diff --git a/doc/userguide/rules/smtp-keywords.rst b/doc/userguide/rules/smtp-keywords.rst index 227a3a25fa30..906af58220e8 100644 --- a/doc/userguide/rules/smtp-keywords.rst +++ b/doc/userguide/rules/smtp-keywords.rst @@ -18,6 +18,67 @@ Signature Example: For additional information on the ``file.name`` keyword, see :doc:`file-keywords`. + +smtp.helo +--------- + +SMTP helo is the parameter passed to the first HELO command from the client. + +Syntax:: + + smtp.helo; content:"localhost"; + +Signature example:: + + alert smtp any any -> any any (msg:"SMTP helo localhost"; smtp.helo; content:"localhost"; sid:2; rev:1;) + +``smtp.helo`` is a 'sticky buffer'. + +``smtp.helo`` can be used as ``fast_pattern``. + +This keyword maps to the eve.json log field ``smtp.helo`` + +smtp.mail_from +-------------- + +SMTP mail from is the parameter passed to the first MAIL FROM command from the client. + +Syntax:: + + smtp.mail_from; content:"spam"; + +Signature example:: + + alert smtp any any -> any any (msg:"SMTP mail from spam"; smtp.mail_from; content:"spam"; sid:2; rev:1;) + +``smtp.mail_from`` is a 'sticky buffer'. + +``smtp.mail_from`` can be used as ``fast_pattern``. + +This keyword maps to the eve.json log field ``smtp.mail_from`` + +smtp.rcpt_to +------------ + +SMTP rcpt to is the one of the parameters passed to one RCPT TO command from the client. + +Syntax:: + + smtp.rcpt_to; content:"sensitive@target"; + +Signature example:: + + alert smtp any any -> any any (msg:"SMTP rcpt to sensitive"; smtp.rcpt_to; content:"sensitive@target"; sid:2; rev:1;) + +``smtp.rcpt_to`` is a 'sticky buffer'. + +``smtp.rcpt_to`` is a 'multi buffer'. + +``smtp.rcpt_to`` can be used as ``fast_pattern``. + +This keyword maps to the eve.json log field ``smtp.rcpt_to[]`` + + Frames ------ diff --git a/src/Makefile.am b/src/Makefile.am index 615816953542..b1576c5e9e3b 100755 --- a/src/Makefile.am +++ b/src/Makefile.am @@ -266,6 +266,7 @@ noinst_HEADERS = \ detect-smb-ntlmssp.h \ detect-smb-share.h \ detect-smb-version.h \ + detect-smtp.h \ detect-ssh-hassh.h \ detect-ssh-hassh-server.h \ detect-ssh-hassh-server-string.h \ @@ -831,6 +832,7 @@ libsuricata_c_a_SOURCES = \ detect-smb-ntlmssp.c \ detect-smb-share.c \ detect-smb-version.c \ + detect-smtp.c \ detect-ssh-hassh.c \ detect-ssh-hassh-server.c \ detect-ssh-hassh-server-string.c \ diff --git a/src/detect-engine-register.c b/src/detect-engine-register.c index 9bf86f64b753..75e782ee5b06 100644 --- a/src/detect-engine-register.c +++ b/src/detect-engine-register.c @@ -85,6 +85,7 @@ #include "detect-smb-share.h" #include "detect-smb-version.h" +#include "detect-smtp.h" #include "detect-base64-decode.h" #include "detect-base64-data.h" @@ -730,6 +731,7 @@ void SigTableSetup(void) DetectVlanIdRegister(); DetectVlanLayersRegister(); + SCDetectSMTPRegister(); ScDetectSNMPRegister(); SCDetectDHCPRegister(); ScDetectWebsocketRegister(); diff --git a/src/detect-smtp.c b/src/detect-smtp.c new file mode 100644 index 000000000000..0c3e46150d50 --- /dev/null +++ b/src/detect-smtp.c @@ -0,0 +1,172 @@ +/* Copyright (C) 2025 Open Information Security Foundation + * + * You can copy, redistribute or modify this Program under the terms of + * the GNU General Public License version 2 as published by the Free + * Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * version 2 along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ + +/** + * \file + * + * \author Philippe Antoine + * + */ + +#include "suricata-common.h" +#include "detect-smtp.h" +#include "detect-engine.h" +#include "detect-engine-content-inspection.h" +#include "detect-engine-helper.h" +#include "detect-parse.h" +#include "app-layer-smtp.h" +#include "rust.h" + +static int g_smtp_helo_buffer_id = 0; +static int g_smtp_mail_from_buffer_id = 0; +static int g_smtp_rcpt_to_buffer_id = 0; + +static int DetectSmtpHeloSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg) +{ + if (DetectBufferSetActiveList(de_ctx, s, g_smtp_helo_buffer_id) < 0) + return -1; + + if (DetectSignatureSetAppProto(s, ALPROTO_SMTP) < 0) + return -1; + + return 0; +} + +static InspectionBuffer *GetSmtpHeloData(DetectEngineThreadCtx *det_ctx, + const DetectEngineTransforms *transforms, Flow *f, const uint8_t _flow_flags, void *txv, + const int list_id) +{ + InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id); + if (buffer->inspect == NULL) { + SMTPState *smtp_state = (SMTPState *)FlowGetAppState(f); + if (smtp_state) { + if (smtp_state->helo == NULL || smtp_state->helo_len == 0) + return NULL; + InspectionBufferSetup(det_ctx, list_id, buffer, smtp_state->helo, smtp_state->helo_len); + InspectionBufferApplyTransforms(buffer, transforms); + } + } + return buffer; +} + +static int DetectSmtpMailFromSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg) +{ + if (DetectBufferSetActiveList(de_ctx, s, g_smtp_mail_from_buffer_id) < 0) + return -1; + + if (DetectSignatureSetAppProto(s, ALPROTO_SMTP) < 0) + return -1; + + return 0; +} + +static InspectionBuffer *GetSmtpMailFromData(DetectEngineThreadCtx *det_ctx, + const DetectEngineTransforms *transforms, Flow *f, const uint8_t _flow_flags, void *txv, + const int list_id) +{ + InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id); + if (buffer->inspect == NULL) { + SMTPTransaction *tx = (SMTPTransaction *)txv; + if (tx->mail_from == NULL || tx->mail_from_len == 0) + return NULL; + InspectionBufferSetup(det_ctx, list_id, buffer, tx->mail_from, tx->mail_from_len); + InspectionBufferApplyTransforms(buffer, transforms); + } + return buffer; +} + +static int DetectSmtpRcptToSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg) +{ + if (DetectBufferSetActiveList(de_ctx, s, g_smtp_rcpt_to_buffer_id) < 0) + return -1; + + if (DetectSignatureSetAppProto(s, ALPROTO_SMTP) < 0) + return -1; + + return 0; +} + +static InspectionBuffer *GetSmtpRcptToData(DetectEngineThreadCtx *det_ctx, + const DetectEngineTransforms *transforms, Flow *f, const uint8_t _flow_flags, void *txv, + const int list_id, uint32_t idx) +{ + InspectionBuffer *buffer = InspectionBufferMultipleForListGet(det_ctx, list_id, idx); + if (buffer == NULL || buffer->initialized) + return buffer; + + SMTPTransaction *tx = (SMTPTransaction *)txv; + if (TAILQ_EMPTY(&tx->rcpt_to_list)) { + InspectionBufferSetupMultiEmpty(buffer); + return NULL; + } + + SMTPString *s; + if (idx == 0) { + s = TAILQ_FIRST(&tx->rcpt_to_list); + } else { + // TODO optimize ? + s = TAILQ_FIRST(&tx->rcpt_to_list); + for (uint32_t i = 0; i < idx; i++) { + s = TAILQ_NEXT(s, next); + } + } + if (s == NULL) { + InspectionBufferSetupMultiEmpty(buffer); + return NULL; + } + + InspectionBufferSetupMulti(buffer, transforms, s->str, s->len); + buffer->flags = DETECT_CI_FLAGS_SINGLE; + return buffer; +} + +void SCDetectSMTPRegister(void) +{ + SCSigTableElmt kw = { 0 }; + kw.name = "smtp.helo"; + kw.desc = "SMTP helo buffer"; + kw.url = "/rules/smtp-keywords.html#smtp-helo"; + kw.Setup = (int (*)(void *, void *, const char *))DetectSmtpHeloSetup; + kw.flags = SIGMATCH_NOOPT | SIGMATCH_INFO_STICKY_BUFFER; + DetectHelperKeywordRegister(&kw); + g_smtp_helo_buffer_id = + DetectHelperBufferMpmRegister("smtp.helo", "SMTP helo", ALPROTO_SMTP, false, + true, // to server + GetSmtpHeloData); + + kw.name = "smtp.mail_from"; + kw.desc = "SMTP mail from buffer"; + kw.url = "/rules/smtp-keywords.html#smtp-mail-from"; + kw.Setup = (int (*)(void *, void *, const char *))DetectSmtpMailFromSetup; + kw.flags = SIGMATCH_NOOPT | SIGMATCH_INFO_STICKY_BUFFER; + DetectHelperKeywordRegister(&kw); + g_smtp_mail_from_buffer_id = + DetectHelperBufferMpmRegister("smtp.mail_from", "SMTP MAIL FROM", ALPROTO_SMTP, false, + true, // to server + GetSmtpMailFromData); + + kw.name = "smtp.rcpt_to"; + kw.desc = "SMTP rcpt to buffer"; + kw.url = "/rules/smtp-keywords.html#smtp-rcpt-to"; + kw.Setup = (int (*)(void *, void *, const char *))DetectSmtpRcptToSetup; + kw.flags = SIGMATCH_NOOPT | SIGMATCH_INFO_STICKY_BUFFER; + DetectHelperKeywordRegister(&kw); + g_smtp_rcpt_to_buffer_id = + DetectHelperMultiBufferMpmRegister("smtp.rcpt_to", "SMTP RCPT TO", ALPROTO_SMTP, false, + true, // to server + GetSmtpRcptToData); +} diff --git a/src/detect-smtp.h b/src/detect-smtp.h new file mode 100644 index 000000000000..937b68d0adc1 --- /dev/null +++ b/src/detect-smtp.h @@ -0,0 +1,29 @@ +/* Copyright (C) 2025 Open Information Security Foundation + * + * You can copy, redistribute or modify this Program under the terms of + * the GNU General Public License version 2 as published by the Free + * Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * version 2 along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ + +/** + * \file + * + * \author Philippe Antoine + */ + +#ifndef SURICATA_DETECT_SMTP_H +#define SURICATA_DETECT_SMTP_H + +void SCDetectSMTPRegister(void); + +#endif /* SURICATA_DETECT_SMTP_H */