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Diffstat (limited to 'src/auths/get_data.c')
| -rw-r--r-- | src/auths/get_data.c | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/src/auths/get_data.c b/src/auths/get_data.c new file mode 100644 index 0000000..e0d79db --- /dev/null +++ b/src/auths/get_data.c @@ -0,0 +1,259 @@ +/************************************************* +* Exim - an Internet mail transport agent * +*************************************************/ + +/* Copyright (c) University of Cambridge 1995 - 2018 */ +/* Copyright (c) The Exim Maintainers 2020 - 2021 */ +/* See the file NOTICE for conditions of use and distribution. */ + +#include "../exim.h" + + +/**************************************************************** +* Decode and split the argument of an AUTH command * +****************************************************************/ + +/* If data was supplied on the AUTH command, decode it, and split it up into +multiple items at binary zeros. The strings are put into $auth1, $auth2, etc, +up to a maximum. To retain backwards compatibility, they are also put int $1, +$2, etc. If the data consists of the string "=" it indicates a single, empty +string. */ + +int +auth_read_input(const uschar * data) +{ +if (Ustrcmp(data, "=") == 0) + { + auth_vars[0] = expand_nstring[++expand_nmax] = US""; + expand_nlength[expand_nmax] = 0; + } +else + { + uschar * clear, * end; + int len; + + if ((len = b64decode(data, &clear)) < 0) return BAD64; + DEBUG(D_auth) debug_printf("auth input decode:"); + for (end = clear + len; clear < end && expand_nmax < EXPAND_MAXN; ) + { + DEBUG(D_auth) debug_printf(" '%s'", clear); + if (expand_nmax < AUTH_VARS) auth_vars[expand_nmax] = clear; + expand_nstring[++expand_nmax] = clear; + while (*clear != 0) clear++; + expand_nlength[expand_nmax] = clear++ - expand_nstring[expand_nmax]; + } + DEBUG(D_auth) debug_printf("\n"); + } +return OK; +} + + + + +/************************************************* +* Issue a challenge and get a response * +*************************************************/ + +/* This function is used by authentication drivers to b64-encode and +output a challenge to the SMTP client, and read the response line. + +Arguments: + aptr set to point to the response (which is in big_buffer) + challenge the challenge data (unencoded, may be binary) + challen the length of the challenge data, in bytes + +Returns: OK on success + BAD64 if response too large for buffer + CANCELLED if response is "*" +*/ + +int +auth_get_data(uschar ** aptr, const uschar * challenge, int challen) +{ +int c; +int p = 0; +smtp_printf("334 %s\r\n", FALSE, b64encode(challenge, challen)); +while ((c = receive_getc(GETC_BUFFER_UNLIMITED)) != '\n' && c != EOF) + { + if (p >= big_buffer_size - 1) return BAD64; + big_buffer[p++] = c; + } +if (p > 0 && big_buffer[p-1] == '\r') p--; +big_buffer[p] = 0; +DEBUG(D_receive) debug_printf("SMTP<< %s\n", big_buffer); +if (Ustrcmp(big_buffer, "*") == 0) return CANCELLED; +*aptr = big_buffer; +return OK; +} + + + +int +auth_prompt(const uschar * challenge) +{ +int rc, len; +uschar * resp, * clear, * end; + +if ((rc = auth_get_data(&resp, challenge, Ustrlen(challenge))) != OK) + return rc; +if ((len = b64decode(resp, &clear)) < 0) + return BAD64; +end = clear + len; + +/* This loop must run at least once, in case the length is zero */ +do + { + if (expand_nmax < AUTH_VARS) auth_vars[expand_nmax] = clear; + expand_nstring[++expand_nmax] = clear; + while (*clear != 0) clear++; + expand_nlength[expand_nmax] = clear++ - expand_nstring[expand_nmax]; + } +while (clear < end && expand_nmax < EXPAND_MAXN); +return OK; +} + + +/*********************************************** +* Send an AUTH-negotiation item * +************************************************/ + +/* Expand and send one client auth item and read the response. +Include the AUTH command and method if tagged as "first". Use the given buffer +for receiving the b6-encoded reply; decode it it return it in the string arg. + +Return: + OK success + FAIL_SEND error after writing a command; errno is set + FAIL failed after reading a response; + either errno is set (for timeouts, I/O failures) or + the buffer contains the SMTP response line + CANCELLED the client