2.\" 3.\" Standard preamble: 4.\" ======================================================================== 5.de Sp \" Vertical space (when we can't use .PP) 6.if t .sp .5v 7.if n .sp 8.. 9.de Vb \" Begin verbatim text 10.ft CW 11.nf 12.ne \\$1 13.. 14.de Ve \" End verbatim text 15.ft R 16.fi 17.. 18.\" Set up some character translations and predefined strings. \*(-- will 19.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left 20.\" double quote, and \*(R" will give a right double quote. \*(C+ will 21.\" give a nicer C++. Capital omega is used to do unbreakable dashes and 22.\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, 23.\" nothing in troff, for use with C<>. 24.tr \(*W- 25.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' 26.ie n \{\ 27. ds -- \(*W- 28. ds PI pi 29. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch 30. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch 31. ds L" "" 32. ds R" "" 33. ds C` "" 34. ds C' "" 35'br\} 36.el\{\ 37. ds -- \|\(em\| 38. ds PI \(*p 39. ds L" `` 40. ds R" '' 41. ds C` 42. ds C' 43'br\} 44.\" 45.\" Escape single quotes in literal strings from groff's Unicode transform. 46.ie \n(.g .ds Aq \(aq 47.el .ds Aq ' 48.\" 49.\" If the F register is >0, we'll generate index entries on stderr for 50.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index 51.\" entries marked with X<> in POD. Of course, you'll have to process the 52.\" output yourself in some meaningful fashion. 53.\" 54.\" Avoid warning from groff about undefined register 'F'. 55.de IX 56.. 57.if !\nF .nr F 0 58.if \nF>0 \{\ 59. de IX 60. tm Index:\\$1\t\\n%\t"\\$2" 61.. 62. if !\nF==2 \{\ 63. nr % 0 64. nr F 2 65. \} 66.\} 67.\" 68.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). 69.\" Fear. Run. Save yourself. No user-serviceable parts. 70. \" fudge factors for nroff and troff 71.if n \{\ 72. ds #H 0 73. ds #V .8m 74. ds #F .3m 75. ds #[ \f1 76. ds #] \fP 77.\} 78.if t \{\ 79. ds #H ((1u-(\\\\n(.fu%2u))*.13m) 80. ds #V .6m 81. ds #F 0 82. ds #[ \& 83. ds #] \& 84.\} 85. \" simple accents for nroff and troff 86.if n \{\ 87. ds ' \& 88. ds ` \& 89. ds ^ \& 90. ds , \& 91. ds ~ ~ 92. ds / 93.\} 94.if t \{\ 95. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" 96. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' 97. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' 98. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' 99. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' 100. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' 101.\} 102. \" troff and (daisy-wheel) nroff accents 103.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' 104.ds 8 \h'\*(#H'\(*b\h'-\*(#H' 105.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] 106.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' 107.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' 108.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] 109.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] 110.ds ae a\h'-(\w'a'u*4/10)'e 111.ds Ae A\h'-(\w'A'u*4/10)'E 112. \" corrections for vroff 113.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' 114.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' 115. \" for low resolution devices (crt and lpr) 116.if \n(.H>23 .if \n(.V>19 \ 117\{\ 118. ds : e 119. ds 8 ss 120. ds o a 121. ds d- d\h'-1'\(ga 122. ds D- D\h'-1'\(hy 123. ds th \o'bp' 124. ds Th \o'LP' 125. ds ae ae 126. ds Ae AE 127.\} 128.rm #[ #] #H #V #F C 129.\" ======================================================================== 130.\" 131.IX Title "SSL_CTX_set_generate_session_id 3"
| 2.\" 3.\" Standard preamble: 4.\" ======================================================================== 5.de Sp \" Vertical space (when we can't use .PP) 6.if t .sp .5v 7.if n .sp 8.. 9.de Vb \" Begin verbatim text 10.ft CW 11.nf 12.ne \\$1 13.. 14.de Ve \" End verbatim text 15.ft R 16.fi 17.. 18.\" Set up some character translations and predefined strings. \*(-- will 19.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left 20.\" double quote, and \*(R" will give a right double quote. \*(C+ will 21.\" give a nicer C++. Capital omega is used to do unbreakable dashes and 22.\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, 23.\" nothing in troff, for use with C<>. 