smime.pod revision 68651
1=pod 2 3=head1 NAME 4 5smime - S/MIME utility 6 7=head1 SYNOPSIS 8 9B<openssl> B<smime> 10[B<-encrypt>] 11[B<-decrypt>] 12[B<-sign>] 13[B<-verify>] 14[B<-pk7out>] 15[B<-des>] 16[B<-des3>] 17[B<-rc2-40>] 18[B<-rc2-64>] 19[B<-rc2-128>] 20[B<-in file>] 21[B<-certfile file>] 22[B<-signer file>] 23[B<-recip file>] 24[B<-in file>] 25[B<-inform SMIME|PEM|DER>] 26[B<-passin arg>] 27[B<-inkey file>] 28[B<-out file>] 29[B<-outform SMIME|PEM|DER>] 30[B<-content file>] 31[B<-to addr>] 32[B<-from ad>] 33[B<-subject s>] 34[B<-text>] 35[B<-rand file(s)>] 36[cert.pem]... 37 38=head1 DESCRIPTION 39 40The B<smime> command handles S/MIME mail. It can encrypt, decrypt, sign and 41verify S/MIME messages. 42 43=head1 COMMAND OPTIONS 44 45There are five operation options that set the type of operation to be performed. 46The meaning of the other options varies according to the operation type. 47 48=over 4 49 50=item B<-encrypt> 51 52encrypt mail for the given recipient certificates. Input file is the message 53to be encrypted. The output file is the encrypted mail in MIME format. 54 55=item B<-decrypt> 56 57decrypt mail using the supplied certificate and private key. Expects an 58encrypted mail message in MIME format for the input file. The decrypted mail 59is written to the output file. 60 61=item B<-sign> 62 63sign mail using the supplied certificate and private key. Input file is 64the message to be signed. The signed message in MIME format is written 65to the output file. 66 67=item B<-verify> 68 69verify signed mail. Expects a signed mail message on input and outputs 70the signed data. Both clear text and opaque signing is supported. 71 72=item B<-pk7out> 73 74takes an input message and writes out a PEM encoded PKCS#7 structure. 75 76=item B<-in filename> 77 78the input message to be encrypted or signed or the MIME message to 79be decrypted or verified. 80 81=item B<-inform SMIME|PEM|DER> 82 83this specifies the input format for the PKCS#7 structure. The default 84is B<SMIME> which reads an S/MIME format message. B<PEM> and B<DER> 85format change this to expect PEM and DER format PKCS#7 structures 86instead. This currently only affects the input format of the PKCS#7 87structure, if no PKCS#7 structure is being input (for example with 88B<-encrypt> or B<-sign>) this option has no effect. 89 90=item B<-out filename> 91 92the message text that has been decrypted or verified or the output MIME 93format message that has been signed or verified. 94 95=item B<-outform SMIME|PEM|DER> 96 97this specifies the output format for the PKCS#7 structure. The default 98is B<SMIME> which write an S/MIME format message. B<PEM> and B<DER> 99format change this to write PEM and DER format PKCS#7 structures 100instead. This currently only affects the output format of the PKCS#7 101structure, if no PKCS#7 structure is being output (for example with 102B<-verify> or B<-decrypt>) this option has no effect. 103 104=item B<-content filename> 105 106This specifies a file containing the detached content, this is only 107useful with the B<-verify> command. This is only usable if the PKCS#7 108structure is using the detached signature form where the content is 109not included. This option will override any content if the input format 110is S/MIME and it uses the multipart/signed MIME content type. 111 112=item B<-text> 113 114this option adds plain text (text/plain) MIME headers to the supplied 115message if encrypting or signing. If decrypting or verifying it strips 116off text headers: if the decrypted or verified message is not of MIME 117type text/plain then an error occurs. 118 119=item B<-CAfile file> 120 121a file containing trusted CA certificates, only used with B<-verify>. 122 123=item B<-CApath dir> 124 125a directory containing trusted CA certificates, only used with 126B<-verify>. This directory must be a standard certificate directory: that 127is a hash of each subject name (using B<x509 -hash>) should be linked 128to each certificate. 129 130=item B<-des -des3 -rc2-40 -rc2-64 -rc2-128> 131 132the encryption algorithm to use. DES (56 bits), triple DES (168 bits) 133or 40, 64 or 128 bit RC2 respectively if not specified 40 bit RC2 is 134used. Only used with B<-encrypt>. 