From: Steve French <smfrench@gmail.com>
To: Ronnie Sahlberg <lsahlber@redhat.com>
Cc: linux-cifs <linux-cifs@vger.kernel.org>
Subject: Re: [PATCH 1/2] cifs: remove support for NTLM and weaker authentication algorithms
Date: Fri, 20 Aug 2021 01:08:38 -0500 [thread overview]
Message-ID: <CAH2r5mv846_uZ9S+QZb4qYZ66W+Ffnb97UYm4zs=JOdh3P+qGA@mail.gmail.com> (raw)
In-Reply-To: <20210819103459.1291412-2-lsahlber@redhat.com>
tentatively merged into cifs-2.6.git for-next, along with followon
patch, pending additional review and testing
On Thu, Aug 19, 2021 at 5:35 AM Ronnie Sahlberg <lsahlber@redhat.com> wrote:
>
> for SMB1.
> This removes the dependency to DES.
>
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
> fs/cifs/Kconfig | 28 -----
> fs/cifs/cifs_debug.c | 11 --
> fs/cifs/cifs_swn.c | 2 -
> fs/cifs/cifsencrypt.c | 81 --------------
> fs/cifs/cifsfs.c | 6 -
> fs/cifs/cifsglob.h | 32 +-----
> fs/cifs/cifspdu.h | 28 -----
> fs/cifs/cifsproto.h | 10 --
> fs/cifs/cifssmb.c | 106 +-----------------
> fs/cifs/connect.c | 32 ------
> fs/cifs/fs_context.c | 14 ---
> fs/cifs/fs_context.h | 3 -
> fs/cifs/sess.c | 255 +-----------------------------------------
> fs/cifs/smbencrypt.c | 117 +------------------
> 14 files changed, 5 insertions(+), 720 deletions(-)
>
> diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
> index 7364950a9ef4..2e8b132efdbc 100644
> --- a/fs/cifs/Kconfig
> +++ b/fs/cifs/Kconfig
> @@ -16,7 +16,6 @@ config CIFS
> select CRYPTO_GCM
> select CRYPTO_ECB
> select CRYPTO_AES
> - select CRYPTO_LIB_DES
> select KEYS
> select DNS_RESOLVER
> select ASN1
> @@ -85,33 +84,6 @@ config CIFS_ALLOW_INSECURE_LEGACY
>
> If unsure, say Y.
>
> -config CIFS_WEAK_PW_HASH
> - bool "Support legacy servers which use weaker LANMAN security"
> - depends on CIFS && CIFS_ALLOW_INSECURE_LEGACY
> - help
> - Modern CIFS servers including Samba and most Windows versions
> - (since 1997) support stronger NTLM (and even NTLMv2 and Kerberos)
> - security mechanisms. These hash the password more securely
> - than the mechanisms used in the older LANMAN version of the
> - SMB protocol but LANMAN based authentication is needed to
> - establish sessions with some old SMB servers.
> -
> - Enabling this option allows the cifs module to mount to older
> - LANMAN based servers such as OS/2 and Windows 95, but such
> - mounts may be less secure than mounts using NTLM or more recent
> - security mechanisms if you are on a public network. Unless you
> - have a need to access old SMB servers (and are on a private
> - network) you probably want to say N. Even if this support
> - is enabled in the kernel build, LANMAN authentication will not be
> - used automatically. At runtime LANMAN mounts are disabled but
> - can be set to required (or optional) either in
> - /proc/fs/cifs (see Documentation/admin-guide/cifs/usage.rst for
> - more detail) or via an option on the mount command. This support
> - is disabled by default in order to reduce the possibility of a
> - downgrade attack.
> -
> - If unsure, say N.
> -
> config CIFS_UPCALL
> bool "Kerberos/SPNEGO advanced session setup"
> depends on CIFS
> diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
> index 8857ac7e7a14..51a824fc926a 100644
> --- a/fs/cifs/cifs_debug.c
> +++ b/fs/cifs/cifs_debug.c
> @@ -250,9 +250,6 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
> #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
> seq_printf(m, ",ALLOW_INSECURE_LEGACY");
> #endif
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> - seq_printf(m, ",WEAK_PW_HASH");
> -#endif
> #ifdef CONFIG_CIFS_POSIX
> seq_printf(m, ",CIFS_POSIX");
> #endif
> @@ -929,14 +926,6 @@ cifs_security_flags_handle_must_flags(unsigned int *flags)
> *flags = CIFSSEC_MUST_NTLMSSP;
> else if ((*flags & CIFSSEC_MUST_NTLMV2) == CIFSSEC_MUST_NTLMV2)
> *flags = CIFSSEC_MUST_NTLMV2;
> - else if ((*flags & CIFSSEC_MUST_NTLM) == CIFSSEC_MUST_NTLM)
> - *flags = CIFSSEC_MUST_NTLM;
> - else if (CIFSSEC_MUST_LANMAN &&
> - (*flags & CIFSSEC_MUST_LANMAN) == CIFSSEC_MUST_LANMAN)
> - *flags = CIFSSEC_MUST_LANMAN;
> - else if (CIFSSEC_MUST_PLNTXT &&
> - (*flags & CIFSSEC_MUST_PLNTXT) == CIFSSEC_MUST_PLNTXT)
> - *flags = CIFSSEC_MUST_PLNTXT;
>
> *flags |= signflags;
> }
> diff --git a/fs/cifs/cifs_swn.c b/fs/cifs/cifs_swn.c
> index 93b47818c6c2..12bde7bfda86 100644
> --- a/fs/cifs/cifs_swn.c