24.tr \(*W- 25.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' 26.ie n \{\ 27. ds -- \(*W- 28. ds PI pi 29. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch 30. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch 31. ds L" "" 32. ds R" "" 33. ds C` "" 34. ds C' "" 35'br\} 36.el\{\ 37. ds -- \|\(em\| 38. ds PI \(*p 39. ds L" `` 40. ds R" '' 41. ds C` 42. ds C' 43'br\} 44.\" 45.\" Escape single quotes in literal strings from groff's Unicode transform. 46.ie \n(.g .ds Aq \(aq 47.el .ds Aq ' 48.\" 49.\" If the F register is >0, we'll generate index entries on stderr for 50.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index 51.\" entries marked with X<> in POD. Of course, you'll have to process the 52.\" output yourself in some meaningful fashion. 53.\" 54.\" Avoid warning from groff about undefined register 'F'. 55.de IX 56.. 57.if !\nF .nr F 0 58.if \nF>0 \{\ 59. de IX 60. tm Index:\\$1\t\\n%\t"\\$2" 61.. 62. if !\nF==2 \{\ 63. nr % 0 64. nr F 2 65. \} 66.\} 67.\" 68.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). 69.\" Fear. Run. Save yourself. No user-serviceable parts. 70. \" fudge factors for nroff and troff 71.if n \{\ 72. ds #H 0 73. ds #V .8m 74. ds #F .3m 75. ds #[ \f1 76. ds #] \fP 77.\} 78.if t \{\ 79. ds #H ((1u-(\\\\n(.fu%2u))*.13m) 80. ds #V .6m 81. ds #F 0 82. ds #[ \& 83. ds #] \& 84.\} 85. \" simple accents for nroff and troff 86.if n \{\ 87. ds ' \& 88. ds ` \& 89. ds ^ \& 90. ds , \& 91. ds ~ ~ 92. ds / 93.\} 94.if t \{\ 95. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" 96. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' 97. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' 98. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' 99. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' 100. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' 101.\} 102. \" troff and (daisy-wheel) nroff accents 103.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' 104.ds 8 \h'\*(#H'\(*b\h'-\*(#H' 105.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] 106.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' 107.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' 108.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] 109.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] 110.ds ae a\h'-(\w'a'u*4/10)'e 111.ds Ae A\h'-(\w'A'u*4/10)'E 112. \" corrections for vroff 113.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' 114.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' 115. \" for low resolution devices (crt and lpr) 116.if \n(.H>23 .if \n(.V>19 \ 117\{\ 118. ds : e 119. ds 8 ss 120. ds o a 121. ds d- d\h'-1'\(ga 122. ds D- D\h'-1'\(hy 123. ds th \o'bp' 124. ds Th \o'LP' 125. ds ae ae 126. ds Ae AE 127.\} 128.rm #[ #] #H #V #F C 129.\" ======================================================================== 130.\" 131.IX Title "SSL_CTX_set_generate_session_id 3"
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133.\" For nroff, turn off justification. Always turn off hyphenation; it makes 134.\" way too many mistakes in technical documents. 135.if n .ad l 136.nh 137.SH "NAME" 138SSL_CTX_set_generate_session_id, SSL_set_generate_session_id, SSL_has_matching_session_id \- manipulate generation of SSL session IDs (server only) 139.SH "SYNOPSIS" 140.IX Header "SYNOPSIS" 141.Vb 1 142\& #include <openssl/ssl.h> 143\& 144\& typedef int (*GEN_SESSION_CB)(const SSL *ssl, unsigned char *id, 145\& unsigned int *id_len); 146\& 147\& int SSL_CTX_set_generate_session_id(SSL_CTX *ctx, GEN_SESSION_CB cb); 148\& int SSL_set_generate_session_id(SSL *ssl, GEN_SESSION_CB, cb); 149\& int SSL_has_matching_session_id(const SSL *ssl, const unsigned char *id, 150\& unsigned int id_len); 151.Ve 152.SH "DESCRIPTION" 153.IX Header "DESCRIPTION" 154\&\fISSL_CTX_set_generate_session_id()\fR sets the callback function for generating 155new session ids for \s-1SSL/TLS\s0 sessions for \fBctx\fR to be \fBcb\fR. 156.PP 157\&\fISSL_set_generate_session_id()\fR sets the callback function for generating 158new session ids for \s-1SSL/TLS\s0 sessions for \fBssl\fR to be \fBcb\fR. 159.PP 160\&\fISSL_has_matching_session_id()\fR checks, whether a session with id \fBid\fR 161(of length \fBid_len\fR) is already contained in the internal session cache 162of the parent context of \fBssl\fR. 163.SH "NOTES" 164.IX Header "NOTES" 165When a new session is established between client and server, the server 166generates a session id. The session id is an arbitrary sequence of bytes. 