfo().length() < MAX_URL*2) or a similar assertion to HttpStateData::httpBuildRequestHeader().

Please also adjust SSP_MakeChallenge() and peer_proxy_negotiate_auth() cases.

return;
Expand Down
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