> +++ b/fs/cifs/cifs_swn.c
> @@ -147,8 +147,6 @@ static int cifs_swn_send_register_message(struct cifs_swn_reg *swnreg)
> goto nlmsg_fail;
> }
> break;
> - case LANMAN:
> - case NTLM:
> case NTLMv2:
> case RawNTLMSSP:
> ret = cifs_swn_auth_info_ntlm(swnreg->tcon, skb);
> diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
> index ecf15d845dbd..7680e0a9bea3 100644
> --- a/fs/cifs/cifsencrypt.c
> +++ b/fs/cifs/cifsencrypt.c
> @@ -250,87 +250,6 @@ int cifs_verify_signature(struct smb_rqst *rqst,
>
> }
>
> -/* first calculate 24 bytes ntlm response and then 16 byte session key */
> -int setup_ntlm_response(struct cifs_ses *ses, const struct nls_table *nls_cp)
> -{
> - int rc = 0;
> - unsigned int temp_len = CIFS_SESS_KEY_SIZE + CIFS_AUTH_RESP_SIZE;
> - char temp_key[CIFS_SESS_KEY_SIZE];
> -
> - if (!ses)
> - return -EINVAL;
> -
> - ses->auth_key.response = kmalloc(temp_len, GFP_KERNEL);
> - if (!ses->auth_key.response)
> - return -ENOMEM;
> -
> - ses->auth_key.len = temp_len;
> -
> - rc = SMBNTencrypt(ses->password, ses->server->cryptkey,
> - ses->auth_key.response + CIFS_SESS_KEY_SIZE, nls_cp);
> - if (rc) {
> - cifs_dbg(FYI, "%s Can't generate NTLM response, error: %d\n",
> - __func__, rc);
> - return rc;
> - }
> -
> - rc = E_md4hash(ses->password, temp_key, nls_cp);
> - if (rc) {
> - cifs_dbg(FYI, "%s Can't generate NT hash, error: %d\n",
> - __func__, rc);
> - return rc;
> - }
> -
> - rc = mdfour(ses->auth_key.response, temp_key, CIFS_SESS_KEY_SIZE);
> - if (rc)
> - cifs_dbg(FYI, "%s Can't generate NTLM session key, error: %d\n",
> - __func__, rc);
> -
> - return rc;
> -}
> -
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -int calc_lanman_hash(const char *password, const char *cryptkey, bool encrypt,
> - char *lnm_session_key)
> -{
> - int i, len;
> - int rc;
> - char password_with_pad[CIFS_ENCPWD_SIZE] = {0};
> -
> - if (password) {
> - for (len = 0; len < CIFS_ENCPWD_SIZE; len++)
> - if (!password[len])
> - break;
> -
> - memcpy(password_with_pad, password, len);
> - }
> -
> - if (!encrypt && global_secflags & CIFSSEC_MAY_PLNTXT) {
> - memcpy(lnm_session_key, password_with_pad,
> - CIFS_ENCPWD_SIZE);
> - return 0;
> - }
> -
> - /* calculate old style session key */
> - /* calling toupper is less broken than repeatedly
> - calling nls_toupper would be since that will never
> - work for UTF8, but neither handles multibyte code pages
> - but the only alternative would be converting to UCS-16 (Unicode)
> - (using a routine something like UniStrupr) then
> - uppercasing and then converting back from Unicode - which
> - would only worth doing it if we knew it were utf8. Basically
> - utf8 and other multibyte codepages each need their own strupper
> - function since a byte at a time will ont work. */
> -
> - for (i = 0; i < CIFS_ENCPWD_SIZE; i++)
> - password_with_pad[i] = toupper(password_with_pad[i]);
> -
> - rc = SMBencrypt(password_with_pad, cryptkey, lnm_session_key);
> -
> - return rc;
> -}
> -#endif /* CIFS_WEAK_PW_HASH */
> -
> /* Build a proper attribute value/target info pairs blob.
> * Fill in netbios and dns domain name and workstation name
> * and client time (total five av pairs and + one end of fields indicator.
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index 64b71c4e2a9d..85c884db909d 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -438,15 +438,9 @@ cifs_show_security(struct seq_file *s, struct cifs_ses *ses)
> seq_puts(s, ",sec=");
>
> switch (ses->sectype) {
> - case LANMAN:
> - seq_puts(s, "lanman");
> - break;
> case NTLMv2:
> seq_puts(s, "ntlmv2");
> break;
> - case NTLM:
> - seq_puts(s, "ntlm");
> - break;
> case Kerberos:
> seq_puts(s, "krb5");
> break;
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index de687a554545..0b821ccfe09f 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -114,8 +114,6 @@ enum statusEnum {
>
> enum securityEnum {
> Unspecified = 0, /* not specified */
> - LANMAN, /* Legacy LANMAN auth */
> - NTLM, /* Legacy NTLM012 auth with NTLM hash */
> NTLMv2, /* Legacy NTLM auth with NTLMv2 hash */
> RawNTLMSSP, /* NTLMSSP without SPNEGO, NTLMv2 hash */
> Kerberos, /* Kerberos via SPNEGO */
> @@ -634,7 +632,6 @@ struct TCP_Server_Info {
> struct session_key session_key;
> unsigned long lstrp; /* when we got last response from this server */
> struct cifs_secmech secmech; /* crypto sec mech functs, descriptors */