167The length of the session id is 16 bytes for SSLv2 sessions and between 1681 and 32 bytes for SSLv3/TLSv1. The session id is not security critical 169but must be unique for the server. Additionally, the session id is 170transmitted in the clear when reusing the session so it must not contain 171sensitive information. 172.PP 173Without a callback being set, an OpenSSL server will generate a unique 174session id from pseudo random numbers of the maximum possible length. 175Using the callback function, the session id can be changed to contain 176additional information like e.g. a host id in order to improve load balancing 177or external caching techniques. 178.PP 179The callback function receives a pointer to the memory location to put 180\&\fBid\fR into and a pointer to the maximum allowed length \fBid_len\fR. The 181buffer at location \fBid\fR is only guaranteed to have the size \fBid_len\fR. 182The callback is only allowed to generate a shorter id and reduce \fBid_len\fR; 183the callback \fBmust never\fR increase \fBid_len\fR or write to the location 184\&\fBid\fR exceeding the given limit. 185.PP 186If a SSLv2 session id is generated and \fBid_len\fR is reduced, it will be 187restored after the callback has finished and the session id will be padded 188with 0x00. It is not recommended to change the \fBid_len\fR for SSLv2 sessions. 189The callback can use the \fISSL_get_version\fR\|(3) function 190to check, whether the session is of type SSLv2. 191.PP 192The location \fBid\fR is filled with 0x00 before the callback is called, so the 193callback may only fill part of the possible length and leave \fBid_len\fR 194untouched while maintaining reproducibility. 195.PP 196Since the sessions must be distinguished, session ids must be unique. 197Without the callback a random number is used, so that the probability 198of generating the same session id is extremely small (2^128 possible ids 199for an SSLv2 session, 2^256 for SSLv3/TLSv1). In order to assure the 200uniqueness of the generated session id, the callback must call 201\&\fISSL_has_matching_session_id()\fR and generate another id if a conflict occurs. 202If an id conflict is not resolved, the handshake will fail. 203If the application codes e.g. a unique host id, a unique process number, and 204a unique sequence number into the session id, uniqueness could easily be 205achieved without randomness added (it should however be taken care that 206no confidential information is leaked this way). If the application can not 207guarantee uniqueness, it is recommended to use the maximum \fBid_len\fR and 208fill in the bytes not used to code special information with random data 209to avoid collisions. 210.PP 211\&\fISSL_has_matching_session_id()\fR will only query the internal session cache, 212not the external one. Since the session id is generated before the 213handshake is completed, it is not immediately added to the cache. If 214another thread is using the same internal session cache, a race condition 215can occur in that another thread generates the same session id. 216Collisions can also occur when using an external session cache, since 217the external cache is not tested with \fISSL_has_matching_session_id()\fR 218and the same race condition applies. 219.PP 220When calling \fISSL_has_matching_session_id()\fR for an SSLv2 session with 221reduced \fBid_len\fR, the match operation will be performed using the 222fixed length required and with a 0x00 padded id. 223.PP 224The callback must return 0 if it cannot generate a session id for whatever 225reason and return 1 on success. 