Found by using auth_basic.t from mdounin nginx-tests under valgrind.
==10470== Invalid write of size 1
==10470== at 0x43603D: ngx_crypt_to64 (ngx_crypt.c:168)
==10470== by 0x43648E: ngx_crypt (ngx_crypt.c:153)
==10470== by 0x489D8B: ngx_http_auth_basic_crypt_handler (ngx_http_auth_basic_module.c:297)
==10470== by 0x48A24A: ngx_http_auth_basic_handler (ngx_http_auth_basic_module.c:240)
==10470== by 0x44EAB9: ngx_http_core_access_phase (ngx_http_core_module.c:1121)
==10470== by 0x44A822: ngx_http_core_run_phases (ngx_http_core_module.c:895)
==10470== by 0x44A932: ngx_http_handler (ngx_http_core_module.c:878)
==10470== by 0x455EEF: ngx_http_process_request (ngx_http_request.c:1852)
==10470== by 0x456527: ngx_http_process_request_headers (ngx_http_request.c:1283)
==10470== by 0x456A91: ngx_http_process_request_line (ngx_http_request.c:964)
==10470== by 0x457097: ngx_http_wait_request_handler (ngx_http_request.c:486)
==10470== by 0x4411EE: ngx_epoll_process_events (ngx_epoll_module.c:691)
==10470== Address 0x5866fab is 0 bytes after a block of size 27 alloc'd
==10470== at 0x4A074CD: malloc (vg_replace_malloc.c:236)
==10470== by 0x43B251: ngx_alloc (ngx_alloc.c:22)
==10470== by 0x421B0D: ngx_malloc (ngx_palloc.c:119)
==10470== by 0x421B65: ngx_pnalloc (ngx_palloc.c:147)
==10470== by 0x436368: ngx_crypt (ngx_crypt.c:140)
==10470== by 0x489D8B: ngx_http_auth_basic_crypt_handler (ngx_http_auth_basic_module.c:297)
==10470== by 0x48A24A: ngx_http_auth_basic_handler (ngx_http_auth_basic_module.c:240)
==10470== by 0x44EAB9: ngx_http_core_access_phase (ngx_http_core_module.c:1121)
==10470== by 0x44A822: ngx_http_core_run_phases (ngx_http_core_module.c:895)
==10470== by 0x44A932: ngx_http_handler (ngx_http_core_module.c:878)
==10470== by 0x455EEF: ngx_http_process_request (ngx_http_request.c:1852)
==10470== by 0x456527: ngx_http_process_request_headers (ngx_http_request.c:1283)
==10470==
Note: use of {SHA} passwords is discouraged as {SHA} password scheme is
vulnerable to attacks using rainbow tables. Use of {SSHA}, $apr1$ or
crypt() algorithms as supported by OS is recommended instead.
The {SHA} password scheme support is added to avoid the need of changing
the scheme recorded in password files from {SHA} to {SSHA} because such
a change hides security problem with {SHA} passwords.
Patch by Louis Opter, with minor changes.