> -#define CIFS_NEGFLAVOR_LANMAN 0 /* wct == 13, LANMAN */
> #define CIFS_NEGFLAVOR_UNENCAP 1 /* wct == 17, but no ext_sec */
> #define CIFS_NEGFLAVOR_EXTENDED 2 /* wct == 17, ext_sec bit set */
> char negflavor; /* NEGOTIATE response flavor */
> @@ -1734,16 +1731,8 @@ static inline bool is_retryable_error(int error)
>
> /* Security Flags: indicate type of session setup needed */
> #define CIFSSEC_MAY_SIGN 0x00001
> -#define CIFSSEC_MAY_NTLM 0x00002
> #define CIFSSEC_MAY_NTLMV2 0x00004
> #define CIFSSEC_MAY_KRB5 0x00008
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -#define CIFSSEC_MAY_LANMAN 0x00010
> -#define CIFSSEC_MAY_PLNTXT 0x00020
> -#else
> -#define CIFSSEC_MAY_LANMAN 0
> -#define CIFSSEC_MAY_PLNTXT 0
> -#endif /* weak passwords */
> #define CIFSSEC_MAY_SEAL 0x00040 /* not supported yet */
> #define CIFSSEC_MAY_NTLMSSP 0x00080 /* raw ntlmssp with ntlmv2 */
>
> @@ -1751,32 +1740,19 @@ static inline bool is_retryable_error(int error)
> /* note that only one of the following can be set so the
> result of setting MUST flags more than once will be to
> require use of the stronger protocol */
> -#define CIFSSEC_MUST_NTLM 0x02002
> #define CIFSSEC_MUST_NTLMV2 0x04004
> #define CIFSSEC_MUST_KRB5 0x08008
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -#define CIFSSEC_MUST_LANMAN 0x10010
> -#define CIFSSEC_MUST_PLNTXT 0x20020
> -#ifdef CONFIG_CIFS_UPCALL
> -#define CIFSSEC_MASK 0xBF0BF /* allows weak security but also krb5 */
> -#else
> -#define CIFSSEC_MASK 0xB70B7 /* current flags supported if weak */
> -#endif /* UPCALL */
> -#else /* do not allow weak pw hash */
> -#define CIFSSEC_MUST_LANMAN 0
> -#define CIFSSEC_MUST_PLNTXT 0
> #ifdef CONFIG_CIFS_UPCALL
> #define CIFSSEC_MASK 0x8F08F /* flags supported if no weak allowed */
> #else
> #define CIFSSEC_MASK 0x87087 /* flags supported if no weak allowed */
> #endif /* UPCALL */
> -#endif /* WEAK_PW_HASH */
> #define CIFSSEC_MUST_SEAL 0x40040 /* not supported yet */
> #define CIFSSEC_MUST_NTLMSSP 0x80080 /* raw ntlmssp with ntlmv2 */
>
> #define CIFSSEC_DEF (CIFSSEC_MAY_SIGN | CIFSSEC_MAY_NTLMV2 | CIFSSEC_MAY_NTLMSSP)
> -#define CIFSSEC_MAX (CIFSSEC_MUST_SIGN | CIFSSEC_MUST_NTLMV2)
> -#define CIFSSEC_AUTH_MASK (CIFSSEC_MAY_NTLM | CIFSSEC_MAY_NTLMV2 | CIFSSEC_MAY_LANMAN | CIFSSEC_MAY_PLNTXT | CIFSSEC_MAY_KRB5 | CIFSSEC_MAY_NTLMSSP)
> +#define CIFSSEC_MAX (CIFSSEC_MUST_NTLMV2)
> +#define CIFSSEC_AUTH_MASK (CIFSSEC_MAY_NTLMV2 | CIFSSEC_MAY_KRB5 | CIFSSEC_MAY_NTLMSSP)
> /*
> *****************************************************************
> * All constants go here
> @@ -1940,10 +1916,6 @@ static inline char *get_security_type_str(enum securityEnum sectype)
> return "Kerberos";
> case NTLMv2:
> return "NTLMv2";
> - case NTLM:
> - return "NTLM";
> - case LANMAN:
> - return "LANMAN";
> default:
> return "Unknown";
> }
> diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
> index f6e235001358..dc920e206336 100644
> --- a/fs/cifs/cifspdu.h
> +++ b/fs/cifs/cifspdu.h
> @@ -14,13 +14,7 @@
> #include <asm/unaligned.h>
> #include "smbfsctl.h"
>
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -#define LANMAN_PROT 0
> -#define LANMAN2_PROT 1
> -#define CIFS_PROT 2
> -#else
> #define CIFS_PROT 0
> -#endif
> #define POSIX_PROT (CIFS_PROT+1)
> #define BAD_PROT 0xFFFF
>
> @@ -505,30 +499,8 @@ typedef struct negotiate_req {
> unsigned char DialectsArray[1];
> } __attribute__((packed)) NEGOTIATE_REQ;
>
> -/* Dialect index is 13 for LANMAN */
> -
> #define MIN_TZ_ADJ (15 * 60) /* minimum grid for timezones in seconds */
>
> -typedef struct lanman_neg_rsp {
> - struct smb_hdr hdr; /* wct = 13 */
> - __le16 DialectIndex;
> - __le16 SecurityMode;
> - __le16 MaxBufSize;
> - __le16 MaxMpxCount;
> - __le16 MaxNumberVcs;
> - __le16 RawMode;
> - __le32 SessionKey;
> - struct {
> - __le16 Time;
> - __le16 Date;
> - } __attribute__((packed)) SrvTime;
> - __le16 ServerTimeZone;
> - __le16 EncryptionKeyLength;
> - __le16 Reserved;
> - __u16 ByteCount;
> - unsigned char EncryptionKey[1];
> -} __attribute__((packed)) LANMAN_NEG_RSP;
> -
> #define READ_RAW_ENABLE 1
> #define WRITE_RAW_ENABLE 2
> #define RAW_ENABLE (READ_RAW_ENABLE | WRITE_RAW_ENABLE)
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index e0def0f0714b..f9740c21ca3d 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -498,19 +498,12 @@ extern int cifs_sign_smb(struct smb_hdr *, struct TCP_Server_Info *, __u32 *);