226.SH "EXAMPLES" 227.IX Header "EXAMPLES" 228The callback function listed will generate a session id with the 229server id given, and will fill the rest with pseudo random bytes: 230.PP 231.Vb 1 232\& const char session_id_prefix = "www\-18"; 233\& 234\& #define MAX_SESSION_ID_ATTEMPTS 10 235\& static int generate_session_id(const SSL *ssl, unsigned char *id, 236\& unsigned int *id_len) 237\& { 238\& unsigned int count = 0; 239\& const char *version; 240\& 241\& version = SSL_get_version(ssl); 242\& if (!strcmp(version, "SSLv2")) 243\& /* we must not change id_len */; 244\& 245\& do { 246\& RAND_pseudo_bytes(id, *id_len); 247\& /* Prefix the session_id with the required prefix. NB: If our 248\& * prefix is too long, clip it \- but there will be worse effects 249\& * anyway, eg. the server could only possibly create 1 session 250\& * ID (ie. the prefix!) so all future session negotiations will 251\& * fail due to conflicts. */ 252\& memcpy(id, session_id_prefix, 253\& (strlen(session_id_prefix) < *id_len) ? 254\& strlen(session_id_prefix) : *id_len); 255\& } 256\& while(SSL_has_matching_session_id(ssl, id, *id_len) && 257\& (++count < MAX_SESSION_ID_ATTEMPTS)); 258\& if(count >= MAX_SESSION_ID_ATTEMPTS) 259\& return 0; 260\& return 1; 261\& } 262.Ve 263.SH "RETURN VALUES" 264.IX Header "RETURN VALUES" 265\&\fISSL_CTX_set_generate_session_id()\fR and \fISSL_set_generate_session_id()\fR 266always return 1. 267.PP 268\&\fISSL_has_matching_session_id()\fR returns 1 if another session with the 269same id is already in the cache. 270.SH "SEE ALSO" 271.IX Header "SEE ALSO" 272\&\fIssl\fR\|(3), \fISSL_get_version\fR\|(3) 273.SH "HISTORY" 274.IX Header "HISTORY" 275\&\fISSL_CTX_set_generate_session_id()\fR, \fISSL_set_generate_session_id()\fR 276and \fISSL_has_matching_session_id()\fR have been introduced in 277OpenSSL 0.9.7.
| 133.\" For nroff, turn off justification. Always turn off hyphenation; it makes 134.\" way too many mistakes in technical documents. 135.if n .ad l 136.nh 137.SH "NAME" 138SSL_CTX_set_generate_session_id, SSL_set_generate_session_id, SSL_has_matching_session_id \- manipulate generation of SSL session IDs (server only) 139.SH "SYNOPSIS" 140.IX Header "SYNOPSIS" 141.Vb 1 142\& #include <openssl/ssl.h> 143\& 144\& typedef int (*GEN_SESSION_CB)(const SSL *ssl, unsigned char *id, 145\& unsigned int *id_len); 146\& 147\& int SSL_CTX_set_generate_session_id(SSL_CTX *ctx, GEN_SESSION_CB cb); 148\& int SSL_set_generate_session_id(SSL *ssl, GEN_SESSION_CB, cb); 149\& int SSL_has_matching_session_id(const SSL *ssl, const unsigned char *id, 150\& unsigned int id_len); 151.Ve 152.SH "DESCRIPTION" 153.IX Header "DESCRIPTION" 154\&\fISSL_CTX_set_generate_session_id()\fR sets the callback function for generating 155new session ids for \s-1SSL/TLS\s0 sessions for \fBctx\fR to be \fBcb\fR. 156.PP 157\&\fISSL_set_generate_session_id()\fR sets the callback function for generating 158new session ids for \s-1SSL/TLS\s0 sessions for \fBssl\fR to be \fBcb\fR. 159.PP 160\&\fISSL_has_matching_session_id()\fR checks, whether a session with id \fBid\fR 161(of length \fBid_len\fR) is already contained in the internal session cache 162of the parent context of \fBssl\fR. 163.SH "NOTES" 164.IX Header "NOTES" 165When a new session is established between client and server, the server 166generates a session id. The session id is an arbitrary sequence of bytes. 167The length of the session id is 16 bytes for SSLv2 sessions and between 1681 and 32 bytes for SSLv3/TLSv1. The session id is not security critical 169but must be unique for the server. Additionally, the session id is 170transmitted in the clear when reusing the session so it must not contain 171sensitive information. 172.PP 173Without a callback being set, an OpenSSL server will generate a unique 174session id from pseudo random numbers of the maximum possible length. 175Using the callback function, the session id can be changed to contain 176additional information like e.g. a host id in order to improve load balancing 177or external caching techniques. 178.PP 179The callback function receives a pointer to the memory location to put 180\&\fBid\fR into and a pointer to the maximum allowed length \fBid_len\fR. The 181buffer at location \fBid\fR is only guaranteed to have the size \fBid_len\fR. 182The callback is only allowed to generate a shorter id and reduce \fBid_len\fR; 183the callback \fBmust never\fR increase \fBid_len\fR or write to the location 184\&\fBid\fR exceeding the given limit. 185.PP 186If a SSLv2 session id is generated and \fBid_len\fR is reduced, it will be 187restored after the callback has finished and the session id will be padded 188with 0x00. It is not recommended to change the \fBid_len\fR for SSLv2 sessions. 