135 136=item B<-nointern> 137 138when verifying a message normally certificates (if any) included in 139the message are searched for the signing certificate. With this option 140only the certificates specified in the B<-certfile> option are used. 141The supplied certificates can still be used as untrusted CAs however. 142 143=item B<-noverify> 144 145do not verify the signers certificate of a signed message. 146 147=item B<-nochain> 148 149do not do chain verification of signers certificates: that is don't 150use the certificates in the signed message as untrusted CAs. 151 152=item B<-nosigs> 153 154don't try to verify the signatures on the message. 155 156=item B<-nocerts> 157 158when signing a message the signer's certificate is normally included 159with this option it is excluded. This will reduce the size of the 160signed message but the verifier must have a copy of the signers certificate 161available locally (passed using the B<-certfile> option for example). 162 163=item B<-noattr> 164 165normally when a message is signed a set of attributes are included which 166include the signing time and supported symmetric algorithms. With this 167option they are not included. 168 169=item B<-binary> 170 171normally the input message is converted to "canonical" format which is 172effectively using CR and LF as end of line: as required by the S/MIME 173specification. When this option is present no translation occurs. This 174is useful when handling binary data which may not be in MIME format. 175 176=item B<-nodetach> 177 178when signing a message use opaque signing: this form is more resistant 179to translation by mail relays but it cannot be read by mail agents that 180do not support S/MIME. Without this option cleartext signing with 181the MIME type multipart/signed is used. 182 183=item B<-certfile file> 184 185allows additional certificates to be specified. When signing these will 186be included with the message. When verifying these will be searched for 187the signers certificates. The certificates should be in PEM format. 188 189=item B<-signer file> 190 191the signers certificate when signing a message. If a message is 192being verified then the signers certificates will be written to this 193file if the verification was successful. 194 195=item B<-recip file> 196 197the recipients certificate when decrypting a message. This certificate 198must match one of the recipients of the message or an error occurs. 199 200=item B<-inkey file> 201 202the private key to use when signing or decrypting. This must match the 203corresponding certificate. If this option is not specified then the 204private key must be included in the certificate file specified with 205the B<-recip> or B<-signer> file. 206 207=item B<-passin arg> 208 209the private key password source. For more information about the format of B<arg> 210see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>. 211 212=item B<-rand file(s)> 213 214a file or files containing random data used to seed the random number 215generator, or an EGD socket (see L<RAND_egd(3)|RAND_egd(3)>). 216Multiple files can be specified separated by a OS-dependent character. 217The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for 218all others. 219 220=item B<cert.pem...> 221 222one or more certificates of message recipients: used when encrypting 223a message. 224 225=item B<-to, -from, -subject> 226 227the relevant mail headers. These are included outside the signed 228portion of a message so they may be included manually. If signing 229then many S/MIME mail clients check the signers certificate's email 230address matches that specified in the From: address. 231 232=back 233 234=head1 NOTES 235 236The MIME message must be sent without any blank lines between the 237headers and the output. Some mail programs will automatically add 238a blank line. Piping the mail directly to sendmail is one way to 239achieve the correct format. 240 241The supplied message to be signed or encrypted must include the 242necessary MIME headers or many S/MIME clients wont display it 243properly (if at all). You can use the B<-text> option to automatically 244add plain text headers. 245 246A "signed and encrypted" message is one where a signed message is 247then encrypted. This can be produced by encrypting an already signed 248message: see the examples section. 