> extern int cifs_verify_signature(struct smb_rqst *rqst,
> struct TCP_Server_Info *server,
> __u32 expected_sequence_number);
> -extern int SMBNTencrypt(unsigned char *, unsigned char *, unsigned char *,
> - const struct nls_table *);
> -extern int setup_ntlm_response(struct cifs_ses *, const struct nls_table *);
> extern int setup_ntlmv2_rsp(struct cifs_ses *, const struct nls_table *);
> extern void cifs_crypto_secmech_release(struct TCP_Server_Info *server);
> extern int calc_seckey(struct cifs_ses *);
> extern int generate_smb30signingkey(struct cifs_ses *);
> extern int generate_smb311signingkey(struct cifs_ses *);
>
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -extern int calc_lanman_hash(const char *password, const char *cryptkey,
> - bool encrypt, char *lnm_session_key);
> -#endif /* CIFS_WEAK_PW_HASH */
> extern int CIFSSMBCopy(unsigned int xid,
> struct cifs_tcon *source_tcon,
> const char *fromName,
> @@ -547,11 +540,8 @@ extern int check_mf_symlink(unsigned int xid, struct cifs_tcon *tcon,
> struct cifs_sb_info *cifs_sb,
> struct cifs_fattr *fattr,
> const unsigned char *path);
> -extern int mdfour(unsigned char *, unsigned char *, int);
> extern int E_md4hash(const unsigned char *passwd, unsigned char *p16,
> const struct nls_table *codepage);
> -extern int SMBencrypt(unsigned char *passwd, const unsigned char *c8,
> - unsigned char *p24);
>
> extern int
> cifs_setup_volume_info(struct smb3_fs_context *ctx, const char *mntopts, const char *devname);
> diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
> index 6ab6cf669438..40187d25140f 100644
> --- a/fs/cifs/cifssmb.c
> +++ b/fs/cifs/cifssmb.c
> @@ -42,10 +42,6 @@ static struct {
> int index;
> char *name;
> } protocols[] = {
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> - {LANMAN_PROT, "\2LM1.2X002"},
> - {LANMAN2_PROT, "\2LANMAN2.1"},
> -#endif /* weak password hashing for legacy clients */
> {CIFS_PROT, "\2NT LM 0.12"},
> {POSIX_PROT, "\2POSIX 2"},
> {BAD_PROT, "\2"}
> @@ -55,10 +51,6 @@ static struct {
> int index;
> char *name;
> } protocols[] = {
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> - {LANMAN_PROT, "\2LM1.2X002"},
> - {LANMAN2_PROT, "\2LANMAN2.1"},
> -#endif /* weak password hashing for legacy clients */
> {CIFS_PROT, "\2NT LM 0.12"},
> {BAD_PROT, "\2"}
> };
> @@ -66,17 +58,9 @@ static struct {
>
> /* define the number of elements in the cifs dialect array */
> #ifdef CONFIG_CIFS_POSIX
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -#define CIFS_NUM_PROT 4
> -#else
> #define CIFS_NUM_PROT 2
> -#endif /* CIFS_WEAK_PW_HASH */
> #else /* not posix */
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -#define CIFS_NUM_PROT 3
> -#else
> #define CIFS_NUM_PROT 1
> -#endif /* CONFIG_CIFS_WEAK_PW_HASH */
> #endif /* CIFS_POSIX */
>
> /*
> @@ -475,89 +459,6 @@ cifs_enable_signing(struct TCP_Server_Info *server, bool mnt_sign_required)
> return 0;
> }
>
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -static int
> -decode_lanman_negprot_rsp(struct TCP_Server_Info *server, NEGOTIATE_RSP *pSMBr)
> -{
> - __s16 tmp;
> - struct lanman_neg_rsp *rsp = (struct lanman_neg_rsp *)pSMBr;
> -
> - if (server->dialect != LANMAN_PROT && server->dialect != LANMAN2_PROT)
> - return -EOPNOTSUPP;
> -
> - server->sec_mode = le16_to_cpu(rsp->SecurityMode);
> - server->maxReq = min_t(unsigned int,
> - le16_to_cpu(rsp->MaxMpxCount),
> - cifs_max_pending);
> - set_credits(server, server->maxReq);
> - server->maxBuf = le16_to_cpu(rsp->MaxBufSize);
> - /* set up max_read for readpages check */
> - server->max_read = server->maxBuf;
> - /* even though we do not use raw we might as well set this
> - accurately, in case we ever find a need for it */
> - if ((le16_to_cpu(rsp->RawMode) & RAW_ENABLE) == RAW_ENABLE) {
> - server->max_rw = 0xFF00;
> - server->capabilities = CAP_MPX_MODE | CAP_RAW_MODE;
> - } else {
> - server->max_rw = 0;/* do not need to use raw anyway */
> - server->capabilities = CAP_MPX_MODE;
> - }
> - tmp = (__s16)le16_to_cpu(rsp->ServerTimeZone);
> - if (tmp == -1) {
> - /* OS/2 often does not set timezone therefore
> - * we must use server time to calc time zone.
> - * Could deviate slightly from the right zone.
> - * Smallest defined timezone difference is 15 minutes
> - * (i.e. Nepal). Rounding up/down is done to match
> - * this requirement.