cancelled authentication (often "fail" in expansion) + the buffer may contain a message; if not, *buffer = 0 + ERROR local problem (typically expansion error); message in buffer + DEFER more items expected +*/ + +int +auth_client_item(void * sx, auth_instance * ablock, const uschar ** inout, + unsigned flags, int timeout, uschar * buffer, int buffsize) +{ +int len, clear_len; +uschar * ss, * clear; + +ss = US expand_cstring(*inout); +if (ss == *inout) ss = string_copy(ss); + +/* Forced expansion failure is not an error; authentication is abandoned. On +all but the first string, we have to abandon the authentication attempt by +sending a line containing "*". Save the failed expansion string, because it +is in big_buffer, and that gets used by the sending function. */ + +if (!ss) + { + if (!(flags & AUTH_ITEM_FIRST)) + { + if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0) + (void) smtp_read_response(sx, US buffer, buffsize, '2', timeout); + } + if (f.expand_string_forcedfail) + { + *buffer = 0; /* No message */ + return CANCELLED; + } + string_format(buffer, buffsize, "expansion of \"%s\" failed in %s " + "authenticator: %s", *inout, ablock->name, expand_string_message); + return ERROR; + } + +len = Ustrlen(ss); + +/* The character ^ is used as an escape for a binary zero character, which is +needed for the PLAIN mechanism. It must be doubled if really needed. + +The parsing ambiguity of ^^^ is taken as ^^ -> ^ ; ^ -> NUL - and there is +no way to get a leading ^ after a NUL. We would need to intro new syntax to +support that (probably preferring to take a more-standard exim list as a source +and concat the elements with intervening NULs. Either a magic marker on the +source string for client_send, or a new option). */ + +for (int i = 0; i < len; i++) + if (ss[i] == '^') + if (ss[i+1] != '^') + ss[i] = 0; + else + if (--len > i+1) memmove(ss + i + 1, ss + i + 2, len - i); + +/* The first string is attached to the AUTH command; others are sent +unembellished. */ + +if (flags & AUTH_ITEM_FIRST) + { + if (smtp_write_command(sx, SCMD_FLUSH, "AUTH %s%s%s\r\n", + ablock->public_name, len == 0 ? "" : " ", b64encode(CUS ss, len)) < 0) + return FAIL_SEND; + } +else + if (smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", b64encode(CUS ss, len)) < 0) + return FAIL_SEND; + +/* If we receive a success response from the server, authentication +has succeeded. There may be more data to send, but is there any point +in provoking an error here? */ + +if (smtp_read_response(sx, buffer, buffsize, '2', timeout)) + { + *inout = NULL; + return OK; + } + +/* Not a success response. If errno != 0 there is some kind of transmission +error. Otherwise, check the response code in the buffer. If it starts with +'3', more data is expected. */ + +if (errno != 0 || buffer[0] != '3') return FAIL; + +/* If there is no more data to send, we have to cancel the authentication +exchange and return ERROR. */ + +if (flags & AUTH_ITEM_LAST) + { + if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0) + (void)smtp_read_response(sx, US buffer, buffsize, '2', timeout); + string_format(buffer, buffsize, "Too few items in client_send in %s " + "authenticator", ablock->name); + return ERROR; + } + +/* Now that we know we'll continue, we put the received data into $auth<n>, +if possible. First, decode it: buffer+4 skips over the SMTP status code. */ + +clear_len = b64decode(buffer+4, &clear); + +/* If decoding failed, the default is to terminate the authentication, and +return FAIL, with the SMTP response still in the buffer. However, if client_ +ignore_invalid_base64 is set, we ignore the error, and put an empty string +into $auth<n>. */ + +if (clear_len < 0) + { + uschar *save_bad = string_copy(buffer); + if (!(flags & AUTH_ITEM_IGN64)) + { + if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0) + (void)smtp_read_response(sx, US buffer, buffsize, '2', timeout); + string_format(buffer, buffsize, "Invalid base64 string in server " + "response \"%s\"", save_bad); + return CANCELLED; + } + DEBUG(D_auth) debug_printf("bad b64 decode for '%s';" + " ignoring due to client_ignore_invalid_base64\n", save_bad); + clear = string_copy(US""); + clear_len = 0; + } + +*inout = clear; +return DEFER; +} + + +/* End of get_data.c */ |