249 250This version of the program only allows one signer per message but it 251will verify multiple signers on received messages. Some S/MIME clients 252choke if a message contains multiple signers. It is possible to sign 253messages "in parallel" by signing an already signed message. 254 255The options B<-encrypt> and B<-decrypt> reflect common usage in S/MIME 256clients. Strictly speaking these process PKCS#7 enveloped data: PKCS#7 257encrypted data is used for other purposes. 258 259=head1 EXIT CODES 260 261=over 4 262 263=item 0 264 265the operation was completely successfully. 266 267=item 1 268 269an error occurred parsing the command options. 270 271=item 2 272 273one of the input files could not be read. 274 275=item 3 276 277an error occurred creating the PKCS#7 file or when reading the MIME 278message. 279 280=item 4 281 282an error occurred decrypting or verifying the message. 283 284=item 5 285 286the message was verified correctly but an error occurred writing out 287the signers certificates. 288 289=back 290 291=head1 EXAMPLES 292 293Create a cleartext signed message: 294 295 openssl smime -sign -in message.txt -text -out mail.msg \ 296 -signer mycert.pem 297 298Create and opaque signed message 299 300 openssl smime -sign -in message.txt -text -out mail.msg -nodetach \ 301 -signer mycert.pem 302 303Create a signed message, include some additional certificates and 304read the private key from another file: 305 306 openssl smime -sign -in in.txt -text -out mail.msg \ 307 -signer mycert.pem -inkey mykey.pem -certfile mycerts.pem 308 309Send a signed message under Unix directly to sendmail, including headers: 310 311 openssl smime -sign -in in.txt -text -signer mycert.pem \ 312 -from steve@openssl.org -to someone@somewhere \ 313 -subject "Signed message" | sendmail someone@somewhere 314 315Verify a message and extract the signer's certificate if successful: 316 317 openssl smime -verify -in mail.msg -signer user.pem -out signedtext.txt 318 319Send encrypted mail using triple DES: 320 321 openssl smime -encrypt -in in.txt -from steve@openssl.org \ 322 -to someone@somewhere -subject "Encrypted message" \ 323 -des3 user.pem -out mail.msg 324 325Sign and encrypt mail: 326 327 openssl smime -sign -in ml.txt -signer my.pem -text \ 328 | openssl smime -encrypt -out mail.msg \ 329 -from steve@openssl.org -to someone@somewhere \ 330 -subject "Signed and Encrypted message" -des3 user.pem 331 332Note: the encryption command does not include the B<-text> option because the message 333being encrypted already has MIME headers. 334 335Decrypt mail: 336 337 openssl smime -decrypt -in mail.msg -recip mycert.pem -inkey key.pem 338 339The output from Netscape form signing is a PKCS#7 structure with the 340detached signature format. You can use this program to verify the 341signature by line wrapping the base64 encoded structure and surrounding 342it with: 343 344 -----BEGIN PKCS7---- 345 -----END PKCS7---- 346 347and using the command, 348 349 openssl smime -verify -inform PEM -in signature.pem -content content.txt 350 351alternatively you can base64 decode the signature and use 352 353 openssl smime -verify -inform DER -in signature.der -content content.txt 354 355=head1 BUGS 356 357The MIME parser isn't very clever: it seems to handle most messages that I've thrown 358at it but it may choke on others. 359 360The code currently will only write out the signer's certificate to a file: if the 361signer has a separate encryption certificate this must be manually extracted. There 362should be some heuristic that determines the correct encryption certificate. 363 364Ideally a database should be maintained of a certificates for each email address. 365 366The code doesn't currently take note of the permitted symmetric encryption 367algorithms as supplied in the SMIMECapabilities signed attribute. this means the 368user has to manually include the correct encryption algorithm. It should store 369the list of permitted ciphers in a database and only use those. 370 371No revocation checking is done on the signer's certificate. 372 373The current code can only handle S/MIME v2 messages, the more complex S/MIME v3 374structures may cause parsing errors. 375 376=cut 377