> - */
> - int val, seconds, remain, result;
> - struct timespec64 ts;
> - time64_t utc = ktime_get_real_seconds();
> - ts = cnvrtDosUnixTm(rsp->SrvTime.Date,
> - rsp->SrvTime.Time, 0);
> - cifs_dbg(FYI, "SrvTime %lld sec since 1970 (utc: %lld) diff: %lld\n",
> - ts.tv_sec, utc,
> - utc - ts.tv_sec);
> - val = (int)(utc - ts.tv_sec);
> - seconds = abs(val);
> - result = (seconds / MIN_TZ_ADJ) * MIN_TZ_ADJ;
> - remain = seconds % MIN_TZ_ADJ;
> - if (remain >= (MIN_TZ_ADJ / 2))
> - result += MIN_TZ_ADJ;
> - if (val < 0)
> - result = -result;
> - server->timeAdj = result;
> - } else {
> - server->timeAdj = (int)tmp;
> - server->timeAdj *= 60; /* also in seconds */
> - }
> - cifs_dbg(FYI, "server->timeAdj: %d seconds\n", server->timeAdj);
> -
> -
> - /* BB get server time for time conversions and add
> - code to use it and timezone since this is not UTC */
> -
> - if (rsp->EncryptionKeyLength ==
> - cpu_to_le16(CIFS_CRYPTO_KEY_SIZE)) {
> - memcpy(server->cryptkey, rsp->EncryptionKey,
> - CIFS_CRYPTO_KEY_SIZE);
> - } else if (server->sec_mode & SECMODE_PW_ENCRYPT) {
> - return -EIO; /* need cryptkey unless plain text */
> - }
> -
> - cifs_dbg(FYI, "LANMAN negotiated\n");
> - return 0;
> -}
> -#else
> -static inline int
> -decode_lanman_negprot_rsp(struct TCP_Server_Info *server, NEGOTIATE_RSP *pSMBr)
> -{
> - cifs_dbg(VFS, "mount failed, cifs module not built with CIFS_WEAK_PW_HASH support\n");
> - return -EOPNOTSUPP;
> -}
> -#endif
> -
> static bool
> should_set_ext_sec_flag(enum securityEnum sectype)
> {
> @@ -626,16 +527,12 @@ CIFSSMBNegotiate(const unsigned int xid, struct cifs_ses *ses)
> server->dialect = le16_to_cpu(pSMBr->DialectIndex);
> cifs_dbg(FYI, "Dialect: %d\n", server->dialect);
> /* Check wct = 1 error case */
> - if ((pSMBr->hdr.WordCount < 13) || (server->dialect == BAD_PROT)) {
> + if ((pSMBr->hdr.WordCount <= 13) || (server->dialect == BAD_PROT)) {
> /* core returns wct = 1, but we do not ask for core - otherwise
> small wct just comes when dialect index is -1 indicating we
> could not negotiate a common dialect */
> rc = -EOPNOTSUPP;
> goto neg_err_exit;
> - } else if (pSMBr->hdr.WordCount == 13) {
> - server->negflavor = CIFS_NEGFLAVOR_LANMAN;
> - rc = decode_lanman_negprot_rsp(server, pSMBr);
> - goto signing_check;
> } else if (pSMBr->hdr.WordCount != 17) {
> /* unknown wct */
> rc = -EOPNOTSUPP;
> @@ -677,7 +574,6 @@ CIFSSMBNegotiate(const unsigned int xid, struct cifs_ses *ses)
> server->capabilities &= ~CAP_EXTENDED_SECURITY;
> }
>
> -signing_check:
> if (!rc)
> rc = cifs_enable_signing(server, ses->sign);
> neg_err_exit:
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 3781eee9360a..0db344807ef1 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -3684,38 +3684,6 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
> *bcc_ptr = 0; /* password is null byte */
> bcc_ptr++; /* skip password */
> /* already aligned so no need to do it below */
> - } else {
> - pSMB->PasswordLength = cpu_to_le16(CIFS_AUTH_RESP_SIZE);
> - /* BB FIXME add code to fail this if NTLMv2 or Kerberos
> - specified as required (when that support is added to
> - the vfs in the future) as only NTLM or the much
> - weaker LANMAN (which we do not send by default) is accepted
> - by Samba (not sure whether other servers allow
> - NTLMv2 password here) */
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> - if ((global_secflags & CIFSSEC_MAY_LANMAN) &&
> - (ses->sectype == LANMAN))
> - calc_lanman_hash(tcon->password, ses->server->cryptkey,
> - ses->server->sec_mode &
> - SECMODE_PW_ENCRYPT ? true : false,
> - bcc_ptr);
> - else
> -#endif /* CIFS_WEAK_PW_HASH */
> - rc = SMBNTencrypt(tcon->password, ses->server->cryptkey,
> - bcc_ptr, nls_codepage);
> - if (rc) {
> - cifs_dbg(FYI, "%s Can't generate NTLM rsp. Error: %d\n",
> - __func__, rc);
> - cifs_buf_release(smb_buffer);
> - return rc;
> - }
> -
> - bcc_ptr += CIFS_AUTH_RESP_SIZE;
> - if (ses->capabilities & CAP_UNICODE) {
> - /* must align unicode strings */
> - *bcc_ptr = 0; /* null byte password */
> - bcc_ptr++;
> - }
> }
>
> if (ses->server->sign)
> diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
> index eed59bc1d913..4515a0883262 100644
> --- a/fs/cifs/fs_context.c
> +++ b/fs/cifs/fs_context.c
> @@ -57,12 +57,9 @@ static const match_table_t cifs_secflavor_tokens = {
> { Opt_sec_krb5p, "krb5p" },
> { Opt_sec_ntlmsspi, "ntlmsspi" },
> { Opt_sec_ntlmssp, "ntlmssp" },
> - { Opt_ntlm, "ntlm" },
> - { Opt_sec_ntlmi, "ntlmi" },
> { Opt_sec_ntlmv2, "nontlm" },
> { Opt_sec_ntlmv2, "ntlmv2" },
> { Opt_sec_ntlmv2i, "ntlmv2i" },
> - { Opt_sec_lanman, "lanman" },
> { Opt_sec_none, "none" },
>
> { Opt_sec_err, NULL }
> @@ -221,23 +218,12 @@ cifs_parse_security_flavors(struct fs_context *fc, char *value, struct smb3_fs_c
> case Opt_sec_ntlmssp:
> ctx->sectype = RawNTLMSSP;
> break;
> - case Opt_sec_ntlmi:
> - ctx->sign = true;
> - fallthrough;
> - case Opt_ntlm:
> - ctx->sectype = NTLM;
> - break;
> case Opt_sec_ntlmv2i:
> ctx->sign = true;
> fallthrough;
> case Opt_sec_ntlmv2:
> ctx->sectype = NTLMv2;
> break;
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> - case Opt_sec_lanman:
> - ctx->sectype = LANMAN;
> - break;
> -#endif
> case Opt_sec_none:
> ctx->nullauth = 1;
> break;
> diff --git a/fs/cifs/fs_context.h b/fs/cifs/fs_context.h
> index b6243972edf3..a42ba71d7a81 100644
> --- a/fs/cifs/fs_context.h
> +++ b/fs/cifs/fs_context.h
> @@ -47,11 +47,8 @@ enum cifs_sec_param {
> Opt_sec_krb5p,
> Opt_sec_ntlmsspi,
> Opt_sec_ntlmssp,
> - Opt_ntlm,
> - Opt_sec_ntlmi,
> Opt_sec_ntlmv2,
> Opt_sec_ntlmv2i,
> - Opt_sec_lanman,
> Opt_sec_none,
>
> Opt_sec_err
> diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
> index c5785fd3f52e..bb4a838eef71 100644
> --- a/fs/cifs/sess.c
> +++ b/fs/cifs/sess.c
> @@ -799,30 +799,16 @@ cifs_select_sectype(struct TCP_Server_Info *server, enum securityEnum requested)
> }
> case CIFS_NEGFLAVOR_UNENCAP:
> switch (requested) {
> - case NTLM:
> case NTLMv2:
> return requested;
> case Unspecified:
> if (global_secflags & CIFSSEC_MAY_NTLMV2)
> return NTLMv2;
> - if (global_secflags & CIFSSEC_MAY_NTLM)
> - return NTLM;
> break;
> default:
> break;
> }
> - fallthrough; /* to attempt LANMAN authentication next */
> - case CIFS_NEGFLAVOR_LANMAN:
> - switch (requested) {
> - case LANMAN:
> - return requested;
> - case Unspecified:
> - if (global_secflags & CIFSSEC_MAY_LANMAN)
> - return LANMAN;
> - fallthrough;
> - default:
> - return Unspecified;
> - }
> + fallthrough;
> default:
> return Unspecified;
> }
> @@ -947,230 +933,6 @@ sess_sendreceive(struct sess_data *sess_data)
> return rc;
> }
>
> -/*
> - * LANMAN and plaintext are less secure and off by default.