189The callback can use the \fISSL_get_version\fR\|(3) function 190to check, whether the session is of type SSLv2. 191.PP 192The location \fBid\fR is filled with 0x00 before the callback is called, so the 193callback may only fill part of the possible length and leave \fBid_len\fR 194untouched while maintaining reproducibility. 195.PP 196Since the sessions must be distinguished, session ids must be unique. 197Without the callback a random number is used, so that the probability 198of generating the same session id is extremely small (2^128 possible ids 199for an SSLv2 session, 2^256 for SSLv3/TLSv1). In order to assure the 200uniqueness of the generated session id, the callback must call 201\&\fISSL_has_matching_session_id()\fR and generate another id if a conflict occurs. 202If an id conflict is not resolved, the handshake will fail. 203If the application codes e.g. a unique host id, a unique process number, and 204a unique sequence number into the session id, uniqueness could easily be 205achieved without randomness added (it should however be taken care that 206no confidential information is leaked this way). If the application can not 207guarantee uniqueness, it is recommended to use the maximum \fBid_len\fR and 208fill in the bytes not used to code special information with random data 209to avoid collisions. 210.PP 211\&\fISSL_has_matching_session_id()\fR will only query the internal session cache, 212not the external one. Since the session id is generated before the 213handshake is completed, it is not immediately added to the cache. If 214another thread is using the same internal session cache, a race condition 215can occur in that another thread generates the same session id. 216Collisions can also occur when using an external session cache, since 217the external cache is not tested with \fISSL_has_matching_session_id()\fR 218and the same race condition applies. 219.PP 220When calling \fISSL_has_matching_session_id()\fR for an SSLv2 session with 221reduced \fBid_len\fR, the match operation will be performed using the 222fixed length required and with a 0x00 padded id. 223.PP 224The callback must return 0 if it cannot generate a session id for whatever 225reason and return 1 on success. 226.SH "EXAMPLES" 227.IX Header "EXAMPLES" 228The callback function listed will generate a session id with the 229server id given, and will fill the rest with pseudo random bytes: 230.PP 231.Vb 1 232\& const char session_id_prefix = "www\-18"; 233\& 234\& #define MAX_SESSION_ID_ATTEMPTS 10 235\& static int generate_session_id(const SSL *ssl, unsigned char *id, 236\& unsigned int *id_len) 237\& { 238\& unsigned int count = 0; 239\& const char *version; 240\& 241\& version = SSL_get_version(ssl); 242\& if (!strcmp(version, "SSLv2")) 243\& /* we must not change id_len */; 244\& 245\& do { 246\& RAND_pseudo_bytes(id, *id_len); 247\& /* Prefix the session_id with the required prefix. NB: If our 248\& * prefix is too long, clip it \- but there will be worse effects 249\& * anyway, eg. the server could only possibly create 1 session 250\& * ID (ie. the prefix!) so all future session negotiations will 251\& * fail due to conflicts. */ 252\& memcpy(id, session_id_prefix, 253\& (strlen(session_id_prefix) < *id_len) ? 254\& strlen(session_id_prefix) : *id_len); 255\& } 256\& while(SSL_has_matching_session_id(ssl, id, *id_len) && 257\& (++count < MAX_SESSION_ID_ATTEMPTS)); 258\& if(count >= MAX_SESSION_ID_ATTEMPTS) 259\& return 0; 260\& return 1; 261\& } 262.Ve 263.SH "RETURN VALUES" 264.IX Header "RETURN VALUES" 265\&\fISSL_CTX_set_generate_session_id()\fR and \fISSL_set_generate_session_id()\fR 266always return 1. 267.PP 268\&\fISSL_has_matching_session_id()\fR returns 1 if another session with the 269same id is already in the cache. 270.SH "SEE ALSO" 271.IX Header "SEE ALSO" 272\&\fIssl\fR\|(3), \fISSL_get_version\fR\|(3) 273.SH "HISTORY" 274.IX Header "HISTORY" 275\&\fISSL_CTX_set_generate_session_id()\fR, \fISSL_set_generate_session_id()\fR 276and \fISSL_has_matching_session_id()\fR have been introduced in 277OpenSSL 0.9.7.
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