> - * So we make this explicitly be turned on in kconfig (in the
> - * build) and turned on at runtime (changed from the default)
> - * in proc/fs/cifs or via mount parm. Unfortunately this is
> - * needed for old Win (e.g. Win95), some obscure NAS and OS/2
> - */
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> -static void
> -sess_auth_lanman(struct sess_data *sess_data)
> -{
> - int rc = 0;
> - struct smb_hdr *smb_buf;
> - SESSION_SETUP_ANDX *pSMB;
> - char *bcc_ptr;
> - struct cifs_ses *ses = sess_data->ses;
> - char lnm_session_key[CIFS_AUTH_RESP_SIZE];
> - __u16 bytes_remaining;
> -
> - /* lanman 2 style sessionsetup */
> - /* wct = 10 */
> - rc = sess_alloc_buffer(sess_data, 10);
> - if (rc)
> - goto out;
> -
> - pSMB = (SESSION_SETUP_ANDX *)sess_data->iov[0].iov_base;
> - bcc_ptr = sess_data->iov[2].iov_base;
> - (void)cifs_ssetup_hdr(ses, pSMB);
> -
> - pSMB->req.hdr.Flags2 &= ~SMBFLG2_UNICODE;
> -
> - if (ses->user_name != NULL) {
> - /* no capabilities flags in old lanman negotiation */
> - pSMB->old_req.PasswordLength = cpu_to_le16(CIFS_AUTH_RESP_SIZE);
> -
> - /* Calculate hash with password and copy into bcc_ptr.
> - * Encryption Key (stored as in cryptkey) gets used if the
> - * security mode bit in Negotiate Protocol response states
> - * to use challenge/response method (i.e. Password bit is 1).
> - */
> - rc = calc_lanman_hash(ses->password, ses->server->cryptkey,
> - ses->server->sec_mode & SECMODE_PW_ENCRYPT ?
> - true : false, lnm_session_key);
> - if (rc)
> - goto out;
> -
> - memcpy(bcc_ptr, (char *)lnm_session_key, CIFS_AUTH_RESP_SIZE);
> - bcc_ptr += CIFS_AUTH_RESP_SIZE;
> - } else {
> - pSMB->old_req.PasswordLength = 0;
> - }
> -
> - /*
> - * can not sign if LANMAN negotiated so no need
> - * to calculate signing key? but what if server
> - * changed to do higher than lanman dialect and
> - * we reconnected would we ever calc signing_key?
> - */
> -
> - cifs_dbg(FYI, "Negotiating LANMAN setting up strings\n");
> - /* Unicode not allowed for LANMAN dialects */
> - ascii_ssetup_strings(&bcc_ptr, ses, sess_data->nls_cp);
> -
> - sess_data->iov[2].iov_len = (long) bcc_ptr -
> - (long) sess_data->iov[2].iov_base;
> -
> - rc = sess_sendreceive(sess_data);
> - if (rc)
> - goto out;
> -
> - pSMB = (SESSION_SETUP_ANDX *)sess_data->iov[0].iov_base;
> - smb_buf = (struct smb_hdr *)sess_data->iov[0].iov_base;
> -
> - /* lanman response has a word count of 3 */
> - if (smb_buf->WordCount != 3) {
> - rc = -EIO;
> - cifs_dbg(VFS, "bad word count %d\n", smb_buf->WordCount);
> - goto out;
> - }
> -
> - if (le16_to_cpu(pSMB->resp.Action) & GUEST_LOGIN)
> - cifs_dbg(FYI, "Guest login\n"); /* BB mark SesInfo struct? */
> -
> - ses->Suid = smb_buf->Uid; /* UID left in wire format (le) */
> - cifs_dbg(FYI, "UID = %llu\n", ses->Suid);
> -
> - bytes_remaining = get_bcc(smb_buf);
> - bcc_ptr = pByteArea(smb_buf);
> -
> - /* BB check if Unicode and decode strings */
> - if (bytes_remaining == 0) {
> - /* no string area to decode, do nothing */
> - } else if (smb_buf->Flags2 & SMBFLG2_UNICODE) {
> - /* unicode string area must be word-aligned */
> - if (((unsigned long) bcc_ptr - (unsigned long) smb_buf) % 2) {
> - ++bcc_ptr;
> - --bytes_remaining;
> - }
> - decode_unicode_ssetup(&bcc_ptr, bytes_remaining, ses,
> - sess_data->nls_cp);
> - } else {
> - decode_ascii_ssetup(&bcc_ptr, bytes_remaining, ses,
> - sess_data->nls_cp);
> - }
> -
> - rc = sess_establish_session(sess_data);
> -out:
> - sess_data->result = rc;
> - sess_data->func = NULL;
> - sess_free_buffer(sess_data);
> -}
> -
> -#endif
> -
> -static void
> -sess_auth_ntlm(struct sess_data *sess_data)
> -{
> - int rc = 0;
> - struct smb_hdr *smb_buf;
> - SESSION_SETUP_ANDX *pSMB;
> - char *bcc_ptr;
> - struct cifs_ses *ses = sess_data->ses;
> - __u32 capabilities;
> - __u16 bytes_remaining;
> -
> - /* old style NTLM sessionsetup */
> - /* wct = 13 */
> - rc = sess_alloc_buffer(sess_data, 13);
> - if (rc)
> - goto out;
> -
> - pSMB = (SESSION_SETUP_ANDX *)sess_data->iov[0].iov_base;
> - bcc_ptr = sess_data->iov[2].iov_base;
> - capabilities = cifs_ssetup_hdr(ses, pSMB);
> -
> - pSMB->req_no_secext.Capabilities = cpu_to_le32(capabilities);
> - if (ses->user_name != NULL) {
> - pSMB->req_no_secext.CaseInsensitivePasswordLength =
> - cpu_to_le16(CIFS_AUTH_RESP_SIZE);
> - pSMB->req_no_secext.CaseSensitivePasswordLength =
> - cpu_to_le16(CIFS_AUTH_RESP_SIZE);
> -
> - /* calculate ntlm response and session key */
> - rc = setup_ntlm_response(ses, sess_data->nls_cp);
> - if (rc) {
> - cifs_dbg(VFS, "Error %d during NTLM authentication\n",
> - rc);
> - goto out;
> - }
> -
> - /* copy ntlm response */
> - memcpy(bcc_ptr, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
> - CIFS_AUTH_RESP_SIZE);
> - bcc_ptr += CIFS_AUTH_RESP_SIZE;
> - memcpy(bcc_ptr, ses->auth_key.response + CIFS_SESS_KEY_SIZE,
> - CIFS_AUTH_RESP_SIZE);
> - bcc_ptr += CIFS_AUTH_RESP_SIZE;
> - } else {
> - pSMB->req_no_secext.CaseInsensitivePasswordLength = 0;
> - pSMB->req_no_secext.CaseSensitivePasswordLength = 0;
> - }
> -
> - if (ses->capabilities & CAP_UNICODE) {
> - /* unicode strings must be word aligned */
> - if (sess_data->iov[0].iov_len % 2) {
> - *bcc_ptr = 0;
> - bcc_ptr++;
> - }
> - unicode_ssetup_strings(&bcc_ptr, ses, sess_data->nls_cp);
> - } else {
> - ascii_ssetup_strings(&bcc_ptr, ses, sess_data->nls_cp);
> - }
> -
> -
> - sess_data->iov[2].iov_len = (long) bcc_ptr -
> - (long) sess_data->iov[2].iov_base;
> -
> - rc = sess_sendreceive(sess_data);
> - if (rc)
> - goto out;
> -
> - pSMB = (SESSION_SETUP_ANDX *)sess_data->iov[0].iov_base;
> - smb_buf = (struct smb_hdr *)sess_data->iov[0].iov_base;
> -
> - if (smb_buf->WordCount != 3) {
> - rc = -EIO;
> - cifs_dbg(VFS, "bad word count %d\n", smb_buf->WordCount);
> - goto out;
> - }
> -
> - if (le16_to_cpu(pSMB->resp.Action) & GUEST_LOGIN)
> - cifs_dbg(FYI, "Guest login\n"); /* BB mark SesInfo struct? */
> -
> - ses->Suid = smb_buf->Uid; /* UID left in wire format (le) */
> - cifs_dbg(FYI, "UID = %llu\n", ses->Suid);
> -
> - bytes_remaining = get_bcc(smb_buf);
> - bcc_ptr = pByteArea(smb_buf);
> -
> - /* BB check if Unicode and decode strings */
> - if (bytes_remaining == 0) {
> - /* no string area to decode, do nothing */
> - } else if (smb_buf->Flags2 & SMBFLG2_UNICODE) {
> - /* unicode string area must be word-aligned */
> - if (((unsigned long) bcc_ptr - (unsigned long) smb_buf) % 2) {
> - ++bcc_ptr;
> - --bytes_remaining;
> - }
> - decode_unicode_ssetup(&bcc_ptr, bytes_remaining, ses,
> - sess_data->nls_cp);
> - } else {
> - decode_ascii_ssetup(&bcc_ptr, bytes_remaining, ses,
> - sess_data->nls_cp);
> - }
> -
> - rc = sess_establish_session(sess_data);
> -out:
> - sess_data->result = rc;
> - sess_data->func = NULL;
> - sess_free_buffer(sess_data);
> - kfree(ses->auth_key.response);
> - ses->auth_key.response = NULL;
> -}
> -
> static void
> sess_auth_ntlmv2(struct sess_data *sess_data)
> {
> @@ -1675,21 +1437,6 @@ static int select_sec(struct cifs_ses *ses, struct sess_data *sess_data)
> }
>
> switch (type) {
> - case LANMAN:
> - /* LANMAN and plaintext are less secure and off by default.
> - * So we make this explicitly be turned on in kconfig (in the
> - * build) and turned on at runtime (changed from the default)
> - * in proc/fs/cifs or via mount parm. Unfortunately this is
> - * needed for old Win (e.g. Win95), some obscure NAS and OS/2 */
> -#ifdef CONFIG_CIFS_WEAK_PW_HASH
> - sess_data->func = sess_auth_lanman;
> - break;
> -#else
> - return -EOPNOTSUPP;
> -#endif
> - case NTLM:
> - sess_data->func = sess_auth_ntlm;
> - break;
> case NTLMv2:
> sess_data->func = sess_auth_ntlmv2;
> break;
> diff --git a/fs/cifs/smbencrypt.c b/fs/cifs/smbencrypt.c
> index 39a938443e3e..5da7eea3323f 100644
> --- a/fs/cifs/smbencrypt.c
> +++ b/fs/cifs/smbencrypt.c
> @@ -18,7 +18,6 @@
> #include <linux/string.h>
> #include <linux/kernel.h>
> #include <linux/random.h>
> -#include <crypto/des.h>
> #include "cifs_fs_sb.h"
> #include "cifs_unicode.h"
> #include "cifspdu.h"
> @@ -38,74 +37,8 @@
> #define SSVALX(buf,pos,val) (CVAL(buf,pos)=(val)&0xFF,CVAL(buf,pos+1)=(val)>>8)
> #define SSVAL(buf,pos,val) SSVALX((buf),(pos),((__u16)(val)))
>
> -static void
> -str_to_key(unsigned char *str, unsigned char *key)
> -{
> - int i;
> -
> - key[0] = str[0] >> 1;
> - key[1] = ((str[0] & 0x01) << 6) | (str[1] >> 2);
> - key[2] = ((str[1] & 0x03) << 5) | (str[2] >> 3);
> - key[3] = ((str[2] & 0x07) << 4) | (str[3] >> 4);
> - key[4] = ((str[3] & 0x0F) << 3) | (str[4] >> 5);
> - key[5] = ((str[4] & 0x1F) << 2) | (str[5] >> 6);
> - key[6] = ((str[5] & 0x3F) << 1) | (str[6] >> 7);
> - key[7] = str[6] & 0x7F;
> - for (i = 0; i < 8; i++)
> - key[i] = (key[i] << 1);
> -}
> -
> -static int
> -smbhash(unsigned char *out, const unsigned char *in, unsigned char *key)
> -{
> - unsigned char key2[8];
> - struct des_ctx ctx;
> -
> - str_to_key(key, key2);
> -
> - if (fips_enabled) {
> - cifs_dbg(VFS, "FIPS compliance enabled: DES not permitted\n");
> - return -ENOENT;
> - }
> -
> - des_expand_key(&ctx, key2, DES_KEY_SIZE);
> - des_encrypt(&ctx, out, in);
> - memzero_explicit(&ctx, sizeof(ctx));
> -
> - return 0;
> -}
> -
> -static int
> -E_P16(unsigned char *p14, unsigned char *p16)
> -{
> - int rc;
> - unsigned char sp8[8] =
> - { 0x4b, 0x47, 0x53, 0x21, 0x40, 0x23, 0x24, 0x25 };
> -
> - rc = smbhash(p16, sp8, p14);
> - if (rc)
> - return rc;
> - rc = smbhash(p16 + 8, sp8, p14 + 7);
> - return rc;
> -}
> -
> -static int
> -E_P24(unsigned char *p21, const unsigned char *c8, unsigned char *p24)
> -{
> - int rc;
> -
> - rc = smbhash(p24, c8, p21);
> - if (rc)
> - return rc;
> - rc = smbhash(p24 + 8, c8, p21 + 7);
> - if (rc)
> - return rc;
> - rc = smbhash(p24 + 16, c8, p21 + 14);
> - return rc;
> -}
> -
> /* produce a md4 message digest from data of length n bytes */
> -int
> +static int
> mdfour(unsigned char *md4_hash, unsigned char *link_str, int link_len)
> {
> int rc;
> @@ -135,32 +68,6 @@ mdfour(unsigned char *md4_hash, unsigned char *link_str, int link_len)
> return rc;
> }
>
> -/*
> - This implements the X/Open SMB password encryption
> - It takes a password, a 8 byte "crypt key" and puts 24 bytes of
> - encrypted password into p24 */
> -/* Note that password must be uppercased and null terminated */
> -int
> -SMBencrypt(unsigned char *passwd, const unsigned char *c8, unsigned char *p24)
> -{
> - int rc;
> - unsigned char p14[14], p16[16], p21[21];
> -
> - memset(p14, '\0', 14);
> - memset(p16, '\0', 16);
> - memset(p21, '\0', 21);
> -
> - memcpy(p14, passwd, 14);
> - rc = E_P16(p14, p16);
> - if (rc)
> - return rc;
> -
> - memcpy(p21, p16, 16);
> - rc = E_P24(p21, c8, p24);
> -
> - return rc;
> -}
> -
> /*
> * Creates the MD4 Hash of the users password in NT UNICODE.
> */
> @@ -186,25 +93,3 @@ E_md4hash(const unsigned char *passwd, unsigned char *p16,
>
> return rc;
> }
> -
> -/* Does the NT MD4 hash then des encryption. */
> -int
> -SMBNTencrypt(unsigned char *passwd, unsigned char *c8, unsigned char *p24,
> - const struct nls_table *codepage)
> -{
> - int rc;
> - unsigned char p16[16], p21[21];
> -
> - memset(p16, '\0', 16);
> - memset(p21, '\0', 21);
> -
> - rc = E_md4hash(passwd, p16, codepage);
> - if (rc) {
> - cifs_dbg(FYI, "%s Can't generate NT hash, error: %d\n",
> - __func__, rc);
> - return rc;
> - }
> - memcpy(p21, p16, 16);
> - rc = E_P24(p21, c8, p24);
> - return rc;
> -}
> --
> 2.30.2
>
--
Thanks,
Steve
next prev parent reply other threads:[~2021-08-20 6:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-19 10:34 crypto updates Ronnie Sahlberg
2021-08-19 10:34 ` [PATCH 1/2] cifs: remove support for NTLM and weaker authentication algorithms Ronnie Sahlberg
2021-08-20 6:08 ` Steve French [this message]
2021-08-21 14:25 ` Tom Talpey
2021-08-25 7:46 ` ronnie sahlberg
2021-08-19 10:34 ` [PATCH 2/2] cifs: fork arc4 and create a separate module for it for cifs and other users Ronnie Sahlberg
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--in-reply-to='CAH2r5mv846_uZ9S+QZb4qYZ66W+Ffnb97UYm4zs=JOdh3P+qGA@mail.gmail.com' \
--to=smfrench@gmail.com \
--cc=linux-cifs@vger.kernel.org \
--cc=lsahlber@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).